fmt.Scan: refactor the implementation so format-driven and normal scanning use the same function.

simplifies the code significantly.
Still TODO:
	- proper format handling
	- strings

R=rsc
CC=golang-dev
http://codereview.appspot.com/1432041

2 files changed, 100 insertions, 160 deletions

diff --git a/src/pkg/fmt/scan.go b/src/pkg/fmt/scan.go
index ec7ba9bf5..9851d4d29 100644
--- a/src/pkg/fmt/scan.go
+++ b/src/pkg/fmt/scan.go
@@ -251,9 +251,23 @@ var intBits = uint(reflect.Typeof(int(0)).Size() * 8)
 var uintptrBits = uint(reflect.Typeof(int(0)).Size() * 8)
 var complexError = os.ErrorString("syntax error scanning complex number")
 
+// okVerb verifies that the verb is present in the list, setting s.err appropriately if not.
+func (s *ss) okVerb(verb int, okVerbs, typ string) bool {
+	if s.err != nil { // don't overwrite error
+		return false
+	}
+	for _, v := range okVerbs {
+		if v == verb {
+			return true
+		}
+	}
+	s.err = os.ErrorString("bad verb %" + string(verb) + " for " + typ)
+	return false
+}
+
 // scanBool converts the token to a boolean value.
-func (s *ss) scanBool(tok string) bool {
-	if s.err != nil {
+func (s *ss) scanBool(verb int, tok string) bool {
+	if !s.okVerb(verb, "tv", "boolean") {
 		return false
 	}
 	var b bool
@@ -261,9 +275,27 @@ func (s *ss) scanBool(tok string) bool {
 	return b
 }
 
+func (s *ss) getBase(verb int) int {
+	s.okVerb(verb, "bdoxXv", "integer") // sets s.err
+	base := 10
+	switch verb {
+	case 'b':
+		base = 2
+	case 'o':
+		base = 8
+	case 'x', 'X':
+		base = 16
+	}
+	return base
+}
+
 // convertInt returns the value of the integer
 // stored in the token, checking for overflow.  Any error is stored in s.err.
-func (s *ss) convertInt(tok string, bitSize uint, base int) (i int64) {
+func (s *ss) convertInt(verb int, tok string, bitSize uint) (i int64) {
+	base := s.getBase(verb)
+	if s.err != nil {
+		return 0
+	}
 	i, s.err = strconv.Btoi64(tok, base)
 	x := (i << (64 - bitSize)) >> (64 - bitSize)
 	if x != i {
@@ -274,7 +306,11 @@ func (s *ss) convertInt(tok string, bitSize uint, base int) (i int64) {
 
 // convertUint returns the value of the unsigned integer
 // stored in the token, checking for overflow.  Any error is stored in s.err.
-func (s *ss) convertUint(tok string, bitSize uint, base int) (i uint64) {
+func (s *ss) convertUint(verb int, tok string, bitSize uint) (i uint64) {
+	base := s.getBase(verb)
+	if s.err != nil {
+		return 0
+	}
 	i, s.err = strconv.Btoui64(tok, base)
 	x := (i << (64 - bitSize)) >> (64 - bitSize)
 	if x != i {
@@ -283,79 +319,6 @@ func (s *ss) convertUint(tok string, bitSize uint, base int) (i uint64) {
 	return i
 }
 
