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@mpvl @nigeltao @dsymonds @adg
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// Copyright 2013 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.
//go:generate go run maketables.go
// Package charmap provides simple character encodings such as IBM Code Page 437
// and Windows 1252.
package charmap // import "golang.org/x/text/encoding/charmap"
import (
"unicode/utf8"
"golang.org/x/text/encoding"
"golang.org/x/text/encoding/internal"
"golang.org/x/text/encoding/internal/identifier"
"golang.org/x/text/transform"
)
// These encodings vary only in the way clients should interpret them. Their
// coded character set is identical and a single implementation can be shared.
var (
// ISO8859_6E is the ISO 8859-6E encoding.
ISO8859_6E encoding.Encoding = &iso8859_6E
// ISO8859_6I is the ISO 8859-6I encoding.
ISO8859_6I encoding.Encoding = &iso8859_6I
// ISO8859_8E is the ISO 8859-8E encoding.
ISO8859_8E encoding.Encoding = &iso8859_8E
// ISO8859_8I is the ISO 8859-8I encoding.
ISO8859_8I encoding.Encoding = &iso8859_8I
iso8859_6E = internal.Encoding{
Encoding: ISO8859_6,
Name: "ISO-8859-6E",
MIB: identifier.ISO88596E,
}
iso8859_6I = internal.Encoding{
Encoding: ISO8859_6,
Name: "ISO-8859-6I",
MIB: identifier.ISO88596I,
}
iso8859_8E = internal.Encoding{
Encoding: ISO8859_8,
Name: "ISO-8859-8E",
MIB: identifier.ISO88598E,
}
iso8859_8I = internal.Encoding{
Encoding: ISO8859_8,
Name: "ISO-8859-8I",
MIB: identifier.ISO88598I,
}
)
// All is a list of all defined encodings in this package.
var All []encoding.Encoding = listAll
// TODO: implement these encodings, in order of importance.
// ASCII, ISO8859_1: Rather common. Close to Windows 1252.
// ISO8859_9: Close to Windows 1254.
// utf8Enc holds a rune's UTF-8 encoding in data[:len].
type utf8Enc struct {
len uint8
data [3]byte
}
// Charmap is an 8-bit character set encoding.
type Charmap struct {
// name is the encoding's name.
name string
// mib is the encoding type of this encoder.
mib identifier.MIB
// asciiSuperset states whether the encoding is a superset of ASCII.
asciiSuperset bool
// low is the lower bound of the encoded byte for a non-ASCII rune. If
// Charmap.asciiSuperset is true then this will be 0x80, otherwise 0x00.
low uint8
// replacement is the encoded replacement character.
replacement byte
// decode is the map from encoded byte to UTF-8.
decode [256]utf8Enc
// encoding is the map from runes to encoded bytes. Each entry is a
// uint32: the high 8 bits are the encoded byte and the low 24 bits are
// the rune. The table entries are sorted by ascending rune.
encode [256]uint32
}
// NewDecoder implements the encoding.Encoding interface.
func (m *Charmap) NewDecoder() *encoding.Decoder {
return &encoding.Decoder{Transformer: charmapDecoder{charmap: m}}
}
// NewEncoder implements the encoding.Encoding interface.
func (m *Charmap) NewEncoder() *encoding.Encoder {
return &encoding.Encoder{Transformer: charmapEncoder{charmap: m}}
}
// String returns the Charmap's name.
func (m *Charmap) String() string {
return m.name
}
// ID implements an internal interface.
func (m *Charmap) ID() (mib identifier.MIB, other string) {
return m.mib, ""
}
// charmapDecoder implements transform.Transformer by decoding to UTF-8.
type charmapDecoder struct {
transform.NopResetter
charmap *Charmap
}
func (m charmapDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
for i, c := range src {
if m.charmap.asciiSuperset && c < utf8.RuneSelf {
if nDst >= len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst] = c
nDst++
nSrc = i + 1
continue
}
decode := &m.charmap.decode[c]
n := int(decode.len)
if nDst+n > len(dst) {
err = transform.ErrShortDst
break
}
// It's 15% faster to avoid calling copy for these tiny slices.
for j := 0; j < n; j++ {
dst[nDst] = decode.data[j]
nDst++
}
nSrc = i + 1
}
return nDst, nSrc, err
}
// DecodeByte returns the Charmap's rune decoding of the byte b.
func (m *Charmap) DecodeByte(b byte) rune {
switch x := &m.decode[b]; x.len {
case 1:
return rune(x.data[0])
case 2:
return rune(x.data[0]&0x1f)<<6 | rune(x.data[1]&0x3f)
default:
return rune(x.data[0]&0x0f)<<12 | rune(x.data[1]&0x3f)<<6 | rune(x.data[2]&0x3f)
}
}
// charmapEncoder implements transform.Transformer by encoding from UTF-8.
type charmapEncoder struct {
transform.NopResetter
charmap *Charmap
}
func (m charmapEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
r, size := rune(0), 0
loop:
for nSrc < len(src) {
if nDst >= len(dst) {
err = transform.ErrShortDst
break
}
r = rune(src[nSrc])
// Decode a 1-byte rune.
if r < utf8.RuneSelf {
if m.charmap.asciiSuperset {
nSrc++
dst[nDst] = uint8(r)
nDst++
continue
}
size = 1
} else {
// Decode a multi-byte rune.
r, size = utf8.DecodeRune(src[nSrc:])
if size == 1 {
// All valid runes of size 1 (those below utf8.RuneSelf) were
// handled above. We have invalid UTF-8 or we haven't seen the
// full character yet.
if !atEOF && !utf8.FullRune(src[nSrc:]) {
err = transform.ErrShortSrc
} else {
err = internal.RepertoireError(m.charmap.replacement)
}
break
}
}
// Binary search in [low, high) for that rune in the m.charmap.encode table.
for low, high := int(m.charmap.low), 0x100; ; {
if low >= high {
err = internal.RepertoireError(m.charmap.replacement)
break loop
}
mid := (low + high) / 2
got := m.charmap.encode[mid]
gotRune := rune(got & (1<<24 - 1))
if gotRune < r {
low = mid + 1
} else if gotRune > r {
high = mid
} else {
dst[nDst] = byte(got >> 24)
nDst++
break
}
}
nSrc += size
}
return nDst, nSrc, err
}
// EncodeRune returns the Charmap's byte encoding of the rune r. ok is whether
// r is in the Charmap's repertoire. If not, b is set to the Charmap's
// replacement byte. This is often the ASCII substitute character '\x1a'.
func (m *Charmap) EncodeRune(r rune) (b byte, ok bool) {
if r < utf8.RuneSelf && m.asciiSuperset {
return byte(r), true
}
for low, high := int(m.low), 0x100; ; {
if low >= high {
return m.replacement, false
}
mid := (low + high) / 2
got := m.encode[mid]
gotRune := rune(got & (1<<24 - 1))
if gotRune < r {
low = mid + 1
} else if gotRune > r {
high = mid
} else {
return byte(got >> 24), true
}
}
}
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