encoding/asn1: export tag and class constants

Fixes #9236

Change-Id: I744d7f071e945ea6e6e50203d931f4678c8b545d
Reviewed-on: https://go-review.googlesource.com/17311
Reviewed-by: Adam Langley <agl@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

4 files changed, 90 insertions, 88 deletions

diff --git a/src/encoding/asn1/asn1.go b/src/encoding/asn1/asn1.go
index 98b137f40b..0070ea82a7 100644
--- a/src/encoding/asn1/asn1.go
+++ b/src/encoding/asn1/asn1.go
@@ -530,17 +530,17 @@ func parseSequenceOf(bytes []byte, sliceType reflect.Type, elemType reflect.Type
 			return
 		}
 		switch t.tag {
-		case tagIA5String, tagGeneralString, tagT61String, tagUTF8String:
+		case TagIA5String, TagGeneralString, TagT61String, TagUTF8String:
 			// We pretend that various other string types are
 			// PRINTABLE STRINGs so that a sequence of them can be
 			// parsed into a []string.
-			t.tag = tagPrintableString
-		case tagGeneralizedTime, tagUTCTime:
+			t.tag = TagPrintableString
+		case TagGeneralizedTime, TagUTCTime:
 			// Likewise, both time types are treated the same.
-			t.tag = tagUTCTime
+			t.tag = TagUTCTime
 		}
 
-		if t.class != classUniversal || t.isCompound != compoundType || t.tag != expectedTag {
+		if t.class != ClassUniversal || t.isCompound != compoundType || t.tag != expectedTag {
 			err = StructuralError{"sequence tag mismatch"}
 			return
 		}
@@ -624,28 +624,28 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 			return
 		}
 		var result interface{}
-		if !t.isCompound && t.class == classUniversal {
+		if !t.isCompound && t.class == ClassUniversal {
 			innerBytes := bytes[offset : offset+t.length]
 			switch t.tag {
-			case tagPrintableString:
+			case TagPrintableString:
 				result, err = parsePrintableString(innerBytes)
-			case tagIA5String:
+			case TagIA5String:
 				result, err = parseIA5String(innerBytes)
-			case tagT61String:
+			case TagT61String:
 				result, err = parseT61String(innerBytes)
-			case tagUTF8String:
+			case TagUTF8String:
 				result, err = parseUTF8String(innerBytes)
-			case tagInteger:
+			case TagInteger:
 				result, err = parseInt64(innerBytes)
-			case tagBitString:
+			case TagBitString:
 				result, err = parseBitString(innerBytes)
-			case tagOID:
+			case TagOID:
 				result, err = parseObjectIdentifier(innerBytes)
-			case tagUTCTime:
+			case TagUTCTime:
 				result, err = parseUTCTime(innerBytes)
-			case tagGeneralizedTime:
+			case TagGeneralizedTime:
 				result, err = parseGeneralizedTime(innerBytes)
-			case tagOctetString:
+			case TagOctetString:
 				result = innerBytes
 			default:
 				// If we don't know how to handle the type, we just leave Value as nil.
@@ -671,9 +671,9 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		return
 	}
 	if params.explicit {
-		expectedClass := classContextSpecific
+		expectedClass := ClassContextSpecific
 		if params.application {
-			expectedClass = classApplication
+			expectedClass = ClassApplication
 		}
 		if offset == len(bytes) {
 			err = StructuralError{"explicit tag has no child"}
@@ -709,10 +709,10 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 	// type string. getUniversalType returns the tag for PrintableString
 	// when it sees a string, so if we see a different string type on the
 	// wire, we change the universal type to match.
-	if universalTag == tagPrintableString {
-		if t.class == classUniversal {
+	if universalTag == TagPrintableString {
+		if t.class == ClassUniversal {
 			switch t.tag {
-			case tagIA5String, tagGeneralString, tagT61String, tagUTF8String:
+			case TagIA5String, TagGeneralString, TagT61String, TagUTF8String:
 				universalTag = t.tag
 			}
 		} else if params.stringType != 0 {
@@ -722,24 +722,24 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 
 	// Special case for time: UTCTime and GeneralizedTime both map to the
 	// Go type time.Time.
-	if universalTag == tagUTCTime && t.tag == tagGeneralizedTime && t.class == classUniversal {
-		universalTag = tagGeneralizedTime
+	if universalTag == TagUTCTime && t.tag == TagGeneralizedTime && t.class == ClassUniversal {
+		universalTag = TagGeneralizedTime
 	}
 
 	if params.set {
-		universalTag = tagSet
+		universalTag = TagSet
 	}
 
-	expectedClass := classUniversal
+	expectedClass := ClassUniversal
 	expectedTag := universalTag
 
 	if !params.explicit && params.tag != nil {
-		expectedClass = classContextSpecific
+		expectedClass = ClassContextSpecific
 		expectedTag = *params.tag
 	}
 
 	if !params.explicit && params.application && params.tag != nil {
-		expectedClass = classApplication
+		expectedClass = ClassApplication
 		expectedTag = *params.tag
 	}
 
