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Bump Go deps

This commit is contained in:
Harvey Kandola 2024-02-19 11:54:27 -05:00
parent f2ba294be8
commit acb59e1b43
91 changed files with 9004 additions and 513 deletions

27
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Copyright (c) 2009 The Go Authors. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.
* Neither the name of Google Inc. nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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Additional IP Rights Grant (Patents)
"This implementation" means the copyrightable works distributed by
Google as part of the Go project.
Google hereby grants to You a perpetual, worldwide, non-exclusive,
no-charge, royalty-free, irrevocable (except as stated in this section)
patent license to make, have made, use, offer to sell, sell, import,
transfer and otherwise run, modify and propagate the contents of this
implementation of Go, where such license applies only to those patent
claims, both currently owned or controlled by Google and acquired in
the future, licensable by Google that are necessarily infringed by this
implementation of Go. This grant does not include claims that would be
infringed only as a consequence of further modification of this
implementation. If you or your agent or exclusive licensee institute or
order or agree to the institution of patent litigation against any
entity (including a cross-claim or counterclaim in a lawsuit) alleging
that this implementation of Go or any code incorporated within this
implementation of Go constitutes direct or contributory patent
infringement, or inducement of patent infringement, then any patent
rights granted to you under this License for this implementation of Go
shall terminate as of the date such litigation is filed.

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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.
// Package encoding defines an interface for character encodings, such as Shift
// JIS and Windows 1252, that can convert to and from UTF-8.
//
// Encoding implementations are provided in other packages, such as
// golang.org/x/text/encoding/charmap and
// golang.org/x/text/encoding/japanese.
package encoding // import "golang.org/x/text/encoding"
import (
"errors"
"io"
"strconv"
"unicode/utf8"
"golang.org/x/text/encoding/internal/identifier"
"golang.org/x/text/transform"
)
// TODO:
// - There seems to be some inconsistency in when decoders return errors
// and when not. Also documentation seems to suggest they shouldn't return
// errors at all (except for UTF-16).
// - Encoders seem to rely on or at least benefit from the input being in NFC
// normal form. Perhaps add an example how users could prepare their output.
// Encoding is a character set encoding that can be transformed to and from
// UTF-8.
type Encoding interface {
// NewDecoder returns a Decoder.
NewDecoder() *Decoder
// NewEncoder returns an Encoder.
NewEncoder() *Encoder
}
// A Decoder converts bytes to UTF-8. It implements transform.Transformer.
//
// Transforming source bytes that are not of that encoding will not result in an
// error per se. Each byte that cannot be transcoded will be represented in the
// output by the UTF-8 encoding of '\uFFFD', the replacement rune.
type Decoder struct {
transform.Transformer
// This forces external creators of Decoders to use names in struct
// initializers, allowing for future extendibility without having to break
// code.
_ struct{}
}
// Bytes converts the given encoded bytes to UTF-8. It returns the converted
// bytes or nil, err if any error occurred.
func (d *Decoder) Bytes(b []byte) ([]byte, error) {
b, _, err := transform.Bytes(d, b)
if err != nil {
return nil, err
}
return b, nil
}
// String converts the given encoded string to UTF-8. It returns the converted
// string or "", err if any error occurred.
func (d *Decoder) String(s string) (string, error) {
s, _, err := transform.String(d, s)
if err != nil {
return "", err
}
return s, nil
}
// Reader wraps another Reader to decode its bytes.
//
// The Decoder may not be used for any other operation as long as the returned
// Reader is in use.
func (d *Decoder) Reader(r io.Reader) io.Reader {
return transform.NewReader(r, d)
}
// An Encoder converts bytes from UTF-8. It implements transform.Transformer.
//
// Each rune that cannot be transcoded will result in an error. In this case,
// the transform will consume all source byte up to, not including the offending
// rune. Transforming source bytes that are not valid UTF-8 will be replaced by
// `\uFFFD`. To return early with an error instead, use transform.Chain to
// preprocess the data with a UTF8Validator.
type Encoder struct {
transform.Transformer
// This forces external creators of Encoders to use names in struct
// initializers, allowing for future extendibility without having to break
// code.
_ struct{}
}
// Bytes converts bytes from UTF-8. It returns the converted bytes or nil, err if
// any error occurred.
func (e *Encoder) Bytes(b []byte) ([]byte, error) {
b, _, err := transform.Bytes(e, b)
if err != nil {
return nil, err
}
return b, nil
}
// String converts a string from UTF-8. It returns the converted string or
// "", err if any error occurred.
func (e *Encoder) String(s string) (string, error) {
s, _, err := transform.String(e, s)
if err != nil {
return "", err
}
return s, nil
}
// Writer wraps another Writer to encode its UTF-8 output.
//
// The Encoder may not be used for any other operation as long as the returned
// Writer is in use.
func (e *Encoder) Writer(w io.Writer) io.Writer {
return transform.NewWriter(w, e)
}
// ASCIISub is the ASCII substitute character, as recommended by
// https://unicode.org/reports/tr36/#Text_Comparison
const ASCIISub = '\x1a'
// Nop is the nop encoding. Its transformed bytes are the same as the source
// bytes; it does not replace invalid UTF-8 sequences.
var Nop Encoding = nop{}
type nop struct{}
func (nop) NewDecoder() *Decoder {
return &Decoder{Transformer: transform.Nop}
}
func (nop) NewEncoder() *Encoder {
return &Encoder{Transformer: transform.Nop}
}
// Replacement is the replacement encoding. Decoding from the replacement
// encoding yields a single '\uFFFD' replacement rune. Encoding from UTF-8 to
// the replacement encoding yields the same as the source bytes except that
// invalid UTF-8 is converted to '\uFFFD'.
//
// It is defined at http://encoding.spec.whatwg.org/#replacement
var Replacement Encoding = replacement{}
type replacement struct{}
func (replacement) NewDecoder() *Decoder {
return &Decoder{Transformer: replacementDecoder{}}
}
func (replacement) NewEncoder() *Encoder {
return &Encoder{Transformer: replacementEncoder{}}
}
func (replacement) ID() (mib identifier.MIB, other string) {
return identifier.Replacement, ""
}
type replacementDecoder struct{ transform.NopResetter }
func (replacementDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
if len(dst) < 3 {
return 0, 0, transform.ErrShortDst
}
if atEOF {
const fffd = "\ufffd"
dst[0] = fffd[0]
dst[1] = fffd[1]
dst[2] = fffd[2]
nDst = 3
}
return nDst, len(src), nil
}
type replacementEncoder struct{ transform.NopResetter }
func (replacementEncoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
r, size := rune(0), 0
for ; nSrc < len(src); nSrc += size {
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
}
r = '\ufffd'
}
}
if nDst+utf8.RuneLen(r) > len(dst) {
err = transform.ErrShortDst
break
}
nDst += utf8.EncodeRune(dst[nDst:], r)
}
return nDst, nSrc, err
}
// HTMLEscapeUnsupported wraps encoders to replace source runes outside the
// repertoire of the destination encoding with HTML escape sequences.
