Crc32c re-implementation with Convenience functions

- Sum32([]byte) --> uint32
   - Sum(io.Reader) --> uint32, error

pkg/utils/checksum/crc32c/crc32c_darwin.go

@@ -23,11 +23,25 @@ import (
 
 var castanagoliTable = crc32.MakeTable(crc32.Castagnoli)
 
-func Crc32c(buffer []byte) (uint32, error) {
+func Sum32(buffer []byte) uint32 {
 	crc := crc32.New(castanagoliTable)
-	if len(buffer) <= 0 {
-		return 0, errors.New("input buffer cannot be null")
-	}
+	crc.Reset()
 	crc.Write(buffer)
-	return crc.Sum32(), nil
+	return crc.Sum32()
+}
+
+func Sum(reader io.Reader) (uint32, error) {
+	h := New()
+	var err error
+	for err == nil {
+		length := 0
+		byteBuffer := make([]byte, 1024*1024)
+		length, err = reader.Read(byteBuffer)
+		byteBuffer = byteBuffer[0:length]
+		h.Write(byteBuffer)
+	}
+	if err != io.EOF {
+		return nil, err
+	}
+	return h.Sum32(), nil
 }