strconv: add QuoteRune, which is analogous to Quote, but for runes rather than strings.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4556059

diff --git a/src/pkg/strconv/quote.go b/src/pkg/strconv/quote.go
index ed588972363d534639241f20458d017987d580a7..bbc0b2658e8826567842bdffd5c6c4afb2fd2d92 100644 (file)
--- a/src/pkg/strconv/quote.go
+++ b/src/pkg/strconv/quote.go
@@ -14,17 +14,14 @@ import (
 
 const lowerhex = "0123456789abcdef"
 
-// Quote returns a double-quoted Go string literal
-// representing s.  The returned string s uses Go escape
-// sequences (\t, \n, \xFF, \u0100) for control characters
-// and non-ASCII characters.
-func Quote(s string) string {
+func quoteWith(s string, quote byte) string {
        var buf bytes.Buffer
-       buf.WriteByte('"')
+       buf.WriteByte(quote)
        for ; len(s) > 0; s = s[1:] {
                switch c := s[0]; {
-               case c == '"':
-                       buf.WriteString(`\"`)
+               case c == quote:
+                       buf.WriteByte('\\')
+                       buf.WriteByte(quote)
                case c == '\\':
                        buf.WriteString(`\\`)
                case ' ' <= c && c <= '~':
@@ -69,8 +66,26 @@ func Quote(s string) string {
                        buf.WriteByte(lowerhex[c&0xF])
                }
        }
-       buf.WriteByte('"')
+       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-ASCII characters.
+func Quote(s string) string {
+       return quoteWith(s, '"')
+}
+
+// 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-ASCII characters.
+func QuoteRune(rune int) string {
+       // TODO: avoid the allocation here.
+       return quoteWith(string(rune), '\'')
 }
 
 // CanBackquote returns whether the string s would be

diff --git a/src/pkg/strconv/quote_test.go b/src/pkg/strconv/quote_test.go
index 1235fcb9aefcf53313ae6c56f314e7dfd28020f8..3232d611cffed919f53fdc44f9045102ff5726f6 100644 (file)
--- a/src/pkg/strconv/quote_test.go
+++ b/src/pkg/strconv/quote_test.go
@@ -25,14 +25,37 @@ var quotetests = []quoteTest{
 }
 
 func TestQuote(t *testing.T) {
-       for i := 0; i < len(quotetests); i++ {
-               tt := quotetests[i]
+       for _, tt := range quotetests {
                if out := Quote(tt.in); out != tt.out {
                        t.Errorf("Quote(%s) = %s, want %s", tt.in, out, tt.out)
                }
        }
 }
 
+type quoteRuneTest struct {
+       in  int
+       out string
+}
+
+var quoterunetests = []quoteRuneTest{
+       {'a', `'a'`},
+       {'\a', `'\a'`},
+       {'\\', `'\\'`},
+       {0xFF, `'\u00ff'`},
+       {0x263a, `'\u263a'`},
+       {0x0010ffff, `'\U0010ffff'`},
+       {0x0010ffff + 1, `'\ufffd'`},
+       {0x04, `'\x04'`},
+}
+
+func TestQuoteRune(t *testing.T) {
+       for _, tt := range quoterunetests {
+               if out := QuoteRune(tt.in); out != tt.out {
+                       t.Errorf("QuoteRune(%U) = %s, want %s", tt.in, out, tt.out)
+               }
+       }
+}
+
 type canBackquoteTest struct {
        in  string
        out bool
@@ -80,8 +103,7 @@ var canbackquotetests = []canBackquoteTest{
 }
 
 func TestCanBackquote(t *testing.T) {
-       for i := 0; i < len(canbackquotetests); i++ {
-               tt := canbackquotetests[i]
+       for _, tt := range canbackquotetests {
                if out := CanBackquote(tt.in); out != tt.out {
                        t.Errorf("CanBackquote(%q) = %v, want %v", tt.in, out, tt.out)
                }
@@ -146,23 +168,20 @@ var misquoted = []string{
 }
 
 func TestUnquote(t *testing.T) {
-       for i := 0; i < len(unquotetests); i++ {
-               tt := unquotetests[i]
+       for _, tt := range unquotetests {
                if out, err := Unquote(tt.in); err != nil && out != tt.out {
                        t.Errorf("Unquote(%#q) = %q, %v want %q, nil", tt.in, out, err, tt.out)
                }
        }
 
        // run the quote tests too, backward
-       for i := 0; i < len(quotetests); i++ {
-               tt := quotetests[i]
+       for _, tt := range quotetests {
                if in, err := Unquote(tt.out); in != tt.in {
                        t.Errorf("Unquote(%#q) = %q, %v, want %q, nil", tt.out, in, err, tt.in)
                }
        }
 
-       for i := 0; i < len(misquoted); i++ {
-               s := misquoted[i]
+       for _, s := range misquoted {
                if out, err := Unquote(s); out != "" || err != os.EINVAL {
                        t.Errorf("Unquote(%#q) = %q, %v want %q, %v", s, out, err, "", os.EINVAL)
                }