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