diff options
Diffstat (limited to 'vendor/golang.org/x/text/encoding')
| -rw-r--r-- | vendor/golang.org/x/text/encoding/unicode/override.go | 82 | ||||
| -rw-r--r-- | vendor/golang.org/x/text/encoding/unicode/unicode.go | 512 |
2 files changed, 594 insertions, 0 deletions
diff --git a/vendor/golang.org/x/text/encoding/unicode/override.go b/vendor/golang.org/x/text/encoding/unicode/override.go new file mode 100644 index 00000000..35d62fcc --- /dev/null +++ b/vendor/golang.org/x/text/encoding/unicode/override.go @@ -0,0 +1,82 @@ +// Copyright 2015 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 unicode + +import ( + "golang.org/x/text/transform" +) + +// BOMOverride returns a new decoder transformer that is identical to fallback, +// except that the presence of a Byte Order Mark at the start of the input +// causes it to switch to the corresponding Unicode decoding. It will only +// consider BOMs for UTF-8, UTF-16BE, and UTF-16LE. +// +// This differs from using ExpectBOM by allowing a BOM to switch to UTF-8, not +// just UTF-16 variants, and allowing falling back to any encoding scheme. +// +// This technique is recommended by the W3C for use in HTML 5: "For +// compatibility with deployed content, the byte order mark (also known as BOM) +// is considered more authoritative than anything else." +// http://www.w3.org/TR/encoding/#specification-hooks +// +// Using BOMOverride is mostly intended for use cases where the first characters +// of a fallback encoding are known to not be a BOM, for example, for valid HTML +// and most encodings. +func BOMOverride(fallback transform.Transformer) transform.Transformer { + // TODO: possibly allow a variadic argument of unicode encodings to allow + // specifying details of which fallbacks are supported as well as + // specifying the details of the implementations. This would also allow for + // support for UTF-32, which should not be supported by default. + return &bomOverride{fallback: fallback} +} + +type bomOverride struct { + fallback transform.Transformer + current transform.Transformer +} + +func (d *bomOverride) Reset() { + d.current = nil + d.fallback.Reset() +} + +var ( + // TODO: we could use decode functions here, instead of allocating a new + // decoder on every NewDecoder as IgnoreBOM decoders can be stateless. + utf16le = UTF16(LittleEndian, IgnoreBOM) + utf16be = UTF16(BigEndian, IgnoreBOM) +) + +const utf8BOM = "\ufeff" + +func (d *bomOverride) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + if d.current != nil { + return d.current.Transform(dst, src, atEOF) + } + if len(src) < 3 && !atEOF { + return 0, 0, transform.ErrShortSrc + } + d.current = d.fallback + bomSize := 0 + if len(src) >= 2 { + if src[0] == 0xFF && src[1] == 0xFE { + d.current = utf16le.NewDecoder() + bomSize = 2 + } else if src[0] == 0xFE && src[1] == 0xFF { + d.current = utf16be.NewDecoder() + bomSize = 2 + } else if len(src) >= 3 && + src[0] == utf8BOM[0] && + src[1] == utf8BOM[1] && + src[2] == utf8BOM[2] { + d.current = transform.Nop + bomSize = 3 + } + } + if bomSize < len(src) { + nDst, nSrc, err = d.current.Transform(dst, src[bomSize:], atEOF) + } + return nDst, nSrc + bomSize, err +} diff --git a/vendor/golang.org/x/text/encoding/unicode/unicode.go b/vendor/golang.org/x/text/encoding/unicode/unicode.go new file mode 100644 index 00000000..dd99ad14 --- /dev/null +++ b/vendor/golang.org/x/text/encoding/unicode/unicode.go @@ -0,0 +1,512 @@ +// 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. + +// Package unicode provides Unicode encodings such as UTF-16. +package unicode // import "golang.org/x/text/encoding/unicode" + +import ( + "bytes" + "errors" + "unicode/utf16" + "unicode/utf8" + + "golang.org/x/text/encoding" + "golang.org/x/text/encoding/internal" + "golang.org/x/text/encoding/internal/identifier" + "golang.org/x/text/internal/utf8internal" + "golang.org/x/text/runes" + "golang.org/x/text/transform" +) + +// TODO: I think the Transformers really should return errors on unmatched +// surrogate pairs and odd numbers of bytes. This is not required by RFC 2781, +// which leaves it open, but is suggested by WhatWG. It will allow for all error +// modes as defined by WhatWG: fatal, HTML and Replacement. This would require +// the introduction of some kind of error type for conveying the erroneous code +// point. + +// UTF8 is the UTF-8 encoding. It neither removes nor adds byte order marks. +var UTF8 encoding.Encoding = utf8enc + +// UTF8BOM is an UTF-8 encoding where the decoder strips a leading byte order +// mark while the encoder adds one. +// +// Some editors add a byte order mark as a signature to UTF-8 files. Although +// the byte order mark is not useful for detecting byte order in UTF-8, it is +// sometimes used as a convention to mark UTF-8-encoded files. This relies on +// the observation that the UTF-8 byte order mark is either an illegal or at +// least very unlikely sequence in any other character encoding. +var UTF8BOM encoding.Encoding = utf8bomEncoding{} + +type utf8bomEncoding struct{} + +func (utf8bomEncoding) String() string { + return "UTF-8-BOM" +} + +func (utf8bomEncoding) ID() (identifier.MIB, string) { + return identifier.Unofficial, "x-utf8bom" +} + +func (utf8bomEncoding) NewEncoder() *encoding.Encoder { + return &encoding.Encoder{ + Transformer: &utf8bomEncoder{t: runes.ReplaceIllFormed()}, + } +} + +func (utf8bomEncoding) NewDecoder() *encoding.Decoder { + return &encoding.Decoder{Transformer: &utf8bomDecoder{}} +} + +var utf8enc = &internal.Encoding{ + &internal.SimpleEncoding{utf8Decoder{}, runes.ReplaceIllFormed()}, + "UTF-8", + identifier.UTF8, +} + +type utf8bomDecoder struct { + checked bool +} + +func (t *utf8bomDecoder) Reset() { + t.checked = false +} + +func (t *utf8bomDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + if !t.checked { + if !atEOF && len(src) < len(utf8BOM) { + if len(src) == 0 { + return 0, 0, nil + } + return 0, 0, transform.ErrShortSrc + } + if bytes.HasPrefix(src, []byte(utf8BOM)) { + nSrc += len(utf8BOM) + src = src[len(utf8BOM):] + } + t.checked = true + } + nDst, n, err := utf8Decoder.Transform(utf8Decoder{}, dst[nDst:], src, atEOF) + nSrc += n + return nDst, nSrc, err +} + +type utf8bomEncoder struct { + written bool + t transform.Transformer +} + +func (t *utf8bomEncoder) Reset() { + t.written = false + t.t.Reset() +} + +func (t *utf8bomEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + if !t.written { + if len(dst) < len(utf8BOM) { + return nDst, 0, transform.ErrShortDst + } + nDst = copy(dst, utf8BOM) + t.written = true + } + n, nSrc, err := utf8Decoder.Transform(utf8Decoder{}, dst[nDst:], src, atEOF) + nDst += n + return nDst, nSrc, err +} + +type utf8Decoder struct{ transform.NopResetter } + +func (utf8Decoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + var pSrc int // point from which to start copy in src + var accept utf8internal.AcceptRange + + // The decoder can only make the input larger, not smaller. + n := len(src) + if len(dst) < n { + err = transform.ErrShortDst + n = len(dst) + atEOF = false + } + for nSrc < n { + c := src[nSrc] + if c < utf8.RuneSelf { + nSrc++ + continue + } + first := utf8internal.First[c] + size := int(first & utf8internal.SizeMask) + if first == utf8internal.FirstInvalid { + goto handleInvalid // invalid starter byte + } + accept = utf8internal.AcceptRanges[first>>utf8internal.AcceptShift] + if nSrc+size > n { + if !atEOF { + // We may stop earlier than necessary here if the short sequence + // has invalid bytes. Not checking for this simplifies the code + // and may avoid duplicate computations in certain conditions. + if err == nil { + err = transform.ErrShortSrc + } + break + } + // Determine the maximal subpart of an ill-formed subsequence. + switch { + case nSrc+1 >= n || src[nSrc+1] < accept.Lo || accept.Hi < src[nSrc+1]: + size = 1 + case nSrc+2 >= n || src[nSrc+2] < utf8internal.LoCB || utf8internal.HiCB < src[nSrc+2]: + size = 2 + default: + size = 3 // As we are short, the maximum is 3. + } + goto handleInvalid + } + if c = src[nSrc+1]; c < accept.Lo || accept.Hi < c { + size = 1 + goto handleInvalid // invalid continuation byte + } else if size == 2 { + } else if c = src[nSrc+2]; c < utf8internal.LoCB || utf8internal.HiCB < c { + size = 2 + goto handleInvalid // invalid continuation byte + } else if size == 3 { + } else if c = src[nSrc+3]; c < utf8internal.LoCB || utf8internal.HiCB < c { + size = 3 + goto handleInvalid // invalid continuation byte + } + nSrc += size + continue + + handleInvalid: + // Copy the scanned input so far. + nDst += copy(dst[nDst:], src[pSrc:nSrc]) + + // Append RuneError to the destination. + const runeError = "\ufffd" + if nDst+len(runeError) > len(dst) { + return nDst, nSrc, transform.ErrShortDst + } + nDst += copy(dst[nDst:], runeError) + + // Skip the maximal subpart of an ill-formed subsequence according to + // the W3C standard way instead of the Go way. This Transform is + // probably the only place in the text repo where it is warranted. + nSrc += size + pSrc = nSrc + + // Recompute the maximum source length. + if sz := len(dst) - nDst; sz < len(src)-nSrc { + err = transform.ErrShortDst + n = nSrc + sz + atEOF = false + } + } + return nDst + copy(dst[nDst:], src[pSrc:nSrc]), nSrc, err +} + +// UTF16 returns a UTF-16 Encoding for the given default endianness and byte +// order mark (BOM) policy. +// +// When decoding from UTF-16 to UTF-8, if the BOMPolicy is IgnoreBOM then +// neither BOMs U+FEFF nor noncharacters U+FFFE in the input stream will affect +// the endianness used for decoding, and will instead be output as their +// standard UTF-8 encodings: "\xef\xbb\xbf" and "\xef\xbf\xbe". If the BOMPolicy +// is UseBOM or ExpectBOM a staring BOM is not written to the UTF-8 output. +// Instead, it overrides the default endianness e for the remainder of the +// transformation. Any subsequent BOMs U+FEFF or noncharacters U+FFFE will not +// affect the endianness used, and will instead be output as their standard +// UTF-8 encodings. For UseBOM, if there is no starting BOM, it will proceed +// with the default Endianness. For ExpectBOM, in that case, the transformation +// will return early with an ErrMissingBOM error. +// +// When encoding from UTF-8 to UTF-16, a BOM will be inserted at the start of +// the output if the BOMPolicy is UseBOM or ExpectBOM. Otherwise, a BOM will not +// be inserted. The UTF-8 input does not need to contain a BOM. +// +// There is no concept of a 'native' endianness. If the UTF-16 data is produced +// and consumed in a greater context that implies a certain endianness, use +// IgnoreBOM. Otherwise, use ExpectBOM and always produce and consume a BOM. +// +// In the language of https://www.unicode.org/faq/utf_bom.html#bom10, IgnoreBOM +// corresponds to "Where the precise type of the data stream is known... the +// BOM should