1 // Copyright 2018 Google Inc. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 //go:build go1.9 16 // +build go1.9 17 18 package s2 19 20 // This file is for the bit manipulation code post-Go 1.9. 21 22 import "math/bits" 23 24 // findMSBSetNonZero64 returns the index (between 0 and 63) of the most 25 // significant set bit. Passing zero to this function return zero. 26 func findMSBSetNonZero64(x uint64) int { 27 if x == 0 { 28 return 0 29 } 30 return 63 - bits.LeadingZeros64(x) 31 } 32 33 // findLSBSetNonZero64 returns the index (between 0 and 63) of the least 34 // significant set bit. Passing zero to this function return zero. 35 func findLSBSetNonZero64(x uint64) int { 36 if x == 0 { 37 return 0 38 } 39 return bits.TrailingZeros64(x) 40 } 41