feature: added io.Copy progress listener

pkg/io/copy/progress/progress_listener.go

@@ -0,0 +1,37 @@
+package progress
+
+import "io"
+
+type WriteProgressCallback func(uint64, uint64)
+
+type WriteProgressListener struct {
+	BytesWritten     uint64
+	ProgressCallback WriteProgressCallback
+}
+
+func (self *WriteProgressListener) Write(p []byte) (int, error) {
+	n := len(p)
+	newTotal := self.BytesWritten + uint64(n)
+
+	if self.ProgressCallback != nil {
+		self.ProgressCallback(self.BytesWritten, newTotal)
+	}
+
+	self.BytesWritten = newTotal
+	return n, nil
+}
+
+func (self *WriteProgressListener) WrapReader(reader io.Reader) io.Reader {
+	return io.TeeReader(reader, self)
+}
+
+func NewProgressListener(callback WriteProgressCallback) *WriteProgressListener {
+	return &WriteProgressListener{
+		BytesWritten:     0,
+		ProgressCallback: callback,
+	}
+}
+
+func WrapReader(reader io.Reader, callback WriteProgressCallback) io.Reader {
+	return NewProgressListener(callback).WrapReader(reader)
+}