1 files changed, 111 insertions, 60 deletions
diff --git a/libgo/go/strconv/quote.go b/libgo/go/strconv/quote.go
index bcbdbc5..b3bbb16 100644
--- a/libgo/go/strconv/quote.go
+++ b/libgo/go/strconv/quote.go
@@ -7,7 +7,6 @@
 package strconv
 
 import (
-	"internal/bytealg"
 	"unicode/utf8"
 )
 
@@ -16,6 +15,11 @@ const (
 	upperhex = "0123456789ABCDEF"
 )
 
+// contains reports whether the string contains the byte c.
+func contains(s string, c byte) bool {
+	return index(s, c) != -1
+}
+
 func quoteWith(s string, quote byte, ASCIIonly, graphicOnly bool) string {
 	return string(appendQuotedWith(make([]byte, 0, 3*len(s)/2), s, quote, ASCIIonly, graphicOnly))
 }
@@ -360,85 +364,132 @@ func UnquoteChar(s string, quote byte) (value rune, multibyte bool, tail string,
 	return
 }
 
+// QuotedPrefix returns the quoted string (as understood by Unquote) at the prefix of s.
+// If s does not start with a valid quoted string, QuotedPrefix returns an error.
+func QuotedPrefix(s string) (string, error) {
+	out, _, err := unquote(s, false)
+	return out, err
+}
+
 // 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 {
+	out, rem, err := unquote(s, true)
+	if len(rem) > 0 {
 		return "", ErrSyntax
 	}
-	quote := s[0]
-	if quote != s[n-1] {
-		return "", ErrSyntax
+	return out, err
+}
+
+// unquote parses a quoted string at the start of the input,
+// returning the parsed prefix, the remaining suffix, and any parse errors.
+// If unescape is true, the parsed prefix is unescaped,
+// otherwise the input prefix is provided verbatim.
+func unquote(in string, unescape bool) (out, rem string, err error) {
+	// Determine the quote form and optimistically find the terminating quote.
+	if len(in) < 2 {
+		return "", in, ErrSyntax
 	}
-	s = s[1 : n-1]
+	quote := in[0]
+	end := index(in[1:], quote)
+	if end < 0 {
+		return "", in, ErrSyntax
+	}
+	end += 2 // position after terminating quote; may be wrong if escape sequences are present
 
-	if quote == '`' {
-		if contains(s, '`') {
-			return "", ErrSyntax
+	switch quote {
+	case '`':
+		switch {
+		case !unescape:
+			out = in[:end] // include quotes
+		case !contains(in[:end], '\r'):
+			out = in[len("`") : end-len("`")] // exclude quotes
+		default:
+			// Carriage return characters ('\r') inside raw string literals
+			// are discarded from the raw string value.
+			buf := make([]byte, 0, end-len("`")-len("\r")-len("`"))
+			for i := len("`"); i < end-len("`"); i++ {
+				if in[i] != '\r' {
+					buf = append(buf, in[i])
+				}
+			}
+			out = string(buf)
 		}
-		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])
+		// NOTE: Prior implementations did not verify that raw strings consist
+		// of valid UTF-8 characters and we continue to not verify it as such.
+		// The Go specification does not explicitly require valid UTF-8,
+		// but only mention that it is implicitly valid for Go source code
+		// (which must be valid UTF-8).
+		return out, in[end:], nil
+	case '"', '\'':
+		// Handle quoted strings without any escape sequences.
+		if !contains(in[:end], '\\') && !contains(in[:end], '\n') {
+			var valid bool
+			switch quote {
+			case '"':
+				valid = utf8.ValidString(in[len(`"`) : end-len(`"`)])
+			case '\'':
+				r, n := utf8.DecodeRuneInString(in[len("'") : end-len("'")])
+				valid = len("'")+n+len("'") == end && (r != utf8.RuneError || n != 1)
+			}
+			if valid {
+				out = in[:end]
+				if unescape {
+					out = out[1 : end-1] // exclude quotes
 				}
+				return out, in[end:], nil
 			}
-			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
+		// Handle quoted strings with escape sequences.
+		var buf []byte
+		in0 := in
+		in = in[1:] // skip starting quote
+		if unescape {
+			buf = make([]byte, 0, 3*end/2) // try to avoid more allocations
+		}
+		for len(in) > 0 && in[0] != quote {
+			// Process the next character,
+			// rejecting any unescaped newline characters which are invalid.
+			r, multibyte, rem, err := UnquoteChar(in, quote)
+			if in[0] == '\n' || err != nil {
+				return "", in0, ErrSyntax
 			}
-		case '\'':
-			r, size := utf8.DecodeRuneInString(s)
-			if size == len(s) && (r != utf8.RuneError || size != 1) {
-				return s, nil
+			in = rem
+
+			// Append the character if unescaping the input.
+			if unescape {
+				if r < utf8.RuneSelf || !multibyte {
+					buf = append(buf, byte(r))
+				} else {
+					var arr [utf8.UTFMax]byte
+					n := utf8.EncodeRune(arr[:], r)
+					buf = append(buf, arr[:n]...)
+				}
 			}
-		}
-	}
 
-	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
+			// Single quoted strings must be a single character.
+			if quote == '\'' {
+				break
+			}
 		}
-		s = ss
-		if c < utf8.RuneSelf || !multibyte {
-			buf = append(buf, byte(c))
-		} else {
-			n := utf8.EncodeRune(runeTmp[:], c)
-			buf = append(buf, runeTmp[:n]...)
+
+		// Verify that the string ends with a terminating quote.
+		if !(len(in) > 0 && in[0] == quote) {
+			return "", in0, ErrSyntax
 		}
-		if quote == '\'' && len(s) != 0 {
-			// single-quoted must be single character
-			return "", ErrSyntax
+		in = in[1:] // skip terminating quote
+
+		if unescape {
+			return string(buf), in, nil
 		}
+		return in0[:len(in0)-len(in)], in, nil
+	default:
+		return "", in, 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.
@@ -446,7 +497,7 @@ func contains(s string, c byte) bool {
 func bsearch16(a []uint16, x uint16) int {
 	i, j := 0, len(a)
 	for i < j {
-		h := i + (j-i)/2
+		h := i + (j-i)>>1
 		if a[h] < x {
 			i = h + 1
 		} else {
@@ -461,7 +512,7 @@ func bsearch16(a []uint16, x uint16) int {
 func bsearch32(a []uint32, x uint32) int {
 	i, j := 0, len(a)
 	for i < j {
-		h := i + (j-i)/2
+		h := i + (j-i)>>1
 		if a[h] < x {
 			i = h + 1
 		} else {