@@ -781,7 +781,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 	case timeType:
 		var time time.Time
 		var err1 error
-		if universalTag == tagUTCTime {
+		if universalTag == TagUTCTime {
 			time, err1 = parseUTCTime(innerBytes)
 		} else {
 			time, err1 = parseGeneralizedTime(innerBytes)
@@ -873,15 +873,15 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 	case reflect.String:
 		var v string
 		switch universalTag {
-		case tagPrintableString:
+		case TagPrintableString:
 			v, err = parsePrintableString(innerBytes)
-		case tagIA5String:
+		case TagIA5String:
 			v, err = parseIA5String(innerBytes)
-		case tagT61String:
+		case TagT61String:
 			v, err = parseT61String(innerBytes)
-		case tagUTF8String:
+		case TagUTF8String:
 			v, err = parseUTF8String(innerBytes)
-		case tagGeneralString:
+		case TagGeneralString:
 			// GeneralString is specified in ISO-2022/ECMA-35,
 			// A brief review suggests that it includes structures
 			// that allow the encoding to change midstring and
diff --git a/src/encoding/asn1/asn1_test.go b/src/encoding/asn1/asn1_test.go
index 7ba968dbac..509a2cb25e 100644
--- a/src/encoding/asn1/asn1_test.go
+++ b/src/encoding/asn1/asn1_test.go
@@ -409,10 +409,10 @@ func newBool(b bool) *bool { return &b }
 
 var parseFieldParametersTestData []parseFieldParametersTest = []parseFieldParametersTest{
 	{"", fieldParameters{}},
-	{"ia5", fieldParameters{stringType: tagIA5String}},
-	{"generalized", fieldParameters{timeType: tagGeneralizedTime}},
-	{"utc", fieldParameters{timeType: tagUTCTime}},
-	{"printable", fieldParameters{stringType: tagPrintableString}},
+	{"ia5", fieldParameters{stringType: TagIA5String}},
+	{"generalized", fieldParameters{timeType: TagGeneralizedTime}},
+	{"utc", fieldParameters{timeType: TagUTCTime}},
+	{"printable", fieldParameters{stringType: TagPrintableString}},
 	{"optional", fieldParameters{optional: true}},
 	{"explicit", fieldParameters{explicit: true, tag: new(int)}},
 	{"application", fieldParameters{application: true, tag: new(int)}},
diff --git a/src/encoding/asn1/common.go b/src/encoding/asn1/common.go
index ab85e0496f..0695180827 100644
--- a/src/encoding/asn1/common.go
+++ b/src/encoding/asn1/common.go
@@ -18,29 +18,31 @@ import (
 
 // Here are some standard tags and classes
 
+// ASN.1 tags represent the type of the following object.
 const (
-	tagBoolean         = 1
-	tagInteger         = 2
-	tagBitString       = 3
-	tagOctetString     = 4
-	tagOID             = 6
-	tagEnum            = 10
-	tagUTF8String      = 12
-	tagSequence        = 16
-	tagSet             = 17
-	tagPrintableString = 19
-	tagT61String       = 20
-	tagIA5String       = 22
-	tagUTCTime         = 23
-	tagGeneralizedTime = 24
-	tagGeneralString   = 27
+	TagBoolean         = 1
+	TagInteger         = 2
+	TagBitString       = 3
+	TagOctetString     = 4
+	TagOID             = 6
+	TagEnum            = 10
+	TagUTF8String      = 12
+	TagSequence        = 16
+	TagSet             = 17
+	TagPrintableString = 19
+	TagT61String       = 20
+	TagIA5String       = 22
+	TagUTCTime         = 23
+	TagGeneralizedTime = 24
+	TagGeneralString   = 27
 )
 
+// ASN.1 class types represent the namespace of the tag.
 const (
-	classUniversal       = 0
-	classApplication     = 1
-	classContextSpecific = 2
-	classPrivate         = 3
+	ClassUniversal       = 0
+	ClassApplication     = 1
+	ClassContextSpecific = 2
+	ClassPrivate         = 3
 )
 
