Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/transformadapter.h

@@ -0,0 +1,80 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_TRANSFORMADAPTER_H__
+#define WEBRTC_BASE_TRANSFORMADAPTER_H__
+
+#include "webrtc/base/stream.h"
+
+namespace rtc {
+///////////////////////////////////////////////////////////////////////////////
+
+class TransformInterface {
+public:
+  virtual ~TransformInterface() { }
+
+  // Transform should convert the in_len bytes of input into the out_len-sized
+  // output buffer.  If flush is true, there will be no more data following
+  // input.
+  // After the transformation, in_len contains the number of bytes consumed, and
+  // out_len contains the number of bytes ready in output.
+  // Note: Transform should not return SR_BLOCK, as there is no asynchronous
+  // notification available.
+  virtual StreamResult Transform(const void * input, size_t * in_len,
+                                 void * output, size_t * out_len,
+                                 bool flush) = 0;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+// TransformAdapter causes all data passed through to be transformed by the
+// supplied TransformInterface object, which may apply compression, encryption,
+// etc.
+
+class TransformAdapter : public StreamAdapterInterface {
+public:
+  // Note that the transformation is unidirectional, in the direction specified
+  // by the constructor.  Operations in the opposite direction result in SR_EOS.
+  TransformAdapter(StreamInterface * stream,
+                   TransformInterface * transform,
+                   bool direction_read);
+  virtual ~TransformAdapter();
+  
+  virtual StreamResult Read(void * buffer, size_t buffer_len,
+                            size_t * read, int * error);
+  virtual StreamResult Write(const void * data, size_t data_len,
+                             size_t * written, int * error);
+  virtual void Close();
+
+  // Apriori, we can't tell what the transformation does to the stream length.
+  virtual bool GetAvailable(size_t* size) const { return false; }
+  virtual bool ReserveSize(size_t size) { return true; }
+
+  // Transformations might not be restartable
+  virtual bool Rewind() { return false; }
+
+private:
+  enum State { ST_PROCESSING, ST_FLUSHING, ST_COMPLETE, ST_ERROR };
+  enum { BUFFER_SIZE = 1024 };
+
+  TransformInterface * transform_;
+  bool direction_read_;
+  State state_;
+  int error_;
+
+  char buffer_[BUFFER_SIZE];
+  size_t len_;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+
+} // namespace rtc
+
+#endif // WEBRTC_BASE_TRANSFORMADAPTER_H__