Add buffered reader

wrappers/buffered_reader.go

@@ -0,0 +1,38 @@
+package wrappers
+
+import "bytes"
+
+type BufferedReader struct {
+	Buffer *bytes.Buffer
+}
+
+func (b *BufferedReader) BufferedRead(p []byte, callback func() error) (int, error) {
+	if b.Buffer.Len() > 0 {
+		return b.flush(p)
+	}
+	if err := callback(); err != nil {
+		return 0, err
+	}
+	return b.flush(p)
+}
+
+func (b *BufferedReader) flush(p []byte) (int, error) {
+	sizeToRead := len(p)
+	if b.Buffer.Len() < sizeToRead {
+		sizeToRead = b.Buffer.Len()
+	}
+
+	data := b.Buffer.Bytes()
+	copy(p, data[:sizeToRead])
+	if sizeToRead == b.Buffer.Len() {
+		b.Buffer.Reset()
+	} else {
+		b.Buffer = bytes.NewBuffer(data[sizeToRead:])
+	}
+
+	return sizeToRead, nil
+}
+
+func NewBufferedReader() BufferedReader {
+	return BufferedReader{Buffer: &bytes.Buffer{}}
+}