tidb gbk_bin 源码
tidb gbk_bin 代码
文件路径：/util/collate/gbk_bin.go
// Copyright 2021 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package collate
import (
"bytes"
"github.com/pingcap/tidb/util/hack"
"golang.org/x/text/encoding"
)
// gbkBinCollator is collator for gbk_bin.
type gbkBinCollator struct {
e *encoding.Encoder
}
// Compare implement Collator interface.
func (g *gbkBinCollator) Compare(a, b string) int {
a = truncateTailingSpace(a)
b = truncateTailingSpace(b)
// compare the character one by one.
for len(a) > 0 && len(b) > 0 {
aLen, bLen := runeLen(a[0]), runeLen(b[0])
aGbk, err := g.e.Bytes(hack.Slice(a[:aLen]))
// if convert error happened, we use '?'(0x3F) replace it.
// It should not happen.
if err != nil {
aGbk = []byte{0x3F}
}
bGbk, err := g.e.Bytes(hack.Slice(b[:bLen]))
if err != nil {
bGbk = []byte{0x3F}
}
compare := bytes.Compare(aGbk, bGbk)
if compare != 0 {
return compare
}
a = a[aLen:]
b = b[bLen:]
}
return sign(len(a) - len(b))
}
// Key implement Collator interface.
func (g *gbkBinCollator) Key(str string) []byte {
return g.KeyWithoutTrimRightSpace(truncateTailingSpace(str))
}
// KeyWithoutTrimRightSpace implement Collator interface.
func (g *gbkBinCollator) KeyWithoutTrimRightSpace(str string) []byte {
buf := make([]byte, 0, len(str))
for len(str) > 0 {
l := runeLen(str[0])
gbk, err := g.e.Bytes(hack.Slice(str[:l]))
if err != nil {
buf = append(buf, byte('?'))
} else {
buf = append(buf, gbk...)
}
str = str[l:]
}
return buf
}
// Pattern implements Collator interface.
func (*gbkBinCollator) Pattern() WildcardPattern {
return &gbkBinPattern{}
}
// use binPattern directly, they are totally same.
type gbkBinPattern struct {
binPattern
}
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