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bits.go
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bits.go
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// Copyright 2023 Sneller, Inc.
//
// 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.
// Package ints provides int-related common functions.
package ints
import (
"unsafe"
"golang.org/x/exp/constraints"
)
// TestBit check if the k-th bit is set in range "in"
func TestBit[T, K constraints.Integer](in []T, k K) bool {
return (in[uintptr(k)/(unsafe.Sizeof(in[0])*8)] & (T(1) << (uintptr(k) % (unsafe.Sizeof(in[0]) * 8)))) != 0
}
// SetBit sets the k-th bit in range "in"
func SetBit[T, K constraints.Integer](in []T, k K) {
in[uintptr(k)/(unsafe.Sizeof(in[0])*8)] |= (T(1) << (uintptr(k) % (unsafe.Sizeof(in[0]) * 8)))
}
// ClearBit clears the k-th bit in range "in"
func ClearBit[T, K constraints.Integer](in []T, k K) {
in[uintptr(k)/(unsafe.Sizeof(in[0])*8)] &= ^(T(1) << (uintptr(k) % (unsafe.Sizeof(in[0]) * 8)))
}
// FlipBit inverts the k-th bit in range "in"
func FlipBit[T, K constraints.Integer](in []T, k K) {
in[uintptr(k)/(unsafe.Sizeof(in[0])*8)] ^= (T(1) << (uintptr(k) % (unsafe.Sizeof(in[0]) * 8)))
}
// SetBits sets the bits [first, last) in range "in"
func SetBits[T, K constraints.Integer](in []T, first, last K) {
bitsPerT := unsafe.Sizeof(in[0]) * 8
mskT := bitsPerT - 1
ones := (uint64(1) << bitsPerT) - 1
firstIdx := uintptr(first) / bitsPerT
firstMask := T(ones << (uintptr(first) & mskT))
lastIdx := uintptr(last-1) / bitsPerT
lastMask := T(ones >> ((uintptr(last-1) & mskT) ^ mskT))
if firstIdx == lastIdx {
in[firstIdx] |= (firstMask & lastMask)
} else {
in[firstIdx] |= firstMask
for i := firstIdx + 1; i != lastIdx; i++ {
in[i] = ^T(0)
}
in[lastIdx] |= lastMask
}
}
// ClearBits clears the bits [first, last) in range "in"
func ClearBits[T, K constraints.Integer](in []T, first, last K) {
bitsPerT := unsafe.Sizeof(in[0]) * 8
mskT := bitsPerT - 1
ones := (uint64(1) << bitsPerT) - 1
firstIdx := uintptr(first) / bitsPerT
firstMask := T(ones << (uintptr(first) & mskT))
lastIdx := uintptr(last-1) / bitsPerT
lastMask := T(ones >> ((uintptr(last-1) & mskT) ^ mskT))
if firstIdx == lastIdx {
in[firstIdx] &= ^(firstMask & lastMask)
} else {
in[firstIdx] &= ^firstMask
for i := firstIdx + 1; i != lastIdx; i++ {
in[i] = T(0)
}
in[lastIdx] &= ^lastMask
}
}
// FlipBits inverts the bits [first, last) in range "in"
func FlipBits[T, K constraints.Integer](in []T, first, last K) {
bitsPerT := unsafe.Sizeof(in[0]) * 8
mskT := bitsPerT - 1
ones := (uint64(1) << bitsPerT) - 1
firstIdx := uintptr(first) / bitsPerT
firstMask := T(ones << (uintptr(first) & mskT))
lastIdx := uintptr(last-1) / bitsPerT
lastMask := T(ones >> ((uintptr(last-1) & mskT) ^ mskT))
if firstIdx == lastIdx {
in[firstIdx] ^= (firstMask & lastMask)
} else {
in[firstIdx] ^= firstMask
for i := firstIdx + 1; i != lastIdx; i++ {
in[i] ^= ^T(0)
}
in[lastIdx] ^= lastMask
}
}