/
bv.go
175 lines (150 loc) · 3.22 KB
/
bv.go
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// 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 gc
const (
WORDBITS = 32
WORDMASK = WORDBITS - 1
WORDSHIFT = 5
)
// A bvec is a bit vector.
type bvec struct {
n int32 // number of bits in vector
b []uint32 // words holding bits
}
func bvalloc(n int32) bvec {
nword := (n + WORDBITS - 1) / WORDBITS
return bvec{n, make([]uint32, nword)}
}
type bulkBvec struct {
words []uint32
nbit int32
nword int32
}
func bvbulkalloc(nbit int32, count int32) bulkBvec {
nword := (nbit + WORDBITS - 1) / WORDBITS
size := int64(nword) * int64(count)
if int64(int32(size*4)) != size*4 {
Fatalf("bvbulkalloc too big: nbit=%d count=%d nword=%d size=%d", nbit, count, nword, size)
}
return bulkBvec{
words: make([]uint32, size),
nbit: nbit,
nword: nword,
}
}
func (b *bulkBvec) next() bvec {
out := bvec{b.nbit, b.words[:b.nword]}
b.words = b.words[b.nword:]
return out
}
func (bv1 bvec) Eq(bv2 bvec) bool {
if bv1.n != bv2.n {
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 bvec) Copy(src bvec) {
copy(dst.b, src.b)
}
func (bv bvec) Get(i int32) bool {
if i < 0 || i >= bv.n {
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 bvec) Set(i int32) {
if i < 0 || i >= bv.n {
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 bvec) Unset(i int32) {
if i < 0 || i >= bv.n {
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 bvec) 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)
for w&1 == 0 {
w >>= 1
i++
}
return i
}
func (bv bvec) IsEmpty() bool {
for i := int32(0); i < bv.n; i += WORDBITS {
if bv.b[i>>WORDSHIFT] != 0 {
return false
}
}
return true
}
func (bv bvec) Not() {
i := int32(0)
w := int32(0)
for ; i < bv.n; i, w = i+WORDBITS, w+1 {
bv.b[w] = ^bv.b[w]
}
}
// union
func (dst bvec) Or(src1, src2 bvec) {
for i, x := range src1.b {
dst.b[i] = x | src2.b[i]
}
}
// intersection
func (dst bvec) And(src1, src2 bvec) {
for i, x := range src1.b {
dst.b[i] = x & src2.b[i]
}
}
// difference
func (dst bvec) AndNot(src1, src2 bvec) {
for i, x := range src1.b {
dst.b[i] = x &^ src2.b[i]
}
}
func (bv bvec) 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 bvec) Clear() {
for i := range bv.b {
bv.b[i] = 0
}
}