fmt: make %q work for integers, printing a quoted character literal.

R=rsc
CC=golang-dev
https://golang.org/cl/4556060

diff --git a/src/pkg/fmt/doc.go b/src/pkg/fmt/doc.go
index 08609ca64b6dcb6d8c847ddd4840dd1f53f74f1c..79fe5758c9344dd0b052e1b06cc0899723f3bb55 100644 (file)
--- a/src/pkg/fmt/doc.go
+++ b/src/pkg/fmt/doc.go
@@ -25,6 +25,7 @@
                %c      the character represented by the corresponding Unicode code point
                %d      base 10
                %o      base 8
+               %q      a single-quoted character literal safely escaped with Go syntax.
                %x      base 16, with lower-case letters for a-f
                %X      base 16, with upper-case letters for A-F
                %U      Unicode format: U+1234; same as "U+%04X"

diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index b3c0c5abed4a1324d0624f8c50c5cc836096c992..caecb6fb846a4ddea44c50c836a596ab521681dc 100644 (file)
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -135,6 +135,17 @@ var fmttests = []struct {
        {"%q", "\u263a", `"\u263a"`},
        {"%q", "\U0010ffff", `"\U0010ffff"`},
 
+       // escaped characters
+       {"%q", 'x', `'x'`},
+       {"%q", 0, `'\x00'`},
+       {"%q", '\n', `'\n'`},
+       {"%q", '\u1234', `'\u1234'`},
+       {"%q", '\U00012345', `'\U00012345'`},
+       {"%q", int64(0x7FFFFFFF), `%!q(int64=2147483647)`},
+       {"%q", uint64(0xFFFFFFFF), `%!q(uint64=4294967295)`},
+       {"%q", '"', `'"'`},
+       {"%q", '\'', `'\''`},
+
        // width
        {"%5s", "abc", "  abc"},
        {"%2s", "\u263a", " \u263a"},

diff --git a/src/pkg/fmt/format.go b/src/pkg/fmt/format.go
index f9d2b4fcaf6b177425d769c7f2fc62aef9ccc7dc..5dcfb967744bf058a02549b7bfe726ebf57d18e1 100644 (file)
--- a/src/pkg/fmt/format.go
+++ b/src/pkg/fmt/format.go
@@ -296,6 +296,13 @@ func (f *fmt) fmt_q(s string) {
        f.padString(quoted)
 }
 
+// fmt_qc formats the integer as a single-quoted, escaped Go character constant.
+// If the character is not valid Unicode, it will print '\ufffd'.
+func (f *fmt) fmt_qc(c int64) {
+       quoted := strconv.QuoteRune(int(c))
+       f.padString(quoted)
+}
+
 // floating-point
 
 func doPrec(f *fmt, def int) int {

diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index 8885cebdf8a7255a4db058ae6a22bfd39823aedb..c18a8ea38d2eb468248f6ac27b3b91bb48ec4308 100644 (file)
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -9,6 +9,7 @@ import (
        "io"
        "os"
        "reflect"
+       "unicode"
        "utf8"
 )
 
@@ -332,6 +333,12 @@ func (p *pp) fmtInt64(v int64, verb int, value interface{}) {
                p.fmt.integer(v, 10, signed, ldigits)
        case 'o':
                p.fmt.integer(v, 8, signed, ldigits)
+       case 'q':
+               if 0 <= v && v <= unicode.MaxRune {
+                       p.fmt.fmt_qc(v)
+               } else {
+                       p.badVerb(verb, value)
+               }
        case 'x':
                p.fmt.integer(v, 16, signed, ldigits)
        case 'U':
@@ -385,6 +392,12 @@ func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}) {
                }
        case 'o':
                p.fmt.integer(int64(v), 8, unsigned, ldigits)
+       case 'q':
+               if 0 <= v && v <= unicode.MaxRune {
+                       p.fmt.fmt_qc(int64(v))
+               } else {
+                       p.badVerb(verb, value)
+               }
        case 'x':
                p.fmt.integer(int64(v), 16, unsigned, ldigits)
        case 'X':