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290 lines
5.6 KiB
290 lines
5.6 KiB
package common
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import (
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"encoding/binary"
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"fmt"
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"math/rand"
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"strings"
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"sync"
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)
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type BitArray struct {
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mtx sync.Mutex
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Bits int `json:"bits"` // NOTE: persisted via reflect, must be exported
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Elems []uint64 `json:"elems"` // NOTE: persisted via reflect, must be exported
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}
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// There is no BitArray whose Size is 0. Use nil instead.
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func NewBitArray(bits int) *BitArray {
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if bits == 0 {
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return nil
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}
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return &BitArray{
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Bits: bits,
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Elems: make([]uint64, (bits+63)/64),
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}
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}
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func (bA *BitArray) Size() int {
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if bA == nil {
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return 0
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}
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return bA.Bits
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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 int) bool {
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if bA == nil {
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return false
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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return bA.getIndex(i)
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}
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func (bA *BitArray) getIndex(i int) 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)<<uint(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 int, v bool) bool {
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if bA == nil {
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return false
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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return bA.setIndex(i, v)
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}
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func (bA *BitArray) setIndex(i int, 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) << uint(i%64))
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} else {
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bA.Elems[i/64] &= ^(uint64(1) << uint(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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if bA == nil {
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return nil
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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return bA.copy()
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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{
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Bits: bA.Bits,
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Elems: c,
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}
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}
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func (bA *BitArray) copyBits(bits int) *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{
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Bits: bits,
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Elems: c,
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}
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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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if bA == nil {
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o.Copy()
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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c := bA.copyBits(MaxInt(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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if bA == nil {
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return nil
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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return bA.and(o)
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}
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func (bA *BitArray) and(o *BitArray) *BitArray {
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c := bA.copyBits(MinInt(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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if bA == nil {
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return nil // Degenerate
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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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 == nil {
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return nil
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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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 := 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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// NOTE: each individual GetIndex() call to o is safe.
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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()) // Note degenerate case where o == nil
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}
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}
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func (bA *BitArray) IsFull() bool {
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if bA == nil {
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return true
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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// Check all elements except the last
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for _, elem := range bA.Elems[:len(bA.Elems)-1] {
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if (^elem) != 0 {
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return false
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}
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}
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// Check that the last element has (lastElemBits) 1's
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lastElemBits := (bA.Bits+63)%64 + 1
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lastElem := bA.Elems[len(bA.Elems)-1]
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return (lastElem+1)&((uint64(1)<<uint(lastElemBits))-1) == 0
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}
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func (bA *BitArray) PickRandom() (int, bool) {
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if bA == nil {
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return 0, false
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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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] & (uint64(1) << uint(bitIdx))) > 0 {
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return 64*elemIdx + bitIdx, true
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}
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}
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PanicSanity("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 := 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] & (uint64(1) << uint(bitIdx))) > 0 {
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return 64*elemIdx + 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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if bA == nil {
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return "nil-BitArray"
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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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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if bA == nil {
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return "nil-BitArray"
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}
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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return bA.stringIndented(indent)
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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 := 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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func (bA *BitArray) Bytes() []byte {
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bA.mtx.Lock()
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defer bA.mtx.Unlock()
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numBytes := (bA.Bits + 7) / 8
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bytes := make([]byte, numBytes)
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for i := 0; i < len(bA.Elems); i++ {
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elemBytes := [8]byte{}
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binary.LittleEndian.PutUint64(elemBytes[:], bA.Elems[i])
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copy(bytes[i*8:], elemBytes[:])
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}
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return bytes
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}
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