Utilities

This document is better viewed at https://docs.openzeppelin.com/contracts/api/utils

Miscellaneous contracts and libraries containing utility functions you can use to improve security, work with new data types, or safely use low-level primitives.

  • Math, SignedMath: Implementation of various arithmetic functions.

  • SafeCast: Checked downcasting functions to avoid silent truncation.

  • ECDSA, MessageHashUtils: Libraries for interacting with ECDSA signatures.

  • P256: Library for verifying and recovering public keys from secp256r1 signatures.

  • RSA: Library with RSA PKCS#1 v1.5 signature verification utilities.

  • SignatureChecker: A library helper to support regular ECDSA from EOAs as well as ERC-1271 signatures for smart contracts.

  • Hashes: Commonly used hash functions.

  • MerkleProof: Functions for verifying Merkle Tree proofs.

  • EIP712: Contract with functions to allow processing signed typed structure data according to EIP-712.

  • ReentrancyGuard: A modifier that can prevent reentrancy during certain functions.

  • ReentrancyGuardTransient: Variant of ReentrancyGuard that uses transient storage (EIP-1153).

  • Pausable: A common emergency response mechanism that can pause functionality while a remediation is pending.

  • Nonces: Utility for tracking and verifying address nonces that only increment.

  • ERC165, ERC165Checker: Utilities for inspecting interfaces supported by contracts.

  • BitMaps: A simple library to manage boolean value mapped to a numerical index in an efficient way.

  • EnumerableMap: A type like Solidity’s mapping, but with key-value enumeration: this will let you know how many entries a mapping has, and iterate over them (which is not possible with mapping).

  • EnumerableSet: Like EnumerableMap, but for sets. Can be used to store privileged accounts, issued IDs, etc.

  • DoubleEndedQueue: An implementation of a double ended queue whose values can be removed added or remove from both sides. Useful for FIFO and LIFO structures.

  • CircularBuffer: A data structure to store the last N values pushed to it.

  • Checkpoints: A data structure to store values mapped to a strictly increasing key. Can be used for storing and accessing values over time.

  • Heap: A library that implements a binary heap in storage.

  • MerkleTree: A library with Merkle Tree data structures and helper functions.

  • Create2: Wrapper around the CREATE2 EVM opcode for safe use without having to deal with low-level assembly.

  • Address: Collection of functions for overloading Solidity’s address type.

  • Arrays: Collection of functions that operate on arrays.

  • Base64: On-chain base64 and base64URL encoding according to RFC-4648.

  • Strings: Common operations for strings formatting.

  • ShortString: Library to encode (and decode) short strings into (or from) a single bytes32 slot for optimizing costs. Short strings are limited to 31 characters.

  • SlotDerivation: Methods for deriving storage slot from ERC-7201 namespaces as well as from constructions such as mapping and arrays.

  • StorageSlot: Methods for accessing specific storage slots formatted as common primitive types.

  • TransientSlot: Primitives for reading from and writing to transient storage (only value types are currently supported).

  • Multicall: Abstract contract with a utility to allow batching together multiple calls in a single transaction. Useful for allowing EOAs to perform multiple operations at once.

  • Context: A utility for abstracting the sender and calldata in the current execution context.

  • Packing: A library for packing and unpacking multiple values into bytes32

  • Panic: A library to revert with Solidity panic codes.

  • Comparators: A library that contains comparator functions to use with with the Heap library.

Because Solidity does not support generic types, EnumerableMap and EnumerableSet are specialized to a limited number of key-value types.

Math

Math 

import "@openzeppelin/contracts/utils/math/Math.sol";

Standard math utilities missing in the Solidity language.

Functions

tryAdd(uint256 a, uint256 b) → bool success, uint256 result internal

Returns the addition of two unsigned integers, with an success flag (no overflow).

trySub(uint256 a, uint256 b) → bool success, uint256 result internal

Returns the subtraction of two unsigned integers, with an success flag (no overflow).

tryMul(uint256 a, uint256 b) → bool success, uint256 result internal

Returns the multiplication of two unsigned integers, with an success flag (no overflow).

tryDiv(uint256 a, uint256 b) → bool success, uint256 result internal

Returns the division of two unsigned integers, with a success flag (no division by zero).

tryMod(uint256 a, uint256 b) → bool success, uint256 result internal

Returns the remainder of dividing two unsigned integers, with a success flag (no division by zero).

ternary(bool condition, uint256 a, uint256 b) → uint256 internal

Branchless ternary evaluation for a ? b : c. Gas costs are constant.

This function may reduce bytecode size and consume less gas when used standalone. However, the compiler may optimize Solidity ternary operations (i.e. a ? b : c) to only compute one branch when needed, making this function more expensive.

max(uint256 a, uint256 b) → uint256 internal

Returns the largest of two numbers.

min(uint256 a, uint256 b) → uint256 internal

Returns the smallest of two numbers.

average(uint256 a, uint256 b) → uint256 internal

Returns the average of two numbers. The result is rounded towards zero.

ceilDiv(uint256 a, uint256 b) → uint256 internal

Returns the ceiling of the division of two numbers.

This differs from standard division with / in that it rounds towards infinity instead of rounding towards zero.

mulDiv(uint256 x, uint256 y, uint256 denominator) → uint256 result internal

Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or denominator == 0.

Original credit to Remco Bloemen under MIT license (https://xn—​2-umb.com/21/muldiv) with further edits by Uniswap Labs also under MIT license.

mulDiv(uint256 x, uint256 y, uint256 denominator, enum Math.Rounding rounding) → uint256 internal

Calculates x * y / denominator with full precision, following the selected rounding direction.

invMod(uint256 a, uint256 n) → uint256 internal

Calculate the modular multiplicative inverse of a number in Z/nZ.

If n is a prime, then Z/nZ is a field. In that case all elements are inversible, except 0. If n is not a prime, then Z/nZ is not a field, and some elements might not be inversible.

If the input value is not inversible, 0 is returned.

If you know for sure that n is (big) a prime, it may be cheaper to use Fermat’s little theorem and get the inverse using Math.modExp(a, n - 2, n). See invModPrime.

invModPrime(uint256 a, uint256 p) → uint256 internal

Variant of invMod. More efficient, but only works if p is known to be a prime greater than 2.

From Fermat’s little theorem, we know that if p is prime, then a(p-1) ≡ 1 mod p. As a consequence, we have a * a(p-2) ≡ 1 mod p, which means that a**(p-2) is the modular multiplicative inverse of a in Fp.

this function does NOT check that p is a prime greater than 2.

modExp(uint256 b, uint256 e, uint256 m) → uint256 internal

Returns the modular exponentiation of the specified base, exponent and modulus (b ** e % m)

Requirements: - modulus can’t be zero - underlying staticcall to precompile must succeed

The result is only valid if the underlying call succeeds. When using this function, make sure the chain you’re using it on supports the precompiled contract for modular exponentiation at address 0x05 as specified in EIP-198. Otherwise, the underlying function will succeed given the lack of a revert, but the result may be incorrectly interpreted as 0.

tryModExp(uint256 b, uint256 e, uint256 m) → bool success, uint256 result internal

Returns the modular exponentiation of the specified base, exponent and modulus (b ** e % m). It includes a success flag indicating if the operation succeeded. Operation will be marked as failed if trying to operate modulo 0 or if the underlying precompile reverted.

The result is only valid if the success flag is true. When using this function, make sure the chain you’re using it on supports the precompiled contract for modular exponentiation at address 0x05 as specified in EIP-198. Otherwise, the underlying function will succeed given the lack of a revert, but the result may be incorrectly interpreted as 0.

modExp(bytes b, bytes e, bytes m) → bytes internal

Variant of modExp that supports inputs of arbitrary length.

tryModExp(bytes b, bytes e, bytes m) → bool success, bytes result internal

Variant of tryModExp that supports inputs of arbitrary length.

sqrt(uint256 a) → uint256 internal

Returns the square root of a number. If the number is not a perfect square, the value is rounded towards zero.

This method is based on Newton’s method for computing square roots; the algorithm is restricted to only using integer operations.

sqrt(uint256 a, enum Math.Rounding rounding) → uint256 internal

Calculates sqrt(a), following the selected rounding direction.

log2(uint256 value) → uint256 internal

Return the log in base 2 of a positive value rounded towards zero. Returns 0 if given 0.

log2(uint256 value, enum Math.Rounding rounding) → uint256 internal

Return the log in base 2, following the selected rounding direction, of a positive value. Returns 0 if given 0.

log10(uint256 value) → uint256 internal

Return the log in base 10 of a positive value rounded towards zero. Returns 0 if given 0.

log10(uint256 value, enum Math.Rounding rounding) → uint256 internal

Return the log in base 10, following the selected rounding direction, of a positive value. Returns 0 if given 0.

log256(uint256 value) → uint256 internal

Return the log in base 256 of a positive value rounded towards zero. Returns 0 if given 0.

Adding one to the result gives the number of pairs of hex symbols needed to represent value as a hex string.

log256(uint256 value, enum Math.Rounding rounding) → uint256 internal

Return the log in base 256, following the selected rounding direction, of a positive value. Returns 0 if given 0.

unsignedRoundsUp(enum Math.Rounding rounding) → bool internal

Returns whether a provided rounding mode is considered rounding up for unsigned integers.

SignedMath 

import "@openzeppelin/contracts/utils/math/SignedMath.sol";

Standard signed math utilities missing in the Solidity language.

Functions

ternary(bool condition, int256 a, int256 b) → int256 internal

Branchless ternary evaluation for a ? b : c. Gas costs are constant.

This function may reduce bytecode size and consume less gas when used standalone. However, the compiler may optimize Solidity ternary operations (i.e. a ? b : c) to only compute one branch when needed, making this function more expensive.

max(int256 a, int256 b) → int256 internal

Returns the largest of two signed numbers.

min(int256 a, int256 b) → int256 internal

Returns the smallest of two signed numbers.

average(int256 a, int256 b) → int256 internal

Returns the average of two signed numbers without overflow. The result is rounded towards zero.

abs(int256 n) → uint256 internal

Returns the absolute unsigned value of a signed value.

SafeCast 

import "@openzeppelin/contracts/utils/math/SafeCast.sol";

Wrappers over Solidity’s uintXX/intXX/bool casting operators with added overflow checks.

Downcasting from uint256/int256 in Solidity does not revert on overflow. This can easily result in undesired exploitation or bugs, since developers usually assume that overflows raise errors. SafeCast restores this intuition by reverting the transaction when such an operation overflows.

Using this library instead of the unchecked operations eliminates an entire class of bugs, so it’s recommended to use it always.

Functions
Errors

toUint248(uint256 value) → uint248 internal

Returns the downcasted uint248 from uint256, reverting on overflow (when the input is greater than largest uint248).

Counterpart to Solidity’s uint248 operator.

Requirements:

  • input must fit into 248 bits

toUint240(uint256 value) → uint240 internal

Returns the downcasted uint240 from uint256, reverting on overflow (when the input is greater than largest uint240).

Counterpart to Solidity’s uint240 operator.

Requirements:

  • input must fit into 240 bits

toUint232(uint256 value) → uint232 internal

Returns the downcasted uint232 from uint256, reverting on overflow (when the input is greater than largest uint232).

Counterpart to Solidity’s uint232 operator.

Requirements:

  • input must fit into 232 bits

toUint224(uint256 value) → uint224 internal

Returns the downcasted uint224 from uint256, reverting on overflow (when the input is greater than largest uint224).

Counterpart to Solidity’s uint224 operator.

Requirements:

  • input must fit into 224 bits

toUint216(uint256 value) → uint216 internal

Returns the downcasted uint216 from uint256, reverting on overflow (when the input is greater than largest uint216).

Counterpart to Solidity’s uint216 operator.

Requirements:

  • input must fit into 216 bits

toUint208(uint256 value) → uint208 internal

Returns the downcasted uint208 from uint256, reverting on overflow (when the input is greater than largest uint208).

Counterpart to Solidity’s uint208 operator.

Requirements:

  • input must fit into 208 bits

toUint200(uint256 value) → uint200 internal

Returns the downcasted uint200 from uint256, reverting on overflow (when the input is greater than largest uint200).

Counterpart to Solidity’s uint200 operator.

Requirements:

  • input must fit into 200 bits

toUint192(uint256 value) → uint192 internal

Returns the downcasted uint192 from uint256, reverting on overflow (when the input is greater than largest uint192).

Counterpart to Solidity’s uint192 operator.

Requirements:

  • input must fit into 192 bits

toUint184(uint256 value) → uint184 internal

Returns the downcasted uint184 from uint256, reverting on overflow (when the input is greater than largest uint184).

Counterpart to Solidity’s uint184 operator.

Requirements:

  • input must fit into 184 bits

toUint176(uint256 value) → uint176 internal

Returns the downcasted uint176 from uint256, reverting on overflow (when the input is greater than largest uint176).

Counterpart to Solidity’s uint176 operator.

Requirements:

  • input must fit into 176 bits

toUint168(uint256 value) → uint168 internal

Returns the downcasted uint168 from uint256, reverting on overflow (when the input is greater than largest uint168).

Counterpart to Solidity’s uint168 operator.

Requirements:

  • input must fit into 168 bits

toUint160(uint256 value) → uint160 internal

Returns the downcasted uint160 from uint256, reverting on overflow (when the input is greater than largest uint160).

Counterpart to Solidity’s uint160 operator.

Requirements:

  • input must fit into 160 bits

toUint152(uint256 value) → uint152 internal

Returns the downcasted uint152 from uint256, reverting on overflow (when the input is greater than largest uint152).

Counterpart to Solidity’s uint152 operator.

Requirements:

  • input must fit into 152 bits

toUint144(uint256 value) → uint144 internal

Returns the downcasted uint144 from uint256, reverting on overflow (when the input is greater than largest uint144).

Counterpart to Solidity’s uint144 operator.

Requirements:

  • input must fit into 144 bits

toUint136(uint256 value) → uint136 internal

Returns the downcasted uint136 from uint256, reverting on overflow (when the input is greater than largest uint136).

Counterpart to Solidity’s uint136 operator.

Requirements:

  • input must fit into 136 bits

toUint128(uint256 value) → uint128 internal

Returns the downcasted uint128 from uint256, reverting on overflow (when the input is greater than largest uint128).

