Trim IPC ChannelReader's buffer.

ipc/ipc_channel_reader.h

 // Copyright (c) 2012 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 IPC_IPC_CHANNEL_READER_H_
 #define IPC_IPC_CHANNEL_READER_H_
 
 #include <set>
 
 #include "base/gtest_prod_util.h"
@@ skipping 111 matching lines @@
   virtual base::ProcessId GetSenderPID() = 0;
 
   // Whether the channel is an endpoint of attachment brokering.
   virtual bool IsAttachmentBrokerEndpoint() = 0;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, AttachmentAlreadyBrokered);
   FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, AttachmentNotYetBrokered);
   FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, ResizeOverflowBuffer);
   FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, InvalidMessageSize);
+  FRIEND_TEST_ALL_PREFIXES(ChannelReaderTest, TrimBuffer);
 
   using AttachmentIdSet = std::set<BrokerableAttachment::AttachmentId>;
   using AttachmentIdVector = std::vector<BrokerableAttachment::AttachmentId>;
 
   // Takes the data received from the IPC channel and translates it into
   // Messages. Complete messages are passed to HandleTranslatedMessage().
   // Returns |false| on unrecoverable error.
   bool TranslateInputData(const char* input_data, int input_data_len);
 
   // Internal messages and messages bound for the attachment broker are
@@ skipping 46 matching lines @@
   Listener* listener_;
 
   // We read from the pipe into this buffer. Managed by DispatchInputData, do
   // not access directly outside that function.
   char input_buf_[Channel::kReadBufferSize];
 
   // Large messages that span multiple pipe buffers, get built-up using
   // this buffer.
   std::string input_overflow_buf_;
 
+  // Maximum overflow buffer size, see Channel::kMaximumReadBufferSize.
+  // This is not a constant because we update it to reflect the reality
+  // of std::string::reserve() implementation.
+  size_t max_input_buffer_size_;
+
   // These messages are waiting to be dispatched. If this vector is non-empty,
   // then the front Message must be blocked on receiving an attachment from the
   // AttachmentBroker.
   ScopedVector<Message> queued_messages_;
 
   // If the next message to be processed is blocked by the broker, then this
   // set contains the AttachmentIds that are needed to unblock the message.
   AttachmentIdSet blocked_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(ChannelReader);
 };
 
 }  // namespace internal
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_READER_H_