Add nil-receiver awareness to all Reader/Writer

backend/generic.go

@@ -115,6 +115,10 @@ func (l *blobReader) Read(p []byte) (int, error) {
 }
 
 func (l *blobReader) Close() error {
+	if l == nil {
+		return nil
+	}
+
 	if !l.closed {
 		err := l.f.Close()
 		l.closed = true

backend/sftp/sftp.go

@@ -554,6 +554,10 @@ func (r *SFTP) ID() string {
 
 // Close closes the sftp connection and terminates the underlying command.
 func (s *SFTP) Close() error {
+	if s == nil {
+		return nil
+	}
+
 	s.c.Close()
 	// TODO: add timeout after which the process is killed
 	return s.cmd.Wait()

backend/writer.go

@@ -24,6 +24,10 @@ func NewHashAppendWriter(w io.Writer, h hash.Hash) *HashAppendWriter {
 }
 
 func (h *HashAppendWriter) Close() error {
+	if h == nil {
+		return nil
+	}
+
 	if !h.closed {
 		h.closed = true
 

crypto/reader.go

@@ -30,7 +30,7 @@ func (d *decryptReader) free() {
 }
 
 func (d *decryptReader) Close() error {
-	if d.buf == nil {
+	if d == nil || d.buf == nil {
 		return nil
 	}
 
@@ -72,14 +72,15 @@ func DecryptFrom(ks *Key, rd io.Reader) (io.ReadCloser, error) {
 	buf := bytes.NewBuffer(getBuffer()[:0])
 	_, err := buf.ReadFrom(rd)
 	if err != nil {
-		return nil, err
+		return (*decryptReader)(nil), err
 	}
 
 	ciphertext := buf.Bytes()
 
 	ciphertext, err = Decrypt(ks, ciphertext, ciphertext)
 	if err != nil {
-		return nil, err
+		freeBuffer(ciphertext)
+		return (*decryptReader)(nil), err
 	}
 
 	return &decryptReader{buf: ciphertext, rd: bytes.NewReader(ciphertext)}, nil

crypto/writer.go

@@ -17,6 +17,10 @@ type encryptWriter struct {
 }
 
 func (e *encryptWriter) Close() error {
+	if e == nil {
+		return nil
+	}
+
 	if e.closed {
 		return errors.New("Close() called on already closed writer")
 	}