Counterpart to Solidity’s uint128 operator.

Requirements:

  • input must fit into 128 bits

toUint120(uint256 value) → uint120 internal

Returns the downcasted uint120 from uint256, reverting on overflow (when the input is greater than largest uint120).

Counterpart to Solidity’s uint120 operator.

Requirements:

  • input must fit into 120 bits

toUint112(uint256 value) → uint112 internal

Returns the downcasted uint112 from uint256, reverting on overflow (when the input is greater than largest uint112).

Counterpart to Solidity’s uint112 operator.

Requirements:

  • input must fit into 112 bits

toUint104(uint256 value) → uint104 internal

Returns the downcasted uint104 from uint256, reverting on overflow (when the input is greater than largest uint104).

Counterpart to Solidity’s uint104 operator.

Requirements:

  • input must fit into 104 bits

toUint96(uint256 value) → uint96 internal

Returns the downcasted uint96 from uint256, reverting on overflow (when the input is greater than largest uint96).

Counterpart to Solidity’s uint96 operator.

Requirements:

  • input must fit into 96 bits

toUint88(uint256 value) → uint88 internal

Returns the downcasted uint88 from uint256, reverting on overflow (when the input is greater than largest uint88).

Counterpart to Solidity’s uint88 operator.

Requirements:

  • input must fit into 88 bits

toUint80(uint256 value) → uint80 internal

Returns the downcasted uint80 from uint256, reverting on overflow (when the input is greater than largest uint80).

Counterpart to Solidity’s uint80 operator.

Requirements:

  • input must fit into 80 bits

toUint72(uint256 value) → uint72 internal

Returns the downcasted uint72 from uint256, reverting on overflow (when the input is greater than largest uint72).

Counterpart to Solidity’s uint72 operator.

Requirements:

  • input must fit into 72 bits

toUint64(uint256 value) → uint64 internal

Returns the downcasted uint64 from uint256, reverting on overflow (when the input is greater than largest uint64).

Counterpart to Solidity’s uint64 operator.

Requirements:

  • input must fit into 64 bits

toUint56(uint256 value) → uint56 internal

Returns the downcasted uint56 from uint256, reverting on overflow (when the input is greater than largest uint56).

Counterpart to Solidity’s uint56 operator.

Requirements:

  • input must fit into 56 bits

toUint48(uint256 value) → uint48 internal

Returns the downcasted uint48 from uint256, reverting on overflow (when the input is greater than largest uint48).

Counterpart to Solidity’s uint48 operator.

Requirements:

  • input must fit into 48 bits

toUint40(uint256 value) → uint40 internal

Returns the downcasted uint40 from uint256, reverting on overflow (when the input is greater than largest uint40).

Counterpart to Solidity’s uint40 operator.

Requirements:

  • input must fit into 40 bits

toUint32(uint256 value) → uint32 internal

Returns the downcasted uint32 from uint256, reverting on overflow (when the input is greater than largest uint32).

Counterpart to Solidity’s uint32 operator.

Requirements:

  • input must fit into 32 bits

toUint24(uint256 value) → uint24 internal

Returns the downcasted uint24 from uint256, reverting on overflow (when the input is greater than largest uint24).

Counterpart to Solidity’s uint24 operator.

Requirements:

  • input must fit into 24 bits

toUint16(uint256 value) → uint16 internal

Returns the downcasted uint16 from uint256, reverting on overflow (when the input is greater than largest uint16).

Counterpart to Solidity’s uint16 operator.

Requirements:

  • input must fit into 16 bits

toUint8(uint256 value) → uint8 internal

Returns the downcasted uint8 from uint256, reverting on overflow (when the input is greater than largest uint8).

Counterpart to Solidity’s uint8 operator.

Requirements:

  • input must fit into 8 bits

toUint256(int256 value) → uint256 internal

Converts a signed int256 into an unsigned uint256.

Requirements:

  • input must be greater than or equal to 0.

toInt248(int256 value) → int248 downcasted internal

Returns the downcasted int248 from int256, reverting on overflow (when the input is less than smallest int248 or greater than largest int248).

Counterpart to Solidity’s int248 operator.

Requirements:

  • input must fit into 248 bits

toInt240(int256 value) → int240 downcasted internal

Returns the downcasted int240 from int256, reverting on overflow (when the input is less than smallest int240 or greater than largest int240).

Counterpart to Solidity’s int240 operator.

Requirements:

  • input must fit into 240 bits

toInt232(int256 value) → int232 downcasted internal

Returns the downcasted int232 from int256, reverting on overflow (when the input is less than smallest int232 or greater than largest int232).

Counterpart to Solidity’s int232 operator.

Requirements:

  • input must fit into 232 bits

toInt224(int256 value) → int224 downcasted internal

Returns the downcasted int224 from int256, reverting on overflow (when the input is less than smallest int224 or greater than largest int224).

Counterpart to Solidity’s int224 operator.

Requirements:

  • input must fit into 224 bits

toInt216(int256 value) → int216 downcasted internal

Returns the downcasted int216 from int256, reverting on overflow (when the input is less than smallest int216 or greater than largest int216).

Counterpart to Solidity’s int216 operator.

Requirements:

  • input must fit into 216 bits

toInt208(int256 value) → int208 downcasted internal

Returns the downcasted int208 from int256, reverting on overflow (when the input is less than smallest int208 or greater than largest int208).

Counterpart to Solidity’s int208 operator.

Requirements:

  • input must fit into 208 bits

toInt200(int256 value) → int200 downcasted internal

Returns the downcasted int200 from int256, reverting on overflow (when the input is less than smallest int200 or greater than largest int200).

Counterpart to Solidity’s int200 operator.

Requirements:

  • input must fit into 200 bits

toInt192(int256 value) → int192 downcasted internal

Returns the downcasted int192 from int256, reverting on overflow (when the input is less than smallest int192 or greater than largest int192).

Counterpart to Solidity’s int192 operator.

Requirements:

  • input must fit into 192 bits

toInt184(int256 value) → int184 downcasted internal

Returns the downcasted int184 from int256, reverting on overflow (when the input is less than smallest int184 or greater than largest int184).

Counterpart to Solidity’s int184 operator.

Requirements:

  • input must fit into 184 bits

toInt176(int256 value) → int176 downcasted internal

Returns the downcasted int176 from int256, reverting on overflow (when the input is less than smallest int176 or greater than largest int176).

Counterpart to Solidity’s int176 operator.

Requirements:

  • input must fit into 176 bits

toInt168(int256 value) → int168 downcasted internal

Returns the downcasted int168 from int256, reverting on overflow (when the input is less than smallest int168 or greater than largest int168).

Counterpart to Solidity’s int168 operator.

Requirements:

  • input must fit into 168 bits

toInt160(int256 value) → int160 downcasted internal

Returns the downcasted int160 from int256, reverting on overflow (when the input is less than smallest int160 or greater than largest int160).

Counterpart to Solidity’s int160 operator.

Requirements:

  • input must fit into 160 bits

toInt152(int256 value) → int152 downcasted internal

Returns the downcasted int152 from int256, reverting on overflow (when the input is less than smallest int152 or greater than largest int152).

Counterpart to Solidity’s int152 operator.

Requirements:

  • input must fit into 152 bits

toInt144(int256 value) → int144 downcasted internal

Returns the downcasted int144 from int256, reverting on overflow (when the input is less than smallest int144 or greater than largest int144).

Counterpart to Solidity’s int144 operator.

Requirements:

  • input must fit into 144 bits

toInt136(int256 value) → int136 downcasted internal

Returns the downcasted int136 from int256, reverting on overflow (when the input is less than smallest int136 or greater than largest int136).

Counterpart to Solidity’s int136 operator.

Requirements:

  • input must fit into 136 bits

toInt128(int256 value) → int128 downcasted internal

Returns the downcasted int128 from int256, reverting on overflow (when the input is less than smallest int128 or greater than largest int128).

Counterpart to Solidity’s int128 operator.

Requirements:

  • input must fit into 128 bits

toInt120(int256 value) → int120 downcasted internal

Returns the downcasted int120 from int256, reverting on overflow (when the input is less than smallest int120 or greater than largest int120).

Counterpart to Solidity’s int120 operator.

Requirements:

  • input must fit into 120 bits

toInt112(int256 value) → int112 downcasted internal

Returns the downcasted int112 from int256, reverting on overflow (when the input is less than smallest int112 or greater than largest int112).

Counterpart to Solidity’s int112 operator.

Requirements:

  • input must fit into 112 bits

toInt104(int256 value) → int104 downcasted internal

Returns the downcasted int104 from int256, reverting on overflow (when the input is less than smallest int104 or greater than largest int104).

Counterpart to Solidity’s int104 operator.

Requirements:

  • input must fit into 104 bits

toInt96(int256 value) → int96 downcasted internal

Returns the downcasted int96 from int256, reverting on overflow (when the input is less than smallest int96 or greater than largest int96).

Counterpart to Solidity’s int96 operator.

Requirements:

  • input must fit into 96 bits

toInt88(int256 value) → int88 downcasted internal

Returns the downcasted int88 from int256, reverting on overflow (when the input is less than smallest int88 or greater than largest int88).

Counterpart to Solidity’s int88 operator.

Requirements:

  • input must fit into 88 bits

toInt80(int256 value) → int80 downcasted internal

Returns the downcasted int80 from int256, reverting on overflow (when the input is less than smallest int80 or greater than largest int80).

Counterpart to Solidity’s int80 operator.

Requirements:

  • input must fit into 80 bits

toInt72(int256 value) → int72 downcasted internal

Returns the downcasted int72 from int256, reverting on overflow (when the input is less than smallest int72 or greater than largest int72).

Counterpart to Solidity’s int72 operator.

Requirements:

  • input must fit into 72 bits

toInt64(int256 value) → int64 downcasted internal

Returns the downcasted int64 from int256, reverting on overflow (when the input is less than smallest int64 or greater than largest int64).

Counterpart to Solidity’s int64 operator.

Requirements:

  • input must fit into 64 bits

toInt56(int256 value) → int56 downcasted internal

Returns the downcasted int56 from int256, reverting on overflow (when the input is less than smallest int56 or greater than largest int56).

Counterpart to Solidity’s int56 operator.

Requirements:

  • input must fit into 56 bits

toInt48(int256 value) → int48 downcasted internal

Returns the downcasted int48 from int256, reverting on overflow (when the input is less than smallest int48 or greater than largest int48).

Counterpart to Solidity’s int48 operator.

Requirements:

  • input must fit into 48 bits

toInt40(int256 value) → int40 downcasted internal

Returns the downcasted int40 from int256, reverting on overflow (when the input is less than smallest int40 or greater than largest int40).

Counterpart to Solidity’s int40 operator.

Requirements:

  • input must fit into 40 bits

toInt32(int256 value) → int32 downcasted internal

Returns the downcasted int32 from int256, reverting on overflow (when the input is less than smallest int32 or greater than largest int32).

Counterpart to Solidity’s int32 operator.

Requirements:

  • input must fit into 32 bits

toInt24(int256 value) → int24 downcasted internal

Returns the downcasted int24 from int256, reverting on overflow (when the input is less than smallest int24 or greater than largest int24).

Counterpart to Solidity’s int24 operator.

Requirements:

  • input must fit into 24 bits

toInt16(int256 value) → int16 downcasted internal

Returns the downcasted int16 from int256, reverting on overflow (when the input is less than smallest int16 or greater than largest int16).

Counterpart to Solidity’s int16 operator.

Requirements:

  • input must fit into 16 bits

toInt8(int256 value) → int8 downcasted internal

Returns the downcasted int8 from int256, reverting on overflow (when the input is less than smallest int8 or greater than largest int8).

Counterpart to Solidity’s int8 operator.

Requirements:

  • input must fit into 8 bits

toInt256(uint256 value) → int256 internal

Converts an unsigned uint256 into a signed int256.

Requirements:

  • input must be less than or equal to maxInt256.

toUint(bool b) → uint256 u internal

Cast a boolean (false or true) to a uint256 (0 or 1) with no jump.

SafeCastOverflowedUintDowncast(uint8 bits, uint256 value) error

Value doesn’t fit in an uint of bits size.

SafeCastOverflowedIntToUint(int256 value) error

An int value doesn’t fit in an uint of bits size.

SafeCastOverflowedIntDowncast(uint8 bits, int256 value) error

Value doesn’t fit in an int of bits size.

SafeCastOverflowedUintToInt(uint256 value) error

An uint value doesn’t fit in an int of bits size.

Cryptography

ECDSA 

import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";

Elliptic Curve Digital Signature Algorithm (ECDSA) operations.

These functions can be used to verify that a message was signed by the holder of the private keys of a given address.

Functions
Errors

tryRecover(bytes32 hash, bytes signature) → address recovered, enum ECDSA.RecoverError err, bytes32 errArg internal

Returns the address that signed a hashed message (hash) with signature or an error. This will not return address(0) without also returning an error description. Errors are documented using an enum (error type) and a bytes32 providing additional information about the error.

If no error is returned, then the address can be used for verification purposes.

The ecrecover EVM precompile allows for malleable (non-unique) signatures: this function rejects them by requiring the s value to be in the lower half order, and the v value to be either 27 or 28.

hash must be the result of a hash operation for the verification to be secure: it is possible to craft signatures that recover to arbitrary addresses for non-hashed data. A safe way to ensure this is by receiving a hash of the original message (which may otherwise be too long), and then calling MessageHashUtils.toEthSignedMessageHash on it.

Documentation for signature generation: - with Web3.js - with ethers

recover(bytes32 hash, bytes signature) → address internal

Returns the address that signed a hashed message (hash) with signature. This address can then be used for verification purposes.

The ecrecover EVM precompile allows for malleable (non-unique) signatures: this function rejects them by requiring the s value to be in the lower half order, and the v value to be either 27 or 28.

hash must be the result of a hash operation for the verification to be secure: it is possible to craft signatures that recover to arbitrary addresses for non-hashed data. A safe way to ensure this is by receiving a hash of the original message (which may otherwise be too long), and then calling MessageHashUtils.toEthSignedMessageHash on it.

tryRecover(bytes32 hash, bytes32 r, bytes32 vs) → address recovered, enum ECDSA.RecoverError err, bytes32 errArg internal

Overload of ECDSA.tryRecover that receives the r and vs short-signature fields separately.

