fmt.Scan: %c

R=rsc
CC=golang-dev
https://golang.org/cl/1518042

src/pkg/fmt/scan.go

@@ -219,7 +219,6 @@ func (s *ss) Token() (tok string, err os.Error) {
 // readRune is a structure to enable reading UTF-8 encoded code points
 // from an io.Reader.  It is used if the Reader given to the scanner does
 // not already implement ReadRuner.
-// TODO: readByteRune for things that can read bytes.
 type readRune struct {
 	reader io.Reader
 	buf    [utf8.UTFMax]byte
@@ -435,9 +434,22 @@ func (s *ss) scanNumber(digits string) string {
 	return s.buf.String()
 }
 
+// scanRune returns the next rune value in the input.
+func (s *ss) scanRune(bitSize uint) int64 {
+	rune := int64(s.mustGetRune())
+	x := (rune << (64 - bitSize)) >> (64 - bitSize)
+	if x != rune {
+		s.errorString("overflow on character value " + string(rune))
+	}
+	return rune
+}
+
 // scanInt returns the value of the integer represented by the next
 // token, checking for overflow.  Any error is stored in s.err.
 func (s *ss) scanInt(verb int, bitSize uint) int64 {
+	if verb == 'c' {
+		return s.scanRune(bitSize)
+	}
 	base, digits := s.getBase(verb)
 	s.skipSpace()
 	s.accept(sign) // If there's a sign, it will be left in the token buffer.
@@ -456,6 +468,9 @@ func (s *ss) scanInt(verb int, bitSize uint) int64 {
 // scanUint returns the value of the unsigned integer represented
 // by the next token, checking for overflow.  Any error is stored in s.err.
 func (s *ss) scanUint(verb int, bitSize uint) uint64 {
+	if verb == 'c' {
+		return uint64(s.scanRune(bitSize))
+	}
 	base, digits := s.getBase(verb)
 	s.skipSpace()
 	tok := s.scanNumber(digits)

src/pkg/fmt/scan_test.go

@@ -198,6 +198,8 @@ var scanfTests = []ScanfTest{
 	ScanfTest{"%t", "false\n", &boolVal, false},
 	ScanfTest{"%v", "-71\n", &intVal, -71},
 	ScanfTest{"%d", "72\n", &intVal, 72},
+	ScanfTest{"%c", "a\n", &intVal, 'a'},
+	ScanfTest{"%c", "\u1234\n", &intVal, '\u1234'},
 	ScanfTest{"%d", "73\n", &int8Val, int8(73)},
 	ScanfTest{"%d", "+74\n", &int16Val, int16(74)},
 	ScanfTest{"%d", "75\n", &int32Val, int32(75)},
@@ -299,12 +301,13 @@ var multiTests = []ScanfMultiTest{
 	ScanfMultiTest{"%d%s", "123abc", args(&i, &s), args(123, "abc"), ""},
 
 	// Custom scanner.
-	ScanfMultiTest{"%2e%f", "eefffff", []interface{}{&x, &y}, []interface{}{Xs("ee"), Xs("fffff")}, ""},
+	ScanfMultiTest{"%2e%f", "eefffff", args(&x, &y), args(Xs("ee"), Xs("fffff")), ""},
 
 	// Errors
-	ScanfMultiTest{"%t", "23 18", []interface{}{&i}, nil, "bad verb"},
-	ScanfMultiTest{"%d %d %d", "23 18", []interface{}{&i, &j}, []interface{}{23, 18}, "too few operands"},
-	ScanfMultiTest{"%d %d", "23 18 27", []interface{}{&i, &j, &k}, []interface{}{23, 18}, "too many operands"},
+	ScanfMultiTest{"%t", "23 18", args(&i), nil, "bad verb"},
+	ScanfMultiTest{"%d %d %d", "23 18", args(&i, &j), args(23, 18), "too few operands"},
+	ScanfMultiTest{"%d %d", "23 18 27", args(&i, &j, &k), args(23, 18), "too many operands"},
+	ScanfMultiTest{"%c", "\u0100", args(&int8Val), nil, "overflow"},
 }
 
 func testScan(t *testing.T, scan func(r io.Reader, a ...interface{}) (int, os.Error)) {