Use values instead of pointers and use io.MultiWriter instead of homegrown impl.

utils/checksum.go

@@ -19,32 +19,23 @@ type ChecksumInfo struct {
 }
 
 // ChecksumsForFile generates size, MD5, SHA1 & SHA256 checksums for given file
-func ChecksumsForFile(path string) (*ChecksumInfo, error) {
+func ChecksumsForFile(path string) (ChecksumInfo, error) {
 	file, err := os.Open(path)
 	if err != nil {
-		return nil, err
+		return ChecksumInfo{}, err
 	}
 	defer file.Close()
 
-	w := NewChecksumWriter(&DevNull{})
+	w := NewChecksumWriter()
 
 	_, err = io.Copy(w, file)
 	if err != nil {
-		return nil, err
+		return ChecksumInfo{}, err
 	}
 
 	return w.Sum(), nil
 }
 
-// DevNull just accepts anything
-type DevNull struct {
-}
-
-// Write to DevNull always succeeds
-func (d *DevNull) Write(p []byte) (n int, err error) {
-	return len(p), nil
-}
-
 // ChecksumWriter is a writer that does checksum calculation on the fly passing data
 // to real writer
 type ChecksumWriter struct {
@@ -59,34 +50,28 @@ var (
 )
 
 // NewChecksumWriter creates checksum calculator for given writer w
-func NewChecksumWriter(w io.Writer) *ChecksumWriter {
+func NewChecksumWriter() *ChecksumWriter {
 	return &ChecksumWriter{
-		w:      w,
 		hashes: []hash.Hash{md5.New(), sha1.New(), sha256.New()},
 	}
 }
 
 // Write implememnts pass-through writing with checksum calculation on the fly
 func (c *ChecksumWriter) Write(p []byte) (n int, err error) {
-	n, err = c.w.Write(p)
-	if err != nil {
-		return n, err
-	}
-
-	c.sum.Size += int64(n)
+	c.sum.Size += int64(len(p))
 
 	for _, h := range c.hashes {
-		h.Write(p[:n])
+		h.Write(p)
 	}
 
-	return
+	return len(p), nil
 }
 
 // Sum returns caculated ChecksumInfo
-func (c *ChecksumWriter) Sum() *ChecksumInfo {
+func (c *ChecksumWriter) Sum() ChecksumInfo {
 	c.sum.MD5 = fmt.Sprintf("%x", c.hashes[0].Sum(nil))
 	c.sum.SHA1 = fmt.Sprintf("%x", c.hashes[1].Sum(nil))
 	c.sum.SHA256 = fmt.Sprintf("%x", c.hashes[2].Sum(nil))
 
-	return &c.sum
+	return c.sum
 }