See ERC-2098 short signatures

recover(bytes32 hash, bytes32 r, bytes32 vs) → address internal

Overload of ECDSA.recover that receives the r and `vs short-signature fields separately.

tryRecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) → address recovered, enum ECDSA.RecoverError err, bytes32 errArg internal

Overload of ECDSA.tryRecover that receives the v, r and s signature fields separately.

recover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) → address internal

Overload of ECDSA.recover that receives the v, r and s signature fields separately.

ECDSAInvalidSignature() error

The signature derives the address(0).

ECDSAInvalidSignatureLength(uint256 length) error

The signature has an invalid length.

ECDSAInvalidSignatureS(bytes32 s) error

The signature has an S value that is in the upper half order.

P256 

import "@openzeppelin/contracts/utils/cryptography/P256.sol";

Implementation of secp256r1 verification and recovery functions.

The secp256r1 curve (also known as P256) is a NIST standard curve with wide support in modern devices and cryptographic standards. Some notable examples include Apple’s Secure Enclave and Android’s Keystore as well as authentication protocols like FIDO2.

Based on the original implementation of itsobvioustech (GNU General Public License v3.0). Heavily inspired in maxrobot and tdrerup implementations.

Available since v5.1.

Functions
Internal Variables

verify(bytes32 h, bytes32 r, bytes32 s, bytes32 qx, bytes32 qy) → bool internal

Verifies a secp256r1 signature using the RIP-7212 precompile and falls back to the Solidity implementation if the precompile is not available. This version should work on all chains, but requires the deployment of more bytecode.

verifyNative(bytes32 h, bytes32 r, bytes32 s, bytes32 qx, bytes32 qy) → bool internal

Same as verify, but it will revert if the required precompile is not available.

Make sure any logic (code or precompile) deployed at that address is the expected one, otherwise the returned value may be misinterpreted as a positive boolean.

verifySolidity(bytes32 h, bytes32 r, bytes32 s, bytes32 qx, bytes32 qy) → bool internal

Same as verify, but only the Solidity implementation is used.

recovery(bytes32 h, uint8 v, bytes32 r, bytes32 s) → bytes32 x, bytes32 y internal

Public key recovery

isValidPublicKey(bytes32 x, bytes32 y) → bool result internal

Checks if (x, y) are valid coordinates of a point on the curve. In particular this function checks that x < P and y < P.

uint256 GX internal constant

Generator (x component)

uint256 GY internal constant

Generator (y component)

uint256 P internal constant

P (size of the field)

uint256 N internal constant

N (order of G)

uint256 A internal constant

A parameter of the weierstrass equation

uint256 B internal constant

B parameter of the weierstrass equation

RSA 

import "@openzeppelin/contracts/utils/cryptography/RSA.sol";

RSA PKCS#1 v1.5 signature verification implementation according to RFC8017.

This library supports PKCS#1 v1.5 padding to avoid malleability via chosen plaintext attacks in practical implementations. The padding follows the EMSA-PKCS1-v1_5-ENCODE encoding definition as per section 9.2 of the RFC. This padding makes RSA semantically secure for signing messages.

Inspired by Adrià Massanet’s work (GNU General Public License v3.0).

Available since v5.1.

Functions

pkcs1Sha256(bytes data, bytes s, bytes e, bytes n) → bool internal

Same as pkcs1Sha256 but using SHA256 to calculate the digest of data.

pkcs1Sha256(bytes32 digest, bytes s, bytes e, bytes n) → bool internal

Verifies a PKCSv1.5 signature given a digest according to the verification method described in section 8.2.2 of RFC8017 with support for explicit or implicit NULL parameters in the DigestInfo (no other optional parameters are supported).

For security reason, this function requires the signature and modulus to have a length of at least 2048 bits. If you use a smaller key, consider replacing it with a larger, more secure, one.
This verification algorithm doesn’t prevent replayability. If called multiple times with the same digest, public key and (valid signature), it will return true every time. Consider including an onchain nonce or unique identifier in the message to prevent replay attacks.
This verification algorithm supports any exponent. NIST recommends using 65537 (or higher). That is the default value many libraries use, such as OpenSSL. Developers may choose to reject public keys using a low exponent out of security concerns.

EIP712 

import "@openzeppelin/contracts/utils/cryptography/EIP712.sol";

EIP-712 is a standard for hashing and signing of typed structured data.

The encoding scheme specified in the EIP requires a domain separator and a hash of the typed structured data, whose encoding is very generic and therefore its implementation in Solidity is not feasible, thus this contract does not implement the encoding itself. Protocols need to implement the type-specific encoding they need in order to produce the hash of their typed data using a combination of abi.encode and keccak256.

This contract implements the EIP-712 domain separator (_domainSeparatorV4) that is used as part of the encoding scheme, and the final step of the encoding to obtain the message digest that is then signed via ECDSA (_hashTypedDataV4).

The implementation of the domain separator was designed to be as efficient as possible while still properly updating the chain id to protect against replay attacks on an eventual fork of the chain.

This contract implements the version of the encoding known as "v4", as implemented by the JSON RPC method eth_signTypedDataV4 in MetaMask.
In the upgradeable version of this contract, the cached values will correspond to the address, and the domain separator of the implementation contract. This will cause the _domainSeparatorV4 function to always rebuild the separator from the immutable values, which is cheaper than accessing a cached version in cold storage.
Functions
Events
IERC5267

constructor(string name, string version) internal

Initializes the domain separator and parameter caches.

The meaning of name and version is specified in EIP-712:

  • name: the user readable name of the signing domain, i.e. the name of the DApp or the protocol.

  • version: the current major version of the signing domain.

These parameters cannot be changed except through a smart contract upgrade.

_domainSeparatorV4() → bytes32 internal

Returns the domain separator for the current chain.

_hashTypedDataV4(bytes32 structHash) → bytes32 internal

Given an already hashed struct, this function returns the hash of the fully encoded EIP712 message for this domain.

This hash can be used together with ECDSA.recover to obtain the signer of a message. For example:

bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
    keccak256("Mail(address to,string contents)"),
    mailTo,
    keccak256(bytes(mailContents))
)));
address signer = ECDSA.recover(digest, signature);

eip712Domain() → bytes1 fields, string name, string version, uint256 chainId, address verifyingContract, bytes32 salt, uint256[] extensions public

See {IERC-5267}.

_EIP712Name() → string internal

The name parameter for the EIP712 domain.

By default this function reads _name which is an immutable value. It only reads from storage if necessary (in case the value is too large to fit in a ShortString).

_EIP712Version() → string internal

The version parameter for the EIP712 domain.

By default this function reads _version which is an immutable value. It only reads from storage if necessary (in case the value is too large to fit in a ShortString).

MessageHashUtils 

import "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";

Signature message hash utilities for producing digests to be consumed by ECDSA recovery or signing.

The library provides methods for generating a hash of a message that conforms to the ERC-191 and EIP 712 specifications.

Functions

toEthSignedMessageHash(bytes32 messageHash) → bytes32 digest internal

Returns the keccak256 digest of an ERC-191 signed data with version 0x45 (personal_sign messages).

The digest is calculated by prefixing a bytes32 messageHash with "\x19Ethereum Signed Message:\n32" and hashing the result. It corresponds with the hash signed when using the eth_sign JSON-RPC method.

The messageHash parameter is intended to be the result of hashing a raw message with keccak256, although any bytes32 value can be safely used because the final digest will be re-hashed.

See ECDSA.recover.

toEthSignedMessageHash(bytes message) → bytes32 internal

Returns the keccak256 digest of an ERC-191 signed data with version 0x45 (personal_sign messages).

The digest is calculated by prefixing an arbitrary message with "\x19Ethereum Signed Message:\n" + len(message) and hashing the result. It corresponds with the hash signed when using the eth_sign JSON-RPC method.

See ECDSA.recover.

toDataWithIntendedValidatorHash(address validator, bytes data) → bytes32 internal

Returns the keccak256 digest of an ERC-191 signed data with version 0x00 (data with intended validator).

The digest is calculated by prefixing an arbitrary data with "\x19\x00" and the intended validator address. Then hashing the result.

See ECDSA.recover.

toTypedDataHash(bytes32 domainSeparator, bytes32 structHash) → bytes32 digest internal

Returns the keccak256 digest of an EIP-712 typed data (ERC-191 version 0x01).

The digest is calculated from a domainSeparator and a structHash, by prefixing them with \x19\x01 and hashing the result. It corresponds to the hash signed by the eth_signTypedData JSON-RPC method as part of EIP-712.

See ECDSA.recover.

SignatureChecker 

import "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";

Signature verification helper that can be used instead of ECDSA.recover to seamlessly support both ECDSA signatures from externally owned accounts (EOAs) as well as ERC-1271 signatures from smart contract wallets like Argent and Safe Wallet (previously Gnosis Safe).

Functions

isValidSignatureNow(address signer, bytes32 hash, bytes signature) → bool internal

Checks if a signature is valid for a given signer and data hash. If the signer is a smart contract, the signature is validated against that smart contract using ERC-1271, otherwise it’s validated using ECDSA.recover.

Unlike ECDSA signatures, contract signatures are revocable, and the outcome of this function can thus change through time. It could return true at block N and false at block N+1 (or the opposite).

isValidERC1271SignatureNow(address signer, bytes32 hash, bytes signature) → bool internal

Checks if a signature is valid for a given signer and data hash. The signature is validated against the signer smart contract using ERC-1271.

Unlike ECDSA signatures, contract signatures are revocable, and the outcome of this function can thus change through time. It could return true at block N and false at block N+1 (or the opposite).

Hashes 

import "@openzeppelin/contracts/utils/cryptography/Hashes.sol";

Library of standard hash functions.

Available since v5.1.

Functions

commutativeKeccak256(bytes32 a, bytes32 b) → bytes32 internal

Commutative Keccak256 hash of a sorted pair of bytes32. Frequently used when working with merkle proofs.

Equivalent to the standardNodeHash in our JavaScript library.

MerkleProof 

import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";

These functions deal with verification of Merkle Tree proofs.

The tree and the proofs can be generated using our JavaScript library. You will find a quickstart guide in the readme.

You should avoid using leaf values that are 64 bytes long prior to hashing, or use a hash function other than keccak256 for hashing leaves. This is because the concatenation of a sorted pair of internal nodes in the Merkle tree could be reinterpreted as a leaf value. OpenZeppelin’s JavaScript library generates Merkle trees that are safe against this attack out of the box.
Consider memory side-effects when using custom hashing functions that access memory in an unsafe way.
This library supports proof verification for merkle trees built using custom commutative hashing functions (i.e. H(a, b) == H(b, a)). Proving leaf inclusion in trees built using non-commutative hashing functions requires additional logic that is not supported by this library.
Functions
Errors

verify(bytes32[] proof, bytes32 root, bytes32 leaf) → bool internal

Returns true if a leaf can be proved to be a part of a Merkle tree defined by root. For this, a proof must be provided, containing sibling hashes on the branch from the leaf to the root of the tree. Each pair of leaves and each pair of pre-images are assumed to be sorted.

This version handles proofs in memory with the default hashing function.

processProof(bytes32[] proof, bytes32 leaf) → bytes32 internal

Returns the rebuilt hash obtained by traversing a Merkle tree up from leaf using proof. A proof is valid if and only if the rebuilt hash matches the root of the tree. When processing the proof, the pairs of leaves & pre-images are assumed to be sorted.

This version handles proofs in memory with the default hashing function.

verify(bytes32[] proof, bytes32 root, bytes32 leaf, function (bytes32,bytes32) view returns (bytes32) hasher) → bool internal

Returns true if a leaf can be proved to be a part of a Merkle tree defined by root. For this, a proof must be provided, containing sibling hashes on the branch from the leaf to the root of the tree. Each pair of leaves and each pair of pre-images are assumed to be sorted.

This version handles proofs in memory with a custom hashing function.

processProof(bytes32[] proof, bytes32 leaf, function (bytes32,bytes32) view returns (bytes32) hasher) → bytes32 internal

Returns the rebuilt hash obtained by traversing a Merkle tree up from leaf using proof. A proof is valid if and only if the rebuilt hash matches the root of the tree. When processing the proof, the pairs of leaves & pre-images are assumed to be sorted.

This version handles proofs in memory with a custom hashing function.

verifyCalldata(bytes32[] proof, bytes32 root, bytes32 leaf) → bool internal

Returns true if a leaf can be proved to be a part of a Merkle tree defined by root. For this, a proof must be provided, containing sibling hashes on the branch from the leaf to the root of the tree. Each pair of leaves and each pair of pre-images are assumed to be sorted.

This version handles proofs in calldata with the default hashing function.

processProofCalldata(bytes32[] proof, bytes32 leaf) → bytes32 internal

Returns the rebuilt hash obtained by traversing a Merkle tree up from leaf using proof. A proof is valid if and only if the rebuilt hash matches the root of the tree. When processing the proof, the pairs of leaves & pre-images are assumed to be sorted.

This version handles proofs in calldata with the default hashing function.

verifyCalldata(bytes32[] proof, bytes32 root, bytes32 leaf, function (bytes32,bytes32) view returns (bytes32) hasher) → bool internal

Returns true if a leaf can be proved to be a part of a Merkle tree defined by root. For this, a proof must be provided, containing sibling hashes on the branch from the leaf to the root of the tree. Each pair of leaves and each pair of pre-images are assumed to be sorted.

This version handles proofs in calldata with a custom hashing function.

processProofCalldata(bytes32[] proof, bytes32 leaf, function (bytes32,bytes32) view returns (bytes32) hasher) → bytes32 internal

Returns the rebuilt hash obtained by traversing a Merkle tree up from leaf using proof. A proof is valid if and only if the rebuilt hash matches the root of the tree. When processing the proof, the pairs of leaves & pre-images are assumed to be sorted.

This version handles proofs in calldata with a custom hashing function.

multiProofVerify(bytes32[] proof, bool[] proofFlags, bytes32 root, bytes32[] leaves) → bool internal

Returns true if the leaves can be simultaneously proven to be a part of a Merkle tree defined by root, according to proof and proofFlags as described in processMultiProof.

This version handles multiproofs in memory with the default hashing function.

