tidb encoding_ascii 代码
文件路径：/parser/charset/encoding_ascii.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,
/ See the License for the specific language governing permissions and
/ limitations under the License.
package charset
import (
"bytes"
go_unicode "unicode"
"golang.org/x/text/encoding"
)
/ EncodingASCIIImpl is the instance of encodingASCII
var EncodingASCIIImpl = &encodingASCII{encodingBase{enc: encoding.Nop}}
func init() {
EncodingASCIIImpl.self = EncodingASCIIImpl
}
/ encodingASCII is the ASCII encoding.
type encodingASCII struct {
encodingBase
}
/ Name implements Encoding interface.
func (*encodingASCII) Name() string {
return CharsetASCII
}
/ Tp implements Encoding interface.
func (*encodingASCII) Tp() EncodingTp {
return EncodingTpASCII
}
/ Peek implements Encoding interface.
func (*encodingASCII) Peek(src []byte) []byte {
if len(src) == 0 {
return src
}
return src[:1]
}
/ IsValid implements Encoding interface.
func (*encodingASCII) IsValid(src []byte) bool {
srcLen := len(src)
for i := 0; i < srcLen; i++ {
if src[i] > go_unicode.MaxASCII {
return false
}
}
return true
}
/ Transform implements Encoding interface.
func (e *encodingASCII) Transform(dest *bytes.Buffer, src []byte, op Op) ([]byte, error) {
if e.IsValid(src) {
return src, nil
}
return e.encodingBase.Transform(dest, src, op)
}
/ Foreach implements Encoding interface.
func (*encodingASCII) Foreach(src []byte, _ Op, fn func(from, to []byte, ok bool) bool) {
for i, w := 0, 0; i < len(src); i += w {
w = 1
ok := true
if src[i] > go_unicode.MaxASCII {
w = len(EncodingUTF8Impl.Peek(src[i:]))
ok = false
}
if !fn(src[i:i+w], src[i:i+w], ok) {
return
}
}
}