-// scanInteger converts the token to an integer in the appropriate base
-// and stores the result according to the type of the field.
-func (s *ss) scanInteger(tok string, field interface{}, base int) {
-	switch v := field.(type) {
-	case *int:
-		*v = int(s.convertInt(tok, intBits, base))
-		return
-	case *int8:
-		*v = int8(s.convertInt(tok, 8, base))
-		return
-	case *int16:
-		*v = int16(s.convertInt(tok, 16, base))
-		return
-	case *int32:
-		*v = int32(s.convertInt(tok, 32, base))
-		return
-	case *int64:
-		*v = s.convertInt(tok, 64, base)
-		return
-	case *uint:
-		*v = uint(s.convertUint(tok, intBits, base))
-		return
-	case *uint8:
-		*v = uint8(s.convertUint(tok, 8, base))
-		return
-	case *uint16:
-		*v = uint16(s.convertUint(tok, 16, base))
-		return
-	case *uint32:
-		*v = uint32(s.convertUint(tok, 32, base))
-		return
-	case *uint64:
-		*v = uint64(s.convertUint(tok, 64, base))
-		return
-	case *uintptr:
-		*v = uintptr(s.convertUint(tok, uintptrBits, base))
-		return
-	}
-	// Not a basic type; probably a renamed type. We need to use reflection.
-	v := reflect.NewValue(field)
-	ptr, ok := v.(*reflect.PtrValue)
-	if !ok {
-		s.typeError(field, "integer")
-		return
-	}
-	switch v := ptr.Elem().(type) {
-	case *reflect.IntValue:
-		v.Set(int(s.convertInt(tok, intBits, base)))
-	case *reflect.Int8Value:
-		v.Set(int8(s.convertInt(tok, 8, base)))
-	case *reflect.Int16Value:
-		v.Set(int16(s.convertInt(tok, 16, base)))
-	case *reflect.Int32Value:
-		v.Set(int32(s.convertInt(tok, 32, base)))
-	case *reflect.Int64Value:
-		v.Set(s.convertInt(tok, 64, base))
-	case *reflect.UintValue:
-		v.Set(uint(s.convertUint(tok, intBits, base)))
-	case *reflect.Uint8Value:
-		v.Set(uint8(s.convertUint(tok, 8, base)))
-	case *reflect.Uint16Value:
-		v.Set(uint16(s.convertUint(tok, 16, base)))
-	case *reflect.Uint32Value:
-		v.Set(uint32(s.convertUint(tok, 32, base)))
-	case *reflect.Uint64Value:
-		v.Set(s.convertUint(tok, 64, base))
-	case *reflect.UintptrValue:
-		v.Set(uintptr(s.convertUint(tok, uintptrBits, base)))
-	default:
-		s.err = os.ErrorString("internal error: unknown int type")
-	}
-}
-
 // complexParts returns the strings representing the real and imaginary parts of the string.
 func (s *ss) complexParts(str string) (real, imag string) {
 	if len(str) > 2 && str[0] == '(' && str[len(str)-1] == ')' {
@@ -436,9 +399,6 @@ func (s *ss) scanFloat64(str string) float64 {
 // If we're reading complex64, atof will parse float32s and convert them
 // to float64's to avoid reproducing this code for each complex type.
 func (s *ss) scanComplex(tok string, atof func(*ss, string) float64) complex128 {
-	if s.err != nil {
-		return 0
-	}
 	sreal, simag := s.complexParts(tok)
 	if s.err != nil {
 		return 0
@@ -455,15 +415,22 @@ func (s *ss) scanComplex(tok string, atof func(*ss, string) float64) complex128
 	return cmplx(real, imag)
 }
 