//
// This wrapper exists to comply to URL and HTML forms requiring a
// non-terminating legacy encoder. The produced sequences may lead to data
// loss as they are indistinguishable from legitimate input. To avoid this
// issue, use UTF-8 encodings whenever possible.
func HTMLEscapeUnsupported(e *Encoder) *Encoder {
return &Encoder{Transformer: &errorHandler{e, errorToHTML}}
}
// ReplaceUnsupported wraps encoders to replace source runes outside the
// repertoire of the destination encoding with an encoding-specific
// replacement.
//
// This wrapper is only provided for backwards compatibility and legacy
// handling. Its use is strongly discouraged. Use UTF-8 whenever possible.
func ReplaceUnsupported(e *Encoder) *Encoder {
return &Encoder{Transformer: &errorHandler{e, errorToReplacement}}
}
type errorHandler struct {
*Encoder
handler func(dst []byte, r rune, err repertoireError) (n int, ok bool)
}
// TODO: consider making this error public in some form.
type repertoireError interface {
Replacement() byte
}
func (h errorHandler) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
nDst, nSrc, err = h.Transformer.Transform(dst, src, atEOF)
for err != nil {
rerr, ok := err.(repertoireError)
if !ok {
return nDst, nSrc, err
}
r, sz := utf8.DecodeRune(src[nSrc:])
n, ok := h.handler(dst[nDst:], r, rerr)
if !ok {
return nDst, nSrc, transform.ErrShortDst
}
err = nil
nDst += n
if nSrc += sz; nSrc < len(src) {
var dn, sn int
dn, sn, err = h.Transformer.Transform(dst[nDst:], src[nSrc:], atEOF)
nDst += dn
nSrc += sn
}
}
return nDst, nSrc, err
}
func errorToHTML(dst []byte, r rune, err repertoireError) (n int, ok bool) {
buf := [8]byte{}
b := strconv.AppendUint(buf[:0], uint64(r), 10)
if n = len(b) + len("&#;"); n >= len(dst) {
return 0, false
}
dst[0] = '&'
dst[1] = '#'
dst[copy(dst[2:], b)+2] = ';'
return n, true
}
func errorToReplacement(dst []byte, r rune, err repertoireError) (n int, ok bool) {
if len(dst) == 0 {
return 0, false
}
dst[0] = err.Replacement()
return 1, true
}
// ErrInvalidUTF8 means that a transformer encountered invalid UTF-8.
var ErrInvalidUTF8 = errors.New("encoding: invalid UTF-8")
// UTF8Validator is a transformer that returns ErrInvalidUTF8 on the first
// input byte that is not valid UTF-8.
var UTF8Validator transform.Transformer = utf8Validator{}
type utf8Validator struct{ transform.NopResetter }
func (utf8Validator) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
n := len(src)
if n > len(dst) {
n = len(dst)
}
for i := 0; i < n; {
if c := src[i]; c < utf8.RuneSelf {
dst[i] = c
i++
continue
}
_, size := utf8.DecodeRune(src[i:])
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.
err = ErrInvalidUTF8
if !atEOF && !utf8.FullRune(src[i:]) {
err = transform.ErrShortSrc
}
return i, i, err
}
if i+size > len(dst) {
return i, i, transform.ErrShortDst
}
for ; size > 0; size-- {
dst[i] = src[i]
i++
}
}
if len(src) > len(dst) {
err = transform.ErrShortDst
}
return n, n, err
}

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// 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.
//go:generate go run gen.go
// Package identifier defines the contract between implementations of Encoding
// and Index by defining identifiers that uniquely identify standardized coded
// character sets (CCS) and character encoding schemes (CES), which we will
// together refer to as encodings, for which Encoding implementations provide
// converters to and from UTF-8. This package is typically only of concern to
// implementers of Indexes and Encodings.
//
// One part of the identifier is the MIB code, which is defined by IANA and
// uniquely identifies a CCS or CES. Each code is associated with data that
// references authorities, official documentation as well as aliases and MIME
// names.
//
// Not all CESs are covered by the IANA registry. The "other" string that is
// returned by ID can be used to identify other character sets or versions of
// existing ones.
//
// It is recommended that each package that provides a set of Encodings provide
// the All and Common variables to reference all supported encodings and
// commonly used subset. This allows Index implementations to include all
// available encodings without explicitly referencing or knowing about them.
package identifier
// Note: this package is internal, but could be made public if there is a need
// for writing third-party Indexes and Encodings.
// References:
// - http://source.icu-project.org/repos/icu/icu/trunk/source/data/mappings/convrtrs.txt
// - http://www.iana.org/assignments/character-sets/character-sets.xhtml
// - http://www.iana.org/assignments/ianacharset-mib/ianacharset-mib
// - http://www.ietf.org/rfc/rfc2978.txt
// - https://www.unicode.org/reports/tr22/
// - http://www.w3.org/TR/encoding/
// - https://encoding.spec.whatwg.org/
// - https://encoding.spec.whatwg.org/encodings.json
// - https://tools.ietf.org/html/rfc6657#section-5
// Interface can be implemented by Encodings to define the CCS or CES for which
// it implements conversions.
type Interface interface {
// ID returns an encoding identifier. Exactly one of the mib and other
// values should be non-zero.
//
// In the usual case it is only necessary to indicate the MIB code. The
// other string can be used to specify encodings for which there is no MIB,
// such as "x-mac-dingbat".
//
// The other string may only contain the characters a-z, A-Z, 0-9, - and _.
ID() (mib MIB, other string)
// NOTE: the restrictions on the encoding are to allow extending the syntax
// with additional information such as versions, vendors and other variants.
}
// A MIB identifies an encoding. It is derived from the IANA MIB codes and adds
// some identifiers for some encodings that are not covered by the IANA
// standard.
//
// See http://www.iana.org/assignments/ianacharset-mib.
type MIB uint16
// These additional MIB types are not defined in IANA. They are added because
// they are common and defined within the text repo.
const (
// Unofficial marks the start of encodings not registered by IANA.
Unofficial MIB = 10000 + iota
// Replacement is the WhatWG replacement encoding.
Replacement
// XUserDefined is the code for x-user-defined.
XUserDefined
// MacintoshCyrillic is the code for x-mac-cyrillic.