Not all Merkle trees admit multiproofs. See processMultiProof for details.
Consider the case where root == proof[0] && leaves.length == 0 as it will return true. The leaves must be validated independently. See processMultiProof.

processMultiProof(bytes32[] proof, bool[] proofFlags, bytes32[] leaves) → bytes32 merkleRoot internal

Returns the root of a tree reconstructed from leaves and sibling nodes in proof. The reconstruction proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another leaf/inner node or a proof sibling node, depending on whether each proofFlags item is true or false respectively.

This version handles multiproofs in memory with the default hashing function.

Not all Merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
The empty set (i.e. the case where proof.length == 1 && leaves.length == 0) is considered a no-op, and therefore a valid multiproof (i.e. it returns proof[0]). Consider disallowing this case if you’re not validating the leaves elsewhere.

multiProofVerify(bytes32[] proof, bool[] proofFlags, bytes32 root, bytes32[] leaves, function (bytes32,bytes32) view returns (bytes32) hasher) → bool internal

Returns true if the leaves can be simultaneously proven to be a part of a Merkle tree defined by root, according to proof and proofFlags as described in processMultiProof.

This version handles multiproofs in memory with a custom hashing function.

Not all Merkle trees admit multiproofs. See processMultiProof for details.
Consider the case where root == proof[0] && leaves.length == 0 as it will return true. The leaves must be validated independently. See processMultiProof.

processMultiProof(bytes32[] proof, bool[] proofFlags, bytes32[] leaves, function (bytes32,bytes32) view returns (bytes32) hasher) → bytes32 merkleRoot internal

Returns the root of a tree reconstructed from leaves and sibling nodes in proof. The reconstruction proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another leaf/inner node or a proof sibling node, depending on whether each proofFlags item is true or false respectively.

This version handles multiproofs in memory with a custom hashing function.

Not all Merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
The empty set (i.e. the case where proof.length == 1 && leaves.length == 0) is considered a no-op, and therefore a valid multiproof (i.e. it returns proof[0]). Consider disallowing this case if you’re not validating the leaves elsewhere.

multiProofVerifyCalldata(bytes32[] proof, bool[] proofFlags, bytes32 root, bytes32[] leaves) → bool internal

Returns true if the leaves can be simultaneously proven to be a part of a Merkle tree defined by root, according to proof and proofFlags as described in processMultiProof.

This version handles multiproofs in calldata with the default hashing function.

Not all Merkle trees admit multiproofs. See processMultiProof for details.
Consider the case where root == proof[0] && leaves.length == 0 as it will return true. The leaves must be validated independently. See processMultiProofCalldata.

processMultiProofCalldata(bytes32[] proof, bool[] proofFlags, bytes32[] leaves) → bytes32 merkleRoot internal

Returns the root of a tree reconstructed from leaves and sibling nodes in proof. The reconstruction proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another leaf/inner node or a proof sibling node, depending on whether each proofFlags item is true or false respectively.

This version handles multiproofs in calldata with the default hashing function.

Not all Merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
The empty set (i.e. the case where proof.length == 1 && leaves.length == 0) is considered a no-op, and therefore a valid multiproof (i.e. it returns proof[0]). Consider disallowing this case if you’re not validating the leaves elsewhere.

multiProofVerifyCalldata(bytes32[] proof, bool[] proofFlags, bytes32 root, bytes32[] leaves, function (bytes32,bytes32) view returns (bytes32) hasher) → bool internal

Returns true if the leaves can be simultaneously proven to be a part of a Merkle tree defined by root, according to proof and proofFlags as described in processMultiProof.

This version handles multiproofs in calldata with a custom hashing function.

Not all Merkle trees admit multiproofs. See processMultiProof for details.
Consider the case where root == proof[0] && leaves.length == 0 as it will return true. The leaves must be validated independently. See processMultiProofCalldata.

processMultiProofCalldata(bytes32[] proof, bool[] proofFlags, bytes32[] leaves, function (bytes32,bytes32) view returns (bytes32) hasher) → bytes32 merkleRoot internal

Returns the root of a tree reconstructed from leaves and sibling nodes in proof. The reconstruction proceeds by incrementally reconstructing all inner nodes by combining a leaf/inner node with either another leaf/inner node or a proof sibling node, depending on whether each proofFlags item is true or false respectively.

This version handles multiproofs in calldata with a custom hashing function.

Not all Merkle trees admit multiproofs. To use multiproofs, it is sufficient to ensure that: 1) the tree is complete (but not necessarily perfect), 2) the leaves to be proven are in the opposite order they are in the tree (i.e., as seen from right to left starting at the deepest layer and continuing at the next layer).
The empty set (i.e. the case where proof.length == 1 && leaves.length == 0) is considered a no-op, and therefore a valid multiproof (i.e. it returns proof[0]). Consider disallowing this case if you’re not validating the leaves elsewhere.

MerkleProofInvalidMultiproof() error

The multiproof provided is not valid.

Security

ReentrancyGuard 

import "@openzeppelin/contracts/utils/ReentrancyGuard.sol";

Contract module that helps prevent reentrant calls to a function.

Inheriting from ReentrancyGuard will make the nonReentrant modifier available, which can be applied to functions to make sure there are no nested (reentrant) calls to them.

Note that because there is a single nonReentrant guard, functions marked as nonReentrant may not call one another. This can be worked around by making those functions private, and then adding external nonReentrant entry points to them.

If EIP-1153 (transient storage) is available on the chain you’re deploying at, consider using ReentrancyGuardTransient instead.
If you would like to learn more about reentrancy and alternative ways to protect against it, check out our blog post Reentrancy After Istanbul.
Modifiers
Functions
Errors

nonReentrant() modifier

Prevents a contract from calling itself, directly or indirectly. Calling a nonReentrant function from another nonReentrant function is not supported. It is possible to prevent this from happening by making the nonReentrant function external, and making it call a private function that does the actual work.

constructor() internal

_reentrancyGuardEntered() → bool internal

Returns true if the reentrancy guard is currently set to "entered", which indicates there is a nonReentrant function in the call stack.

ReentrancyGuardReentrantCall() error

Unauthorized reentrant call.

ReentrancyGuardTransient 

import "@openzeppelin/contracts/utils/ReentrancyGuardTransient.sol";

Variant of ReentrancyGuard that uses transient storage.

This variant only works on networks where EIP-1153 is available.

Available since v5.1.

Modifiers
Functions
Errors

nonReentrant() modifier

Prevents a contract from calling itself, directly or indirectly. Calling a nonReentrant function from another nonReentrant function is not supported. It is possible to prevent this from happening by making the nonReentrant function external, and making it call a private function that does the actual work.

_reentrancyGuardEntered() → bool internal

Returns true if the reentrancy guard is currently set to "entered", which indicates there is a nonReentrant function in the call stack.

ReentrancyGuardReentrantCall() error

Unauthorized reentrant call.

Pausable 

import "@openzeppelin/contracts/utils/Pausable.sol";

Contract module which allows children to implement an emergency stop mechanism that can be triggered by an authorized account.

This module is used through inheritance. It will make available the modifiers whenNotPaused and whenPaused, which can be applied to the functions of your contract. Note that they will not be pausable by simply including this module, only once the modifiers are put in place.

Modifiers
Functions
Events
Errors

whenNotPaused() modifier

Modifier to make a function callable only when the contract is not paused.

Requirements:

  • The contract must not be paused.

whenPaused() modifier

Modifier to make a function callable only when the contract is paused.

Requirements:

  • The contract must be paused.

constructor() internal

Initializes the contract in unpaused state.

paused() → bool public

Returns true if the contract is paused, and false otherwise.

_requireNotPaused() internal

Throws if the contract is paused.

_requirePaused() internal

Throws if the contract is not paused.

_pause() internal

Triggers stopped state.

Requirements:

  • The contract must not be paused.

_unpause() internal

Returns to normal state.

Requirements:

  • The contract must be paused.

Paused(address account) event

Emitted when the pause is triggered by account.

Unpaused(address account) event

Emitted when the pause is lifted by account.

EnforcedPause() error

The operation failed because the contract is paused.

ExpectedPause() error

The operation failed because the contract is not paused.

Nonces 

import "@openzeppelin/contracts/utils/Nonces.sol";

Provides tracking nonces for addresses. Nonces will only increment.

Functions
Errors

nonces(address owner) → uint256 public

Returns the next unused nonce for an address.

_useNonce(address owner) → uint256 internal

Consumes a nonce.

Returns the current value and increments nonce.

_useCheckedNonce(address owner, uint256 nonce) internal

Same as _useNonce but checking that nonce is the next valid for owner.

InvalidAccountNonce(address account, uint256 currentNonce) error

The nonce used for an account is not the expected current nonce.

Introspection

This set of interfaces and contracts deal with type introspection of contracts, that is, examining which functions can be called on them. This is usually referred to as a contract’s interface.

Ethereum contracts have no native concept of an interface, so applications must usually simply trust they are not making an incorrect call. For trusted setups this is a non-issue, but often unknown and untrusted third-party addresses need to be interacted with. There may even not be any direct calls to them! (e.g. ERC-20 tokens may be sent to a contract that lacks a way to transfer them out of it, locking them forever). In these cases, a contract declaring its interface can be very helpful in preventing errors.

IERC165 

import "@openzeppelin/contracts/utils/introspection/IERC165.sol";

Interface of the ERC-165 standard, as defined in the ERC.

Implementers can declare support of contract interfaces, which can then be queried by others (ERC165Checker).

For an implementation, see ERC165.

Functions

supportsInterface(bytes4 interfaceId) → bool external

Returns true if this contract implements the interface defined by interfaceId. See the corresponding ERC section to learn more about how these ids are created.

This function call must use less than 30 000 gas.

ERC165 

import "@openzeppelin/contracts/utils/introspection/ERC165.sol";

Implementation of the IERC165 interface.

Contracts that want to implement ERC-165 should inherit from this contract and override supportsInterface to check for the additional interface id that will be supported. For example:

function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
    return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
}
Functions

supportsInterface(bytes4 interfaceId) → bool public

See IERC165.supportsInterface.

ERC165Checker 

import "@openzeppelin/contracts/utils/introspection/ERC165Checker.sol";

Library used to query support of an interface declared via IERC165.

Note that these functions return the actual result of the query: they do not revert if an interface is not supported. It is up to the caller to decide what to do in these cases.

Functions

supportsERC165(address account) → bool internal

Returns true if account supports the IERC165 interface.

supportsInterface(address account, bytes4 interfaceId) → bool internal

Returns true if account supports the interface defined by interfaceId. Support for IERC165 itself is queried automatically.

See IERC165.supportsInterface.

getSupportedInterfaces(address account, bytes4[] interfaceIds) → bool[] internal

Returns a boolean array where each value corresponds to the interfaces passed in and whether they’re supported or not. This allows you to batch check interfaces for a contract where your expectation is that some interfaces may not be supported.

See IERC165.supportsInterface.

supportsAllInterfaces(address account, bytes4[] interfaceIds) → bool internal

Returns true if account supports all the interfaces defined in interfaceIds. Support for IERC165 itself is queried automatically.

Batch-querying can lead to gas savings by skipping repeated checks for IERC165 support.

See IERC165.supportsInterface.

supportsERC165InterfaceUnchecked(address account, bytes4 interfaceId) → bool internal

Assumes that account contains a contract that supports ERC-165, otherwise the behavior of this method is undefined. This precondition can be checked with supportsERC165.

Some precompiled contracts will falsely indicate support for a given interface, so caution should be exercised when using this function.

Interface identification is specified in ERC-165.

Data Structures

BitMaps 

import "@openzeppelin/contracts/utils/structs/BitMaps.sol";

Library for managing uint256 to bool mapping in a compact and efficient way, provided the keys are sequential. Largely inspired by Uniswap’s merkle-distributor.

BitMaps pack 256 booleans across each bit of a single 256-bit slot of uint256 type. Hence booleans corresponding to 256 sequential indices would only consume a single slot, unlike the regular bool which would consume an entire slot for a single value.

This results in gas savings in two ways:

  • Setting a zero value to non-zero only once every 256 times

  • Accessing the same warm slot for every 256 sequential indices

Functions

get(struct BitMaps.BitMap bitmap, uint256 index) → bool internal

Returns whether the bit at index is set.

setTo(struct BitMaps.BitMap bitmap, uint256 index, bool value) internal

Sets the bit at index to the boolean value.

set(struct BitMaps.BitMap bitmap, uint256 index) internal

Sets the bit at index.

unset(struct BitMaps.BitMap bitmap, uint256 index) internal

Unsets the bit at index.

EnumerableMap 

import "@openzeppelin/contracts/utils/structs/EnumerableMap.sol";

Library for managing an enumerable variant of Solidity’s mapping type.

Maps have the following properties:

  • Entries are added, removed, and checked for existence in constant time (O(1)).

  • Entries are enumerated in O(n). No guarantees are made on the ordering.

contract Example {
    // Add the library methods
    using EnumerableMap for EnumerableMap.UintToAddressMap;

    // Declare a set state variable
    EnumerableMap.UintToAddressMap private myMap;
}

The following map types are supported:

  • uint256 → address (UintToAddressMap) since v3.0.0

  • address → uint256 (AddressToUintMap) since v4.6.0

  • bytes32 → bytes32 (Bytes32ToBytes32Map) since v4.6.0

  • uint256 → uint256 (UintToUintMap) since v4.7.0

  • bytes32 → uint256 (Bytes32ToUintMap) since v4.7.0

  • uint256 → bytes32 (UintToBytes32Map) since v5.1.0

  • address → address (AddressToAddressMap) since v5.1.0

  • address → bytes32 (AddressToBytes32Map) since v5.1.0

  • bytes32 → address (Bytes32ToAddressMap) since v5.1.0

Trying to delete such a structure from storage will likely result in data corruption, rendering the structure unusable. See ethereum/solidity#11843 for more info.

In order to clean an EnumerableMap, you can either remove all elements one by one or create a fresh instance using an array of EnumerableMap.
Functions
Errors

set(struct EnumerableMap.Bytes32ToBytes32Map map, bytes32 key, bytes32 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.Bytes32ToBytes32Map map, bytes32 key) → bool internal

Removes a key-value pair from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.Bytes32ToBytes32Map map, bytes32 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.Bytes32ToBytes32Map map) → uint256 internal

Returns the number of key-value pairs in the map. O(1).

at(struct EnumerableMap.Bytes32ToBytes32Map map, uint256 index) → bytes32 key, bytes32 value internal

Returns the key-value pair stored at position index in the map. O(1).