+const floatVerbs = "eEfFgGv"
+
 // scanOne scans a single value, deriving the scanner from the type of the argument.
-func (s *ss) scanOne(field interface{}) {
+func (s *ss) scanOne(verb int, field interface{}) {
+	// If the parameter has its own Scan method, use that.
+	if v, ok := field.(Scanner); ok {
+		s.err = v.Scan(s)
+		return
+	}
 	tok := s.token()
 	if s.err != nil {
 		return
 	}
 	switch v := field.(type) {
 	case *bool:
-		*v = s.scanBool(tok)
+		*v = s.scanBool(verb, tok)
 	case *complex:
 		*v = complex(s.scanComplex(tok, (*ss).scanFloat))
 	case *complex64:
@@ -471,62 +438,73 @@ func (s *ss) scanOne(field interface{}) {
 	case *complex128:
 		*v = s.scanComplex(tok, (*ss).scanFloat64)
 	case *int:
-		*v = int(s.convertInt(tok, intBits, 10))
+		*v = int(s.convertInt(verb, tok, intBits))
 	case *int8:
-		*v = int8(s.convertInt(tok, 8, 10))
+		*v = int8(s.convertInt(verb, tok, 8))
 	case *int16:
-		*v = int16(s.convertInt(tok, 16, 10))
+		*v = int16(s.convertInt(verb, tok, 16))
 	case *int32:
-		*v = int32(s.convertInt(tok, 32, 10))
+		*v = int32(s.convertInt(verb, tok, 32))
 	case *int64:
-		*v = s.convertInt(tok, intBits, 10)
+		*v = s.convertInt(verb, tok, intBits)
 	case *uint:
-		*v = uint(s.convertUint(tok, intBits, 10))
+		*v = uint(s.convertUint(verb, tok, intBits))
 	case *uint8:
-		*v = uint8(s.convertUint(tok, 8, 10))
+		*v = uint8(s.convertUint(verb, tok, 8))
 	case *uint16:
-		*v = uint16(s.convertUint(tok, 16, 10))
+		*v = uint16(s.convertUint(verb, tok, 16))
 	case *uint32:
-		*v = uint32(s.convertUint(tok, 32, 10))
+		*v = uint32(s.convertUint(verb, tok, 32))
 	case *uint64:
-		*v = s.convertUint(tok, 64, 10)
+		*v = s.convertUint(verb, tok, 64)
 	case *uintptr:
-		*v = uintptr(s.convertUint(tok, uintptrBits, 10))
+		*v = uintptr(s.convertUint(verb, tok, uintptrBits))
 	case *float:
-		if s.err == nil {
+		if s.okVerb(verb, floatVerbs, "float") {
 			*v, s.err = strconv.Atof(tok)
-		} else {
-			*v = 0
 		}
 	case *float32:
-		if s.err == nil {
+		if s.okVerb(verb, floatVerbs, "float32") {
 			*v, s.err = strconv.Atof32(tok)
-		} else {
-			*v = 0
 		}
 	case *float64:
-		if s.err == nil {
+		if s.okVerb(verb, floatVerbs, "float64") {
 			*v, s.err = strconv.Atof64(tok)
-		} else {
-			*v = 0
 		}
 	case *string:
 		*v = tok
 	default:
-		t := reflect.Typeof(v)
-		str := t.String()
-		ptr, ok := t.(*reflect.PtrType)
+		val := reflect.NewValue(v)
+		ptr, ok := val.(*reflect.PtrValue)
 		if !ok {
-			s.err = os.ErrorString("Scan: type not a pointer: " + str)
+			s.err = os.ErrorString("Scan: type not a pointer: " + val.Type().String())
 			return
 		}
-		switch ptr.Elem().(type) {
-		case *reflect.IntType, *reflect.Int8Type, *reflect.Int16Type, *reflect.Int32Type, *reflect.Int64Type:
-			s.scanInteger(tok, v, 10)
-		case *reflect.UintType, *reflect.Uint8Type, *reflect.Uint16Type, *reflect.Uint32Type, *reflect.Uint64Type, *reflect.UintptrType:
-			s.scanInteger(tok, v, 10)
+		switch v := ptr.Elem().(type) {
+		case *reflect.IntValue:
+			v.Set(int(s.convertInt(verb, tok, intBits)))
+		case *reflect.Int8Value:
+			v.Set(int8(s.convertInt(verb, tok, 8)))
+		case *reflect.Int16Value:
+			v.Set(int16(s.convertInt(verb, tok, 16)))
+		case *reflect.Int32Value:
+			v.Set(int32(s.convertInt(verb, tok, 32)))
+		case *reflect.Int64Value:
+			v.Set(s.convertInt(verb, tok, 64))
+		case *reflect.UintValue:
+			v.Set(uint(s.convertUint(verb, tok, intBits)))
+		case *reflect.Uint8Value:
+			v.Set(uint8(s.convertUint(verb, tok, 8)))
+		case *reflect.Uint16Value:
+			v.Set(uint16(s.convertUint(verb, tok, 16)))
+		case *reflect.Uint32Value:
+			v.Set(uint32(s.convertUint(verb, tok, 32)))
+		case *reflect.Uint64Value:
+			v.Set(s.convertUint(verb, tok, 64))
+		case *reflect.UintptrValue:
+			v.Set(uintptr(s.convertUint(verb, tok, uintptrBits)))
 		default:
-			s.err = os.ErrorString("Scan: can't handle type: " + t.String())
+			s.err = os.ErrorString("Scan: can't handle type: " + val.Type().String())
 		}
 	}
 }
@@ -535,15 +513,7 @@ func (s *ss) scanOne(field interface{}) {
 // At the moment, it handles only pointers to basic types.
 func (s *ss) doScan(a []interface{}) int {
 	for fieldnum, field := range a {
-		// If the parameter has its own Scan method, use that.
-		if v, ok := field.(Scanner); ok {
-			s.err = v.Scan(s)
-			if s.err != nil {
-				return fieldnum
-			}
-			continue
-		}
-		s.scanOne(field)
+		s.scanOne('v', field)
 		if s.err != nil {
 			return fieldnum
 		}
@@ -592,48 +562,18 @@ func (s *ss) doScanf(format string, a []interface{}) int {
 			// TODO: WHAT NOW?
 			continue
 		}
+
 		if fieldnum >= len(a) { // out of operands
 			s.err = os.ErrorString("too few operands for format %" + format[i-w:])
-			return fieldnum
+			break
 		}
 		field := a[fieldnum]
-		fieldnum++
 
