// Copyright 2009 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 makeisprint.go -output isprint.go
package strconv
import (
"internal/bytealg"
"unicode/utf8"
)
const (
lowerhex = "0123456789abcdef"
upperhex = "0123456789ABCDEF"
)
func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
return string(appendQuotedWith(make([]byte, 0, 3*len(s)/2), s, quote, ASCIIonly, graphicOnly))
}
func quoteRuneWith(r rune, quote byte, ASCIIonly, graphicOnly bool) string {
return string(appendQuotedRuneWith(nil, r, quote, ASCIIonly, graphicOnly))
}
func appendQuotedWith(buf []byte, s string, quote byte, ASCIIonly, graphicOnly bool) []byte {
// Often called with big strings, so preallocate. If there's quoting,
// this is conservative but still helps a lot.
if cap(buf)-len(buf) < len(s) {
nBuf := make([]byte, len(buf), len(buf)+1+len(s)+1)
copy(nBuf, buf)
buf = nBuf
}
buf = append(buf, quote)
for width := 0; len(s) > 0; s = s[width:] {
r := rune(s[0])
width = 1
if r >= utf8.RuneSelf {
r, width = utf8.DecodeRuneInString(s)
}
if width == 1 && r == utf8.RuneError {
buf = append(buf, `\x`...)
buf = append(buf, lowerhex[s[0]>>4])
buf = append(buf, lowerhex[s[0]&0xF])
continue
}
buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
}
buf = append(buf, quote)
return buf
}
func appendQuotedRuneWith(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
buf = append(buf, quote)
if !utf8.ValidRune(r) {
r = utf8.RuneError
}
buf = appendEscapedRune(buf, r, quote, ASCIIonly, graphicOnly)
buf = append(buf, quote)
return buf
}
func appendEscapedRune(buf []byte, r rune, quote byte, ASCIIonly, graphicOnly bool) []byte {
var runeTmp [utf8.UTFMax]byte
if r == rune(quote) || r == '\\' { // always backslashed
buf = append(buf, '\\')
buf = append(buf, byte(r))
return buf
}
if ASCIIonly {
if r < utf8.RuneSelf && IsPrint(r) {
buf = append(buf, byte(r))
return buf
}
} else if IsPrint(r) || graphicOnly && isInGraphicList(r) {
n := utf8.EncodeRune(runeTmp[:], r)
buf = append(buf, runeTmp[:n]...)
return buf
}
switch r {
case '\a':
buf = append(buf, `\a`...)
case '\b':
buf = append(buf, `\b`...)
case '\f':
buf = append(buf, `\f`...)
case '\n':
buf = append(buf, `\n`...)
case '\r':
buf = append(buf, `\r`...)
case '\t':
buf = append(buf, `\t`...)
case '\v':
buf = append(buf, `\v`...)
default:
switch {
case r < ' ':
buf = append(buf, `\x`...)
buf = append(buf, lowerhex[byte(r)>>4])
buf = append(buf, lowerhex[byte(r)&0xF])
case r > utf8.MaxRune:
r = 0xFFFD
fallthrough
case r < 0x10000:
buf = append(buf, `\u`...)
for s := 12; s >= 0; s -= 4 {
buf = append(buf, lowerhex[r>>uint(s)&0xF])
}
default:
buf = append(buf, `\U`...)
for s := 28; s >= 0; s -= 4 {
buf = append(buf, lowerhex[r>>uint(s)&0xF])
}
}
}
return buf
}
// Quote returns a double-quoted Go string literal representing s. The
// returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
// control characters and non-printable characters as defined by
// IsPrint.
func Quote(s string) string {
return quoteWith(s, '"', false, false)
}
// AppendQuote appends a double-quoted Go string literal representing s,
// as generated by Quote, to dst and returns the extended buffer.
func AppendQuote(dst []byte, s string) []byte {
return appendQuotedWith(dst, s, '"', false, false)
}
// QuoteToASCII returns a double-quoted Go string literal representing s.
// The returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
// non-ASCII characters and non-printable characters as defined by IsPrint.
func QuoteToASCII(s string) string {
return quoteWith(s, '"', true, false)
}
// AppendQuoteToASCII appends a double-quoted Go string literal representing s,
// as generated by QuoteToASCII, to dst and returns the extended buffer.
func AppendQuoteToASCII(dst []byte, s string) []byte {
return appendQuotedWith(dst, s, '"', true, false)
}
// QuoteToGraphic returns a double-quoted Go string literal representing s.