MacintoshCyrillic
)

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// 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 internal contains code that is shared among encoding implementations.
package internal
import (
"golang.org/x/text/encoding"
"golang.org/x/text/encoding/internal/identifier"
"golang.org/x/text/transform"
)
// Encoding is an implementation of the Encoding interface that adds the String
// and ID methods to an existing encoding.
type Encoding struct {
encoding.Encoding
Name string
MIB identifier.MIB
}
// _ verifies that Encoding implements identifier.Interface.
var _ identifier.Interface = (*Encoding)(nil)
func (e *Encoding) String() string {
return e.Name
}
func (e *Encoding) ID() (mib identifier.MIB, other string) {
return e.MIB, ""
}
// SimpleEncoding is an Encoding that combines two Transformers.
type SimpleEncoding struct {
Decoder transform.Transformer
Encoder transform.Transformer
}
func (e *SimpleEncoding) NewDecoder() *encoding.Decoder {
return &encoding.Decoder{Transformer: e.Decoder}
}
func (e *SimpleEncoding) NewEncoder() *encoding.Encoder {
return &encoding.Encoder{Transformer: e.Encoder}
}
// FuncEncoding is an Encoding that combines two functions returning a new
// Transformer.
type FuncEncoding struct {
Decoder func() transform.Transformer
Encoder func() transform.Transformer
}
func (e FuncEncoding) NewDecoder() *encoding.Decoder {
return &encoding.Decoder{Transformer: e.Decoder()}
}
func (e FuncEncoding) NewEncoder() *encoding.Encoder {
return &encoding.Encoder{Transformer: e.Encoder()}
}
// A RepertoireError indicates a rune is not in the repertoire of a destination
// encoding. It is associated with an encoding-specific suggested replacement
// byte.
type RepertoireError byte
// Error implements the error interface.
func (r RepertoireError) Error() string {
return "encoding: rune not supported by encoding."
}
// Replacement returns the replacement string associated with this error.
func (r RepertoireError) Replacement() byte { return byte(r) }
var ErrASCIIReplacement = RepertoireError(encoding.ASCIISub)

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// 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
}

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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.
// 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
}

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// 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 utf8internal contains low-level utf8-related constants, tables, etc.
// that are used internally by the text package.
package utf8internal
// The default lowest and highest continuation byte.
const (
LoCB = 0x80 // 1000 0000
HiCB = 0xBF // 1011 1111
)
// Constants related to getting information of first bytes of UTF-8 sequences.
const (
// ASCII identifies a UTF-8 byte as ASCII.
ASCII = as
// FirstInvalid indicates a byte is invalid as a first byte of a UTF-8
// sequence.
FirstInvalid = xx
// SizeMask is a mask for the size bits. Use use x&SizeMask to get the size.
SizeMask = 7
// AcceptShift is the right-shift count for the first byte info byte to get
// the index into the AcceptRanges table. See AcceptRanges.
AcceptShift = 4
// The names of these constants are chosen to give nice alignment in the
// table below. The first nibble is an index into acceptRanges or F for
// special one-byte cases. The second nibble is the Rune length or the
// Status for the special one-byte case.
xx = 0xF1 // invalid: size 1
as = 0xF0 // ASCII: size 1
s1 = 0x02 // accept 0, size 2
s2 = 0x13 // accept 1, size 3
s3 = 0x03 // accept 0, size 3
s4 = 0x23 // accept 2, size 3
s5 = 0x34 // accept 3, size 4
s6 = 0x04 // accept 0, size 4
s7 = 0x44 // accept 4, size 4
)
// First is information about the first byte in a UTF-8 sequence.
var First = [256]uint8{
// 1 2 3 4 5 6 7 8 9 A B C D E F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F
// 1 2 3 4 5 6 7 8 9 A B C D E F
xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F
xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF
xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF
s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF
s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF
}
// AcceptRange gives the range of valid values for the second byte in a UTF-8
// sequence for any value for First that is not ASCII or FirstInvalid.
type AcceptRange struct {
Lo uint8 // lowest value for second byte.
Hi uint8 // highest value for second byte.
}
// AcceptRanges is a slice of AcceptRange values. For a given byte sequence b
//
// AcceptRanges[First[b[0]]>>AcceptShift]
//
// will give the value of AcceptRange for the multi-byte UTF-8 sequence starting
// at b[0].
var AcceptRanges = [...]AcceptRange{
0: {LoCB, HiCB},
1: {0xA0, HiCB},
2: {LoCB, 0x9F},
3: {0x90, HiCB},
4: {LoCB, 0x8F},
}

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// 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 runes
import (
"unicode/utf8"
"golang.org/x/text/transform"
)
// Note: below we pass invalid UTF-8 to the tIn and tNotIn transformers as is.
// This is done for various reasons:
// - To retain the semantics of the Nop transformer: if input is passed to a Nop
// one would expect it to be unchanged.
// - It would be very expensive to pass a converted RuneError to a transformer:
// a transformer might need more source bytes after RuneError, meaning that
// the only way to pass it safely is to create a new buffer and manage the
// intermingling of RuneErrors and normal input.
// - Many transformers leave ill-formed UTF-8 as is, so this is not
// inconsistent. Generally ill-formed UTF-8 is only replaced if it is a
// logical consequence of the operation (as for Map) or if it otherwise would
// pose security concerns (as for Remove).
// - An alternative would be to return an error on ill-formed UTF-8, but this
// would be inconsistent with other operations.
// If returns a transformer that applies tIn to consecutive runes for which
// s.Contains(r) and tNotIn to consecutive runes for which !s.Contains(r). Reset
// is called on tIn and tNotIn at the start of each run. A Nop transformer will
// substitute a nil value passed to tIn or tNotIn. Invalid UTF-8 is translated
// to RuneError to determine which transformer to apply, but is passed as is to
// the respective transformer.
func If(s Set, tIn, tNotIn transform.Transformer) Transformer {
if tIn == nil && tNotIn == nil {
return Transformer{transform.Nop}
}
if tIn == nil {
tIn = transform.Nop
}
if tNotIn == nil {
tNotIn = transform.Nop
}
sIn, ok := tIn.(transform.SpanningTransformer)
if !ok {
sIn = dummySpan{tIn}
}
sNotIn, ok := tNotIn.(transform.SpanningTransformer)
if !ok {
sNotIn = dummySpan{tNotIn}
}
a := &cond{
tIn: sIn,
tNotIn: sNotIn,
f: s.Contains,
}
a.Reset()
return Transformer{a}
}
type dummySpan struct{ transform.Transformer }
func (d dummySpan) Span(src []byte, atEOF bool) (n int, err error) {
return 0, transform.ErrEndOfSpan
}
type cond struct {
tIn, tNotIn transform.SpanningTransformer
f func(rune) bool
check func(rune) bool // current check to perform
t transform.SpanningTransformer // current transformer to use
}
// Reset implements transform.Transformer.
func (t *cond) Reset() {
t.check = t.is
t.t = t.tIn
t.t.Reset() // notIn will be reset on first usage.
