implement a caching reader needed for crypto streams

utils/caching_reader.go

@@ -0,0 +1,35 @@
+package utils
+
+import "bytes"
+
+// CachingReader wraps a reader and saves all data it reads
+type CachingReader struct {
+	buf bytes.Buffer
+	r   ReadStream
+}
+
+// NewCachingReader returns a new CachingReader
+func NewCachingReader(r ReadStream) *CachingReader {
+	return &CachingReader{r: r}
+}
+
+// Read implements io.Reader
+func (r *CachingReader) Read(p []byte) (int, error) {
+	n, err := r.r.Read(p)
+	r.buf.Write(p[:n])
+	return n, err
+}
+
+// ReadByte implements io.ByteReader
+func (r *CachingReader) ReadByte() (byte, error) {
+	b, err := r.r.ReadByte()
+	if err == nil {
+		r.buf.WriteByte(b)
+	}
+	return b, err
+}
+
+// Get the data cached
+func (r *CachingReader) Get() []byte {
+	return r.buf.Bytes()
+}