Note that there are no guarantees on the ordering of entries inside the array, and it may change when more entries are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.Bytes32ToBytes32Map map, bytes32 key) → bool exists, bytes32 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.Bytes32ToBytes32Map map, bytes32 key) → bytes32 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.Bytes32ToBytes32Map map) → bytes32[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.UintToUintMap map, uint256 key, uint256 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.UintToUintMap map, uint256 key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.UintToUintMap map, uint256 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.UintToUintMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.UintToUintMap map, uint256 index) → uint256 key, uint256 value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.UintToUintMap map, uint256 key) → bool exists, uint256 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.UintToUintMap map, uint256 key) → uint256 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.UintToUintMap map) → uint256[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.UintToAddressMap map, uint256 key, address value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.UintToAddressMap map, uint256 key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.UintToAddressMap map, uint256 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.UintToAddressMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.UintToAddressMap map, uint256 index) → uint256 key, address value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.UintToAddressMap map, uint256 key) → bool exists, address value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.UintToAddressMap map, uint256 key) → address internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.UintToAddressMap map) → uint256[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.UintToBytes32Map map, uint256 key, bytes32 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.UintToBytes32Map map, uint256 key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.UintToBytes32Map map, uint256 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.UintToBytes32Map map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.UintToBytes32Map map, uint256 index) → uint256 key, bytes32 value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.UintToBytes32Map map, uint256 key) → bool exists, bytes32 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.UintToBytes32Map map, uint256 key) → bytes32 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.UintToBytes32Map map) → uint256[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.AddressToUintMap map, address key, uint256 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.AddressToUintMap map, address key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.AddressToUintMap map, address key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.AddressToUintMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.AddressToUintMap map, uint256 index) → address key, uint256 value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.AddressToUintMap map, address key) → bool exists, uint256 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.AddressToUintMap map, address key) → uint256 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.AddressToUintMap map) → address[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.AddressToAddressMap map, address key, address value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.AddressToAddressMap map, address key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.AddressToAddressMap map, address key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.AddressToAddressMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.AddressToAddressMap map, uint256 index) → address key, address value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.AddressToAddressMap map, address key) → bool exists, address value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.AddressToAddressMap map, address key) → address internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.AddressToAddressMap map) → address[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.AddressToBytes32Map map, address key, bytes32 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.AddressToBytes32Map map, address key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.AddressToBytes32Map map, address key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.AddressToBytes32Map map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.AddressToBytes32Map map, uint256 index) → address key, bytes32 value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.AddressToBytes32Map map, address key) → bool exists, bytes32 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.AddressToBytes32Map map, address key) → bytes32 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.AddressToBytes32Map map) → address[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.Bytes32ToUintMap map, bytes32 key, uint256 value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.Bytes32ToUintMap map, bytes32 key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.Bytes32ToUintMap map, bytes32 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.Bytes32ToUintMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.Bytes32ToUintMap map, uint256 index) → bytes32 key, uint256 value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.Bytes32ToUintMap map, bytes32 key) → bool exists, uint256 value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.Bytes32ToUintMap map, bytes32 key) → uint256 internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.Bytes32ToUintMap map) → bytes32[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

set(struct EnumerableMap.Bytes32ToAddressMap map, bytes32 key, address value) → bool internal

Adds a key-value pair to a map, or updates the value for an existing key. O(1).

Returns true if the key was added to the map, that is if it was not already present.

remove(struct EnumerableMap.Bytes32ToAddressMap map, bytes32 key) → bool internal

Removes a value from a map. O(1).

Returns true if the key was removed from the map, that is if it was present.

contains(struct EnumerableMap.Bytes32ToAddressMap map, bytes32 key) → bool internal

Returns true if the key is in the map. O(1).

length(struct EnumerableMap.Bytes32ToAddressMap map) → uint256 internal

Returns the number of elements in the map. O(1).

at(struct EnumerableMap.Bytes32ToAddressMap map, uint256 index) → bytes32 key, address value internal

Returns the element stored at position index in the map. O(1). Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

tryGet(struct EnumerableMap.Bytes32ToAddressMap map, bytes32 key) → bool exists, address value internal

Tries to returns the value associated with key. O(1). Does not revert if key is not in the map.

get(struct EnumerableMap.Bytes32ToAddressMap map, bytes32 key) → address internal

Returns the value associated with key. O(1).

Requirements:

  • key must be in the map.

keys(struct EnumerableMap.Bytes32ToAddressMap map) → bytes32[] internal

Return the an array containing all the keys

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the map grows to a point where copying to memory consumes too much gas to fit in a block.

EnumerableMapNonexistentKey(bytes32 key) error

Query for a nonexistent map key.

EnumerableSet 

import "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";

Library for managing sets of primitive types.

Sets have the following properties:

  • Elements are added, removed, and checked for existence in constant time (O(1)).

  • Elements are enumerated in O(n). No guarantees are made on the ordering.

contract Example {
    // Add the library methods
    using EnumerableSet for EnumerableSet.AddressSet;

    // Declare a set state variable
    EnumerableSet.AddressSet private mySet;
}

As of v3.3.0, sets of type bytes32 (Bytes32Set), address (AddressSet) and uint256 (UintSet) are supported.

Trying to delete such a structure from storage will likely result in data corruption, rendering the structure unusable. See ethereum/solidity#11843 for more info.

In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an array of EnumerableSet.
Functions

add(struct EnumerableSet.Bytes32Set set, bytes32 value) → bool internal

Add a value to a set. O(1).

Returns true if the value was added to the set, that is if it was not already present.

remove(struct EnumerableSet.Bytes32Set set, bytes32 value) → bool internal

Removes a value from a set. O(1).

Returns true if the value was removed from the set, that is if it was present.

contains(struct EnumerableSet.Bytes32Set set, bytes32 value) → bool internal

Returns true if the value is in the set. O(1).

length(struct EnumerableSet.Bytes32Set set) → uint256 internal

Returns the number of values in the set. O(1).

at(struct EnumerableSet.Bytes32Set set, uint256 index) → bytes32 internal

Returns the value stored at position index in the set. O(1).

Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

values(struct EnumerableSet.Bytes32Set set) → bytes32[] internal

Return the entire set in an array

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.

add(struct EnumerableSet.AddressSet set, address value) → bool internal

Add a value to a set. O(1).

Returns true if the value was added to the set, that is if it was not already present.

remove(struct EnumerableSet.AddressSet set, address value) → bool internal

Removes a value from a set. O(1).

Returns true if the value was removed from the set, that is if it was present.

contains(struct EnumerableSet.AddressSet set, address value) → bool internal

Returns true if the value is in the set. O(1).

length(struct EnumerableSet.AddressSet set) → uint256 internal

Returns the number of values in the set. O(1).

at(struct EnumerableSet.AddressSet set, uint256 index) → address internal

Returns the value stored at position index in the set. O(1).

Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

values(struct EnumerableSet.AddressSet set) → address[] internal

Return the entire set in an array

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.

add(struct EnumerableSet.UintSet set, uint256 value) → bool internal

Add a value to a set. O(1).

Returns true if the value was added to the set, that is if it was not already present.

remove(struct EnumerableSet.UintSet set, uint256 value) → bool internal

Removes a value from a set. O(1).

Returns true if the value was removed from the set, that is if it was present.

contains(struct EnumerableSet.UintSet set, uint256 value) → bool internal

Returns true if the value is in the set. O(1).

length(struct EnumerableSet.UintSet set) → uint256 internal

Returns the number of values in the set. O(1).

at(struct EnumerableSet.UintSet set, uint256 index) → uint256 internal

Returns the value stored at position index in the set. O(1).

Note that there are no guarantees on the ordering of values inside the array, and it may change when more values are added or removed.

Requirements:

  • index must be strictly less than length.

values(struct EnumerableSet.UintSet set) → uint256[] internal

Return the entire set in an array

This operation will copy the entire storage to memory, which can be quite expensive. This is designed to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that this function has an unbounded cost, and using it as part of a state-changing function may render the function uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.

DoubleEndedQueue 

import "@openzeppelin/contracts/utils/structs/DoubleEndedQueue.sol";

A sequence of items with the ability to efficiently push and pop items (i.e. insert and remove) on both ends of the sequence (called front and back). Among other access patterns, it can be used to implement efficient LIFO and FIFO queues. Storage use is optimized, and all operations are O(1) constant time. This includes clear, given that the existing queue contents are left in storage.

The struct is called Bytes32Deque. Other types can be cast to and from bytes32. This data structure can only be used in storage, and not in memory.

DoubleEndedQueue.Bytes32Deque queue;
Functions

pushBack(struct DoubleEndedQueue.Bytes32Deque deque, bytes32 value) internal

Inserts an item at the end of the queue.

Reverts with Panic.RESOURCE_ERROR if the queue is full.

popBack(struct DoubleEndedQueue.Bytes32Deque deque) → bytes32 value internal

Removes the item at the end of the queue and returns it.

Reverts with Panic.EMPTY_ARRAY_POP if the queue is empty.

pushFront(struct DoubleEndedQueue.Bytes32Deque deque, bytes32 value) internal

Inserts an item at the beginning of the queue.

Reverts with Panic.RESOURCE_ERROR if the queue is full.

popFront(struct DoubleEndedQueue.Bytes32Deque deque) → bytes32 value internal

Removes the item at the beginning of the queue and returns it.

Reverts with Panic.EMPTY_ARRAY_POP if the queue is empty.

front(struct DoubleEndedQueue.Bytes32Deque deque) → bytes32 value internal

Returns the item at the beginning of the queue.

Reverts with Panic.ARRAY_OUT_OF_BOUNDS if the queue is empty.

back(struct DoubleEndedQueue.Bytes32Deque deque) → bytes32 value internal

Returns the item at the end of the queue.

Reverts with Panic.ARRAY_OUT_OF_BOUNDS if the queue is empty.

at(struct DoubleEndedQueue.Bytes32Deque deque, uint256 index) → bytes32 value internal

Return the item at a position in the queue given by index, with the first item at 0 and last item at length(deque) - 1.

Reverts with Panic.ARRAY_OUT_OF_BOUNDS if the index is out of bounds.

clear(struct DoubleEndedQueue.Bytes32Deque deque) internal

Resets the queue back to being empty.

The current items are left behind in storage. This does not affect the functioning of the queue, but misses out on potential gas refunds.

length(struct DoubleEndedQueue.Bytes32Deque deque) → uint256 internal

Returns the number of items in the queue.

empty(struct DoubleEndedQueue.Bytes32Deque deque) → bool internal

Returns true if the queue is empty.

CircularBuffer 

import "@openzeppelin/contracts/utils/structs/CircularBuffer.sol";

A fixed-size buffer for keeping bytes32 items in storage.

This data structure allows for pushing elements to it, and when its length exceeds the specified fixed size, new items take the place of the oldest element in the buffer, keeping at most N elements in the structure.

Elements can’t be removed but the data structure can be cleared. See clear.

Complexity: - insertion (push): O(1) - lookup (last): O(1) - inclusion (includes): O(N) (worst case) - reset (clear): O(1)

  • The struct is called Bytes32CircularBuffer. Other types can be cast to and from bytes32. This data structure can only be used in storage, and not in memory.

Example usage:

contract Example {
    // Add the library methods
    using CircularBuffer for CircularBuffer.Bytes32CircularBuffer;

    // Declare a buffer storage variable
    CircularBuffer.Bytes32CircularBuffer private myBuffer;
}

Available since v5.1.

Functions
Errors

setup(struct CircularBuffer.Bytes32CircularBuffer self, uint256 size) internal

Initialize a new CircularBuffer of given size.

If the CircularBuffer was already setup and used, calling that function again will reset it to a blank state.

The size of the buffer will affect the execution of includes function, as it has a complexity of O(N). Consider a large buffer size may render the function unusable.

clear(struct CircularBuffer.Bytes32CircularBuffer self) internal

Clear all data in the buffer without resetting memory, keeping the existing size.

push(struct CircularBuffer.Bytes32CircularBuffer self, bytes32 value) internal

Push a new value to the buffer. If the buffer is already full, the new value replaces the oldest value in the buffer.

count(struct CircularBuffer.Bytes32CircularBuffer self) → uint256 internal

Number of values currently in the buffer. This value is 0 for an empty buffer, and cannot exceed the size of the buffer.

length(struct CircularBuffer.Bytes32CircularBuffer self) → uint256 internal

Length of the buffer. This is the maximum number of elements kept in the buffer.

last(struct CircularBuffer.Bytes32CircularBuffer self, uint256 i) → bytes32 internal

Getter for the i-th value in the buffer, from the end.

Reverts with Panic.ARRAY_OUT_OF_BOUNDS if trying to access an element that was not pushed, or that was dropped to make room for newer elements.

includes(struct CircularBuffer.Bytes32CircularBuffer self, bytes32 value) → bool internal

Check if a given value is in the buffer.

InvalidBufferSize() error

Error emitted when trying to setup a buffer with a size of 0.

Checkpoints 

import "@openzeppelin/contracts/utils/structs/Checkpoints.sol";

This library defines the Trace* struct, for checkpointing values as they change at different points in time, and later looking up past values by block number. See Votes as an example.

To create a history of checkpoints define a variable type Checkpoints.Trace* in your contract, and store a new checkpoint for the current transaction block using the push function.

Functions
Errors

push(struct Checkpoints.Trace224 self, uint32 key, uint224 value) → uint224 oldValue, uint224 newValue internal

Pushes a (key, value) pair into a Trace224 so that it is stored as the checkpoint.

Returns previous value and new value.

