56 lines
1.4 KiB
Go
56 lines
1.4 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build !amd64
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package bits
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// TrailingZeros64 returns the number of bits before the least significant 1
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// bit in x; in other words, it returns the index of the least significant 1
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// bit in x. If x is 0, TrailingZeros64 returns 64.
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func TrailingZeros64(x uint64) int {
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if x == 0 {
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return 64
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}
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i := 0
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for ; x&1 == 0; i++ {
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x >>= 1
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}
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return i
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}
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// MostSignificantOne64 returns the index of the most significant 1 bit in
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// x. If x is 0, MostSignificantOne64 returns 64.
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func MostSignificantOne64(x uint64) int {
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if x == 0 {
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return 64
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}
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i := 63
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for ; x&(1<<63) == 0; i-- {
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x <<= 1
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}
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return i
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}
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// ForEachSetBit64 calls f once for each set bit in x, with argument i equal to
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// the set bit's index.
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func ForEachSetBit64(x uint64, f func(i int)) {
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for i := 0; x != 0; i++ {
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if x&1 != 0 {
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f(i)
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}
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x >>= 1
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}
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}
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