finished merging earlier decoder code

app/decoder/decoder.cpp

@@ -0,0 +1,28 @@
+#include "decoder.h"
+
+Decoder::Decoder() :
+  open_(false)
+{
+}
+
+Decoder::Decoder(Stream *fs) :
+  open_(false),
+  stream_(fs)
+{
+}
+
+Decoder::~Decoder()
+{
+}
+
+Stream *Decoder::stream()
+{
+  return stream_;
+}
+
+void Decoder::set_stream(Stream *fs)
+{
+  Close();
+
+  stream_ = fs;
+}