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diff --git a/mojo/system/data_pipe.h b/mojo/system/data_pipe.h
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+// Copyright 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.
+
+#ifndef MOJO_SYSTEM_DATA_PIPE_H_
+#define MOJO_SYSTEM_DATA_PIPE_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "mojo/public/system/core.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace system {
+
+class Waiter;
+class WaiterList;
+
+// |DataPipe| is a base class for secondary objects implementing data pipes,
+// similar to |MessagePipe| (see the explanatory comment in core_impl.cc). It is
+// typically owned by the dispatcher(s) corresponding to the local endpoints.
+// Its subclasses implement the three cases: local producer and consumer, local
+// producer and remote consumer, and remote producer and local consumer. This
+// class is thread-safe.
+class MOJO_SYSTEM_IMPL_EXPORT DataPipe :
+    public base::RefCountedThreadSafe<DataPipe> {
+ public:
+  // These are called by the producer dispatcher to implement its methods of
+  // corresponding names.
+  void ProducerCancelAllWaiters();
+  void ProducerClose();
+  // This does not validate |elements| or |num_elements| (or |*num_elements|).
+  MojoResult ProducerWriteData(const void* elements,
+                               uint32_t* num_elements,
+                               MojoWriteDataFlags flags);
+  // This does not validate |buffer| or |buffer_num_elements|.
+  MojoResult ProducerBeginWriteData(void** buffer,
+                                    uint32_t* buffer_num_elements,
+                                    MojoWriteDataFlags flags);
+  MojoResult ProducerEndWriteData(uint32_t num_elements_written);
+  MojoResult ProducerAddWaiter(Waiter* waiter,
+                               MojoWaitFlags flags,
+                               MojoResult wake_result);
+  void ProducerRemoveWaiter(Waiter* waiter);
+
+/* TODO(vtl)
+  void ConsumerCancelAllWaiters();
+  void ConsumerClose();
+...
+  MojoResult ConsumerAddWaiter(Waiter* waiter,
+                               MojoWaitFlags flags,
+                               MojoResult wake_result);
+  void ConsumerRemoveWaiter(Waiter* waiter);
+*/
+
+  // Thread-safe and fast (doesn't take the lock).
+  size_t element_size() const { return element_size_; }
+
+ protected:
+  DataPipe(bool has_local_producer, bool has_local_consumer);
+
+  void Init(size_t element_size);
+
+  virtual void ProducerCloseImplNoLock() = 0;
+  virtual MojoResult ProducerBeginWriteDataImplNoLock(
+      void** buffer,
+      uint32_t* buffer_num_elements,
+      MojoWriteDataFlags flags) = 0;
+  virtual MojoResult ProducerEndWriteDataImplNoLock(
+      uint32_t num_elements_written) = 0;
+  virtual MojoWaitFlags ProducerSatisfiedFlagsNoLock() = 0;
+  virtual MojoWaitFlags ProducerSatisfiableFlagsNoLock() = 0;
+
+ private:
+  friend class base::RefCountedThreadSafe<DataPipe>;
+  virtual ~DataPipe();
+
+  bool has_local_producer_no_lock() const {
+    return !!producer_waiter_list_.get();
+  }
+  bool has_local_consumer_no_lock() const {
+    return !!consumer_waiter_list_.get();
+  }
+
+  // Set by |Init()| and never changed afterwards.
+  size_t element_size_;
+
+  base::Lock lock_;  // Protects the following members.
+  scoped_ptr<WaiterList> producer_waiter_list_;
+  scoped_ptr<WaiterList> consumer_waiter_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataPipe);
+};
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_SYSTEM_DATA_PIPE_H_