//////////////////////////////////////////////////////////////////////////////// /// DISCLAIMER /// /// Copyright 2016 by EMC Corporation, All Rights Reserved /// /// Licensed under the Apache License, Version 2.0 (the "License"); /// you may not use this file except in compliance with the License. /// You may obtain a copy of the License at /// /// http://www.apache.org/licenses/LICENSE-2.0 /// /// Unless required by applicable law or agreed to in writing, software /// distributed under the License is distributed on an "AS IS" BASIS, /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. /// See the License for the specific language governing permissions and /// limitations under the License. /// /// Copyright holder is EMC Corporation /// /// @author Andrey Abramov /// @author Vasiliy Nabatchikov //////////////////////////////////////////////////////////////////////////////// #include "shared.hpp" #include "math_utils.hpp" NS_ROOT NS_BEGIN( math ) uint32_t log2_64( uint64_t value ) { if ( 0 == value ) return 0; static const uint32_t tab64[64] = { 63, 0, 58, 1, 59, 47, 53, 2, 60, 39, 48, 27, 54, 33, 42, 3, 61, 51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22, 4, 62, 57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21, 56, 45, 25, 31, 35, 16, 9, 12, 44, 24, 15, 8, 23, 7, 6, 5 }; value |= value >> 1; value |= value >> 2; value |= value >> 4; value |= value >> 8; value |= value >> 16; value |= value >> 32; return tab64[( static_cast< uint64_t >( ( value - ( value >> 1 ) ) * 0x07EDD5E59A4E28C2 ) ) >> 58]; } uint32_t log2_32( uint32_t value ) { static const uint32_t tab32[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 }; value |= value >> 1; value |= value >> 2; value |= value >> 4; value |= value >> 8; value |= value >> 16; return tab32[static_cast< uint32_t >( value * 0x07C4ACDD ) >> 27]; } uint32_t log(uint64_t x, uint64_t base) { assert(base > 1); uint32_t res = 0; while (x >= base) { ++res; x /= base; } return res; } NS_END // math NS_END // root