78 lines
1.2 KiB
Go
78 lines
1.2 KiB
Go
package rlepluslazy
|
|
|
|
import (
|
|
"github.com/multiformats/go-varint"
|
|
"golang.org/x/xerrors"
|
|
)
|
|
|
|
func DecodeRLE(buf []byte) (RunIterator, error) {
|
|
bv := readBitvec(buf)
|
|
|
|
ver := bv.Get(2) // Read version
|
|
if ver != Version {
|
|
return nil, ErrWrongVersion
|
|
}
|
|
|
|
it := &rleIterator{bv: bv}
|
|
|
|
// next run is previous in relation to prep
|
|
// so we invert the value
|
|
it.nextRun.Val = bv.Get(1) != 1
|
|
if err := it.prep(); err != nil {
|
|
return nil, err
|
|
}
|
|
return it, nil
|
|
}
|
|
|
|
type rleIterator struct {
|
|
bv *rbitvec
|
|
|
|
nextRun Run
|
|
}
|
|
|
|
func (it *rleIterator) HasNext() bool {
|
|
return it.nextRun.Valid()
|
|
}
|
|
|
|
func (it *rleIterator) NextRun() (Run, error) {
|
|
ret := it.nextRun
|
|
return ret, it.prep()
|
|
}
|
|
|
|
func (it *rleIterator) prep() error {
|
|
x := it.bv.Get(1)
|
|
|
|
switch x {
|
|
case 1:
|
|
it.nextRun.Len = 1
|
|
|
|
case 0:
|
|
y := it.bv.Get(1)
|
|
switch y {
|
|
case 1:
|
|
it.nextRun.Len = uint64(it.bv.Get(4))
|
|
case 0:
|
|
var buf = make([]byte, 0, 10)
|
|
for {
|
|
b := it.bv.Get(8)
|
|
buf = append(buf, b)
|
|
if b&0x80 == 0 {
|
|
break
|
|
}
|
|
if len(buf) > 10 {
|
|
return xerrors.Errorf("run too long: %w", ErrDecode)
|
|
}
|
|
}
|
|
var err error
|
|
it.nextRun.Len, _, err = varint.FromUvarint(buf)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
}
|
|
}
|
|
|
|
it.nextRun.Val = !it.nextRun.Val
|
|
return nil
|
|
}
|