111 lines
1.9 KiB
Go
111 lines
1.9 KiB
Go
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package rlepluslazy
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import (
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"encoding/binary"
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"errors"
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"fmt"
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bitvector "github.com/filecoin-project/go-lotus/lib/rlepluslazy/internal"
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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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vec *bitvector.BitVector
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}
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func FromBuf(buf []byte) (*RLE, error) {
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rle := &RLE{vec: bitvector.NewBitVector(buf, bitvector.LSB0)}
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if err := rle.check(); err != nil {
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return nil, xerrors.Errorf("could not create RLE+ for a buffer: %w", err)
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}
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return rle, nil
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}
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func (rle *RLE) check() error {
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ver := rle.vec.Take(0, 2, bitvector.LSB0)
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if ver != Version {
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return ErrWrongVersion
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}
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return nil
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}
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func (rle *RLE) Iterator() (*iterator, error) {
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vit := rle.vec.Iterator(bitvector.LSB0)
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vit(2) // Take version
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it := &iterator{next: vit}
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if err := it.prep(vit(1)); err != nil {
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return nil, err
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}
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return it, nil
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}
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type iterator struct {
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next func(uint) byte
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curIdx uint64
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rep uint64
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}
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func (it *iterator) HasNext() bool {
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return it.rep != 0
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}
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func (it *iterator) prep(curBit byte) error {
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loop:
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for it.rep == 0 {
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x := it.next(1)
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switch x {
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case 1:
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it.rep = 1
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case 0:
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y := it.next(1)
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switch y {
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case 1:
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it.rep = uint64(it.next(4))
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case 0:
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var buf = make([]byte, 0, 10)
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for {
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b := it.next(8)
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buf = append(buf, b)
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if b&0x80 == 0 {
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break
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}
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if len(buf) > 10 {
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return xerrors.Errorf("run too long: %w", ErrDecode)
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}
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}
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it.rep, _ = binary.Uvarint(buf)
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}
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// run with 0 length means end
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if it.rep == 0 {
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break loop
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}
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}
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if curBit == 0 {
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curBit = 1
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it.curIdx = it.curIdx + it.rep
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it.rep = 0
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}
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}
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return nil
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}
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func (it *iterator) Next() (uint64, error) {
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it.rep--
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res := it.curIdx
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it.curIdx++
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return res, it.prep(0)
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}
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