Never accept key as a user input, since an arbitrary type(uint32).max key set will disable the library.

lowerLookup(struct Checkpoints.Trace224 self, uint32 key) → uint224 internal

Returns the value in the first (oldest) checkpoint with key greater or equal than the search key, or zero if there is none.

upperLookup(struct Checkpoints.Trace224 self, uint32 key) → uint224 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

upperLookupRecent(struct Checkpoints.Trace224 self, uint32 key) → uint224 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

This is a variant of upperLookup that is optimised to find "recent" checkpoint (checkpoints with high keys).

latest(struct Checkpoints.Trace224 self) → uint224 internal

Returns the value in the most recent checkpoint, or zero if there are no checkpoints.

latestCheckpoint(struct Checkpoints.Trace224 self) → bool exists, uint32 _key, uint224 _value internal

Returns whether there is a checkpoint in the structure (i.e. it is not empty), and if so the key and value in the most recent checkpoint.

length(struct Checkpoints.Trace224 self) → uint256 internal

Returns the number of checkpoint.

at(struct Checkpoints.Trace224 self, uint32 pos) → struct Checkpoints.Checkpoint224 internal

Returns checkpoint at given position.

push(struct Checkpoints.Trace208 self, uint48 key, uint208 value) → uint208 oldValue, uint208 newValue internal

Pushes a (key, value) pair into a Trace208 so that it is stored as the checkpoint.

Returns previous value and new value.

Never accept key as a user input, since an arbitrary type(uint48).max key set will disable the library.

lowerLookup(struct Checkpoints.Trace208 self, uint48 key) → uint208 internal

Returns the value in the first (oldest) checkpoint with key greater or equal than the search key, or zero if there is none.

upperLookup(struct Checkpoints.Trace208 self, uint48 key) → uint208 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

upperLookupRecent(struct Checkpoints.Trace208 self, uint48 key) → uint208 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

This is a variant of upperLookup that is optimised to find "recent" checkpoint (checkpoints with high keys).

latest(struct Checkpoints.Trace208 self) → uint208 internal

Returns the value in the most recent checkpoint, or zero if there are no checkpoints.

latestCheckpoint(struct Checkpoints.Trace208 self) → bool exists, uint48 _key, uint208 _value internal

Returns whether there is a checkpoint in the structure (i.e. it is not empty), and if so the key and value in the most recent checkpoint.

length(struct Checkpoints.Trace208 self) → uint256 internal

Returns the number of checkpoint.

at(struct Checkpoints.Trace208 self, uint32 pos) → struct Checkpoints.Checkpoint208 internal

Returns checkpoint at given position.

push(struct Checkpoints.Trace160 self, uint96 key, uint160 value) → uint160 oldValue, uint160 newValue internal

Pushes a (key, value) pair into a Trace160 so that it is stored as the checkpoint.

Returns previous value and new value.

Never accept key as a user input, since an arbitrary type(uint96).max key set will disable the library.

lowerLookup(struct Checkpoints.Trace160 self, uint96 key) → uint160 internal

Returns the value in the first (oldest) checkpoint with key greater or equal than the search key, or zero if there is none.

upperLookup(struct Checkpoints.Trace160 self, uint96 key) → uint160 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

upperLookupRecent(struct Checkpoints.Trace160 self, uint96 key) → uint160 internal

Returns the value in the last (most recent) checkpoint with key lower or equal than the search key, or zero if there is none.

This is a variant of upperLookup that is optimised to find "recent" checkpoint (checkpoints with high keys).

latest(struct Checkpoints.Trace160 self) → uint160 internal

Returns the value in the most recent checkpoint, or zero if there are no checkpoints.

latestCheckpoint(struct Checkpoints.Trace160 self) → bool exists, uint96 _key, uint160 _value internal

Returns whether there is a checkpoint in the structure (i.e. it is not empty), and if so the key and value in the most recent checkpoint.

length(struct Checkpoints.Trace160 self) → uint256 internal

Returns the number of checkpoint.

at(struct Checkpoints.Trace160 self, uint32 pos) → struct Checkpoints.Checkpoint160 internal

Returns checkpoint at given position.

CheckpointUnorderedInsertion() error

A value was attempted to be inserted on a past checkpoint.

Heap 

import "@openzeppelin/contracts/utils/structs/Heap.sol";

Library for managing binary heap that can be used as priority queue.

Heaps are represented as a tree of values where the first element (index 0) is the root, and where the node at index i is the child of the node at index (i-1)/2 and the parent of nodes at index 2*i+1 and 2*i+2. Each node stores an element of the heap.

The structure is ordered so that each node is bigger than its parent. An immediate consequence is that the highest priority value is the one at the root. This value can be looked up in constant time (O(1)) at heap.tree[0]

The structure is designed to perform the following operations with the corresponding complexities:

  • peek (get the highest priority value): O(1)

  • insert (insert a value): O(log(n))

  • pop (remove the highest priority value): O(log(n))

  • replace (replace the highest priority value with a new value): O(log(n))

  • length (get the number of elements): O(1)

  • clear (remove all elements): O(1)

This library allows for the use of custom comparator functions. Given that manipulating memory can lead to unexpected behavior. Consider verifying that the comparator does not manipulate the Heap’s state directly and that it follows the Solidity memory safety rules.

Available since v5.1.

Functions

peek(struct Heap.Uint256Heap self) → uint256 internal

Lookup the root element of the heap.

pop(struct Heap.Uint256Heap self) → uint256 internal

Remove (and return) the root element for the heap using the default comparator.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

pop(struct Heap.Uint256Heap self, function (uint256,uint256) view returns (bool) comp) → uint256 internal

Remove (and return) the root element for the heap using the provided comparator.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

insert(struct Heap.Uint256Heap self, uint256 value) internal

Insert a new element in the heap using the default comparator.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

insert(struct Heap.Uint256Heap self, uint256 value, function (uint256,uint256) view returns (bool) comp) internal

Insert a new element in the heap using the provided comparator.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

replace(struct Heap.Uint256Heap self, uint256 newValue) → uint256 internal

Return the root element for the heap, and replace it with a new value, using the default comparator. This is equivalent to using pop and insert, but requires only one rebalancing operation.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

replace(struct Heap.Uint256Heap self, uint256 newValue, function (uint256,uint256) view returns (bool) comp) → uint256 internal

Return the root element for the heap, and replace it with a new value, using the provided comparator. This is equivalent to using pop and insert, but requires only one rebalancing operation.

All inserting and removal from a heap should always be done using the same comparator. Mixing comparator during the lifecycle of a heap will result in undefined behavior.

length(struct Heap.Uint256Heap self) → uint256 internal

Returns the number of elements in the heap.

clear(struct Heap.Uint256Heap self) internal

Removes all elements in the heap.

MerkleTree 

import "@openzeppelin/contracts/utils/structs/MerkleTree.sol";

Library for managing Merkle Tree data structures.

Each tree is a complete binary tree with the ability to sequentially insert leaves, changing them from a zero to a non-zero value and updating its root. This structure allows inserting commitments (or other entries) that are not stored, but can be proven to be part of the tree at a later time if the root is kept. See MerkleProof.

A tree is defined by the following parameters:

  • Depth: The number of levels in the tree, it also defines the maximum number of leaves as 2**depth.

  • Zero value: The value that represents an empty leaf. Used to avoid regular zero values to be part of the tree.

  • Hashing function: A cryptographic hash function used to produce internal nodes. Defaults to Hashes.commutativeKeccak256.

Building trees using non-commutative hashing functions (i.e. H(a, b) != H(b, a)) is supported. However, proving the inclusion of a leaf in such trees is not possible with the MerkleProof library since it only supports commutative hashing functions.

Available since v5.1.

Functions

setup(struct MerkleTree.Bytes32PushTree self, uint8 treeDepth, bytes32 zero) → bytes32 initialRoot internal

Initialize a Bytes32PushTree using Hashes.commutativeKeccak256 to hash internal nodes. The capacity of the tree (i.e. number of leaves) is set to 2**treeDepth.

Calling this function on MerkleTree that was already setup and used will reset it to a blank state.

Once a tree is setup, any push to it must use the same hashing function. This means that values should be pushed to it using the default push function.

The zero value should be carefully chosen since it will be stored in the tree representing empty leaves. It should be a value that is not expected to be part of the tree.

setup(struct MerkleTree.Bytes32PushTree self, uint8 treeDepth, bytes32 zero, function (bytes32,bytes32) view returns (bytes32) fnHash) → bytes32 initialRoot internal

Same as setup, but allows to specify a custom hashing function.

Once a tree is setup, any push to it must use the same hashing function. This means that values should be pushed to it using the custom push function, which should be the same one as used during the setup.

Providing a custom hashing function is a security-sensitive operation since it may compromise the soundness of the tree.
Consider verifying that the hashing function does not manipulate the memory state directly and that it follows the Solidity memory safety rules. Otherwise, it may lead to unexpected behavior.

push(struct MerkleTree.Bytes32PushTree self, bytes32 leaf) → uint256 index, bytes32 newRoot internal

Insert a new leaf in the tree, and compute the new root. Returns the position of the inserted leaf in the tree, and the resulting root.

Hashing the leaf before calling this function is recommended as a protection against second pre-image attacks.

This variant uses Hashes.commutativeKeccak256 to hash internal nodes. It should only be used on merkle trees that were setup using the same (default) hashing function (i.e. by calling the default setup function).

push(struct MerkleTree.Bytes32PushTree self, bytes32 leaf, function (bytes32,bytes32) view returns (bytes32) fnHash) → uint256 index, bytes32 newRoot internal

Insert a new leaf in the tree, and compute the new root. Returns the position of the inserted leaf in the tree, and the resulting root.

Hashing the leaf before calling this function is recommended as a protection against second pre-image attacks.

This variant uses a custom hashing function to hash internal nodes. It should only be called with the same function as the one used during the initial setup of the merkle tree.

depth(struct MerkleTree.Bytes32PushTree self) → uint256 internal

Tree’s depth (set at initialization)

Libraries

Create2 

import "@openzeppelin/contracts/utils/Create2.sol";

Helper to make usage of the CREATE2 EVM opcode easier and safer. CREATE2 can be used to compute in advance the address where a smart contract will be deployed, which allows for interesting new mechanisms known as 'counterfactual interactions'.

See the EIP for more information.

Functions
Errors

deploy(uint256 amount, bytes32 salt, bytes bytecode) → address addr internal

Deploys a contract using CREATE2. The address where the contract will be deployed can be known in advance via computeAddress.

The bytecode for a contract can be obtained from Solidity with type(contractName).creationCode.

Requirements:

  • bytecode must not be empty.

  • salt must have not been used for bytecode already.

  • the factory must have a balance of at least amount.

  • if amount is non-zero, bytecode must have a payable constructor.

computeAddress(bytes32 salt, bytes32 bytecodeHash) → address internal

Returns the address where a contract will be stored if deployed via deploy. Any change in the bytecodeHash or salt will result in a new destination address.

computeAddress(bytes32 salt, bytes32 bytecodeHash, address deployer) → address addr internal

Returns the address where a contract will be stored if deployed via deploy from a contract located at deployer. If deployer is this contract’s address, returns the same value as computeAddress.

Create2EmptyBytecode() error

There’s no code to deploy.

Address 

import "@openzeppelin/contracts/utils/Address.sol";

Collection of functions related to the address type

Functions
Errors

sendValue(address payable recipient, uint256 amount) internal

Replacement for Solidity’s transfer: sends amount wei to recipient, forwarding all available gas and reverting on errors.

EIP1884 increases the gas cost of certain opcodes, possibly making contracts go over the 2300 gas limit imposed by transfer, making them unable to receive funds via transfer. sendValue removes this limitation.

Learn more.

because control is transferred to recipient, care must be taken to not create reentrancy vulnerabilities. Consider using ReentrancyGuard or the checks-effects-interactions pattern.

functionCall(address target, bytes data) → bytes internal

Performs a Solidity function call using a low level call. A plain call is an unsafe replacement for a function call: use this function instead.

If target reverts with a revert reason or custom error, it is bubbled up by this function (like regular Solidity function calls). However, if the call reverted with no returned reason, this function reverts with a {Errors.FailedCall} error.

Returns the raw returned data. To convert to the expected return value, use abi.decode.

Requirements:

  • target must be a contract.

  • calling target with data must not revert.

functionCallWithValue(address target, bytes data, uint256 value) → bytes internal

Same as functionCall, but also transferring value wei to target.

Requirements:

  • the calling contract must have an ETH balance of at least value.

  • the called Solidity function must be payable.

functionStaticCall(address target, bytes data) → bytes internal

Same as functionCall, but performing a static call.

functionDelegateCall(address target, bytes data) → bytes internal

Same as functionCall, but performing a delegate call.

verifyCallResultFromTarget(address target, bool success, bytes returndata) → bytes internal

Tool to verify that a low level call to smart-contract was successful, and reverts if the target was not a contract or bubbling up the revert reason (falling back to {Errors.FailedCall}) in case of an unsuccessful call.

verifyCallResult(bool success, bytes returndata) → bytes internal

Tool to verify that a low level call was successful, and reverts if it wasn’t, either by bubbling the revert reason or with a default {Errors.FailedCall} error.

AddressEmptyCode(address target) error

There’s no code at target (it is not a contract).

Arrays 

import "@openzeppelin/contracts/utils/Arrays.sol";

Collection of functions related to array types.

Functions

sort(uint256[] array, function (uint256,uint256) pure returns (bool) comp) → uint256[] internal

Sort an array of uint256 (in memory) following the provided comparator function.

This function does the sorting "in place", meaning that it overrides the input. The object is returned for convenience, but that returned value can be discarded safely if the caller has a memory pointer to the array.

this function’s cost is O(n · log(n)) in average and O(n²) in the worst case, with n the length of the array. Using it in view functions that are executed through eth_call is safe, but one should be very careful when executing this as part of a transaction. If the array being sorted is too large, the sort operation may consume more gas than is available in a block, leading to potential DoS.
Consider memory side-effects when using custom comparator functions that access memory in an unsafe way.

sort(uint256[] array) → uint256[] internal

Variant of sort that sorts an array of uint256 in increasing order.

sort(address[] array, function (address,address) pure returns (bool) comp) → address[] internal

Sort an array of address (in memory) following the provided comparator function.

This function does the sorting "in place", meaning that it overrides the input. The object is returned for convenience, but that returned value can be discarded safely if the caller has a memory pointer to the array.

this function’s cost is O(n · log(n)) in average and O(n²) in the worst case, with n the length of the array. Using it in view functions that are executed through eth_call is safe, but one should be very careful when executing this as part of a transaction. If the array being sorted is too large, the sort operation may consume more gas than is available in a block, leading to potential DoS.
Consider memory side-effects when using custom comparator functions that access memory in an unsafe way.

sort(address[] array) → address[] internal

Variant of sort that sorts an array of address in increasing order.

sort(bytes32[] array, function (bytes32,bytes32) pure returns (bool) comp) → bytes32[] internal

Sort an array of bytes32 (in memory) following the provided comparator function.

