fmt.Scan: scan []byte arguments

R=rsc
CC=golang-dev
https://golang.org/cl/1486041

src/pkg/fmt/print.go

@@ -119,7 +119,6 @@
 package fmt
 
 // BUG: format precision and flags are not yet implemented for scanning.
-// BUG: %sqx are not yet implemented for scanning byte slices.
 
 import (
 	"bytes"

src/pkg/fmt/scan.go

@@ -649,6 +649,10 @@ func (s *ss) scanOne(verb int, field interface{}) {
 		}
 	case *string:
 		*v = s.convertString(verb)
+	case *[]byte:
+		// We scan to string and convert so we get a copy of the data.
+		// If we scanned to bytes, the slice would point at the buffer.
+		*v = []byte(s.convertString(verb))
 	default:
 		val := reflect.NewValue(v)
 		ptr, ok := val.(*reflect.PtrValue)
@@ -683,6 +687,17 @@ func (s *ss) scanOne(verb int, field interface{}) {
 			v.Set(uintptr(s.scanUint(verb, uintptrBits)))
 		case *reflect.StringValue:
 			v.Set(s.convertString(verb))
+		case *reflect.SliceValue:
+			// For now, can only handle (renamed) []byte.
+			typ := v.Type().(*reflect.SliceType)
+			if _, ok := typ.Elem().(*reflect.Uint8Type); !ok {
+				goto CantHandle
+			}
+			str := s.convertString(verb)
+			v.Set(reflect.MakeSlice(typ, len(str), len(str)))
+			for i := 0; i < len(str); i++ {
+				v.Elem(i).(*reflect.Uint8Value).Set(str[i])
+			}
 		case *reflect.FloatValue:
 			v.Set(float(s.convertFloat(s.token())))
 		case *reflect.Float32Value:
@@ -696,6 +711,7 @@ func (s *ss) scanOne(verb int, field interface{}) {
 		case *reflect.Complex128Value:
 			v.Set(s.scanComplex(verb, (*ss).convertFloat64))
 		default:
+		CantHandle:
 			s.errorString("Scan: can't handle type: " + val.Type().String())
 		}
 	}
@@ -738,12 +754,12 @@ func (s *ss) doScan(a []interface{}) (numProcessed int, err os.Error) {
 	return
 }
 
-// advance determines whether the next characters in the input matches
+// advance determines whether the next characters in the input match
 // those of the format.  It returns the number of bytes (sic) consumed
 // in the format. Newlines included, all runs of space characters in
-// either input or format behave as a single space. This routines also
+// either input or format behave as a single space. This routine also
-// handles the %% case.  If the return value is zero, either the format
+// handles the %% case.  If the return value is zero, either format
-// is sitting on a % or the input is empty.
+// starts with a % (with no following %) or the input is empty.
 func (s *ss) advance(format string) (i int) {
 	for i < len(format) {
 		fmtc, w := utf8.DecodeRuneInString(format[i:])
@@ -797,9 +813,9 @@ func (s *ss) doScanf(format string, a []interface{}) (numProcessed int, err os.E
 			i += w
 			continue
 		}
-		// Either we have a percent character or we ran out of input.
+		// Either we failed to advance, we have a percent character, or we ran out of input.
 		if format[i] != '%' {
-			// Out of format.  Have we run out of input?
+			// Can't advance format.  Do we have arguments still to process?
 			if i < len(a) {
 				s.errorString("too many arguments for format")
 			}

src/pkg/fmt/scan_test.go

@@ -40,6 +40,7 @@ type (
 	renamedUint64     uint64
 	renamedUintptr    uintptr
 	renamedString     string
+	renamedBytes      []byte
 	renamedFloat      float
 	renamedFloat32    float32
 	renamedFloat64    float64
@@ -64,6 +65,7 @@ var (
 	float32Val           float32
 	float64Val           float64
 	stringVal            string
+	bytesVal             []byte
 	complexVal           complex
 	complex64Val         complex64
 	complex128Val        complex128
@@ -80,6 +82,7 @@ var (
 	renamedUint64Val     renamedUint64
 	renamedUintptrVal    renamedUintptr
 	renamedStringVal     renamedString
+	renamedBytesVal      renamedBytes
 	renamedFloatVal      renamedFloat
 	renamedFloat32Val    renamedFloat32
 	renamedFloat64Val    renamedFloat64
@@ -140,6 +143,7 @@ var scanTests = []ScanTest{
 	ScanTest{"2.3e1\n", &float32Val, float32(2.3e1)},
 	ScanTest{"2.3e2\n", &float64Val, float64(2.3e2)},
 	ScanTest{"2.35\n", &stringVal, "2.35"},
+	ScanTest{"2345678\n", &bytesVal, []byte("2345678")},
 	ScanTest{"(3.4e1-2i)\n", &complexVal, 3.4e1 - 2i},
 	ScanTest{"-3.45e1-3i\n", &complex64Val, complex64(-3.45e1 - 3i)},
 	ScanTest{"-.45e1-1e2i\n", &complex128Val, complex128(-.45e1 - 100i)},
@@ -162,6 +166,7 @@ var scanTests = []ScanTest{
 	ScanTest{"112\n", &renamedUint64Val, renamedUint64(112)},
 	ScanTest{"113\n", &renamedUintptrVal, renamedUintptr(113)},
 	ScanTest{"114\n", &renamedStringVal, renamedString("114")},
+	ScanTest{"115\n", &renamedBytesVal, renamedBytes([]byte("115"))},
 
 	// Custom scanner.
 	ScanTest{"  xxx ", &xVal, Xs("xxx")},
@@ -196,6 +201,12 @@ var scanfTests = []ScanfTest{
 	ScanfTest{"%q", `"quoted\twith\\do\u0075bl\x65s"` + "\n", &stringVal, "quoted\twith\\doubles"},
 	ScanfTest{"%q", "`quoted with backs`\n", &stringVal, "quoted with backs"},
 
+	// Byte slices
+	ScanfTest{"%s", "bytes-%s\n", &bytesVal, []byte("bytes-%s")},
+	ScanfTest{"%x", "62797465732d2578\n", &bytesVal, []byte("bytes-%x")},
+	ScanfTest{"%q", `"bytes\rwith\vdo\u0075bl\x65s"` + "\n", &bytesVal, []byte("bytes\rwith\vdoubles")},
+	ScanfTest{"%q", "`bytes with backs`\n", &bytesVal, []byte("bytes with backs")},
+
 	// Renamed types
 	ScanfTest{"%v\n", "true\n", &renamedBoolVal, renamedBool(true)},
 	ScanfTest{"%t\n", "F\n", &renamedBoolVal, renamedBool(false)},
@@ -213,6 +224,7 @@ var scanfTests = []ScanfTest{
 	ScanfTest{"%d", "112\n", &renamedUint64Val, renamedUint64(112)},
 	ScanfTest{"%d", "113\n", &renamedUintptrVal, renamedUintptr(113)},
 	ScanfTest{"%s", "114\n", &renamedStringVal, renamedString("114")},
+	ScanfTest{"%q", "\"1155\"\n", &renamedBytesVal, renamedBytes([]byte("1155"))},
 	ScanfTest{"%g", "115.1\n", &renamedFloatVal, renamedFloat(115.1)},
 	ScanfTest{"%g", "116e1\n", &renamedFloat32Val, renamedFloat32(116e1)},
 	ScanfTest{"%g", "-11.7e+1", &renamedFloat64Val, renamedFloat64(-11.7e+1)},