}
func (t *cond) is(r rune) bool {
if t.f(r) {
return true
}
t.check = t.isNot
t.t = t.tNotIn
t.tNotIn.Reset()
return false
}
func (t *cond) isNot(r rune) bool {
if !t.f(r) {
return true
}
t.check = t.is
t.t = t.tIn
t.tIn.Reset()
return false
}
// This implementation of Span doesn't help all too much, but it needs to be
// there to satisfy this package's Transformer interface.
// TODO: there are certainly room for improvements, though. For example, if
// t.t == transform.Nop (which will a common occurrence) it will save a bundle
// to special-case that loop.
func (t *cond) Span(src []byte, atEOF bool) (n int, err error) {
p := 0
for n < len(src) && err == nil {
// Don't process too much at a time as the Spanner that will be
// called on this block may terminate early.
const maxChunk = 4096
max := len(src)
if v := n + maxChunk; v < max {
max = v
}
atEnd := false
size := 0
current := t.t
for ; p < max; p += size {
r := rune(src[p])
if r < utf8.RuneSelf {
size = 1
} else if r, size = utf8.DecodeRune(src[p:]); size == 1 {
if !atEOF && !utf8.FullRune(src[p:]) {
err = transform.ErrShortSrc
break
}
}
if !t.check(r) {
// The next rune will be the start of a new run.
atEnd = true
break
}
}
n2, err2 := current.Span(src[n:p], atEnd || (atEOF && p == len(src)))
n += n2
if err2 != nil {
return n, err2
}
// At this point either err != nil or t.check will pass for the rune at p.
p = n + size
}
return n, err
}
func (t *cond) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
p := 0
for nSrc < len(src) && err == nil {
// Don't process too much at a time, as the work might be wasted if the
// destination buffer isn't large enough to hold the result or a
// transform returns an error early.
const maxChunk = 4096
max := len(src)
if n := nSrc + maxChunk; n < len(src) {
max = n
}
atEnd := false
size := 0
current := t.t
for ; p < max; p += size {
r := rune(src[p])
if r < utf8.RuneSelf {
size = 1
} else if r, size = utf8.DecodeRune(src[p:]); size == 1 {
if !atEOF && !utf8.FullRune(src[p:]) {
err = transform.ErrShortSrc
break
}
}
if !t.check(r) {
// The next rune will be the start of a new run.
atEnd = true
break
}
}
nDst2, nSrc2, err2 := current.Transform(dst[nDst:], src[nSrc:p], atEnd || (atEOF && p == len(src)))
nDst += nDst2
nSrc += nSrc2
if err2 != nil {
return nDst, nSrc, err2
}
// At this point either err != nil or t.check will pass for the rune at p.
p = nSrc + size
}
return nDst, nSrc, err
}

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// Copyright 2014 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 runes provide transforms for UTF-8 encoded text.
package runes // import "golang.org/x/text/runes"
import (
"unicode"
"unicode/utf8"
"golang.org/x/text/transform"
)
// A Set is a collection of runes.
type Set interface {
// Contains returns true if r is contained in the set.
Contains(r rune) bool
}
type setFunc func(rune) bool
func (s setFunc) Contains(r rune) bool {
return s(r)
}
// Note: using funcs here instead of wrapping types result in cleaner
// documentation and a smaller API.
// In creates a Set with a Contains method that returns true for all runes in
// the given RangeTable.
func In(rt *unicode.RangeTable) Set {
return setFunc(func(r rune) bool { return unicode.Is(rt, r) })
}
// NotIn creates a Set with a Contains method that returns true for all runes not
// in the given RangeTable.
func NotIn(rt *unicode.RangeTable) Set {
return setFunc(func(r rune) bool { return !unicode.Is(rt, r) })
}
// Predicate creates a Set with a Contains method that returns f(r).
func Predicate(f func(rune) bool) Set {
return setFunc(f)
}
// Transformer implements the transform.Transformer interface.
type Transformer struct {
t transform.SpanningTransformer
}
func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
return t.t.Transform(dst, src, atEOF)
}
func (t Transformer) Span(b []byte, atEOF bool) (n int, err error) {
return t.t.Span(b, atEOF)
}
func (t Transformer) Reset() { t.t.Reset() }
// Bytes returns a new byte slice with the result of converting b using t. It
// calls Reset on t. It returns nil if any error was found. This can only happen
// if an error-producing Transformer is passed to If.
func (t Transformer) Bytes(b []byte) []byte {
b, _, err := transform.Bytes(t, b)
if err != nil {
return nil
}
return b
}
// String returns a string with the result of converting s using t. It calls
// Reset on t. It returns the empty string if any error was found. This can only
// happen if an error-producing Transformer is passed to If.
func (t Transformer) String(s string) string {
s, _, err := transform.String(t, s)
if err != nil {
return ""
}
return s
}
// TODO:
// - Copy: copying strings and bytes in whole-rune units.
// - Validation (maybe)
// - Well-formed-ness (maybe)
const runeErrorString = string(utf8.RuneError)
// Remove returns a Transformer that removes runes r for which s.Contains(r).
// Illegal input bytes are replaced by RuneError before being passed to f.
func Remove(s Set) Transformer {
if f, ok := s.(setFunc); ok {
// This little trick cuts the running time of BenchmarkRemove for sets
// created by Predicate roughly in half.
// TODO: special-case RangeTables as well.
return Transformer{remove(f)}
}
return Transformer{remove(s.Contains)}
}
// TODO: remove transform.RemoveFunc.
type remove func(r rune) bool
func (remove) Reset() {}
// Span implements transform.Spanner.
func (t remove) Span(src []byte, atEOF bool) (n int, err error) {
for r, size := rune(0), 0; n < len(src); {
if r = rune(src[n]); r < utf8.RuneSelf {
size = 1
} else if r, size = utf8.DecodeRune(src[n:]); size == 1 {
// Invalid rune.
if !atEOF && !utf8.FullRune(src[n:]) {
err = transform.ErrShortSrc
} else {
err = transform.ErrEndOfSpan
}
break
}
if t(r) {
err = transform.ErrEndOfSpan
break
}
n += size
}
return
}
// Transform implements transform.Transformer.
func (t remove) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
for r, size := rune(0), 0; nSrc < len(src); {
if r = rune(src[nSrc]); r < utf8.RuneSelf {
size = 1
} else if r, size = utf8.DecodeRune(src[nSrc:]); size == 1 {
// Invalid rune.
if !atEOF && !utf8.FullRune(src[nSrc:]) {
err = transform.ErrShortSrc
break
}
// We replace illegal bytes with RuneError. Not doing so might
// otherwise turn a sequence of invalid UTF-8 into valid UTF-8.