not be used" and ExpectBOM corresponds to "A particular +// protocol... may require use of the BOM". +func UTF16(e Endianness, b BOMPolicy) encoding.Encoding { + return utf16Encoding{config{e, b}, mibValue[e][b&bomMask]} +} + +// mibValue maps Endianness and BOMPolicy settings to MIB constants. Note that +// some configurations map to the same MIB identifier. RFC 2781 has requirements +// and recommendations. Some of the "configurations" are merely recommendations, +// so multiple configurations could match. +var mibValue = map[Endianness][numBOMValues]identifier.MIB{ + BigEndian: [numBOMValues]identifier.MIB{ + IgnoreBOM: identifier.UTF16BE, + UseBOM: identifier.UTF16, // BigEnding default is preferred by RFC 2781. + // TODO: acceptBOM | strictBOM would map to UTF16BE as well. + }, + LittleEndian: [numBOMValues]identifier.MIB{ + IgnoreBOM: identifier.UTF16LE, + UseBOM: identifier.UTF16, // LittleEndian default is allowed and preferred on Windows. + // TODO: acceptBOM | strictBOM would map to UTF16LE as well. + }, + // ExpectBOM is not widely used and has no valid MIB identifier. +} + +// All lists a configuration for each IANA-defined UTF-16 variant. +var All = []encoding.Encoding{ + UTF8, + UTF16(BigEndian, UseBOM), + UTF16(BigEndian, IgnoreBOM), + UTF16(LittleEndian, IgnoreBOM), +} + +// BOMPolicy is a UTF-16 encoding's byte order mark policy. +type BOMPolicy uint8 + +const ( + writeBOM BOMPolicy = 0x01 + acceptBOM BOMPolicy = 0x02 + requireBOM BOMPolicy = 0x04 + bomMask BOMPolicy = 0x07 + + // HACK: numBOMValues == 8 triggers a bug in the 1.4 compiler (cannot have a + // map of an array of length 8 of a type that is also used as a key or value + // in another map). See golang.org/issue/11354. + // TODO: consider changing this value back to 8 if the use of 1.4.* has + // been minimized. + numBOMValues = 8 + 1 + + // IgnoreBOM means to ignore any byte order marks. + IgnoreBOM BOMPolicy = 0 + // Common and RFC 2781-compliant interpretation for UTF-16BE/LE. + + // UseBOM means that the UTF-16 form may start with a byte order mark, which + // will be used to override the default encoding. + UseBOM BOMPolicy = writeBOM | acceptBOM + // Common and RFC 2781-compliant interpretation for UTF-16. + + // ExpectBOM means that the UTF-16 form must start with a byte order mark, + // which will be used to override the default encoding. + ExpectBOM BOMPolicy = writeBOM | acceptBOM | requireBOM + // Used in Java as Unicode (not to be confused with Java's UTF-16) and + // ICU's UTF-16,version=1. Not compliant with RFC 2781. + + // TODO (maybe): strictBOM: BOM must match Endianness. This would allow: + // - UTF-16(B|L)E,version=1: writeBOM | acceptBOM | requireBOM | strictBOM + // (UnicodeBig and UnicodeLittle in Java) + // - RFC 2781-compliant, but less common interpretation for UTF-16(B|L)E: + // acceptBOM | strictBOM (e.g. assigned to CheckBOM). + // This addition would be consistent with supporting ExpectBOM. +) + +// Endianness is a UTF-16 encoding's default endianness. +type Endianness bool + +const ( + // BigEndian is UTF-16BE. + BigEndian Endianness = false + // LittleEndian is UTF-16LE. + LittleEndian Endianness = true +) + +// ErrMissingBOM means that decoding UTF-16 input with ExpectBOM did not find a +// starting byte order mark. +var ErrMissingBOM = errors.New("encoding: missing byte order mark") + +type utf16Encoding struct { + config + mib identifier.MIB +} + +type config struct { + endianness Endianness + bomPolicy BOMPolicy +} + +func (u utf16Encoding) NewDecoder() *encoding.Decoder { + return &encoding.Decoder{Transformer: &utf16Decoder{ + initial: