1 files changed, 310 insertions, 0 deletions
diff --git a/src/pkg/strconv/quote.go b/src/pkg/strconv/quote.go
new file mode 100644
index 000000000..05e49d32d
--- /dev/null
+++ b/src/pkg/strconv/quote.go
@@ -0,0 +1,310 @@
+// 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.
+
+package strconv
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"unicode"
+	"utf8"
+)
+
+const lowerhex = "0123456789abcdef"
+
+func quoteWith(s string, quote byte, ASCIIonly bool) string {
+	var buf bytes.Buffer
+	buf.WriteByte(quote)
+	for width := 0; len(s) > 0; s = s[width:] {
+		rune := int(s[0])
+		width = 1
+		if rune >= utf8.RuneSelf {
+			rune, width = utf8.DecodeRuneInString(s)
+		}
+		if width == 1 && rune == utf8.RuneError {
+			buf.WriteString(`\x`)
+			buf.WriteByte(lowerhex[s[0]>>4])
+			buf.WriteByte(lowerhex[s[0]&0xF])
+			continue
+		}
+		if rune == int(quote) || rune == '\\' { // always backslashed
+			buf.WriteByte('\\')
+			buf.WriteByte(byte(rune))
+			continue
+		}
+		if ASCIIonly {
+			if rune <= unicode.MaxASCII && unicode.IsPrint(rune) {
+				buf.WriteRune(rune)
+				continue
+			}
+		} else if unicode.IsPrint(rune) {
+			buf.WriteRune(rune)
+			continue
+		}
+		switch rune {
+		case '\a':
+			buf.WriteString(`\a`)
+		case '\b':
+			buf.WriteString(`\b`)
+		case '\f':
+			buf.WriteString(`\f`)
+		case '\n':
+			buf.WriteString(`\n`)
+		case '\r':
+			buf.WriteString(`\r`)
+		case '\t':
+			buf.WriteString(`\t`)
+		case '\v':
+			buf.WriteString(`\v`)
+		default:
+			switch {
+			case rune < ' ':
+				buf.WriteString(`\x`)
+				buf.WriteByte(lowerhex[s[0]>>4])
+				buf.WriteByte(lowerhex[s[0]&0xF])
+			case rune > unicode.MaxRune:
+				rune = 0xFFFD
+				fallthrough
+			case rune < 0x10000:
+				buf.WriteString(`\u`)
+				for s := 12; s >= 0; s -= 4 {
+					buf.WriteByte(lowerhex[rune>>uint(s)&0xF])
+				}
+			default:
+				buf.WriteString(`\U`)
+				for s := 28; s >= 0; s -= 4 {
+					buf.WriteByte(lowerhex[rune>>uint(s)&0xF])
+				}
+			}
+		}
+	}
+	buf.WriteByte(quote)
+	return buf.String()
+
+}
+
+// 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
+// unicode.IsPrint.
+func Quote(s string) string {
+	return quoteWith(s, '"', 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
+// unicode.IsPrint.
+func QuoteToASCII(s string) string {
+	return quoteWith(s, '"', 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
+// unicode.IsPrint.
+func QuoteRune(rune int) string {
+	// TODO: avoid the allocation here.
+	return quoteWith(string(rune), '\'', 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 unicode.IsPrint.
+func QuoteRuneToASCII(rune int) string {
+	// TODO: avoid the allocation here.
+	return quoteWith(string(rune), '\'', true)
+}
+
+// CanBackquote returns whether the string s would be
+// a valid Go string literal if enclosed in backquotes.
+func CanBackquote(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if (s[i] < ' ' && s[i] != '\t') || s[i] == '`' {
+			return false
+		}
+	}
+	return true
+}
+
+func unhex(b byte) (v int, ok bool) {
+	c := int(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 int, multibyte bool, tail string, err os.Error) {
+	// easy cases
+	switch c := s[0]; {
+	case c == quote && (quote == '\'' || quote == '"'):
+		err = os.EINVAL
+		return
+	case c >= utf8.RuneSelf:
+		r, size := utf8.DecodeRuneInString(s)
+		return r, true, s[size:], nil
+	case c != '\\':
+		return int(s[0]), false, s[1:], nil
+	}
+
+	// hard case: c is backslash
+	if len(s) <= 1 {
+		err = os.EINVAL
+		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
+		}
+		v := 0
+		if len(s) < n {
+			err = os.EINVAL
+			return
+		}
+		for j := 0; j < n; j++ {
+			x, ok := unhex(s[j])
+			if !ok {
+				err = os.EINVAL
+				return
+			}
+			v = v<<4 | x
+		}
+		s = s[n:]
+		if c == 'x' {
+			// single-byte string, possibly not UTF-8
+			value = v
+			break
+		}
+		if v > unicode.MaxRune {
+			err = os.EINVAL
+			return
+		}
+		value = v
+		multibyte = true
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		v := int(c) - '0'
+		if len(s) < 2 {
+			err = os.EINVAL
+			return
+		}
+		for j := 0; j < 2; j++ { // one digit already; two more
+			x := int(s[j]) - '0'
+			if x < 0 || x > 7 {
+				return
+			}
+			v = (v << 3) | x
+		}
+		s = s[2:]
+		if v > 255 {
+			err = os.EINVAL
+			return
+		}
+		value = v
+	case '\\':
+		value = '\\'
+	case '\'', '"':
+		if c != quote {
+			err = os.EINVAL
+			return
+		}
+		value = int(c)
+	default:
+		err = os.EINVAL
+		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) (t string, err os.Error) {
+	n := len(s)
+	if n < 2 {
+		return "", os.EINVAL
+	}
+	quote := s[0]
+	if quote != s[n-1] {
+		return "", os.EINVAL
+	}
+	s = s[1 : n-1]
+
+	if quote == '`' {
+		if strings.Contains(s, "`") {
+			return "", os.EINVAL
+		}
+		return s, nil
+	}
+	if quote != '"' && quote != '\'' {
+		return "", os.EINVAL
+	}
+
+	var buf bytes.Buffer
+	for len(s) > 0 {
+		c, multibyte, ss, err := UnquoteChar(s, quote)
+		if err != nil {
+			return "", err
+		}
+		s = ss
+		if c < utf8.RuneSelf || !multibyte {
+			buf.WriteByte(byte(c))
+		} else {
+			buf.WriteString(string(c))
+		}
+		if quote == '\'' && len(s) != 0 {
+			// single-quoted must be single character
+			return "", os.EINVAL
+		}
+	}
+	return buf.String(), nil
+}