| // SPDX-License-Identifier: MIT |
| /** |
| _____ ___ ___ __ ____ _ __ |
| / ___/____ / (_)___/ (_) /___ __ / __ )(_) /______ |
| \__ \/ __ \/ / / __ / / __/ / / / / __ / / __/ ___/ |
| ___/ / /_/ / / / /_/ / / /_/ /_/ / / /_/ / / /_(__ ) |
| /____/\____/_/_/\__,_/_/\__/\__, / /_____/_/\__/____/ |
| /____/ |
|
|
| - 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]); |
| } |
| } |
| } |
|
|
