github.com/MerlinKodo/gvisor@v0.0.0-20231110090155-957f62ecf90e/pkg/bits/uint64_arch.go (about)

     1  // Copyright 2018 The gVisor Authors.
     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 amd64 || arm64
    16  // +build amd64 arm64
    17  
    18  package bits
    19  
    20  // TrailingZeros64 returns the number of bits before the least significant 1
    21  // bit in x; in other words, it returns the index of the least significant 1
    22  // bit in x. If x is 0, TrailingZeros64 returns 64.
    23  func TrailingZeros64(x uint64) int
    24  
    25  // MostSignificantOne64 returns the index of the most significant 1 bit in
    26  // x. If x is 0, MostSignificantOne64 returns 64.
    27  func MostSignificantOne64(x uint64) int
    28  
    29  // ForEachSetBit64 calls f once for each set bit in x, with argument i equal to
    30  // the set bit's index.
    31  func ForEachSetBit64(x uint64, f func(i int)) {
    32  	for x != 0 {
    33  		i := TrailingZeros64(x)
    34  		f(i)
    35  		x &^= MaskOf64(i)
    36  	}
    37  }