// The resulting byte sequence may subsequently contain runes
// for which t(r) is true that were passed unnoticed.
if !t(utf8.RuneError) {
if nDst+3 > len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst+0] = runeErrorString[0]
dst[nDst+1] = runeErrorString[1]
dst[nDst+2] = runeErrorString[2]
nDst += 3
}
nSrc++
continue
}
if t(r) {
nSrc += size
continue
}
if nDst+size > len(dst) {
err = transform.ErrShortDst
break
}
for i := 0; i < size; i++ {
dst[nDst] = src[nSrc]
nDst++
nSrc++
}
}
return
}
// Map returns a Transformer that maps the runes in the input using the given
// mapping. Illegal bytes in the input are converted to utf8.RuneError before
// being passed to the mapping func.
func Map(mapping func(rune) rune) Transformer {
return Transformer{mapper(mapping)}
}
type mapper func(rune) rune
func (mapper) Reset() {}
// Span implements transform.Spanner.
func (t mapper) Span(src []byte, atEOF bool) (n int, err error) {
for r, size := rune(0), 0; n < len(src); n += size {
if r = rune(src[n]); r < utf8.RuneSelf {
size = 1
} else if r, size = utf8.DecodeRune(src[n:]); size == 1 {
// Invalid rune.
if !atEOF && !utf8.FullRune(src[n:]) {
err = transform.ErrShortSrc
} else {
err = transform.ErrEndOfSpan
}
break
}
if t(r) != r {
err = transform.ErrEndOfSpan
break
}
}
return n, err
}
// Transform implements transform.Transformer.
func (t mapper) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
var replacement rune
var b [utf8.UTFMax]byte
for r, size := rune(0), 0; nSrc < len(src); {
if r = rune(src[nSrc]); r < utf8.RuneSelf {
if replacement = t(r); replacement < utf8.RuneSelf {
if nDst == len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst] = byte(replacement)
nDst++
nSrc++
continue
}
size = 1
} else if r, size = utf8.DecodeRune(src[nSrc:]); size == 1 {
// Invalid rune.
if !atEOF && !utf8.FullRune(src[nSrc:]) {
err = transform.ErrShortSrc
break
}
if replacement = t(utf8.RuneError); replacement == utf8.RuneError {
if nDst+3 > len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst+0] = runeErrorString[0]
dst[nDst+1] = runeErrorString[1]
dst[nDst+2] = runeErrorString[2]
nDst += 3
nSrc++
continue
}
} else if replacement = t(r); replacement == r {
if nDst+size > len(dst) {
err = transform.ErrShortDst
break
}
for i := 0; i < size; i++ {
dst[nDst] = src[nSrc]
nDst++
nSrc++
}
continue
}
n := utf8.EncodeRune(b[:], replacement)
if nDst+n > len(dst) {
err = transform.ErrShortDst
break
}
for i := 0; i < n; i++ {
dst[nDst] = b[i]
nDst++
}
nSrc += size
}
return
}
// ReplaceIllFormed returns a transformer that replaces all input bytes that are
// not part of a well-formed UTF-8 code sequence with utf8.RuneError.
func ReplaceIllFormed() Transformer {
return Transformer{&replaceIllFormed{}}
}
type replaceIllFormed struct{ transform.NopResetter }
func (t replaceIllFormed) Span(src []byte, atEOF bool) (n int, err error) {
for n < len(src) {
// ASCII fast path.
if src[n] < utf8.RuneSelf {
n++
continue
}
r, size := utf8.DecodeRune(src[n:])
// Look for a valid non-ASCII rune.
if r != utf8.RuneError || size != 1 {
n += size
continue
}
// Look for short source data.
if !atEOF && !utf8.FullRune(src[n:]) {
err = transform.ErrShortSrc
break
}
// We have an invalid rune.
err = transform.ErrEndOfSpan
break
}
return n, err
}
func (t replaceIllFormed) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
for nSrc < len(src) {
// ASCII fast path.
if r := src[nSrc]; r < utf8.RuneSelf {
if nDst == len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst] = r
nDst++
nSrc++
continue
}
// Look for a valid non-ASCII rune.
if _, size := utf8.DecodeRune(src[nSrc:]); size != 1 {
if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
err = transform.ErrShortDst
break
}
nDst += size
nSrc += size
continue
}
// Look for short source data.
if !atEOF && !utf8.FullRune(src[nSrc:]) {
err = transform.ErrShortSrc
break
}
// We have an invalid rune.
if nDst+3 > len(dst) {
err = transform.ErrShortDst
break
}
dst[nDst+0] = runeErrorString[0]
dst[nDst+1] = runeErrorString[1]
dst[nDst+2] = runeErrorString[2]
nDst += 3
nSrc++
}
return nDst, nSrc, err
}

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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.
// Package transform provides reader and writer wrappers that transform the
// bytes passing through as well as various transformations. Example
// transformations provided by other packages include normalization and
// conversion between character sets.
package transform // import "golang.org/x/text/transform"
import (
"bytes"
"errors"
"io"
"unicode/utf8"
)
var (
// ErrShortDst means that the destination buffer was too short to
// receive all of the transformed bytes.
ErrShortDst = errors.New("transform: short destination buffer")
// ErrShortSrc means that the source buffer has insufficient data to
// complete the transformation.
ErrShortSrc = errors.New("transform: short source buffer")
// ErrEndOfSpan means that the input and output (the transformed input)
// are not identical.
ErrEndOfSpan = errors.New("transform: input and output are not identical")
// errInconsistentByteCount means that Transform returned success (nil
// error) but also returned nSrc inconsistent with the src argument.
errInconsistentByteCount = errors.New("transform: inconsistent byte count returned")
// errShortInternal means that an internal buffer is not large enough
// to make progress and the Transform operation must be aborted.
errShortInternal = errors.New("transform: short internal buffer")
)
// Transformer transforms bytes.
type Transformer interface {
// Transform writes to dst the transformed bytes read from src, and
// returns the number of dst bytes written and src bytes read. The
// atEOF argument tells whether src represents the last bytes of the
// input.
//
// Callers should always process the nDst bytes produced and account
// for the nSrc bytes consumed before considering the error err.
