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utf16.go
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utf16.go
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/*
Copyright 2021 The Vitess Authors.
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 unicode
import (
"unicode/utf16"
"unicode/utf8"
"vitess.io/vitess/go/mysql/collations/charset/types"
)
// 0xd800-0xdc00 encodes the high 10 bits of a pair.
// 0xdc00-0xe000 encodes the low 10 bits of a pair.
// the value is those 20 bits plus 0x10000.
const (
surr1 = 0xd800
surr2 = 0xdc00
surr3 = 0xe000
surrSelf = 0x10000
)
type Charset_utf16be struct{}
func (Charset_utf16be) Name() string {
return "utf16"
}
func (Charset_utf16be) IsSuperset(other types.Charset) bool {
switch other.(type) {
case Charset_utf16be, Charset_ucs2:
return true
default:
return false
}
}
func (Charset_utf16be) EncodeRune(dst []byte, r rune) int {
_ = dst[3]
if r <= 0xffff {
dst[0] = uint8(r >> 8)
dst[1] = uint8(r)
return 2
} else {
r1, r2 := utf16.EncodeRune(r)
dst[0] = uint8(r1 >> 8)
dst[1] = uint8(r1)
dst[2] = uint8(r2 >> 8)
dst[3] = uint8(r2)
return 4
}
}
func (Charset_utf16be) DecodeRune(b []byte) (rune, int) {
if len(b) < 2 {
return utf8.RuneError, 0
}
r1 := uint16(b[1]) | uint16(b[0])<<8
if r1 < surr1 || surr3 <= r1 {
return rune(r1), 2
}
if len(b) < 4 {
return utf8.RuneError, 0
}
r2 := uint16(b[3]) | uint16(b[2])<<8
if surr1 <= r1 && r1 < surr2 && surr2 <= r2 && r2 < surr3 {
return (rune(r1)-surr1)<<10 | (rune(r2) - surr2) + surrSelf, 4
}
return utf8.RuneError, 1
}
func (Charset_utf16be) SupportsSupplementaryChars() bool {
return true
}
func (Charset_utf16be) MaxWidth() int {
return 4
}
type Charset_utf16le struct{}
func (Charset_utf16le) Name() string {
return "utf16le"
}
func (Charset_utf16le) IsSuperset(other types.Charset) bool {
switch other.(type) {
case Charset_utf16le:
return true
default:
return false
}
}
func (Charset_utf16le) EncodeRune(dst []byte, r rune) int {
_ = dst[3]
if r <= 0xffff {
dst[0] = uint8(r)
dst[1] = uint8(r >> 8)
return 2
} else {
r1, r2 := utf16.EncodeRune(r)
dst[0] = uint8(r1)
dst[1] = uint8(r1 >> 8)
dst[2] = uint8(r2)
dst[3] = uint8(r2 >> 8)
return 4
}
}
func (Charset_utf16le) DecodeRune(b []byte) (rune, int) {
if len(b) < 2 {
return utf8.RuneError, 0
}
r1 := uint16(b[0]) | uint16(b[1])<<8
if r1 < surr1 || surr3 <= r1 {
return rune(r1), 2
}
if len(b) < 4 {
return utf8.RuneError, 0
}
r2 := uint16(b[2]) | uint16(b[3])<<8
if surr1 <= r1 && r1 < surr2 && surr2 <= r2 && r2 < surr3 {
return (rune(r1)-surr1)<<10 | (rune(r2) - surr2) + surrSelf, 4
}
return utf8.RuneError, 1
}
func (Charset_utf16le) SupportsSupplementaryChars() bool {
return true
}
func (Charset_utf16le) MaxWidth() int {
return 4
}
type Charset_ucs2 struct{}
func (Charset_ucs2) Name() string {
return "ucs2"
}
func (Charset_ucs2) IsSuperset(other types.Charset) bool {
switch other.(type) {
case Charset_ucs2:
return true
default:
return false
}
}
func (Charset_ucs2) EncodeRune(dst []byte, r rune) int {
_ = dst[1]
if r <= 0xffff {
dst[0] = uint8(r >> 8)
dst[1] = uint8(r)
return 2
}
return -1
}
func (Charset_ucs2) DecodeRune(p []byte) (rune, int) {
if len(p) < 2 {
return utf8.RuneError, 0
}
return rune(p[0])<<8 | rune(p[1]), 2
}
func (Charset_ucs2) SupportsSupplementaryChars() bool {
return false
}
func (Charset_ucs2) Length(src []byte) int {
cnt := len(src)
if cnt%2 != 0 {
return cnt/2 + 1
}
return cnt / 2
}
func (Charset_ucs2) MaxWidth() int {
return 2
}