-		// If the parameter has its own Scan method, use that.
-		if v, ok := field.(Scanner); ok {
-			s.err = v.Scan(s)
-			if s.err != nil {
-				return fieldnum - 1
-			}
-			continue
-		}
-		if c == 'v' {
-			// Default format works; just call doScan, but note that it will scan for the token
-			s.scanOne(field)
-		} else {
-			tok := s.token()
-			switch c {
-			case 't':
-				if v, ok := field.(*bool); ok {
-					*v = s.scanBool(tok)
-				} else {
-					s.typeError(field, "boolean")
-				}
-			case 'b':
-				s.scanInteger(tok, field, 2)
-			case 'o':
-				s.scanInteger(tok, field, 8)
-			case 'd':
-				s.scanInteger(tok, field, 10)
-			case 'x', 'X':
-				s.scanInteger(tok, field, 16)
-			default:
-				s.err = os.ErrorString("unknown scanning verb %" + format[i-w:])
-			}
-			if s.err != nil {
-				return fieldnum - 1
-			}
+		s.scanOne(c, field)
+		if s.err != nil {
+			break
 		}
+		fieldnum++
 	}
 	return fieldnum
 }
diff --git a/src/pkg/fmt/scan_test.go b/src/pkg/fmt/scan_test.go
index ca51cf0a2..55808e964 100644
--- a/src/pkg/fmt/scan_test.go
+++ b/src/pkg/fmt/scan_test.go
@@ -170,15 +170,15 @@ var scanfTests = []ScanfTest{
 
 	// Renamed types
 	ScanfTest{"%v", "101\n", &renamedIntVal, renamedInt(101)},
-	ScanfTest{"%d", "102\n", &renamedIntVal, renamedInt(102)},
+	ScanfTest{"%o", "0146\n", &renamedIntVal, renamedInt(102)},
 	ScanfTest{"%v", "103\n", &renamedUintVal, renamedUint(103)},
 	ScanfTest{"%d", "104\n", &renamedUintVal, renamedUint(104)},
 	ScanfTest{"%d", "105\n", &renamedInt8Val, renamedInt8(105)},
 	ScanfTest{"%d", "106\n", &renamedInt16Val, renamedInt16(106)},
 	ScanfTest{"%d", "107\n", &renamedInt32Val, renamedInt32(107)},
 	ScanfTest{"%d", "108\n", &renamedInt64Val, renamedInt64(108)},
-	ScanfTest{"%d", "109\n", &renamedUint8Val, renamedUint8(109)},
-	ScanfTest{"%d", "110\n", &renamedUint16Val, renamedUint16(110)},
+	ScanfTest{"%x", "6D\n", &renamedUint8Val, renamedUint8(109)},
+	ScanfTest{"%o", "0156\n", &renamedUint16Val, renamedUint16(110)},
 	ScanfTest{"%d", "111\n", &renamedUint32Val, renamedUint32(111)},
 	ScanfTest{"%d", "112\n", &renamedUint64Val, renamedUint64(112)},
 	ScanfTest{"%d", "113\n", &renamedUintptrVal, renamedUintptr(113)},