74 lines
1.2 KiB
Go
74 lines
1.2 KiB
Go
package rlepluslazy
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import (
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"encoding/binary"
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"golang.org/x/xerrors"
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)
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func DecodeRLE(buf []byte) (RunIterator, error) {
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bv := readBitvec(buf)
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ver := bv.Get(2) // Read version
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if ver != Version {
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return nil, ErrWrongVersion
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}
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it := &rleIterator{bv: bv}
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// next run is previous in relation to prep
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// so we invert the value
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it.nextRun.Val = bv.Get(1) != 1
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if err := it.prep(); 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 rleIterator struct {
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bv *rbitvec
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nextRun Run
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}
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func (it *rleIterator) HasNext() bool {
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return it.nextRun.Valid()
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}
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func (it *rleIterator) NextRun() (Run, error) {
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ret := it.nextRun
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return ret, it.prep()
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}
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func (it *rleIterator) prep() error {
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x := it.bv.Get(1)
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switch x {
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case 1:
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it.nextRun.Len = 1
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case 0:
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y := it.bv.Get(1)
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switch y {
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case 1:
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it.nextRun.Len = uint64(it.bv.Get(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.bv.Get(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.nextRun.Len, _ = binary.Uvarint(buf)
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}
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}
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it.nextRun.Val = !it.nextRun.Val
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return nil
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}
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