[GCM] Initial work to set up directory structure and introduce socket integration

google_apis/gcm/base/socket_stream.h

Index: google_apis/gcm/base/socket_stream.h
diff --git a/google_apis/gcm/base/socket_stream.h b/google_apis/gcm/base/socket_stream.h
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+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Protobuf ZeroCopy[Input/Output]Stream implementations capable of using a
+// net::StreamSocket. Built to work with Protobuf CodedStreams.
+
+#ifndef GOOGLE_APIS_GCM_BASE_SOCKET_STREAM_H_
+#define GOOGLE_APIS_GCM_BASE_SOCKET_STREAM_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "google/protobuf/io/zero_copy_stream.h"
+#include "google_apis/gcm/base/gcm_export.h"
+#include "net/base/net_errors.h"
+
+namespace net {
+class DrainableIOBuffer;
+class IOBuffer;
+class StreamSocket;
+}  // namespace net
+
+namespace gcm {
+
+// A helper class for interacting with a net::StreamSocket that is receiving
+// protobuf encoded messages. A SocketInputStream does not take ownership of
+// the socket itself, and it is expected that the life of the input stream
+// should match the life of the socket itself (while the socket remains
+// connected). If an error is encounters, the input stream will store the error
+// in |last_error_|, and GetState() will be set to CLOSED.
+// Typical usage:
+// 1. Check the GetState() of the input stream before using it. If CLOSED, the
+//    input stream must be rebuilt (and the socket likely needs to be
+//    reconnected as an error was encountered).
+// 2. If GetState() is EMPTY, call Refresh(..), passing the maximum byte size
+//    for a message, and wait until completion. It is invalid to attempt to
+//    Refresh an input stream or read data from the stream while a Refresh is
+//    pending.
+// 3. Check GetState() again to ensure the Refresh was successful.
+// 4. Use a CodedInputStream to read from the ZeroCopyInputStream interface of
+//    the SocketInputStream. Next(..) will return true until there is no data
+//    remaining.
+// 5. Call RebuildBuffer when done reading, to shift any unread data to the
+//    start of the buffer.
+// 6. Repeat as necessary.
+class GCM_EXPORT SocketInputStream
+    : public google::protobuf::io::ZeroCopyInputStream {
+ public:
+  enum State {
+    // No valid data to read. This means the buffer is either empty or all data
+    // in the buffer has already been consumed.
+    EMPTY,
+    // Valid data to read.
+    READY,
+    // In the process of reading new data from the socket.
+    READING,
+    // An permanent error occurred and the stream is now closed.
+    CLOSED,
+  };
+
+  // |socket| should already be connected.
+  explicit SocketInputStream(net::StreamSocket* socket);
+  virtual ~SocketInputStream();
+
+  // ZeroCopyInputStream implementation.
+  virtual bool Next(const void** data, int* size) OVERRIDE;
+  virtual void BackUp(int count) OVERRIDE;
+  virtual bool Skip(int count) OVERRIDE;  // Not implemented.
+  virtual int64 ByteCount() const OVERRIDE;
+
+  // The remaining amount of valid data available to be read.
+  size_t UnreadByteCount() const;
+
+  // Reads from the socket, appending a max of |byte_limit| bytes onto the read
+  // buffer. net::ERR_IO_PENDING is returned if the refresh can't complete
+  // synchronously, in which case the callback is invoked upon completion. If
+  // the refresh can complete synchronously, even in case of an error, returns
+  // net::OK without invoking callback.
+  // Note: GetState() (and possibly last_error()) should be checked upon
+  // completion to determine whether the Refresh encountered an error.
+  net::Error Refresh(const base::Closure& callback, int byte_limit);
+
+  // Rebuilds the buffer state by copying over any unread data to the beginning
+  // of the buffer and resetting the buffer read/write positions.
+  // Note: it is not valid to call Rebuild() if GetState() == CLOSED. The stream
+  // must be recreated from scratch in such a scenario.
+  void RebuildBuffer();
+
+  // Returns the last fatal error encountered. Only valid if GetState() ==
+  // CLOSED.
+  net::Error last_error() const;
+
+  // Returns the current state.
+  State GetState() const;
+
+ private:
+  // Clears the local state.
+  void ResetInternal();
+
+  // Callback for Socket::Read calls.