// The returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
// non-ASCII characters and non-printable characters as defined by IsGraphic.
func QuoteToGraphic(s string) string {
return quoteWith(s, '"', false, true)
}
// AppendQuoteToGraphic appends a double-quoted Go string literal representing s,
// as generated by QuoteToGraphic, to dst and returns the extended buffer.
func AppendQuoteToGraphic(dst []byte, s string) []byte {
return appendQuotedWith(dst, s, '"', false, true)
}
// QuoteRune returns a single-quoted Go character literal representing the
// rune. The returned string uses Go escape sequences (\t, \n, \xFF, \u0100)
// for control characters and non-printable characters as defined by IsPrint.
func QuoteRune(r rune) string {
return quoteRuneWith(r, '\'', false, false)
}
// AppendQuoteRune appends a single-quoted Go character literal representing the rune,
// as generated by QuoteRune, to dst and returns the extended buffer.
func AppendQuoteRune(dst []byte, r rune) []byte {
return appendQuotedRuneWith(dst, r, '\'', false, false)
}
// QuoteRuneToASCII returns a single-quoted Go character literal representing
// the rune. The returned string uses Go escape sequences (\t, \n, \xFF,
// \u0100) for non-ASCII characters and non-printable characters as defined
// by IsPrint.
func QuoteRuneToASCII(r rune) string {
return quoteRuneWith(r, '\'', true, false)
}
// AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
// as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
return appendQuotedRuneWith(dst, r, '\'', true, false)
}
// QuoteRuneToGraphic returns a single-quoted Go character literal representing
// the rune. The returned string uses Go escape sequences (\t, \n, \xFF,
// \u0100) for non-ASCII characters and non-printable characters as defined
// by IsGraphic.
func QuoteRuneToGraphic(r rune) string {
return quoteRuneWith(r, '\'', false, true)
}
// AppendQuoteRuneToGraphic appends a single-quoted Go character literal representing the rune,
// as generated by QuoteRuneToGraphic, to dst and returns the extended buffer.
func AppendQuoteRuneToGraphic(dst []byte, r rune) []byte {
return appendQuotedRuneWith(dst, r, '\'', false, true)
}
// CanBackquote reports whether the string s can be represented
// unchanged as a single-line backquoted string without control
// characters other than tab.
func CanBackquote(s string) bool {
for len(s) > 0 {
r, wid := utf8.DecodeRuneInString(s)
s = s[wid:]
if wid > 1 {
if r == '\ufeff' {
return false // BOMs are invisible and should not be quoted.
}
continue // All other multibyte runes are correctly encoded and assumed printable.
}
if r == utf8.RuneError {
return false
}
if (r < ' ' && r != '\t') || r == '`' || r == '\u007F' {
return false
}
}
return true
}
func unhex(b byte) (v rune, ok bool) {
c := rune(b)
switch {
case '0' <= c && c <= '9':
return c - '0', true
case 'a' <= c && c <= 'f':
return c - 'a' + 10, true
case 'A' <= c && c <= 'F':
return c - 'A' + 10, true
}
return
}
// UnquoteChar decodes the first character or byte in the escaped string
// or character literal represented by the string s.
// It returns four values:
//
// 1) value, the decoded Unicode code point or byte value;
// 2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
// 3) tail, the remainder of the string after the character; and
// 4) an error that will be nil if the character is syntactically valid.
//
// The second argument, quote, specifies the type of literal being parsed
// and therefore which escaped quote character is permitted.
// If set to a single quote, it permits the sequence \' and disallows unescaped '.
// If set to a double quote, it permits \" and disallows unescaped ".
// If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
func UnquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
// easy cases
if len(s) == 0 {
err = ErrSyntax
return
}
switch c := s[0]; {
case c == quote && (quote == '\'' || quote == '"'):
err = ErrSyntax
return
case c >= utf8.RuneSelf:
r, size := utf8.DecodeRuneInString(s)
return r, true, s[size:], nil
case c != '\\':
return rune(s[0]), false, s[1:], nil
}
// hard case: c is backslash
if len(s) <= 1 {
err = ErrSyntax
return
}
c := s[1]
s = s[2:]
switch c {
case 'a':
value = '\a'
case 'b':
value = '\b'
case 'f':
value = '\f'
case 'n':
value = '\n'
case 'r':
value = '\r'
case 't':
value = '\t'
case 'v':
value = '\v'
case 'x', 'u', 'U':
n := 0
switch c {
case 'x':
n = 2
case 'u':
n = 4
case 'U':
n = 8
}
var v rune
if len(s) < n {
err = ErrSyntax
return
}
for j := 0; j < n; j++ {
x, ok := unhex(s[j])
if !ok {
err = ErrSyntax
return
}
v = v<<4 | x
}
s = s[n:]
if c == 'x' {
// single-byte string, possibly not UTF-8
value = v
break
}
if v > utf8.MaxRune {
err = ErrSyntax
return
}
value = v
multibyte = true
case '0', '1', '2', '3', '4', '5', '6', '7':
v := rune(c) - '0'
if len(s) < 2 {
err = ErrSyntax
return
}
for j := 0; j < 2; j++ { // one digit already; two more
x := rune(s[j]) - '0'
if x < 0 || x > 7 {
err = ErrSyntax
return
}
v = (v << 3) | x
}
s = s[2:]
if v > 255 {
err = ErrSyntax
return
}
value = v
case '\\':
value = '\\'
case '\'', '"':
if c != quote {
err = ErrSyntax
return
}
value = rune(c)
default:
err = ErrSyntax
return
}
tail = s
return
}
// Unquote interprets s as a single-quoted, double-quoted,
// or backquoted Go string literal, returning the string value
// that s quotes. (If s is single-quoted, it would be a Go
// character literal; Unquote returns the corresponding
// one-character string.)
