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/**
_____ ___ ___ __ ____ _ __
/ ___/____ / (_)___/ (_) /___ __ / __ )(_) /______
\__ \/ __ \/ / / __ / / __/ / / / / __ / / __/ ___/
___/ / /_/ / / / /_/ / / /_/ /_/ / / /_/ / / /_(__ )
/____/\____/_/_/\__,_/_/\__/\__, / /_____/_/\__/____/
/____/
- npm: https://www.npmjs.com/package/solidity-bits
- github: https://github.com/estarriolvetch/solidity-bits
*/
pragma solidity ^0.8.0;
import "./BitScan.sol";
import "./Popcount.sol";
/**
* @dev This Library is a modified version of Openzeppelin's BitMaps library with extra features.
*
* 1. Functions of finding the index of the closest set bit from a given index are added.
* The indexing of each bucket is modifed to count from the MSB to the LSB instead of from the LSB to the MSB.
* The modification of indexing makes finding the closest previous set bit more efficient in gas usage.
* 2. Setting and unsetting the bitmap consecutively.
* 3. Accounting number of set bits within a given range.
*
*/
/**
* @dev Library for managing uint256 to bool mapping in a compact and efficient way, providing the keys are sequential.
* Largelly inspired by Uniswap's https://github.com/Uniswap/merkle-distributor/blob/master/contracts/MerkleDistributor.sol[merkle-distributor].
*/
library BitMaps {
using BitScan for uint256;
uint256 private constant MASK_INDEX_ZERO = (1 << 255);
uint256 private constant MASK_FULL = type(uint256).max;
struct BitMap {
mapping(uint256 => uint256) _data;
}
/**
* @dev Returns whether the bit at `index` is set.
*/
function get(BitMap storage bitmap, uint256 index) internal view returns (bool) {
uint256 bucket = index >> 8;
uint256 mask = MASK_INDEX_ZERO >> (index & 0xff);
return bitmap._data[bucket] & mask != 0;
}
/**
* @dev Sets the bit at `index` to the boolean `value`.
*/
function setTo(
BitMap storage bitmap,
uint256 index,
bool value
) internal {
if (value) {
set(bitmap, index);
} else {
unset(bitmap, index);
}
}
/**
* @dev Sets the bit at `index`.
*/
function set(BitMap storage bitmap, uint256 index) internal {
uint256 bucket = index >> 8;
uint256 mask = MASK_INDEX_ZERO >> (index & 0xff);
bitmap._data[bucket] |= mask;
}
/**
* @dev Unsets the bit at `index`.
*/
function unset(BitMap storage bitmap, uint256 index) internal {
uint256 bucket = index >> 8;
uint256 mask = MASK_INDEX_ZERO >> (index & 0xff);
bitmap._data[bucket] &= ~mask;
}
/**
* @dev Consecutively sets `amount` of bits starting from the bit at `startIndex`.
*/
function setBatch(BitMap storage bitmap, uint256 startIndex, uint256 amount) internal {
uint256 bucket = startIndex >> 8;
uint256 bucketStartIndex = (startIndex & 0xff);
unchecked {
if(bucketStartIndex + amount < 256) {
bitmap._data[bucket] |= MASK_FULL << (256 - amount) >> bucketStartIndex;
} else {
bitmap._data[bucket] |= MASK_FULL >> bucketStartIndex;
amount -= (256 - bucketStartIndex);
bucket++;
while(amount > 256) {
bitmap._data[bucket] = MASK_FULL;
amount -= 256;
bucket++;
}
bitmap._data[bucket] |= MASK_FULL << (256 - amount);
}
}
}
/**
* @dev Consecutively unsets `amount` of bits starting from the bit at `startIndex`.
*/
function unsetBatch(BitMap storage bitmap, uint256 startIndex, uint256 amount) internal {
uint256 bucket = startIndex >> 8;
uint256 bucketStartIndex = (startIndex & 0xff);
unchecked {
if(bucketStartIndex + amount < 256) {
bitmap._data[bucket] &= ~(MASK_FULL << (256 - amount) >> bucketStartIndex);
} else {
bitmap._data[bucket] &= ~(MASK_FULL >> bucketStartIndex);
amount -= (256 - bucketStartIndex);
bucket++;
while(amount > 256) {
bitmap._data[bucket] = 0;
amount -= 256;
bucket++;
}
bitmap._data[bucket] &= ~(MASK_FULL << (256 - amount));
}
}
}
/**
* @dev Returns number of set bits within a range.
*/
function popcountA(BitMap storage bitmap, uint256 startIndex, uint256 amount) internal view returns(uint256 count) {
uint256 bucket = startIndex >> 8;
uint256 bucketStartIndex = (startIndex & 0xff);
unchecked {
if(bucketStartIndex + amount < 256) {
count += Popcount.popcount256A(
bitmap._data[bucket] & (MASK_FULL << (256 - amount) >> bucketStartIndex)
);
} else {
count += Popcount.popcount256A(
bitmap._data[bucket] & (MASK_FULL >> bucketStartIndex)
);
amount -= (256 - bucketStartIndex);
bucket++;
while(amount > 256) {
count += Popcount.popcount256A(bitmap._data[bucket]);
amount -= 256;
bucket++;
}
count += Popcount.popcount256A(
bitmap._data[bucket] & (MASK_FULL << (256 - amount))
);
}
}
}
/**
* @dev Returns number of set bits within a range.
*/
function popcountB(BitMap storage bitmap, uint256 startIndex, uint256 amount) internal view returns(uint256 count) {
uint256 bucket = startIndex >> 8;
uint256 bucketStartIndex = (startIndex & 0xff);
unchecked {
if(bucketStartIndex + amount < 256) {
count += Popcount.popcount256B(
bitmap._data[bucket] & (MASK_FULL << (256 - amount) >> bucketStartIndex)
);
} else {
count += Popcount.popcount256B(
bitmap._data[bucket] & (MASK_FULL >> bucketStartIndex)
);
amount -= (256 - bucketStartIndex);
bucket++;
while(amount > 256) {
count += Popcount.popcount256B(bitmap._data[bucket]);
amount -= 256;
bucket++;
}
count += Popcount.popcount256B(
bitmap._data[bucket] & (MASK_FULL << (256 - amount))
);
}
}
}
/**
* @dev Find the closest index of the set bit before `index`.
*/
function scanForward(BitMap storage bitmap, uint256 index) internal view returns (uint256 setBitIndex) {
uint256 bucket = index >> 8;
// index within the bucket
uint256 bucketIndex = (index & 0xff);
// load a bitboard from the bitmap.
uint256 bb = bitmap._data[bucket];
// offset the bitboard to scan from `bucketIndex`.
bb = bb >> (0xff ^ bucketIndex); // bb >> (255 - bucketIndex)
if(bb > 0) {
unchecked {
setBitIndex = (bucket << 8) | (bucketIndex - bb.bitScanForward256());
}
} else {
while(true) {
require(bucket > 0, "BitMaps: The set bit before the index doesn't exist.");
unchecked {
bucket--;
}
// No offset. Always scan from the least significiant bit now.
bb = bitmap._data[bucket];
if(bb > 0) {
unchecked {
setBitIndex = (bucket << 8) | (255 - bb.bitScanForward256());
break;
}
}
}
}
}
function getBucket(BitMap storage bitmap, uint256 bucket) internal view returns (uint256) {
return bitmap._data[bucket];
}
}
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