u.config, + current: u.config, + }} +} + +func (u utf16Encoding) NewEncoder() *encoding.Encoder { + return &encoding.Encoder{Transformer: &utf16Encoder{ + endianness: u.endianness, + initialBOMPolicy: u.bomPolicy, + currentBOMPolicy: u.bomPolicy, + }} +} + +func (u utf16Encoding) ID() (mib identifier.MIB, other string) { + return u.mib, "" +} + +func (u utf16Encoding) String() string { + e, b := "B", "" + if u.endianness == LittleEndian { + e = "L" + } + switch u.bomPolicy { + case ExpectBOM: + b = "Expect" + case UseBOM: + b = "Use" + case IgnoreBOM: + b = "Ignore" + } + return "UTF-16" + e + "E (" + b + " BOM)" +} + +type utf16Decoder struct { + initial config + current config +} + +func (u *utf16Decoder) Reset() { + u.current = u.initial +} + +func (u *utf16Decoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + if len(src) < 2 && atEOF && u.current.bomPolicy&requireBOM != 0 { + return 0, 0, ErrMissingBOM + } + if len(src) == 0 { + return 0, 0, nil + } + if len(src) >= 2 && u.current.bomPolicy&acceptBOM != 0 { + switch { + case src[0] == 0xfe && src[1] == 0xff: + u.current.endianness = BigEndian + nSrc = 2 + case src[0] == 0xff && src[1] == 0xfe: + u.current.endianness = LittleEndian + nSrc = 2 + default: + if u.current.bomPolicy&requireBOM != 0 { + return 0, 0, ErrMissingBOM + } + } + u.current.bomPolicy = IgnoreBOM + } + + var r rune + var dSize, sSize int + for nSrc < len(src) { + if nSrc+1 < len(src) { + x := uint16(src[nSrc+0])<<8 | uint16(src[nSrc+1]) + if u.current.endianness == LittleEndian { + x = x>>8 | x<<8 + } + r, sSize = rune(x), 2 + if utf16.IsSurrogate(r) { + if nSrc+3 < len(src) { + x = uint16(src[nSrc+2])<<8 | uint16(src[nSrc+3]) + if u.current.endianness == LittleEndian { + x = x>>8 | x<<8 + } + // Save for next iteration if it is not a high surrogate. + if isHighSurrogate(rune(x)) { + r, sSize = utf16.DecodeRune(r, rune(x)), 4 + } + } else if !atEOF { + err = transform.ErrShortSrc + break + } + } + if dSize = utf8.RuneLen(r); dSize < 0 { + r, dSize = utf8.RuneError, 3 + } + } else if atEOF { + // Single trailing byte. + r, dSize, sSize = utf8.RuneError, 3, 1 + } else { + err = transform.ErrShortSrc + break + } + if nDst+dSize > len(dst) { + err = transform.ErrShortDst + break + } + nDst += utf8.EncodeRune(dst[nDst:], r) + nSrc += sSize + } + return nDst, nSrc, err +} + +func isHighSurrogate(r rune) bool { + return 0xDC00 <= r && r <= 0xDFFF +} + +type utf16Encoder struct { + endianness Endianness + initialBOMPolicy BOMPolicy + currentBOMPolicy BOMPolicy +} + +func (u *utf16Encoder) Reset() { + u.currentBOMPolicy = u.initialBOMPolicy +} + +func (u *utf16Encoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { + if u.currentBOMPolicy&writeBOM != 0 { + if len(dst) < 2 { + return 0, 0, transform.ErrShortDst + } + dst[0], dst[1] = 0xfe, 0xff + u.currentBOMPolicy = IgnoreBOM + nDst = 2 + } + + r, size := rune(0), 0 + for nSrc < len(src) { + r = rune(src[nSrc]) + + // Decode a 1-byte rune. + if r < utf8.RuneSelf { + 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 + break + } + } + } + + if r <= 0xffff { + if nDst+2 > len(dst) { + err = transform.ErrShortDst + break + } + dst[nDst+0] = uint8(r >> 8) + dst[nDst+1] = uint8(r) + nDst += 2 + } else { + if nDst+4 > len(dst) { + err = transform.ErrShortDst + break + } + r1, r2 := utf16.EncodeRune(r) + dst[nDst+0] = uint8(r1 >> 8) + dst[nDst+1] = uint8(r1) + dst[nDst+2] = uint8(r2 >> 8) + dst[nDst+3] = uint8(r2) + nDst += 4 + } + nSrc += size + } + + if u.endianness == LittleEndian { + for i := 0; i < nDst; i += 2 { + dst[i], dst[i+1] = dst[i+1], dst[i] + } + } + return nDst, nSrc, err +} |