//
// A nil error means that all of the transformed bytes (whether freshly
// transformed from src or left over from previous Transform calls)
// were written to dst. A nil error can be returned regardless of
// whether atEOF is true. If err is nil then nSrc must equal len(src);
// the converse is not necessarily true.
//
// ErrShortDst means that dst was too short to receive all of the
// transformed bytes. ErrShortSrc means that src had insufficient data
// to complete the transformation. If both conditions apply, then
// either error may be returned. Other than the error conditions listed
// here, implementations are free to report other errors that arise.
Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error)
// Reset resets the state and allows a Transformer to be reused.
Reset()
}
// SpanningTransformer extends the Transformer interface with a Span method
// that determines how much of the input already conforms to the Transformer.
type SpanningTransformer interface {
Transformer
// Span returns a position in src such that transforming src[:n] results in
// identical output src[:n] for these bytes. It does not necessarily return
// the largest such n. The atEOF argument tells whether src represents the
// last bytes of the input.
//
// Callers should always account for the n bytes consumed before
// considering the error err.
//
// A nil error means that all input bytes are known to be identical to the
// output produced by the Transformer. A nil error can be returned
// regardless of whether atEOF is true. If err is nil, then n must
// equal len(src); the converse is not necessarily true.
//
// ErrEndOfSpan means that the Transformer output may differ from the
// input after n bytes. Note that n may be len(src), meaning that the output
// would contain additional bytes after otherwise identical output.
// ErrShortSrc means that src had insufficient data to determine whether the
// remaining bytes would change. Other than the error conditions listed
// here, implementations are free to report other errors that arise.
//
// Calling Span can modify the Transformer state as a side effect. In
// effect, it does the transformation just as calling Transform would, only
// without copying to a destination buffer and only up to a point it can
// determine the input and output bytes are the same. This is obviously more
// limited than calling Transform, but can be more efficient in terms of
// copying and allocating buffers. Calls to Span and Transform may be
// interleaved.
Span(src []byte, atEOF bool) (n int, err error)
}
// NopResetter can be embedded by implementations of Transformer to add a nop
// Reset method.
type NopResetter struct{}
// Reset implements the Reset method of the Transformer interface.
func (NopResetter) Reset() {}
// Reader wraps another io.Reader by transforming the bytes read.
type Reader struct {
r io.Reader
t Transformer
err error
// dst[dst0:dst1] contains bytes that have been transformed by t but
// not yet copied out via Read.
dst []byte
dst0, dst1 int
// src[src0:src1] contains bytes that have been read from r but not
// yet transformed through t.
src []byte
src0, src1 int
// transformComplete is whether the transformation is complete,
// regardless of whether or not it was successful.
transformComplete bool
}
const defaultBufSize = 4096
// NewReader returns a new Reader that wraps r by transforming the bytes read
// via t. It calls Reset on t.
func NewReader(r io.Reader, t Transformer) *Reader {
t.Reset()
return &Reader{
r: r,
t: t,
dst: make([]byte, defaultBufSize),
src: make([]byte, defaultBufSize),
}
}
// Read implements the io.Reader interface.
func (r *Reader) Read(p []byte) (int, error) {
n, err := 0, error(nil)
for {
// Copy out any transformed bytes and return the final error if we are done.
if r.dst0 != r.dst1 {
n = copy(p, r.dst[r.dst0:r.dst1])
r.dst0 += n
if r.dst0 == r.dst1 && r.transformComplete {
return n, r.err
}
return n, nil
} else if r.transformComplete {
return 0, r.err
}
// Try to transform some source bytes, or to flush the transformer if we
// are out of source bytes. We do this even if r.r.Read returned an error.
// As the io.Reader documentation says, "process the n > 0 bytes returned
// before considering the error".
if r.src0 != r.src1 || r.err != nil {
r.dst0 = 0
r.dst1, n, err = r.t.Transform(r.dst, r.src[r.src0:r.src1], r.err == io.EOF)
r.src0 += n
switch {
case err == nil:
if r.src0 != r.src1 {
r.err = errInconsistentByteCount
}
// The Transform call was successful; we are complete if we
// cannot read more bytes into src.
r.transformComplete = r.err != nil
continue
case err == ErrShortDst && (r.dst1 != 0 || n != 0):
// Make room in dst by copying out, and try again.
continue
case err == ErrShortSrc && r.src1-r.src0 != len(r.src) && r.err == nil:
// Read more bytes into src via the code below, and try again.
default:
r.transformComplete = true
// The reader error (r.err) takes precedence over the
// transformer error (err) unless r.err is nil or io.EOF.
if r.err == nil || r.err == io.EOF {
r.err = err
}
continue
}
}
// Move any untransformed source bytes to the start of the buffer
// and read more bytes.
if r.src0 != 0 {
r.src0, r.src1 = 0, copy(r.src, r.src[r.src0:r.src1])
}
n, r.err = r.r.Read(r.src[r.src1:])
r.src1 += n
}
}
// TODO: implement ReadByte (and ReadRune??).
// Writer wraps another io.Writer by transforming the bytes read.
// The user needs to call Close to flush unwritten bytes that may
// be buffered.
type Writer struct {
w io.Writer
t Transformer
dst []byte
// src[:n] contains bytes that have not yet passed through t.
src []byte
n int
}
// NewWriter returns a new Writer that wraps w by transforming the bytes written
// via t. It calls Reset on t.
func NewWriter(w io.Writer, t Transformer) *Writer {
t.Reset()
return &Writer{
w: w,
t: t,
dst: make([]byte, defaultBufSize),
src: make([]byte, defaultBufSize),
}
}
// Write implements the io.Writer interface. If there are not enough
// bytes available to complete a Transform, the bytes will be buffered
// for the next write. Call Close to convert the remaining bytes.
func (w *Writer) Write(data []byte) (n int, err error) {
src := data
if w.n > 0 {
// Append bytes from data to the last remainder.
