From 98dc8115365372f5b788f35f55c54067c58adc69 Mon Sep 17 00:00:00 2001
From: Alexander Neumann <alexander@bumpern.de>
Date: Fri, 1 May 2015 17:13:03 +0200
Subject: [PATCH] Add nil-receiver awareness to all Reader/Writer

---
 backend/generic.go   | 4 ++++
 backend/sftp/sftp.go | 4 ++++
 backend/writer.go    | 4 ++++
 crypto/reader.go     | 7 ++++---
 crypto/writer.go     | 4 ++++
 5 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/backend/generic.go b/backend/generic.go
index 0720809bd..0244cdab1 100644
--- a/backend/generic.go
+++ b/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
diff --git a/backend/sftp/sftp.go b/backend/sftp/sftp.go
index aa0fdd2af..09dad6242 100644
--- a/backend/sftp/sftp.go
+++ b/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()
diff --git a/backend/writer.go b/backend/writer.go
index 17e7d0653..ae2c5bfd9 100644
--- a/backend/writer.go
+++ b/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
 
diff --git a/crypto/reader.go b/crypto/reader.go
index fe27f5344..20c451cf3 100644
--- a/crypto/reader.go
+++ b/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
diff --git a/crypto/writer.go b/crypto/writer.go
index 3de2df69c..63a09438e 100644
--- a/crypto/writer.go
+++ b/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")
 	}