 type tagAndLength struct {
@@ -96,15 +98,15 @@ func parseFieldParameters(str string) (ret fieldParameters) {
 				ret.tag = new(int)
 			}
 		case part == "generalized":
-			ret.timeType = tagGeneralizedTime
+			ret.timeType = TagGeneralizedTime
 		case part == "utc":
-			ret.timeType = tagUTCTime
+			ret.timeType = TagUTCTime
 		case part == "ia5":
-			ret.stringType = tagIA5String
+			ret.stringType = TagIA5String
 		case part == "printable":
-			ret.stringType = tagPrintableString
+			ret.stringType = TagPrintableString
 		case part == "utf8":
-			ret.stringType = tagUTF8String
+			ret.stringType = TagUTF8String
 		case strings.HasPrefix(part, "default:"):
 			i, err := strconv.ParseInt(part[8:], 10, 64)
 			if err == nil {
@@ -136,33 +138,33 @@ func parseFieldParameters(str string) (ret fieldParameters) {
 func getUniversalType(t reflect.Type) (tagNumber int, isCompound, ok bool) {
 	switch t {
 	case objectIdentifierType:
-		return tagOID, false, true
+		return TagOID, false, true
 	case bitStringType:
-		return tagBitString, false, true
+		return TagBitString, false, true
 	case timeType:
-		return tagUTCTime, false, true
+		return TagUTCTime, false, true
 	case enumeratedType:
-		return tagEnum, false, true
+		return TagEnum, false, true
 	case bigIntType:
-		return tagInteger, false, true
+		return TagInteger, false, true
 	}
 	switch t.Kind() {
 	case reflect.Bool:
-		return tagBoolean, false, true
+		return TagBoolean, false, true
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		return tagInteger, false, true
+		return TagInteger, false, true
 	case reflect.Struct:
-		return tagSequence, true, true
+		return TagSequence, true, true
 	case reflect.Slice:
 		if t.Elem().Kind() == reflect.Uint8 {
-			return tagOctetString, false, true
+			return TagOctetString, false, true
 		}
 		if strings.HasSuffix(t.Name(), "SET") {
-			return tagSet, true, true
+			return TagSet, true, true
 		}
-		return tagSequence, true, true
+		return TagSequence, true, true
 	case reflect.String:
-		return tagPrintableString, false, true
+		return TagPrintableString, false, true
 	}
 	return 0, false, false
 }
diff --git a/src/encoding/asn1/marshal.go b/src/encoding/asn1/marshal.go
index 1bcb9b31a4..6e858584a6 100644
--- a/src/encoding/asn1/marshal.go
+++ b/src/encoding/asn1/marshal.go
@@ -414,7 +414,7 @@ func marshalBody(out *forkableWriter, value reflect.Value, params fieldParameter
 		return nil
 	case timeType:
 		t := value.Interface().(time.Time)
-		if params.timeType == tagGeneralizedTime || outsideUTCRange(t) {
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(t) {
 			return marshalGeneralizedTime(out, t)
 		} else {
 			return marshalUTCTime(out, t)
@@ -493,9 +493,9 @@ func marshalBody(out *forkableWriter, value reflect.Value, params fieldParameter
 		return
 	case reflect.String:
 		switch params.stringType {
-		case tagIA5String:
+		case TagIA5String:
 			return marshalIA5String(out, v.String())
-		case tagPrintableString:
+		case TagPrintableString:
 			return marshalPrintableString(out, v.String())
 		default:
 			return marshalUTF8String(out, v.String())
@@ -555,18 +555,18 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 		err = StructuralError{fmt.Sprintf("unknown Go type: %v", v.Type())}
 		return
 	}
-	class := classUniversal
+	class := ClassUniversal
 
-	if params.timeType != 0 && tag != tagUTCTime {
+	if params.timeType != 0 && tag != TagUTCTime {
 		return StructuralError{"explicit time type given to non-time member"}
 	}
 
-	if params.stringType != 0 && tag != tagPrintableString {
+	if params.stringType != 0 && tag != TagPrintableString {
 		return StructuralError{"explicit string type given to non-string member"}
 	}
 
 	switch tag {
-	case tagPrintableString:
+	case TagPrintableString:
 		if params.stringType == 0 {
 			// This is a string without an explicit string type. We'll use
 			// a PrintableString if the character set in the string is
@@ -576,24 +576,24 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 					if !utf8.ValidString(v.String()) {
 						return errors.New("asn1: string not valid UTF-8")
 					}
-					tag = tagUTF8String
+					tag = TagUTF8String
 					break
 				}
 			}
 		} else {
 			tag = params.stringType
 		}
-	case tagUTCTime:
-		if params.timeType == tagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
-			tag = tagGeneralizedTime
+	case TagUTCTime:
+		if params.timeType == TagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
+			tag = TagGeneralizedTime
 		}
 	}
 
 	if params.set {
-		if tag != tagSequence {
+		if tag != TagSequence {
 			return StructuralError{"non sequence tagged as set"}
 		}
-		tag = tagSet
+		tag = TagSet
 	}
 
 	tags, body := out.fork()
@@ -613,7 +613,7 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 	if !params.explicit && params.tag != nil {
 		// implicit tag.
 		tag = *params.tag
-		class = classContextSpecific
+		class = ClassContextSpecific
 	}
 
 	err = marshalTagAndLength(tags, tagAndLength{class, tag, bodyLen, isCompound})
@@ -623,7 +623,7 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 
 	if params.explicit {
 		err = marshalTagAndLength(explicitTag, tagAndLength{
-			class:      classContextSpecific,
+			class:      ClassContextSpecific,
 			tag:        *params.tag,
 			length:     bodyLen + tags.Len(),
 			isCompound: true,