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