// TODO: limit the amount copied on first try.
n = copy(w.src[w.n:], data)
w.n += n
src = w.src[:w.n]
}
for {
nDst, nSrc, err := w.t.Transform(w.dst, src, false)
if _, werr := w.w.Write(w.dst[:nDst]); werr != nil {
return n, werr
}
src = src[nSrc:]
if w.n == 0 {
n += nSrc
} else if len(src) <= n {
// Enough bytes from w.src have been consumed. We make src point
// to data instead to reduce the copying.
w.n = 0
n -= len(src)
src = data[n:]
if n < len(data) && (err == nil || err == ErrShortSrc) {
continue
}
}
switch err {
case ErrShortDst:
// This error is okay as long as we are making progress.
if nDst > 0 || nSrc > 0 {
continue
}
case ErrShortSrc:
if len(src) < len(w.src) {
m := copy(w.src, src)
// If w.n > 0, bytes from data were already copied to w.src and n
// was already set to the number of bytes consumed.
if w.n == 0 {
n += m
}
w.n = m
err = nil
} else if nDst > 0 || nSrc > 0 {
// Not enough buffer to store the remainder. Keep processing as
// long as there is progress. Without this case, transforms that
// require a lookahead larger than the buffer may result in an
// error. This is not something one may expect to be common in
// practice, but it may occur when buffers are set to small
// sizes during testing.
continue
}
case nil:
if w.n > 0 {
err = errInconsistentByteCount
}
}
return n, err
}
}
// Close implements the io.Closer interface.
func (w *Writer) Close() error {
src := w.src[:w.n]
for {
nDst, nSrc, err := w.t.Transform(w.dst, src, true)
if _, werr := w.w.Write(w.dst[:nDst]); werr != nil {
return werr
}
if err != ErrShortDst {
return err
}
src = src[nSrc:]
}
}
type nop struct{ NopResetter }
func (nop) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
n := copy(dst, src)
if n < len(src) {
err = ErrShortDst
}
return n, n, err
}
func (nop) Span(src []byte, atEOF bool) (n int, err error) {
return len(src), nil
}
type discard struct{ NopResetter }
func (discard) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
return 0, len(src), nil
}
var (
// Discard is a Transformer for which all Transform calls succeed
// by consuming all bytes and writing nothing.
Discard Transformer = discard{}
// Nop is a SpanningTransformer that copies src to dst.
Nop SpanningTransformer = nop{}
)
// chain is a sequence of links. A chain with N Transformers has N+1 links and
// N+1 buffers. Of those N+1 buffers, the first and last are the src and dst
// buffers given to chain.Transform and the middle N-1 buffers are intermediate
// buffers owned by the chain. The i'th link transforms bytes from the i'th
// buffer chain.link[i].b at read offset chain.link[i].p to the i+1'th buffer
// chain.link[i+1].b at write offset chain.link[i+1].n, for i in [0, N).
type chain struct {
link []link
err error
// errStart is the index at which the error occurred plus 1. Processing
// errStart at this level at the next call to Transform. As long as
// errStart > 0, chain will not consume any more source bytes.
errStart int
}
func (c *chain) fatalError(errIndex int, err error) {
if i := errIndex + 1; i > c.errStart {
c.errStart = i
c.err = err
}
}
type link struct {
t Transformer
// b[p:n] holds the bytes to be transformed by t.
b []byte
p int
n int
}
func (l *link) src() []byte {
return l.b[l.p:l.n]
}
func (l *link) dst() []byte {
return l.b[l.n:]
}
// Chain returns a Transformer that applies t in sequence.
func Chain(t ...Transformer) Transformer {
if len(t) == 0 {
return nop{}
}
c := &chain{link: make([]link, len(t)+1)}
for i, tt := range t {
c.link[i].t = tt
}
// Allocate intermediate buffers.
b := make([][defaultBufSize]byte, len(t)-1)
for i := range b {
c.link[i+1].b = b[i][:]
}
return c
}
// Reset resets the state of Chain. It calls Reset on all the Transformers.
func (c *chain) Reset() {
for i, l := range c.link {
if l.t != nil {
l.t.Reset()
}
c.link[i].p, c.link[i].n = 0, 0
}
}
// TODO: make chain use Span (is going to be fun to implement!)
// Transform applies the transformers of c in sequence.
func (c *chain) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
// Set up src and dst in the chain.
srcL := &c.link[0]
dstL := &c.link[len(c.link)-1]
srcL.b, srcL.p, srcL.n = src, 0, len(src)
dstL.b, dstL.n = dst, 0
var lastFull, needProgress bool // for detecting progress
// i is the index of the next Transformer to apply, for i in [low, high].
// low is the lowest index for which c.link[low] may still produce bytes.
// high is the highest index for which c.link[high] has a Transformer.
// The error returned by Transform determines whether to increase or
// decrease i. We try to completely fill a buffer before converting it.
for low, i, high := c.errStart, c.errStart, len(c.link)-2; low <= i && i <= high; {
in, out := &c.link[i], &c.link[i+1]
nDst, nSrc, err0 := in.t.Transform(out.dst(), in.src(), atEOF && low == i)
out.n += nDst
in.p += nSrc
if i > 0 && in.p == in.n {
in.p, in.n = 0, 0
}
needProgress, lastFull = lastFull, false
switch err0 {
case ErrShortDst:
// Process the destination buffer next. Return if we are already
// at the high index.
if i == high {
return dstL.n, srcL.p, ErrShortDst
}
if out.n != 0 {
i++
// If the Transformer at the next index is not able to process any
// source bytes there is nothing that can be done to make progress
// and the bytes will remain unprocessed. lastFull is used to
// detect this and break out of the loop with a fatal error.
lastFull = true
continue
}
// The destination buffer was too small, but is completely empty.
// Return a fatal error as this transformation can never complete.
c.fatalError(i, errShortInternal)
case ErrShortSrc:
if i == 0 {
// Save ErrShortSrc in err. All other errors take precedence.
err = ErrShortSrc
break
}
// Source bytes were depleted before filling up the destination buffer.
// Verify we made some progress, move the remaining bytes to the errStart
// and try to get more source bytes.
if needProgress && nSrc == 0 || in.n-in.p == len(in.b) {
// There were not enough source bytes to proceed while the source
// buffer cannot hold any more bytes. Return a fatal error as this
// transformation can never complete.
c.fatalError(i, errShortInternal)
break
}
// in.b is an internal buffer and we can make progress.
in.p, in.n = 0, copy(in.b, in.src())
fallthrough
case nil:
// if i == low, we have depleted the bytes at index i or any lower levels.
// In that case we increase low and i. In all other cases we decrease i to
// fetch more bytes before proceeding to the next index.
if i > low {
i--
continue
}
default:
c.fatalError(i, err0)
}
// Exhausted level low or fatal error: increase low and continue
// to process the bytes accepted so far.
i++
low = i
}
// If c.errStart > 0, this means we found a fatal error. We will clear
// all upstream buffers. At this point, no more progress can be made
// downstream, as Transform would have bailed while handling ErrShortDst.
if c.errStart > 0 {
for i := 1; i < c.errStart; i++ {
c.link[i].p, c.link[i].n = 0, 0
}
err, c.errStart, c.err = c.err, 0, nil
}
return dstL.n, srcL.p, err
}
// Deprecated: Use runes.Remove instead.
func RemoveFunc(f func(r rune) bool) Transformer {
return removeF(f)
}
type removeF func(r rune) bool
func (removeF) Reset() {}
// Transform implements the Transformer interface.
func (t removeF) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
for r, sz := rune(0), 0; len(src) > 0; src = src[sz:] {
if r = rune(src[0]); r < utf8.RuneSelf {
sz = 1
} else {
r, sz = utf8.DecodeRune(src)
if sz == 1 {
// Invalid rune.
if !atEOF && !utf8.FullRune(src) {
err = ErrShortSrc
break
}
// We replace illegal bytes with RuneError. Not doing so might
// otherwise turn a sequence of invalid UTF-8 into valid UTF-8.