This function does the sorting "in place", meaning that it overrides the input. The object is returned for convenience, but that returned value can be discarded safely if the caller has a memory pointer to the array.

this function’s cost is O(n · log(n)) in average and O(n²) in the worst case, with n the length of the array. Using it in view functions that are executed through eth_call is safe, but one should be very careful when executing this as part of a transaction. If the array being sorted is too large, the sort operation may consume more gas than is available in a block, leading to potential DoS.
Consider memory side-effects when using custom comparator functions that access memory in an unsafe way.

sort(bytes32[] array) → bytes32[] internal

Variant of sort that sorts an array of bytes32 in increasing order.

findUpperBound(uint256[] array, uint256 element) → uint256 internal

Searches a sorted array and returns the first index that contains a value greater or equal to element. If no such index exists (i.e. all values in the array are strictly less than element), the array length is returned. Time complexity O(log n).

The array is expected to be sorted in ascending order, and to contain no repeated elements.
Deprecated. This implementation behaves as lowerBound but lacks support for repeated elements in the array. The lowerBound function should be used instead.

lowerBound(uint256[] array, uint256 element) → uint256 internal

Searches an array sorted in ascending order and returns the first index that contains a value greater or equal than element. If no such index exists (i.e. all values in the array are strictly less than element), the array length is returned. Time complexity O(log n).

See C++'s lower_bound.

upperBound(uint256[] array, uint256 element) → uint256 internal

Searches an array sorted in ascending order and returns the first index that contains a value strictly greater than element. If no such index exists (i.e. all values in the array are strictly less than element), the array length is returned. Time complexity O(log n).

See C++'s upper_bound.

lowerBoundMemory(uint256[] array, uint256 element) → uint256 internal

Same as lowerBound, but with an array in memory.

upperBoundMemory(uint256[] array, uint256 element) → uint256 internal

Same as upperBound, but with an array in memory.

unsafeAccess(address[] arr, uint256 pos) → struct StorageSlot.AddressSlot internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeAccess(bytes32[] arr, uint256 pos) → struct StorageSlot.Bytes32Slot internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeAccess(uint256[] arr, uint256 pos) → struct StorageSlot.Uint256Slot internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeMemoryAccess(address[] arr, uint256 pos) → address res internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeMemoryAccess(bytes32[] arr, uint256 pos) → bytes32 res internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeMemoryAccess(uint256[] arr, uint256 pos) → uint256 res internal

Access an array in an "unsafe" way. Skips solidity "index-out-of-range" check.

Only use if you are certain pos is lower than the array length.

unsafeSetLength(address[] array, uint256 len) internal

Helper to set the length of an dynamic array. Directly writing to .length is forbidden.

this does not clear elements if length is reduced, of initialize elements if length is increased.

unsafeSetLength(bytes32[] array, uint256 len) internal

Helper to set the length of an dynamic array. Directly writing to .length is forbidden.

this does not clear elements if length is reduced, of initialize elements if length is increased.

unsafeSetLength(uint256[] array, uint256 len) internal

Helper to set the length of an dynamic array. Directly writing to .length is forbidden.

this does not clear elements if length is reduced, of initialize elements if length is increased.

Base64 

import "@openzeppelin/contracts/utils/Base64.sol";

Provides a set of functions to operate with Base64 strings.

Functions
Internal Variables

encode(bytes data) → string internal

Converts a bytes to its Bytes64 string representation.

encodeURL(bytes data) → string internal

Converts a bytes to its Bytes64Url string representation. Output is not padded with = as specified in rfc4648.

string _TABLE internal constant

Base64 Encoding/Decoding Table See sections 4 and 5 of https://datatracker.ietf.org/doc/html/rfc4648

string _TABLE_URL internal constant

Strings 

import "@openzeppelin/contracts/utils/Strings.sol";

String operations.

Functions
Errors

toString(uint256 value) → string internal

Converts a uint256 to its ASCII string decimal representation.

toStringSigned(int256 value) → string internal

Converts a int256 to its ASCII string decimal representation.

toHexString(uint256 value) → string internal

Converts a uint256 to its ASCII string hexadecimal representation.

toHexString(uint256 value, uint256 length) → string internal

Converts a uint256 to its ASCII string hexadecimal representation with fixed length.

toHexString(address addr) → string internal

Converts an address with fixed length of 20 bytes to its not checksummed ASCII string hexadecimal representation.

toChecksumHexString(address addr) → string internal

Converts an address with fixed length of 20 bytes to its checksummed ASCII string hexadecimal representation, according to EIP-55.

equal(string a, string b) → bool internal

Returns true if the two strings are equal.

StringsInsufficientHexLength(uint256 value, uint256 length) error

The value string doesn’t fit in the specified length.

ShortStrings 

import "@openzeppelin/contracts/utils/ShortStrings.sol";

This library provides functions to convert short memory strings into a ShortString type that can be used as an immutable variable.

Strings of arbitrary length can be optimized using this library if they are short enough (up to 31 bytes) by packing them with their length (1 byte) in a single EVM word (32 bytes). Additionally, a fallback mechanism can be used for every other case.

Usage example:

contract Named {
    using ShortStrings for *;

    ShortString private immutable _name;
    string private _nameFallback;

    constructor(string memory contractName) {
        _name = contractName.toShortStringWithFallback(_nameFallback);
    }

    function name() external view returns (string memory) {
        return _name.toStringWithFallback(_nameFallback);
    }
}
Functions
Errors

toShortString(string str) → ShortString internal

Encode a string of at most 31 chars into a ShortString.

This will trigger a StringTooLong error is the input string is too long.

toString(ShortString sstr) → string internal

Decode a ShortString back to a "normal" string.

byteLength(ShortString sstr) → uint256 internal

Return the length of a ShortString.

toShortStringWithFallback(string value, string store) → ShortString internal

Encode a string into a ShortString, or write it to storage if it is too long.

toStringWithFallback(ShortString value, string store) → string internal

Decode a string that was encoded to ShortString or written to storage using {setWithFallback}.

byteLengthWithFallback(ShortString value, string store) → uint256 internal

Return the length of a string that was encoded to ShortString or written to storage using {setWithFallback}.

This will return the "byte length" of the string. This may not reflect the actual length in terms of actual characters as the UTF-8 encoding of a single character can span over multiple bytes.

StringTooLong(string str) error

InvalidShortString() error

SlotDerivation 

import "@openzeppelin/contracts/utils/SlotDerivation.sol";

Library for computing storage (and transient storage) locations from namespaces and deriving slots corresponding to standard patterns. The derivation method for array and mapping matches the storage layout used by the solidity language / compiler.

See Solidity docs for mappings and dynamic arrays..

Example usage:

contract Example {
    // Add the library methods
    using StorageSlot for bytes32;
    using SlotDerivation for bytes32;

    // Declare a namespace
    string private constant _NAMESPACE = "<namespace>" // eg. OpenZeppelin.Slot

    function setValueInNamespace(uint256 key, address newValue) internal {
        _NAMESPACE.erc7201Slot().deriveMapping(key).getAddressSlot().value = newValue;
    }

    function getValueInNamespace(uint256 key) internal view returns (address) {
        return _NAMESPACE.erc7201Slot().deriveMapping(key).getAddressSlot().value;
    }
}
Consider using this library along with StorageSlot.
This library provides a way to manipulate storage locations in a non-standard way. Tooling for checking upgrade safety will ignore the slots accessed through this library.

Available since v5.1.

Functions

erc7201Slot(string namespace) → bytes32 slot internal

Derive an ERC-7201 slot from a string (namespace).

offset(bytes32 slot, uint256 pos) → bytes32 result internal

Add an offset to a slot to get the n-th element of a structure or an array.

deriveArray(bytes32 slot) → bytes32 result internal

Derive the location of the first element in an array from the slot where the length is stored.

deriveMapping(bytes32 slot, address key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, bool key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, bytes32 key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, uint256 key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, int256 key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, string key) → bytes32 result internal

Derive the location of a mapping element from the key.

deriveMapping(bytes32 slot, bytes key) → bytes32 result internal

Derive the location of a mapping element from the key.

StorageSlot 

import "@openzeppelin/contracts/utils/StorageSlot.sol";

Library for reading and writing primitive types to specific storage slots.

Storage slots are often used to avoid storage conflict when dealing with upgradeable contracts. This library helps with reading and writing to such slots without the need for inline assembly.

The functions in this library return Slot structs that contain a value member that can be used to read or write.

Example usage to set ERC-1967 implementation slot:

contract ERC1967 {
    // Define the slot. Alternatively, use the SlotDerivation library to derive the slot.
    bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;

    function _getImplementation() internal view returns (address) {
        return StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value;
    }

    function _setImplementation(address newImplementation) internal {
        require(newImplementation.code.length > 0);
        StorageSlot.getAddressSlot(_IMPLEMENTATION_SLOT).value = newImplementation;
    }
}
Consider using this library along with SlotDerivation.
Functions

getAddressSlot(bytes32 slot) → struct StorageSlot.AddressSlot r internal

Returns an AddressSlot with member value located at slot.

getBooleanSlot(bytes32 slot) → struct StorageSlot.BooleanSlot r internal

Returns a BooleanSlot with member value located at slot.

getBytes32Slot(bytes32 slot) → struct StorageSlot.Bytes32Slot r internal

Returns a Bytes32Slot with member value located at slot.

getUint256Slot(bytes32 slot) → struct StorageSlot.Uint256Slot r internal

Returns a Uint256Slot with member value located at slot.

getInt256Slot(bytes32 slot) → struct StorageSlot.Int256Slot r internal

Returns a Int256Slot with member value located at slot.

getStringSlot(bytes32 slot) → struct StorageSlot.StringSlot r internal

Returns a StringSlot with member value located at slot.

getStringSlot(string store) → struct StorageSlot.StringSlot r internal

Returns an StringSlot representation of the string storage pointer store.

getBytesSlot(bytes32 slot) → struct StorageSlot.BytesSlot r internal

Returns a BytesSlot with member value located at slot.

getBytesSlot(bytes store) → struct StorageSlot.BytesSlot r internal

Returns an BytesSlot representation of the bytes storage pointer store.

TransientSlot 

import "@openzeppelin/contracts/utils/TransientSlot.sol";

Library for reading and writing value-types to specific transient storage slots.

Transient slots are often used to store temporary values that are removed after the current transaction. This library helps with reading and writing to such slots without the need for inline assembly.

  • Example reading and writing values using transient storage:

contract Lock {
    using TransientSlot for *;

    // Define the slot. Alternatively, use the SlotDerivation library to derive the slot.
    bytes32 internal constant _LOCK_SLOT = 0xf4678858b2b588224636b8522b729e7722d32fc491da849ed75b3fdf3c84f542;

    modifier locked() {
        require(!_LOCK_SLOT.asBoolean().tload());

        _LOCK_SLOT.asBoolean().tstore(true);
        _;
        _LOCK_SLOT.asBoolean().tstore(false);
    }
}
Consider using this library along with SlotDerivation.
Functions

asAddress(bytes32 slot) → TransientSlot.AddressSlot internal

Cast an arbitrary slot to a AddressSlot.

asBoolean(bytes32 slot) → TransientSlot.BooleanSlot internal

Cast an arbitrary slot to a BooleanSlot.

asBytes32(bytes32 slot) → TransientSlot.Bytes32Slot internal

Cast an arbitrary slot to a Bytes32Slot.

asUint256(bytes32 slot) → TransientSlot.Uint256Slot internal

Cast an arbitrary slot to a Uint256Slot.

asInt256(bytes32 slot) → TransientSlot.Int256Slot internal

Cast an arbitrary slot to a Int256Slot.

tload(TransientSlot.AddressSlot slot) → address value internal

Load the value held at location slot in transient storage.

tstore(TransientSlot.AddressSlot slot, address value) internal

Store value at location slot in transient storage.

tload(TransientSlot.BooleanSlot slot) → bool value internal

Load the value held at location slot in transient storage.

tstore(TransientSlot.BooleanSlot slot, bool value) internal

Store value at location slot in transient storage.

tload(TransientSlot.Bytes32Slot slot) → bytes32 value internal

Load the value held at location slot in transient storage.

tstore(TransientSlot.Bytes32Slot slot, bytes32 value) internal

Store value at location slot in transient storage.

tload(TransientSlot.Uint256Slot slot) → uint256 value internal

Load the value held at location slot in transient storage.

tstore(TransientSlot.Uint256Slot slot, uint256 value) internal

Store value at location slot in transient storage.

tload(TransientSlot.Int256Slot slot) → int256 value internal

Load the value held at location slot in transient storage.

tstore(TransientSlot.Int256Slot slot, int256 value) internal

Store value at location slot in transient storage.

Multicall 

import "@openzeppelin/contracts/utils/Multicall.sol";

Provides a function to batch together multiple calls in a single external call.

Consider any assumption about calldata validation performed by the sender may be violated if it’s not especially careful about sending transactions invoking multicall. For example, a relay address that filters function selectors won’t filter calls nested within a multicall operation.

Since 5.0.1 and 4.9.4, this contract identifies non-canonical contexts (i.e. msg.sender is not {_msgSender}). If a non-canonical context is identified, the following self delegatecall appends the last bytes of msg.data to the subcall. This makes it safe to use with ERC2771Context. Contexts that don’t affect the resolution of {_msgSender} are not propagated to subcalls.
Functions

multicall(bytes[] data) → bytes[] results external

Receives and executes a batch of function calls on this contract.

Context 

import "@openzeppelin/contracts/utils/Context.sol";

Provides information about the current execution context, including the sender of the transaction and its data. While these are generally available via msg.sender and msg.data, they should not be accessed in such a direct manner, since when dealing with meta-transactions the account sending and paying for execution may not be the actual sender (as far as an application is concerned).

This contract is only required for intermediate, library-like contracts.

Functions

_msgSender() → address internal

_msgData() → bytes internal

_contextSuffixLength() → uint256 internal

Packing 

import "@openzeppelin/contracts/utils/Packing.sol";

Helper library packing and unpacking multiple values into bytesXX.

