fix: update code

Signed-off-by: Junjie Gao <junjiegao@microsoft.com>

internal/encoding/asn1/asn1.go

@@ -42,36 +42,36 @@ func ConvertToDER(ber []byte) ([]byte, error) {
 }
 
 // decode decodes BER-encoded ASN.1 data structures.
-func decode(r ReadOnlySlice) (value, error) {
+func decode(r readOnlySlice) (value, error) {
 	identifier, isPrimitiveValue, err := identifierValue(r)
 	if err != nil {
 		return nil, err
 	}
-	expectedLength, err := decodeLength(r)
+	contentLength, err := decodeLength(r)
 	if err != nil {
 		return nil, err
 	}
-	content, err := r.Slice(r.Offset(), r.Offset()+expectedLength)
+	content, err := r.Slice(r.Offset(), r.Offset()+contentLength)
 	if err != nil {
 		return nil, err
 	}
-	if err = r.Seek(r.Offset() + expectedLength); err != nil {
+	if err = r.Seek(r.Offset() + contentLength); err != nil {
 		return nil, err
 	}
 
 	if isPrimitiveValue {
-		return newPrimitiveValue(identifier, content)
+		return newPrimitiveValue(identifier, content), nil
 	}
-	return newConstructedValue(identifier, expectedLength, content)
+	return newConstructedValue(identifier, content)
 }
 
 // identifierValue decodes identifierValue octets.
-func identifierValue(r ReadOnlySlice) (ReadOnlySlice, bool, error) {
+func identifierValue(r readOnlySlice) (readOnlySlice, bool, error) {
 	b, err := r.ReadByte()
 	if err != nil {
 		return nil, false, err
 	}
-	isPrimitiveValue := isPrimitive(b)
+	isPrimitive := b&0x20 == 0
 
 	tagBytesCount := 1
 	// high-tag-number form
@@ -92,13 +92,7 @@ func identifierValue(r ReadOnlySlice) (ReadOnlySlice, bool, error) {
 	if err != nil {
 		return nil, false, err
 	}
-	return identifier, isPrimitiveValue, nil
-}
-
-// isPrimitive checks the primitive flag in the identifier.
-// Returns true if the value is primitive.
-func isPrimitive(identifier byte) bool {
-	return identifier&0x20 == 0
+	return identifier, isPrimitive, nil
 }
 
 // decodeLength decodes length octets.

internal/encoding/asn1/constructed.go

@@ -2,13 +2,13 @@ package asn1
 
 // constructedValue represents a value in constructed encoding.
 type constructedValue struct {
-	identifier ReadOnlySlice
+	identifier readOnlySlice
 	length     int
 	members    []value
 }
 
 // newConstructedValue builds the constructed value.
-func newConstructedValue(identifier ReadOnlySlice, expectedLength int, content ReadOnlySlice) (value, error) {
+func newConstructedValue(identifier readOnlySlice, content readOnlySlice) (value, error) {
 	var members []value
 	encodedLength := 0
 	for content.Offset() < content.Length() {

internal/encoding/asn1/primitive.go

@@ -2,16 +2,16 @@ package asn1
 
 // primitiveValue represents a value in primitive encoding.
 type primitiveValue struct {
-	identifier ReadOnlySlice
-	content    ReadOnlySlice
+	identifier readOnlySlice
+	content    readOnlySlice
 }
 
 // newPrimitiveValue builds the primitive value.
-func newPrimitiveValue(identifier ReadOnlySlice, content ReadOnlySlice) (value, error) {
+func newPrimitiveValue(identifier readOnlySlice, content readOnlySlice) value {
 	return primitiveValue{
 		identifier: identifier,
 		content:    content,
-	}, nil
+	}
 }
 
 // Encode encodes the primitive value to the value writer in DER.

internal/encoding/asn1/slice.go

@@ -2,28 +2,42 @@ package asn1
 
 import "io"
 
-type ReadOnlySlice interface {
+// readOnlySlice is an interface that represents a read-only slice of bytes.
+type readOnlySlice interface {
 	io.ByteReader
 	io.Reader
+
+	// Length returns the length of the slice.
 	Length() int
+
+	// Offset returns the current offset of the slice.
 	Offset() int
+
+	// Seek sets the current offset of the slice to the given value.
 	Seek(offset int) error
-	Slice(begin int, end int) (ReadOnlySlice, error)
+
+	// Slice returns a new ReadOnlySlice that represents a sub-slice of the current slice.
+	// The sub-slice starts at the given begin index and ends at the given end index (exclusive).
+	Slice(begin int, end int) (readOnlySlice, error)
 }
 
-type readOnlySlice struct {
+// byteSlice is a struct that implements the ReadOnlySlice interface.
+type byteSlice struct {
 	data   []byte
 	offset int
 }
 
-func newReadOnlySlice(data []byte) ReadOnlySlice {
-	return &readOnlySlice{
+// newReadOnlySlice creates a new ReadOnlySlice from the given byte slice.
+func newReadOnlySlice(data []byte) readOnlySlice {
+	return &byteSlice{
 		data:   data,
 		offset: 0,
 	}
 }
 
-func (r *readOnlySlice) ReadByte() (byte, error) {
+// ReadByte reads and returns a single byte from the slice.
+// If the end of the slice has been reached, it returns an error.
+func (r *byteSlice) ReadByte() (byte, error) {
 	if r.offset >= len(r.data) {
 		return 0, ErrEarlyEOF
 	}
@@ -32,7 +46,8 @@ func (r *readOnlySlice) ReadByte() (byte, error) {
 	return b, nil
 }
 
-func (r *readOnlySlice) Read(p []byte) (int, error) {
+// Read reads up to len(p) bytes from the slice into p.
+func (r *byteSlice) Read(p []byte) (int, error) {
 	if r.offset >= len(r.data) {
 		return 0, io.EOF
 	}
@@ -41,27 +56,31 @@ func (r *readOnlySlice) Read(p []byte) (int, error) {
 	return n, nil
 }
 
-func (r *readOnlySlice) Length() int {
+// Length returns the length of the slice.
+func (r *byteSlice) Length() int {
 	return len(r.data)
 }
 
-func (r *readOnlySlice) Offset() int {
+// Offset returns the current offset of the slice.
+func (r *byteSlice) Offset() int {
 	return r.offset
 }
 
-func (r *readOnlySlice) Seek(offset int) error {
+// Seek sets the current offset of the slice to the given value.
+func (r *byteSlice) Seek(offset int) error {
 	if offset < 0 || offset > len(r.data) {
 		return ErrInvalidOffset
 	}
 	r.offset = offset
 	return nil
 }
 
-func (r *readOnlySlice) Slice(begin int, end int) (ReadOnlySlice, error) {
+// Slice returns a new ReadOnlySlice that represents a sub-slice of the current slice.
+func (r *byteSlice) Slice(begin int, end int) (readOnlySlice, error) {
 	if begin < 0 || end < 0 || begin > end || end > len(r.data) {
 		return nil, ErrInvalidSlice
 	}
-	return &readOnlySlice{
+	return &byteSlice{
 		data:   r.data[begin:end],
 		offset: 0,
 	}, nil