Current File : //usr/local/go/src/cmd/compile/internal/bitvec/bv.go
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package bitvec
import (
"math/bits"
"cmd/compile/internal/base"
)
const (
wordBits = 32
wordMask = wordBits - 1
wordShift = 5
)
// A BitVec is a bit vector.
type BitVec struct {
N int32 // number of bits in vector
B []uint32 // words holding bits
}
func New(n int32) BitVec {
nword := (n + wordBits - 1) / wordBits
return BitVec{n, make([]uint32, nword)}
}
type Bulk struct {
words []uint32
nbit int32
nword int32
}
func NewBulk(nbit int32, count int32) Bulk {
nword := (nbit + wordBits - 1) / wordBits
size := int64(nword) * int64(count)
if int64(int32(size*4)) != size*4 {
base.Fatalf("NewBulk too big: nbit=%d count=%d nword=%d size=%d", nbit, count, nword, size)
}
return Bulk{
words: make([]uint32, size),
nbit: nbit,
nword: nword,
}
}
func (b *Bulk) Next() BitVec {
out := BitVec{b.nbit, b.words[:b.nword]}
b.words = b.words[b.nword:]
return out
}
func (bv1 BitVec) Eq(bv2 BitVec) bool {
if bv1.N != bv2.N {
base.Fatalf("bvequal: lengths %d and %d are not equal", bv1.N, bv2.N)
}
for i, x := range bv1.B {
if x != bv2.B[i] {
return false
}
}
return true
}
func (dst BitVec) Copy(src BitVec) {
copy(dst.B, src.B)
}
func (bv BitVec) Get(i int32) bool {
if i < 0 || i >= bv.N {
base.Fatalf("bvget: index %d is out of bounds with length %d\n", i, bv.N)
}
mask := uint32(1 << uint(i%wordBits))
return bv.B[i>>wordShift]&mask != 0
}
func (bv BitVec) Set(i int32) {
if i < 0 || i >= bv.N {
base.Fatalf("bvset: index %d is out of bounds with length %d\n", i, bv.N)
}
mask := uint32(1 << uint(i%wordBits))
bv.B[i/wordBits] |= mask
}
func (bv BitVec) Unset(i int32) {
if i < 0 || i >= bv.N {
base.Fatalf("bvunset: index %d is out of bounds with length %d\n", i, bv.N)
}
mask := uint32(1 << uint(i%wordBits))
bv.B[i/wordBits] &^= mask
}
// bvnext returns the smallest index >= i for which bvget(bv, i) == 1.
// If there is no such index, bvnext returns -1.
func (bv BitVec) Next(i int32) int32 {
if i >= bv.N {
return -1
}
// Jump i ahead to next word with bits.
if bv.B[i>>wordShift]>>uint(i&wordMask) == 0 {
i &^= wordMask
i += wordBits
for i < bv.N && bv.B[i>>wordShift] == 0 {
i += wordBits
}
}
if i >= bv.N {
return -1
}
// Find 1 bit.
w := bv.B[i>>wordShift] >> uint(i&wordMask)
i += int32(bits.TrailingZeros32(w))
return i
}
func (bv BitVec) IsEmpty() bool {
for _, x := range bv.B {
if x != 0 {
return false
}
}
return true
}
func (bv BitVec) Not() {
for i, x := range bv.B {
bv.B[i] = ^x
}
}
// union
func (dst BitVec) Or(src1, src2 BitVec) {
if len(src1.B) == 0 {
return
}
_, _ = dst.B[len(src1.B)-1], src2.B[len(src1.B)-1] // hoist bounds checks out of the loop
for i, x := range src1.B {
dst.B[i] = x | src2.B[i]
}
}
// intersection
func (dst BitVec) And(src1, src2 BitVec) {
if len(src1.B) == 0 {
return
}
_, _ = dst.B[len(src1.B)-1], src2.B[len(src1.B)-1] // hoist bounds checks out of the loop
for i, x := range src1.B {
dst.B[i] = x & src2.B[i]
}
}
// difference
func (dst BitVec) AndNot(src1, src2 BitVec) {
if len(src1.B) == 0 {
return
}
_, _ = dst.B[len(src1.B)-1], src2.B[len(src1.B)-1] // hoist bounds checks out of the loop
for i, x := range src1.B {
dst.B[i] = x &^ src2.B[i]
}
}
func (bv BitVec) String() string {
s := make([]byte, 2+bv.N)
copy(s, "#*")
for i := int32(0); i < bv.N; i++ {
ch := byte('0')
if bv.Get(i) {
ch = '1'
}
s[2+i] = ch
}
return string(s)
}
func (bv BitVec) Clear() {
for i := range bv.B {
bv.B[i] = 0
}
}
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