Mojo: DataPipe: Implement "may discard" for two-phase writes.

mojo/system/data_pipe.h

 // 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"
@@ skipping 65 matching lines @@
   void ConsumerRemoveWaiter(Waiter* waiter);
 
  protected:
   DataPipe(bool has_local_producer,
            bool has_local_consumer,
            const MojoCreateDataPipeOptions& validated_options);
 
   friend class base::RefCountedThreadSafe<DataPipe>;
   virtual ~DataPipe();
 
-  void AwakeProducerWaitersForStateChangeNoLock();
-  void AwakeConsumerWaitersForStateChangeNoLock();
-
   virtual void ProducerCloseImplNoLock() = 0;
   // |*num_bytes| will be a nonzero multiple of |element_num_bytes_|.
   virtual MojoResult ProducerWriteDataImplNoLock(const void* elements,
                                                  uint32_t* num_bytes,
                                                  bool all_or_none) = 0;
   virtual MojoResult ProducerBeginWriteDataImplNoLock(
       void** buffer,
       uint32_t* buffer_num_bytes,
       bool all_or_none) = 0;
   virtual MojoResult ProducerEndWriteDataImplNoLock(
       uint32_t num_bytes_written) = 0;
+  // Note: A producer should not be writable during a two-phase write.
   virtual MojoWaitFlags ProducerSatisfiedFlagsNoLock() = 0;
   virtual MojoWaitFlags ProducerSatisfiableFlagsNoLock() = 0;
 
   virtual void ConsumerCloseImplNoLock() = 0;
   // |*num_bytes| will be a nonzero multiple of |element_num_bytes_|.
   virtual MojoResult ConsumerReadDataImplNoLock(void* elements,
                                                 uint32_t* num_bytes,
                                                 bool all_or_none) = 0;
   virtual MojoResult ConsumerDiscardDataImplNoLock(uint32_t* num_bytes,
                                                    bool all_or_none) = 0;
   // |*num_bytes| will be a nonzero multiple of |element_num_bytes_|.
   virtual MojoResult ConsumerQueryDataImplNoLock(uint32_t* num_bytes) = 0;
   virtual MojoResult ConsumerBeginReadDataImplNoLock(const void** buffer,
                                                      uint32_t* buffer_num_bytes,
                                                      bool all_or_none) = 0;
   virtual MojoResult ConsumerEndReadDataImplNoLock(uint32_t num_bytes_read) = 0;
+  // Note: A consumer should not be writable during a two-phase read.
   virtual MojoWaitFlags ConsumerSatisfiedFlagsNoLock() = 0;
   virtual MojoWaitFlags ConsumerSatisfiableFlagsNoLock() = 0;
 
   // Thread-safe and fast (they don't take the lock):
   // TODO(vtl): FIXME -- "may discard" not respected
   bool may_discard() const { return may_discard_; }
   size_t element_num_bytes() const { return element_num_bytes_; }
   size_t capacity_num_bytes() const { return capacity_num_bytes_; }
 
   // Must be called under lock.
@@ skipping 25 matching lines @@
   bool producer_in_two_phase_write_no_lock() const {
     lock_.AssertAcquired();
     return producer_two_phase_max_num_bytes_written_ > 0;
   }
   bool consumer_in_two_phase_read_no_lock() const {
     lock_.AssertAcquired();
     return consumer_two_phase_max_num_bytes_read_ > 0;
   }
 
  private:
+  void AwakeProducerWaitersForStateChangeNoLock();
+  void AwakeConsumerWaitersForStateChangeNoLock();
+
   bool has_local_producer_no_lock() const {
     lock_.AssertAcquired();
     return !!producer_waiter_list_.get();
   }
   bool has_local_consumer_no_lock() const {
     lock_.AssertAcquired();
     return !!consumer_waiter_list_.get();
   }
 
   const bool may_discard_;
@@ skipping 11 matching lines @@
   uint32_t producer_two_phase_max_num_bytes_written_;
   uint32_t consumer_two_phase_max_num_bytes_read_;
 
   DISALLOW_COPY_AND_ASSIGN(DataPipe);
 };
 
 }  // namespace system
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_DATA_PIPE_H_