+  void RefreshCompletionCallback(const base::Closure& callback, int result);
+
+  // Permanently closes the stream.
+  void CloseStream(net::Error error, const base::Closure& callback);
+
+  // Internal net components.
+  net::StreamSocket* const socket_;
+  const scoped_refptr<net::IOBuffer> io_buffer_;
+  // IOBuffer implementation that wraps the data within |io_buffer_| that hasn't
+  // been written to yet by Socket::Read calls.
+  const scoped_refptr<net::DrainableIOBuffer> read_buffer_;
+
+  // Starting position of the data within |io_buffer_| to consume on subsequent
+  // Next(..) call.  0 <= next_pos_ <= read_buffer_.BytesConsumed()
+  // Note: next_pos == read_buffer_.BytesConsumed() implies GetState() == EMPTY.
+  int next_pos_;
+
+  // If < net::ERR_IO_PENDING, the last net error received.
+  // Note: last_error_ == net::ERR_IO_PENDING implies GetState() == READING.
+  net::Error last_error_;
+
+  base::WeakPtrFactory<SocketInputStream> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SocketInputStream);
+};
+
+// A helper class for writing to a SocketStream with protobuf encoded data.
+// A SocketOutputStream does not take ownership of the socket itself, and it is
+// expected that the life of the output stream should match the life of the
+// socket itself (while the socket remains connected).
+// Typical usage:
+// 1. Check the GetState() of the output stream before using it. If CLOSED, the
+//    output stream must be rebuilt (and the socket likely needs to be
+//    reconnected, as an error was encountered).
+// 2. If EMPTY, the output stream can be written via a CodedOutputStream using
+//    the ZeroCopyOutputStream interface.
+// 3. Once done writing, GetState() should be READY, so call Flush(..) to write
+//    the buffer into the StreamSocket. Wait for the callback to be invoked
+//    (it's invalid to write to an output stream while it's flushing).
+// 4. Check the GetState() again to ensure the Flush was successful. GetState()
+//    should be EMPTY again.
+// 5. Repeat.
+class GCM_EXPORT SocketOutputStream
+    : public google::protobuf::io::ZeroCopyOutputStream {
+ public:
+  enum State {
+    // No valid data yet.
+    EMPTY,
+    // Ready for flushing (some data is present).
+    READY,
+    // In the process of flushing into the socket.
+    FLUSHING,
+    // A permanent error occurred, and the stream is now closed.
+    CLOSED,
+  };
+
+  // |socket| should already be connected.
+  explicit SocketOutputStream(net::StreamSocket* socket);
+  virtual ~SocketOutputStream();
+
+  // ZeroCopyOutputStream implementation.
+  virtual bool Next(void** data, int* size) OVERRIDE;
+  virtual void BackUp(int count) OVERRIDE;
+  virtual int64 ByteCount() const OVERRIDE;
+
+  // Writes the buffer into the Socket.
+  net::Error Flush(const base::Closure& callback);
+
+  // Returns the last fatal error encountered. Only valid if GetState() ==
+  // CLOSED.
+  net::Error last_error() const;
+
+  // Returns the current state.
+  State GetState() const;
+
+ private:
+  void FlushCompletionCallback(const base::Closure& callback, int result);
+
+  // Internal net components.
+  net::StreamSocket* const socket_;
+  const scoped_refptr<net::IOBuffer> io_buffer_;
+  // IOBuffer implementation that wraps the data within |io_buffer_| that hasn't
+  // been written to the socket yet.
+  const scoped_refptr<net::DrainableIOBuffer> write_buffer_;
+
+  // Starting position of the data within |io_buffer_| to consume on subsequent
+  // Next(..) call.  0 <= write_buffer_.BytesConsumed() <= next_pos_
+  // Note: next_pos == 0 implies GetState() == EMPTY.
+  int next_pos_;
+
+  // If < net::ERR_IO_PENDING, the last net error received.
+  // Note: last_error_ == net::ERR_IO_PENDING implies GetState() == FLUSHING.
+  net::Error last_error_;
+
+  base::WeakPtrFactory<SocketOutputStream> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SocketOutputStream);
+};
+
+}  // namespace gcm
+
+#endif  // GOOGLE_APIS_GCM_BASE_SOCKET_STREAM_H_