func Unquote(s string) (string, error) {
n := len(s)
if n < 2 {
return "", ErrSyntax
}
quote := s[0]
if quote != s[n-1] {
return "", ErrSyntax
}
s = s[1 : n-1]
if quote == '`' {
if contains(s, '`') {
return "", ErrSyntax
}
if contains(s, '\r') {
// -1 because we know there is at least one \r to remove.
buf := make([]byte, 0, len(s)-1)
for i := 0; i < len(s); i++ {
if s[i] != '\r' {
buf = append(buf, s[i])
}
}
return string(buf), nil
}
return s, nil
}
if quote != '"' && quote != '\'' {
return "", ErrSyntax
}
if contains(s, '\n') {
return "", ErrSyntax
}
// Is it trivial? Avoid allocation.
if !contains(s, '\\') && !contains(s, quote) {
switch quote {
case '"':
if utf8.ValidString(s) {
return s, nil
}
case '\'':
r, size := utf8.DecodeRuneInString(s)
if size == len(s) && (r != utf8.RuneError || size != 1) {
return s, nil
}
}
}
var runeTmp [utf8.UTFMax]byte
buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
for len(s) > 0 {
c, multibyte, ss, err := UnquoteChar(s, quote)
if err != nil {
return "", err
}
s = ss
if c < utf8.RuneSelf || !multibyte {
buf = append(buf, byte(c))
} else {
n := utf8.EncodeRune(runeTmp[:], c)
buf = append(buf, runeTmp[:n]...)
}
if quote == '\'' && len(s) != 0 {
// single-quoted must be single character
return "", ErrSyntax
}
}
return string(buf), nil
}
// contains reports whether the string contains the byte c.
func contains(s string, c byte) bool {
return bytealg.IndexByteString(s, c) != -1
}
// bsearch16 returns the smallest i such that a[i] >= x.
// If there is no such i, bsearch16 returns len(a).
func bsearch16(a []uint16, x uint16) int {
i, j := 0, len(a)
for i < j {
h := i + (j-i)/2
if a[h] < x {
i = h + 1
} else {
j = h
}
}
return i
}
// bsearch32 returns the smallest i such that a[i] >= x.
// If there is no such i, bsearch32 returns len(a).
func bsearch32(a []uint32, x uint32) int {
i, j := 0, len(a)
for i < j {
h := i + (j-i)/2
if a[h] < x {
i = h + 1
} else {
j = h
}
}
return i
}
// TODO: IsPrint is a local implementation of unicode.IsPrint, verified by the tests
// to give the same answer. It allows this package not to depend on unicode,
// and therefore not pull in all the Unicode tables. If the linker were better
// at tossing unused tables, we could get rid of this implementation.
// That would be nice.
// IsPrint reports whether the rune is defined as printable by Go, with
// the same definition as unicode.IsPrint: letters, numbers, punctuation,
// symbols and ASCII space.
func IsPrint(r rune) bool {
// Fast check for Latin-1
if r <= 0xFF {
if 0x20 <= r && r <= 0x7E {
// All the ASCII is printable from space through DEL-1.
return true
}
if 0xA1 <= r && r <= 0xFF {
// Similarly for ¡ through ÿ...
return r != 0xAD // ...except for the bizarre soft hyphen.
}
return false
}
// Same algorithm, either on uint16 or uint32 value.
// First, find first i such that isPrint[i] >= x.
// This is the index of either the start or end of a pair that might span x.
// The start is even (isPrint[i&^1]) and the end is odd (isPrint[i|1]).
// If we find x in a range, make sure x is not in isNotPrint list.
if 0 <= r && r < 1<<16 {
rr, isPrint, isNotPrint := uint16(r), isPrint16, isNotPrint16
i := bsearch16(isPrint, rr)
if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
return false
}
j := bsearch16(isNotPrint, rr)
return j >= len(isNotPrint) || isNotPrint[j] != rr
}
rr, isPrint, isNotPrint := uint32(r), isPrint32, isNotPrint32
i := bsearch32(isPrint, rr)
if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
return false
}
if r >= 0x20000 {
return true
}
r -= 0x10000
j := bsearch16(isNotPrint, uint16(r))
return j >= len(isNotPrint) || isNotPrint[j] != uint16(r)
}
// IsGraphic reports whether the rune is defined as a Graphic by Unicode. Such
// characters include letters, marks, numbers, punctuation, symbols, and
// spaces, from categories L, M, N, P, S, and Zs.
func IsGraphic(r rune) bool {
if IsPrint(r) {
return true
}
return isInGraphicList(r)
}
// isInGraphicList reports whether the rune is in the isGraphic list. This separation
// from IsGraphic allows quoteWith to avoid two calls to IsPrint.
// Should be called only if IsPrint fails.
func isInGraphicList(r rune) bool {
// We know r must fit in 16 bits - see makeisprint.go.
if r > 0xFFFF {
return false
}
rr := uint16(r)
i := bsearch16(isGraphic, rr)
return i < len(isGraphic) && rr == isGraphic[i]
}
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