forked from tikv/client-go
/
bytes.go
83 lines (70 loc) · 2.17 KB
/
bytes.go
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// Copyright 2018 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package codec
import (
"bytes"
"github.com/pkg/errors"
)
const (
encGroupSize = 8
encMarker = byte(0xFF)
encPad = byte(0x0)
)
var pads = make([]byte, encGroupSize)
// DecodeBytes decodes a TiDB encoded byte slice.
func DecodeBytes(b []byte) ([]byte, []byte, error) {
buf := make([]byte, 0, len(b)/(encGroupSize+1)*encGroupSize)
for {
if len(b) < encGroupSize+1 {
return nil, nil, errors.New("insufficient bytes to decode value")
}
groupBytes := b[:encGroupSize+1]
group := groupBytes[:encGroupSize]
marker := groupBytes[encGroupSize]
padCount := encMarker - marker
if padCount > encGroupSize {
return nil, nil, errors.Errorf("invalid marker byte, group bytes %q", groupBytes)
}
realGroupSize := encGroupSize - padCount
buf = append(buf, group[:realGroupSize]...)
b = b[encGroupSize+1:]
if padCount != 0 {
// Check validity of padding bytes.
if !bytes.Equal(group[realGroupSize:], pads[:padCount]) {
return nil, nil, errors.Errorf("invalid padding byte, group bytes %q", groupBytes)
}
break
}
}
return b, buf, nil
}
// EncodeBytes encodes a byte slice into TiDB's encoded form.
func EncodeBytes(b []byte) []byte {
dLen := len(b)
reallocSize := (dLen/encGroupSize + 1) * (encGroupSize + 1)
result := make([]byte, 0, reallocSize)
for idx := 0; idx <= dLen; idx += encGroupSize {
remain := dLen - idx
padCount := 0
if remain >= encGroupSize {
result = append(result, b[idx:idx+encGroupSize]...)
} else {
padCount = encGroupSize - remain
result = append(result, b[idx:]...)
result = append(result, pads[:padCount]...)
}
marker := encMarker - byte(padCount)
result = append(result, marker)
}
return result
}