File size: 2,709 Bytes
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/**
_____ ___ ___ __ ____ _ __
/ ___/____ / (_)___/ (_) /___ __ / __ )(_) /______
\__ \/ __ \/ / / __ / / __/ / / / / __ / / __/ ___/
___/ / /_/ / / / /_/ / / /_/ /_/ / / /_/ / / /_(__ )
/____/\____/_/_/\__,_/_/\__/\__, / /_____/_/\__/____/
/____/
- npm: https://www.npmjs.com/package/solidity-bits
- github: https://github.com/estarriolvetch/solidity-bits
*/
pragma solidity ^0.8.0;
library BitScan {
uint256 constant private DEBRUIJN_256 = 0x818283848586878898a8b8c8d8e8f929395969799a9b9d9e9faaeb6bedeeff;
bytes constant private LOOKUP_TABLE_256 = hex"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";
/**
@dev Isolate the least significant set bit.
*/
function isolateLS1B256(uint256 bb) pure internal returns (uint256) {
require(bb > 0);
unchecked {
return bb & (0 - bb);
}
}
/**
@dev Isolate the most significant set bit.
*/
function isolateMS1B256(uint256 bb) pure internal returns (uint256) {
require(bb > 0);
unchecked {
bb |= bb >> 128;
bb |= bb >> 64;
bb |= bb >> 32;
bb |= bb >> 16;
bb |= bb >> 8;
bb |= bb >> 4;
bb |= bb >> 2;
bb |= bb >> 1;
return (bb >> 1) + 1;
}
}
/**
@dev Find the index of the lest significant set bit. (trailing zero count)
*/
function bitScanForward256(uint256 bb) pure internal returns (uint8) {
unchecked {
return uint8(LOOKUP_TABLE_256[(isolateLS1B256(bb) * DEBRUIJN_256) >> 248]);
}
}
/**
@dev Find the index of the most significant set bit.
*/
function bitScanReverse256(uint256 bb) pure internal returns (uint8) {
unchecked {
return 255 - uint8(LOOKUP_TABLE_256[((isolateMS1B256(bb) * DEBRUIJN_256) >> 248)]);
}
}
function log2(uint256 bb) pure internal returns (uint8) {
unchecked {
return uint8(LOOKUP_TABLE_256[(isolateMS1B256(bb) * DEBRUIJN_256) >> 248]);
}
}
}
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