40 lines
1.2 KiB
Go
40 lines
1.2 KiB
Go
// Copyright 2018 Google Inc. 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.
|
|
|
|
// +build go1.9
|
|
|
|
package s2
|
|
|
|
// This file is for the bit manipulation code post-Go 1.9.
|
|
|
|
import "math/bits"
|
|
|
|
// findMSBSetNonZero64 returns the index (between 0 and 63) of the most
|
|
// significant set bit. Passing zero to this function return zero.
|
|
func findMSBSetNonZero64(x uint64) int {
|
|
if x == 0 {
|
|
return 0
|
|
}
|
|
return 63 - bits.LeadingZeros64(x)
|
|
}
|
|
|
|
// findLSBSetNonZero64 returns the index (between 0 and 63) of the least
|
|
// significant set bit. Passing zero to this function return zero.
|
|
func findLSBSetNonZero64(x uint64) int {
|
|
if x == 0 {
|
|
return 0
|
|
}
|
|
return bits.TrailingZeros64(x)
|
|
}
|