+++ /dev/null
-package strconv
-
-import (
- "errors"
- "unicode/utf8"
-)
-
-// ErrSyntax indicates that a value does not have the right syntax for the target type.
-var ErrSyntax = errors.New("invalid syntax")
-
-// 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) (t string, err 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 != '"' {
- return "", ErrSyntax
- }
- if !contains(s, '$') && !contains(s, '{') && contains(s, '\n') {
- return "", ErrSyntax
- }
-
- // Is it trivial? Avoid allocation.
- if !contains(s, '\\') && !contains(s, quote) && !contains(s, '$') {
- switch quote {
- case '"':
- 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 {
- // If we're starting a '${}' then let it through un-unquoted.
- // Specifically: we don't unquote any characters within the `${}`
- // section.
- if s[0] == '$' && len(s) > 1 && s[1] == '{' {
- buf = append(buf, '$', '{')
- s = s[2:]
-
- // Continue reading until we find the closing brace, copying as-is
- braces := 1
- for len(s) > 0 && braces > 0 {
- r, size := utf8.DecodeRuneInString(s)
- if r == utf8.RuneError {
- return "", ErrSyntax
- }
-
- s = s[size:]
-
- n := utf8.EncodeRune(runeTmp[:], r)
- buf = append(buf, runeTmp[:n]...)
-
- switch r {
- case '{':
- braces++
- case '}':
- braces--
- }
- }
- if braces != 0 {
- return "", ErrSyntax
- }
- if len(s) == 0 {
- // If there's no string left, we're done!
- break
- } else {
- // If there's more left, we need to pop back up to the top of the loop
- // in case there's another interpolation in this string.
- continue
- }
- }
-
- if s[0] == '\n' {
- return "", ErrSyntax
- }
-
- 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 {
- for i := 0; i < len(s); i++ {
- if s[i] == c {
- return true
- }
- }
- return false
-}
-
-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
-}
-
-func unquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
- // easy cases
- 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
-}
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