183 lines
3.1 KiB
Go
183 lines
3.1 KiB
Go
package rlepluslazy
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import (
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"errors"
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"fmt"
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"golang.org/x/xerrors"
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)
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const Version = 0
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var (
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ErrWrongVersion = errors.New("invalid RLE+ version")
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ErrDecode = fmt.Errorf("invalid encoding for RLE+ version %d", Version)
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)
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type RLE struct {
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buf []byte
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changes []change
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}
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type change struct {
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set bool
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reset bool
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index uint64
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}
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func (c change) valid() bool {
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return c.reset || c.set
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}
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func FromBuf(buf []byte) (*RLE, error) {
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rle := &RLE{buf: buf}
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if len(buf) > 0 && buf[0]&3 != Version {
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return nil, xerrors.Errorf("could not create RLE+ for a buffer: %w", ErrWrongVersion)
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}
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return rle, nil
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}
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func (rle *RLE) RunIterator() (RunIterator, error) {
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source, err := DecodeRLE(rle.buf)
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return source, err
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}
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/*
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if err != nil {
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return nil, err
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}
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if len(rle.changes) == 0 {
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return source, nil
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}
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ch := rle.changes
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// using stable sort because we want to preserve change order
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sort.SliceStable(ch, func(i int, j int) bool {
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return ch[i].index < ch[j].index
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})
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for i := range ch {
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if i+1 >= len(ch) {
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break
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}
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if ch[i].index == ch[i+1].index {
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ch[i].set = false
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ch[i].reset = false
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}
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}
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sets := make([]uint64, 0, len(ch)/2)
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clears := make([]uint64, 0, len(ch)/2)
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for _, c := range ch {
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if c.set {
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sets = append(sets, c.index)
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} else if c.reset {
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clears = append(clears, c.index)
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}
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}
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setRuns, err := RunsFromSlice(sets)
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if err != nil {
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return nil, err
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}
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clearRuns, err := RunsFromSlice(clears)
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if err != nil {
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return nil, err
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}
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it := &chit{source: source, sets: setRuns, clears: clearRuns}
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return nil, nil
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}
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type chit struct {
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source RunIterator
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sets RunIterator
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clears RunIterator
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next Run
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nextSource Run
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nextSet Run
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nextClear Run
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}
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func (it *chit) prep() error {
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var err error
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if !it.nextSource.Valid() && it.source.HasNext() {
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it.nextSource, err = it.source.NextRun()
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if err != nil {
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return err
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}
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}
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if !it.nextSet.Valid() && it.sets.HasNext() {
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it.nextSet, err = it.sets.NextRun()
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if err != nil {
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return err
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}
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}
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if !it.nextClear.Valid() && it.clears.HasNext() {
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it.nextClear, err = it.clears.NextRun()
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if err != nil {
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return err
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}
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}
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for len(it.changes) != 0 && !it.changes[0].valid() {
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it.changes = it.changes[1:]
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}
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var ch change
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if len(it.changes) != 0 {
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ch = it.changes[0]
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}
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if it.source.HasNext() {
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var err error
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it.nextRun, err = it.source.NextRun()
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if err != nil {
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return err
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}
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}
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if ch.valid() && ch.index < it.runIndex+it.nextRun.Len {
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if ch.set != it.nextRun.Val {
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// split run
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whole := it.nextRun
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it.nextRun.Len = ch.index - it.runIndex
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}
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// if we are here then change was valid so len(it.changes) != 0
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it.changes = it.changes[1:]
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} else {
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it.runIndex = it.runIndex + it.nextRun.Len
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}
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return nil
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}
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func (it *chit) HasNext() bool {
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return it.nextRun.Valid()
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}
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func (it *chit) NextRun() (Run, error) {
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return it.nextRun, it.prep()
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}
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func (rle *RLE) Set(index uint64) {
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rle.changes = append(rle.changes, change{set: true, index: index})
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}
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func (rle *RLE) Clear(index uint64) {
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rle.changes = append(rle.changes, change{reset: true, index: index})
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}
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func (rle *RLE) Merge(other *RLE) RunIterator {
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return nil
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}
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*/
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