asn1: add support for unmarshalling structs with int32 members

Also improve error message for unsupported integer types

R=agl, rsc
CC=golang-dev
https://golang.org/cl/4873049

src/pkg/asn1/asn1.go

@@ -681,9 +681,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		}
 		err = err1
 		return
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		switch val.Type().Kind() {
-		case reflect.Int:
+	case reflect.Int, reflect.Int32:
 		parsedInt, err1 := parseInt(innerBytes)
 		if err1 == nil {
 			val.SetInt(int64(parsedInt))
@@ -697,7 +695,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		}
 		err = err1
 		return
-		}
+	// TODO(dfc) Add support for the remaining integer types
 	case reflect.Struct:
 		structType := fieldType
 
@@ -760,7 +758,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		}
 		return
 	}
-	err = StructuralError{"unknown Go type"}
+	err = StructuralError{"unsupported: " + v.Type().String()}
 	return
 }
 
@@ -787,7 +785,7 @@ func setDefaultValue(v reflect.Value, params fieldParameters) (ok bool) {
 // Because Unmarshal uses the reflect package, the structs
 // being written to must use upper case field names.
 //
-// An ASN.1 INTEGER can be written to an int or int64.
+// An ASN.1 INTEGER can be written to an int, int32 or int64.
 // If the encoded value does not fit in the Go type,
 // Unmarshal returns a parse error.
 //

src/pkg/asn1/asn1_test.go

@@ -42,6 +42,37 @@ func TestParseInt64(t *testing.T) {
 	}
 }
 
+type int32Test struct {
+	in  []byte
+	ok  bool
+	out int32
+}
+
+var int32TestData = []int32Test{
+	{[]byte{0x00}, true, 0},
+	{[]byte{0x7f}, true, 127},
+	{[]byte{0x00, 0x80}, true, 128},
+	{[]byte{0x01, 0x00}, true, 256},
+	{[]byte{0x80}, true, -128},
+	{[]byte{0xff, 0x7f}, true, -129},
+	{[]byte{0xff, 0xff, 0xff, 0xff}, true, -1},
+	{[]byte{0xff}, true, -1},
+	{[]byte{0x80, 0x00, 0x00, 0x00}, true, -2147483648},
+	{[]byte{0x80, 0x00, 0x00, 0x00, 0x00}, false, 0},
+}
+
+func TestParseInt32(t *testing.T) {
+	for i, test := range int32TestData {
+		ret, err := parseInt(test.in)
+		if (err == nil) != test.ok {
+			t.Errorf("#%d: Incorrect error result (did fail? %v, expected: %v)", i, err == nil, test.ok)
+		}
+		if test.ok && int32(ret) != test.out {
+			t.Errorf("#%d: Bad result: %v (expected %v)", i, ret, test.out)
+		}
+	}
+}
+
 var bigIntTests = []struct {
 	in     []byte
 	base10 string