// The resulting byte sequence may subsequently contain runes
// for which t(r) is true that were passed unnoticed.
if !t(r) {
if nDst+3 > len(dst) {
err = ErrShortDst
break
}
nDst += copy(dst[nDst:], "\uFFFD")
}
nSrc++
continue
}
}
if !t(r) {
if nDst+sz > len(dst) {
err = ErrShortDst
break
}
nDst += copy(dst[nDst:], src[:sz])
}
nSrc += sz
}
return
}
// grow returns a new []byte that is longer than b, and copies the first n bytes
// of b to the start of the new slice.
func grow(b []byte, n int) []byte {
m := len(b)
if m <= 32 {
m = 64
} else if m <= 256 {
m *= 2
} else {
m += m >> 1
}
buf := make([]byte, m)
copy(buf, b[:n])
return buf
}
const initialBufSize = 128
// String returns a string with the result of converting s[:n] using t, where
// n <= len(s). If err == nil, n will be len(s). It calls Reset on t.
func String(t Transformer, s string) (result string, n int, err error) {
t.Reset()
if s == "" {
// Fast path for the common case for empty input. Results in about a
// 86% reduction of running time for BenchmarkStringLowerEmpty.
if _, _, err := t.Transform(nil, nil, true); err == nil {
return "", 0, nil
}
}
// Allocate only once. Note that both dst and src escape when passed to
// Transform.
buf := [2 * initialBufSize]byte{}
dst := buf[:initialBufSize:initialBufSize]
src := buf[initialBufSize : 2*initialBufSize]
// The input string s is transformed in multiple chunks (starting with a
// chunk size of initialBufSize). nDst and nSrc are per-chunk (or
// per-Transform-call) indexes, pDst and pSrc are overall indexes.
nDst, nSrc := 0, 0
pDst, pSrc := 0, 0
// pPrefix is the length of a common prefix: the first pPrefix bytes of the
// result will equal the first pPrefix bytes of s. It is not guaranteed to
// be the largest such value, but if pPrefix, len(result) and len(s) are
// all equal after the final transform (i.e. calling Transform with atEOF
// being true returned nil error) then we don't need to allocate a new
// result string.
pPrefix := 0
for {
// Invariant: pDst == pPrefix && pSrc == pPrefix.
n := copy(src, s[pSrc:])
nDst, nSrc, err = t.Transform(dst, src[:n], pSrc+n == len(s))
pDst += nDst
pSrc += nSrc
// TODO: let transformers implement an optional Spanner interface, akin
// to norm's QuickSpan. This would even allow us to avoid any allocation.
if !bytes.Equal(dst[:nDst], src[:nSrc]) {
break
}
pPrefix = pSrc
if err == ErrShortDst {
// A buffer can only be short if a transformer modifies its input.
break
} else if err == ErrShortSrc {
if nSrc == 0 {
// No progress was made.
break
}
// Equal so far and !atEOF, so continue checking.
} else if err != nil || pPrefix == len(s) {
return string(s[:pPrefix]), pPrefix, err
}
}
// Post-condition: pDst == pPrefix + nDst && pSrc == pPrefix + nSrc.
// We have transformed the first pSrc bytes of the input s to become pDst
// transformed bytes. Those transformed bytes are discontiguous: the first
// pPrefix of them equal s[:pPrefix] and the last nDst of them equal
// dst[:nDst]. We copy them around, into a new dst buffer if necessary, so
// that they become one contiguous slice: dst[:pDst].
if pPrefix != 0 {
newDst := dst
if pDst > len(newDst) {
newDst = make([]byte, len(s)+nDst-nSrc)
}
copy(newDst[pPrefix:pDst], dst[:nDst])
copy(newDst[:pPrefix], s[:pPrefix])
dst = newDst
}
// Prevent duplicate Transform calls with atEOF being true at the end of
// the input. Also return if we have an unrecoverable error.
if (err == nil && pSrc == len(s)) ||
(err != nil && err != ErrShortDst && err != ErrShortSrc) {
return string(dst[:pDst]), pSrc, err
}
// Transform the remaining input, growing dst and src buffers as necessary.
for {
n := copy(src, s[pSrc:])
atEOF := pSrc+n == len(s)
nDst, nSrc, err := t.Transform(dst[pDst:], src[:n], atEOF)
pDst += nDst
pSrc += nSrc
// If we got ErrShortDst or ErrShortSrc, do not grow as long as we can
// make progress. This may avoid excessive allocations.
if err == ErrShortDst {
if nDst == 0 {
dst = grow(dst, pDst)
}
} else if err == ErrShortSrc {
if atEOF {
return string(dst[:pDst]), pSrc, err
}
if nSrc == 0 {
src = grow(src, 0)
}
} else if err != nil || pSrc == len(s) {
return string(dst[:pDst]), pSrc, err
}
}
}
// Bytes returns a new byte slice with the result of converting b[:n] using t,
// where n <= len(b). If err == nil, n will be len(b). It calls Reset on t.
func Bytes(t Transformer, b []byte) (result []byte, n int, err error) {
return doAppend(t, 0, make([]byte, len(b)), b)
}
// Append appends the result of converting src[:n] using t to dst, where
// n <= len(src), If err == nil, n will be len(src). It calls Reset on t.
func Append(t Transformer, dst, src []byte) (result []byte, n int, err error) {
if len(dst) == cap(dst) {
n := len(src) + len(dst) // It is okay for this to be 0.
b := make([]byte, n)
dst = b[:copy(b, dst)]
}
return doAppend(t, len(dst), dst[:cap(dst)], src)
}
func doAppend(t Transformer, pDst int, dst, src []byte) (result []byte, n int, err error) {
t.Reset()
pSrc := 0
for {
nDst, nSrc, err := t.Transform(dst[pDst:], src[pSrc:], true)
pDst += nDst
pSrc += nSrc
if err != ErrShortDst {
return dst[:pDst], pSrc, err
}
// Grow the destination buffer, but do not grow as long as we can make
// progress. This may avoid excessive allocations.
if nDst == 0 {
dst = grow(dst, pDst)
}
}
}