Example usage:

library MyPacker {
    type MyType is bytes32;

    function _pack(address account, bytes4 selector, uint64 period) external pure returns (MyType) {
        bytes12 subpack = Packing.pack_4_8(selector, bytes8(period));
        bytes32 pack = Packing.pack_20_12(bytes20(account), subpack);
        return MyType.wrap(pack);
    }

    function _unpack(MyType self) external pure returns (address, bytes4, uint64) {
        bytes32 pack = MyType.unwrap(self);
        return (
            address(Packing.extract_32_20(pack, 0)),
            Packing.extract_32_4(pack, 20),
            uint64(Packing.extract_32_8(pack, 24))
        );
    }
}

Available since v5.1.

Functions
Errors

pack_1_1(bytes1 left, bytes1 right) → bytes2 result internal

pack_2_2(bytes2 left, bytes2 right) → bytes4 result internal

pack_2_4(bytes2 left, bytes4 right) → bytes6 result internal

pack_2_6(bytes2 left, bytes6 right) → bytes8 result internal

pack_4_2(bytes4 left, bytes2 right) → bytes6 result internal

pack_4_4(bytes4 left, bytes4 right) → bytes8 result internal

pack_4_8(bytes4 left, bytes8 right) → bytes12 result internal

pack_4_12(bytes4 left, bytes12 right) → bytes16 result internal

pack_4_16(bytes4 left, bytes16 right) → bytes20 result internal

pack_4_20(bytes4 left, bytes20 right) → bytes24 result internal

pack_4_24(bytes4 left, bytes24 right) → bytes28 result internal

pack_4_28(bytes4 left, bytes28 right) → bytes32 result internal

pack_6_2(bytes6 left, bytes2 right) → bytes8 result internal

pack_6_6(bytes6 left, bytes6 right) → bytes12 result internal

pack_8_4(bytes8 left, bytes4 right) → bytes12 result internal

pack_8_8(bytes8 left, bytes8 right) → bytes16 result internal

pack_8_12(bytes8 left, bytes12 right) → bytes20 result internal

pack_8_16(bytes8 left, bytes16 right) → bytes24 result internal

pack_8_20(bytes8 left, bytes20 right) → bytes28 result internal

pack_8_24(bytes8 left, bytes24 right) → bytes32 result internal

pack_12_4(bytes12 left, bytes4 right) → bytes16 result internal

pack_12_8(bytes12 left, bytes8 right) → bytes20 result internal

pack_12_12(bytes12 left, bytes12 right) → bytes24 result internal

pack_12_16(bytes12 left, bytes16 right) → bytes28 result internal

pack_12_20(bytes12 left, bytes20 right) → bytes32 result internal

pack_16_4(bytes16 left, bytes4 right) → bytes20 result internal

pack_16_8(bytes16 left, bytes8 right) → bytes24 result internal

pack_16_12(bytes16 left, bytes12 right) → bytes28 result internal

pack_16_16(bytes16 left, bytes16 right) → bytes32 result internal

pack_20_4(bytes20 left, bytes4 right) → bytes24 result internal

pack_20_8(bytes20 left, bytes8 right) → bytes28 result internal

pack_20_12(bytes20 left, bytes12 right) → bytes32 result internal

pack_24_4(bytes24 left, bytes4 right) → bytes28 result internal

pack_24_8(bytes24 left, bytes8 right) → bytes32 result internal

pack_28_4(bytes28 left, bytes4 right) → bytes32 result internal

extract_2_1(bytes2 self, uint8 offset) → bytes1 result internal

replace_2_1(bytes2 self, bytes1 value, uint8 offset) → bytes2 result internal

extract_4_1(bytes4 self, uint8 offset) → bytes1 result internal

replace_4_1(bytes4 self, bytes1 value, uint8 offset) → bytes4 result internal

extract_4_2(bytes4 self, uint8 offset) → bytes2 result internal

replace_4_2(bytes4 self, bytes2 value, uint8 offset) → bytes4 result internal

extract_6_1(bytes6 self, uint8 offset) → bytes1 result internal

replace_6_1(bytes6 self, bytes1 value, uint8 offset) → bytes6 result internal

extract_6_2(bytes6 self, uint8 offset) → bytes2 result internal

replace_6_2(bytes6 self, bytes2 value, uint8 offset) → bytes6 result internal

extract_6_4(bytes6 self, uint8 offset) → bytes4 result internal

replace_6_4(bytes6 self, bytes4 value, uint8 offset) → bytes6 result internal

extract_8_1(bytes8 self, uint8 offset) → bytes1 result internal

replace_8_1(bytes8 self, bytes1 value, uint8 offset) → bytes8 result internal

extract_8_2(bytes8 self, uint8 offset) → bytes2 result internal

replace_8_2(bytes8 self, bytes2 value, uint8 offset) → bytes8 result internal

extract_8_4(bytes8 self, uint8 offset) → bytes4 result internal

replace_8_4(bytes8 self, bytes4 value, uint8 offset) → bytes8 result internal

extract_8_6(bytes8 self, uint8 offset) → bytes6 result internal

replace_8_6(bytes8 self, bytes6 value, uint8 offset) → bytes8 result internal

extract_12_1(bytes12 self, uint8 offset) → bytes1 result internal

replace_12_1(bytes12 self, bytes1 value, uint8 offset) → bytes12 result internal

extract_12_2(bytes12 self, uint8 offset) → bytes2 result internal

replace_12_2(bytes12 self, bytes2 value, uint8 offset) → bytes12 result internal

extract_12_4(bytes12 self, uint8 offset) → bytes4 result internal

replace_12_4(bytes12 self, bytes4 value, uint8 offset) → bytes12 result internal

extract_12_6(bytes12 self, uint8 offset) → bytes6 result internal

replace_12_6(bytes12 self, bytes6 value, uint8 offset) → bytes12 result internal

extract_12_8(bytes12 self, uint8 offset) → bytes8 result internal

replace_12_8(bytes12 self, bytes8 value, uint8 offset) → bytes12 result internal

extract_16_1(bytes16 self, uint8 offset) → bytes1 result internal

replace_16_1(bytes16 self, bytes1 value, uint8 offset) → bytes16 result internal

extract_16_2(bytes16 self, uint8 offset) → bytes2 result internal

replace_16_2(bytes16 self, bytes2 value, uint8 offset) → bytes16 result internal

extract_16_4(bytes16 self, uint8 offset) → bytes4 result internal

replace_16_4(bytes16 self, bytes4 value, uint8 offset) → bytes16 result internal

extract_16_6(bytes16 self, uint8 offset) → bytes6 result internal

replace_16_6(bytes16 self, bytes6 value, uint8 offset) → bytes16 result internal

extract_16_8(bytes16 self, uint8 offset) → bytes8 result internal

replace_16_8(bytes16 self, bytes8 value, uint8 offset) → bytes16 result internal

extract_16_12(bytes16 self, uint8 offset) → bytes12 result internal

replace_16_12(bytes16 self, bytes12 value, uint8 offset) → bytes16 result internal

extract_20_1(bytes20 self, uint8 offset) → bytes1 result internal

replace_20_1(bytes20 self, bytes1 value, uint8 offset) → bytes20 result internal

extract_20_2(bytes20 self, uint8 offset) → bytes2 result internal

replace_20_2(bytes20 self, bytes2 value, uint8 offset) → bytes20 result internal

extract_20_4(bytes20 self, uint8 offset) → bytes4 result internal

replace_20_4(bytes20 self, bytes4 value, uint8 offset) → bytes20 result internal

extract_20_6(bytes20 self, uint8 offset) → bytes6 result internal

replace_20_6(bytes20 self, bytes6 value, uint8 offset) → bytes20 result internal

extract_20_8(bytes20 self, uint8 offset) → bytes8 result internal

replace_20_8(bytes20 self, bytes8 value, uint8 offset) → bytes20 result internal

extract_20_12(bytes20 self, uint8 offset) → bytes12 result internal

replace_20_12(bytes20 self, bytes12 value, uint8 offset) → bytes20 result internal

extract_20_16(bytes20 self, uint8 offset) → bytes16 result internal

replace_20_16(bytes20 self, bytes16 value, uint8 offset) → bytes20 result internal

extract_24_1(bytes24 self, uint8 offset) → bytes1 result internal

replace_24_1(bytes24 self, bytes1 value, uint8 offset) → bytes24 result internal

extract_24_2(bytes24 self, uint8 offset) → bytes2 result internal

replace_24_2(bytes24 self, bytes2 value, uint8 offset) → bytes24 result internal

extract_24_4(bytes24 self, uint8 offset) → bytes4 result internal

replace_24_4(bytes24 self, bytes4 value, uint8 offset) → bytes24 result internal

extract_24_6(bytes24 self, uint8 offset) → bytes6 result internal

replace_24_6(bytes24 self, bytes6 value, uint8 offset) → bytes24 result internal

extract_24_8(bytes24 self, uint8 offset) → bytes8 result internal

replace_24_8(bytes24 self, bytes8 value, uint8 offset) → bytes24 result internal

extract_24_12(bytes24 self, uint8 offset) → bytes12 result internal

replace_24_12(bytes24 self, bytes12 value, uint8 offset) → bytes24 result internal

extract_24_16(bytes24 self, uint8 offset) → bytes16 result internal

replace_24_16(bytes24 self, bytes16 value, uint8 offset) → bytes24 result internal

extract_24_20(bytes24 self, uint8 offset) → bytes20 result internal

replace_24_20(bytes24 self, bytes20 value, uint8 offset) → bytes24 result internal

extract_28_1(bytes28 self, uint8 offset) → bytes1 result internal

replace_28_1(bytes28 self, bytes1 value, uint8 offset) → bytes28 result internal

extract_28_2(bytes28 self, uint8 offset) → bytes2 result internal

replace_28_2(bytes28 self, bytes2 value, uint8 offset) → bytes28 result internal

extract_28_4(bytes28 self, uint8 offset) → bytes4 result internal

replace_28_4(bytes28 self, bytes4 value, uint8 offset) → bytes28 result internal

extract_28_6(bytes28 self, uint8 offset) → bytes6 result internal

replace_28_6(bytes28 self, bytes6 value, uint8 offset) → bytes28 result internal

extract_28_8(bytes28 self, uint8 offset) → bytes8 result internal

replace_28_8(bytes28 self, bytes8 value, uint8 offset) → bytes28 result internal

extract_28_12(bytes28 self, uint8 offset) → bytes12 result internal

replace_28_12(bytes28 self, bytes12 value, uint8 offset) → bytes28 result internal

extract_28_16(bytes28 self, uint8 offset) → bytes16 result internal

replace_28_16(bytes28 self, bytes16 value, uint8 offset) → bytes28 result internal

extract_28_20(bytes28 self, uint8 offset) → bytes20 result internal

replace_28_20(bytes28 self, bytes20 value, uint8 offset) → bytes28 result internal

extract_28_24(bytes28 self, uint8 offset) → bytes24 result internal

replace_28_24(bytes28 self, bytes24 value, uint8 offset) → bytes28 result internal

extract_32_1(bytes32 self, uint8 offset) → bytes1 result internal

replace_32_1(bytes32 self, bytes1 value, uint8 offset) → bytes32 result internal

extract_32_2(bytes32 self, uint8 offset) → bytes2 result internal

replace_32_2(bytes32 self, bytes2 value, uint8 offset) → bytes32 result internal

extract_32_4(bytes32 self, uint8 offset) → bytes4 result internal

replace_32_4(bytes32 self, bytes4 value, uint8 offset) → bytes32 result internal

extract_32_6(bytes32 self, uint8 offset) → bytes6 result internal

replace_32_6(bytes32 self, bytes6 value, uint8 offset) → bytes32 result internal

extract_32_8(bytes32 self, uint8 offset) → bytes8 result internal

replace_32_8(bytes32 self, bytes8 value, uint8 offset) → bytes32 result internal

extract_32_12(bytes32 self, uint8 offset) → bytes12 result internal

replace_32_12(bytes32 self, bytes12 value, uint8 offset) → bytes32 result internal

extract_32_16(bytes32 self, uint8 offset) → bytes16 result internal

replace_32_16(bytes32 self, bytes16 value, uint8 offset) → bytes32 result internal

extract_32_20(bytes32 self, uint8 offset) → bytes20 result internal

replace_32_20(bytes32 self, bytes20 value, uint8 offset) → bytes32 result internal

extract_32_24(bytes32 self, uint8 offset) → bytes24 result internal

replace_32_24(bytes32 self, bytes24 value, uint8 offset) → bytes32 result internal

extract_32_28(bytes32 self, uint8 offset) → bytes28 result internal

replace_32_28(bytes32 self, bytes28 value, uint8 offset) → bytes32 result internal

OutOfRangeAccess() error

Panic 

import "@openzeppelin/contracts/utils/Panic.sol";

Helper library for emitting standardized panic codes.

contract Example {
     using Panic for uint256;

     // Use any of the declared internal constants
     function foo() { Panic.GENERIC.panic(); }

     // Alternatively
     function foo() { Panic.panic(Panic.GENERIC); }
}

Follows the list from libsolutil.

Available since v5.1.

Functions
Internal Variables

panic(uint256 code) internal

Reverts with a panic code. Recommended to use with the internal constants with predefined codes.

uint256 GENERIC internal constant

generic / unspecified error

uint256 ASSERT internal constant

used by the assert() builtin

uint256 UNDER_OVERFLOW internal constant

arithmetic underflow or overflow

uint256 DIVISION_BY_ZERO internal constant

division or modulo by zero

uint256 ENUM_CONVERSION_ERROR internal constant

enum conversion error

uint256 STORAGE_ENCODING_ERROR internal constant

invalid encoding in storage

uint256 EMPTY_ARRAY_POP internal constant

empty array pop

uint256 ARRAY_OUT_OF_BOUNDS internal constant

array out of bounds access

uint256 RESOURCE_ERROR internal constant

resource error (too large allocation or too large array)

uint256 INVALID_INTERNAL_FUNCTION internal constant

calling invalid internal function

Comparators 

import "@openzeppelin/contracts/utils/Comparators.sol";

Provides a set of functions to compare values.

Available since v5.1.

Functions

lt(uint256 a, uint256 b) → bool internal

gt(uint256 a, uint256 b) → bool internal

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