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171 lines
3.5 KiB
171 lines
3.5 KiB
package binary
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import (
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"fmt"
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"math/rand"
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"strings"
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. "github.com/tendermint/tendermint/common"
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)
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// Not goroutine safe
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type BitArray struct {
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Bits uint // NOTE: persisted via reflect, must be exported
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Elems []uint64 // NOTE: persisted via reflect, must be exported
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}
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func NewBitArray(bits uint) BitArray {
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return BitArray{bits, make([]uint64, (bits+63)/64)}
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}
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func (bA BitArray) Size() uint {
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return bA.Bits
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}
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func (bA BitArray) IsZero() bool {
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return bA.Bits == 0
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}
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// NOTE: behavior is undefined if i >= bA.Bits
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func (bA BitArray) GetIndex(i uint) bool {
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if i >= bA.Bits {
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return false
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}
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return bA.Elems[i/64]&uint64(1<<(i%64)) > 0
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}
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// NOTE: behavior is undefined if i >= bA.Bits
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func (bA BitArray) SetIndex(i uint, v bool) bool {
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if i >= bA.Bits {
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return false
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}
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if v {
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bA.Elems[i/64] |= uint64(1 << (i % 64))
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} else {
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bA.Elems[i/64] &= ^uint64(1 << (i % 64))
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}
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return true
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}
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func (bA BitArray) Copy() BitArray {
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c := make([]uint64, len(bA.Elems))
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copy(c, bA.Elems)
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return BitArray{bA.Bits, c}
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}
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func (bA BitArray) copyBits(bits uint) BitArray {
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c := make([]uint64, (bits+63)/64)
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copy(c, bA.Elems)
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return BitArray{bits, c}
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}
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// Returns a BitArray of larger bits size.
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func (bA BitArray) Or(o BitArray) BitArray {
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c := bA.copyBits(MaxUint(bA.Bits, o.Bits))
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for i := 0; i < len(c.Elems); i++ {
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c.Elems[i] |= o.Elems[i]
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}
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return c
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}
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// Returns a BitArray of smaller bit size.
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func (bA BitArray) And(o BitArray) BitArray {
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c := bA.copyBits(MinUint(bA.Bits, o.Bits))
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for i := 0; i < len(c.Elems); i++ {
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c.Elems[i] &= o.Elems[i]
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}
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return c
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}
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func (bA BitArray) Not() BitArray {
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c := bA.Copy()
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for i := 0; i < len(c.Elems); i++ {
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c.Elems[i] = ^c.Elems[i]
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}
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return c
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}
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func (bA BitArray) Sub(o BitArray) BitArray {
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if bA.Bits > o.Bits {
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c := bA.Copy()
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for i := 0; i < len(o.Elems)-1; i++ {
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c.Elems[i] &= ^c.Elems[i]
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}
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i := uint(len(o.Elems) - 1)
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if i >= 0 {
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for idx := i * 64; idx < o.Bits; idx++ {
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c.SetIndex(idx, c.GetIndex(idx) && !o.GetIndex(idx))
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}
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}
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return c
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} else {
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return bA.And(o.Not())
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}
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}
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func (bA BitArray) PickRandom() (uint, bool) {
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length := len(bA.Elems)
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if length == 0 {
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return 0, false
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}
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randElemStart := rand.Intn(length)
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for i := 0; i < length; i++ {
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elemIdx := ((i + randElemStart) % length)
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if elemIdx < length-1 {
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if bA.Elems[elemIdx] > 0 {
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randBitStart := rand.Intn(64)
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for j := 0; j < 64; j++ {
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bitIdx := ((j + randBitStart) % 64)
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if (bA.Elems[elemIdx] & (1 << uint(bitIdx))) > 0 {
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return 64*uint(elemIdx) + uint(bitIdx), true
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}
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}
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panic("should not happen")
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}
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} else {
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// Special case for last elem, to ignore straggler bits
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elemBits := int(bA.Bits) % 64
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if elemBits == 0 {
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elemBits = 64
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}
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randBitStart := rand.Intn(elemBits)
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for j := 0; j < elemBits; j++ {
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bitIdx := ((j + randBitStart) % elemBits)
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if (bA.Elems[elemIdx] & (1 << uint(bitIdx))) > 0 {
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return 64*uint(elemIdx) + uint(bitIdx), true
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}
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}
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}
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}
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return 0, false
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}
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func (bA BitArray) String() string {
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return bA.StringIndented("")
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}
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func (bA BitArray) StringIndented(indent string) string {
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lines := []string{}
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bits := ""
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for i := uint(0); i < bA.Bits; i++ {
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if bA.GetIndex(i) {
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bits += "X"
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} else {
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bits += "_"
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}
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if i%100 == 99 {
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lines = append(lines, bits)
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bits = ""
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}
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if i%10 == 9 {
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bits += " "
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}
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if i%50 == 49 {
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bits += " "
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}
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}
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if len(bits) > 0 {
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lines = append(lines, bits)
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}
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return fmt.Sprintf("BA{%v:%v}", bA.Bits, strings.Join(lines, indent))
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}
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