mirror of git://gcc.gnu.org/git/gcc.git
109 lines
2.7 KiB
Go
109 lines
2.7 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Package utf16 implements encoding and decoding of UTF-16 sequences.
|
|
package utf16
|
|
|
|
// The conditions replacementChar==unicode.ReplacementChar and
|
|
// maxRune==unicode.MaxRune are verified in the tests.
|
|
// Defining them locally avoids this package depending on package unicode.
|
|
|
|
const (
|
|
replacementChar = '\uFFFD' // Unicode replacement character
|
|
maxRune = '\U0010FFFF' // Maximum valid Unicode code point.
|
|
)
|
|
|
|
const (
|
|
// 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.
|
|
surr1 = 0xd800
|
|
surr2 = 0xdc00
|
|
surr3 = 0xe000
|
|
|
|
surrSelf = 0x10000
|
|
)
|
|
|
|
// IsSurrogate returns true if the specified Unicode code point
|
|
// can appear in a surrogate pair.
|
|
func IsSurrogate(r rune) bool {
|
|
return surr1 <= r && r < surr3
|
|
}
|
|
|
|
// DecodeRune returns the UTF-16 decoding of a surrogate pair.
|
|
// If the pair is not a valid UTF-16 surrogate pair, DecodeRune returns
|
|
// the Unicode replacement code point U+FFFD.
|
|
func DecodeRune(r1, r2 rune) rune {
|
|
if surr1 <= r1 && r1 < surr2 && surr2 <= r2 && r2 < surr3 {
|
|
return (r1-surr1)<<10 | (r2 - surr2) + 0x10000
|
|
}
|
|
return replacementChar
|
|
}
|
|
|
|
// EncodeRune returns the UTF-16 surrogate pair r1, r2 for the given rune.
|
|
// If the rune is not a valid Unicode code point or does not need encoding,
|
|
// EncodeRune returns U+FFFD, U+FFFD.
|
|
func EncodeRune(r rune) (r1, r2 rune) {
|
|
if r < surrSelf || r > maxRune || IsSurrogate(r) {
|
|
return replacementChar, replacementChar
|
|
}
|
|
r -= surrSelf
|
|
return surr1 + (r>>10)&0x3ff, surr2 + r&0x3ff
|
|
}
|
|
|
|
// Encode returns the UTF-16 encoding of the Unicode code point sequence s.
|
|
func Encode(s []rune) []uint16 {
|
|
n := len(s)
|
|
for _, v := range s {
|
|
if v >= surrSelf {
|
|
n++
|
|
}
|
|
}
|
|
|
|
a := make([]uint16, n)
|
|
n = 0
|
|
for _, v := range s {
|
|
switch {
|
|
case v < 0, surr1 <= v && v < surr3, v > maxRune:
|
|
v = replacementChar
|
|
fallthrough
|
|
case v < surrSelf:
|
|
a[n] = uint16(v)
|
|
n++
|
|
default:
|
|
r1, r2 := EncodeRune(v)
|
|
a[n] = uint16(r1)
|
|
a[n+1] = uint16(r2)
|
|
n += 2
|
|
}
|
|
}
|
|
return a[0:n]
|
|
}
|
|
|
|
// Decode returns the Unicode code point sequence represented
|
|
// by the UTF-16 encoding s.
|
|
func Decode(s []uint16) []rune {
|
|
a := make([]rune, len(s))
|
|
n := 0
|
|
for i := 0; i < len(s); i++ {
|
|
switch r := s[i]; {
|
|
case surr1 <= r && r < surr2 && i+1 < len(s) &&
|
|
surr2 <= s[i+1] && s[i+1] < surr3:
|
|
// valid surrogate sequence
|
|
a[n] = DecodeRune(rune(r), rune(s[i+1]))
|
|
i++
|
|
n++
|
|
case surr1 <= r && r < surr3:
|
|
// invalid surrogate sequence
|
|
a[n] = replacementChar
|
|
n++
|
|
default:
|
|
// normal rune
|
|
a[n] = rune(r)
|
|
n++
|
|
}
|
|
}
|
|
return a[0:n]
|
|
}
|