Moves files

internal/hashing/writer.go

@@ -0,0 +1,31 @@
+package hashing
+
+import (
+	"hash"
+	"io"
+)
+
+// Writer transparently hashes all data while writing it to the underlying writer.
+type Writer struct {
+	w io.Writer
+	h hash.Hash
+}
+
+// NewWriter wraps the writer w and feeds all data written to the hash h.
+func NewWriter(w io.Writer, h hash.Hash) *Writer {
+	return &Writer{
+		h: h,
+		w: io.MultiWriter(w, h),
+	}
+}
+
+// Write wraps the write method of the underlying writer and also hashes all data.
+func (h *Writer) Write(p []byte) (int, error) {
+	n, err := h.w.Write(p)
+	return n, err
+}
+
+// Sum returns the hash of all data written so far.
+func (h *Writer) Sum(d []byte) []byte {
+	return h.h.Sum(d)
+}