From fb2cd7b48510531b238b46c4659195f5bf202225 Mon Sep 17 00:00:00 2001
From: Alexander Neumann <alexander@bumpern.de>
Date: Mon, 16 Feb 2015 00:24:43 +0100
Subject: [PATCH] HashingWriter: Track size

---
 backend/writer.go      | 13 ++++++++++---
 backend/writer_test.go |  4 ++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/backend/writer.go b/backend/writer.go
index 55ffb3279..17e7d0653 100644
--- a/backend/writer.go
+++ b/backend/writer.go
@@ -43,8 +43,9 @@ func (h *HashAppendWriter) Write(p []byte) (n int, err error) {
 }
 
 type HashingWriter struct {
-	w io.Writer
-	h hash.Hash
+	w    io.Writer
+	h    hash.Hash
+	size int
 }
 
 func NewHashingWriter(w io.Writer, h hash.Hash) *HashingWriter {
@@ -55,9 +56,15 @@ func NewHashingWriter(w io.Writer, h hash.Hash) *HashingWriter {
 }
 
 func (h *HashingWriter) Write(p []byte) (int, error) {
-	return h.w.Write(p)
+	n, err := h.w.Write(p)
+	h.size += n
+	return n, err
 }
 
 func (h *HashingWriter) Sum(d []byte) []byte {
 	return h.h.Sum(d)
 }
+
+func (h *HashingWriter) Size() int {
+	return h.size
+}
diff --git a/backend/writer_test.go b/backend/writer_test.go
index bf4655c25..85d55f8f2 100644
--- a/backend/writer_test.go
+++ b/backend/writer_test.go
@@ -68,6 +68,10 @@ func TestHashingWriter(t *testing.T) {
 			"HashAppendWriter: invalid number of bytes written: got %d, expected %d",
 			n, size)
 
+		assert(t, wr.Size() == size,
+			"HashAppendWriter: invalid number of bytes returned: got %d, expected %d",
+			wr.Size, size)
+
 		resultingHash := wr.Sum(nil)
 		assert(t, bytes.Equal(expectedHash[:], resultingHash),
 			"HashAppendWriter: hashes do not match: expected %02x, got %02x",