Checksumming files.

utils/checksum.go

@@ -0,0 +1,59 @@
+package utils
+
+import (
+	"crypto/md5"
+	"crypto/sha1"
+	"crypto/sha256"
+	"fmt"
+	"hash"
+	"io"
+	"os"
+)
+
+type ChecksumInfo struct {
+	Size   int64
+	MD5    string
+	SHA1   string
+	SHA256 string
+}
+
+// ChecksumsForFile generates size, MD5, SHA1 & SHA256 checksums for given file
+func ChecksumsForFile(path string) (*ChecksumInfo, error) {
+	result := &ChecksumInfo{}
+
+	st, err := os.Stat(path)
+	if err != nil {
+		return nil, err
+	}
+
+	result.Size = st.Size()
+
+	hashes := []hash.Hash{md5.New(), sha1.New(), sha256.New()}
+
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	buf := make([]byte, 8192)
+	for {
+		n, err := file.Read(buf)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+
+		for _, h := range hashes {
+			h.Write(buf[:n])
+		}
+	}
+
+	result.MD5 = fmt.Sprintf("%x", hashes[0].Sum(nil))
+	result.SHA1 = fmt.Sprintf("%x", hashes[1].Sum(nil))
+	result.SHA256 = fmt.Sprintf("%x", hashes[2].Sum(nil))
+
+	return result, nil
+}