// 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
}
