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60 lines
2.0 KiB
60 lines
2.0 KiB
// SPDX-License-Identifier: MIT
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// OpenZeppelin Contracts (last updated v5.0.0) (utils/structs/BitMaps.sol)
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pragma solidity ^0.8.20;
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/**
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* @dev Library for managing uint256 to bool mapping in a compact and efficient way, provided the keys are sequential.
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* Largely inspired by Uniswap's https://github.com/Uniswap/merkle-distributor/blob/master/contracts/MerkleDistributor.sol[merkle-distributor].
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*
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* BitMaps pack 256 booleans across each bit of a single 256-bit slot of `uint256` type.
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* Hence booleans corresponding to 256 _sequential_ indices would only consume a single slot,
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* unlike the regular `bool` which would consume an entire slot for a single value.
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*
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* This results in gas savings in two ways:
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*
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* - Setting a zero value to non-zero only once every 256 times
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* - Accessing the same warm slot for every 256 _sequential_ indices
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*/
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library BitMaps {
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struct BitMap {
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mapping(uint256 bucket => uint256) _data;
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}
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/**
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* @dev Returns whether the bit at `index` is set.
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*/
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function get(BitMap storage bitmap, uint256 index) internal view returns (bool) {
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uint256 bucket = index >> 8;
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uint256 mask = 1 << (index & 0xff);
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return bitmap._data[bucket] & mask != 0;
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}
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/**
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* @dev Sets the bit at `index` to the boolean `value`.
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*/
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function setTo(BitMap storage bitmap, uint256 index, bool value) internal {
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if (value) {
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set(bitmap, index);
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} else {
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unset(bitmap, index);
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}
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}
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/**
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* @dev Sets the bit at `index`.
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*/
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function set(BitMap storage bitmap, uint256 index) internal {
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uint256 bucket = index >> 8;
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uint256 mask = 1 << (index & 0xff);
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bitmap._data[bucket] |= mask;
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}
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/**
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* @dev Unsets the bit at `index`.
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*/
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function unset(BitMap storage bitmap, uint256 index) internal {
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uint256 bucket = index >> 8;
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uint256 mask = 1 << (index & 0xff);
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bitmap._data[bucket] &= ~mask;
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}
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}
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