EDK: Add implementation of data pipe consumer read threshold stuff.

mojo/edk/system/local_data_pipe_impl.cc

 // 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.
 
 // TODO(vtl): I currently potentially overflow in doing index calculations.
 // E.g., |start_index_| and |current_num_bytes_| fit into a |uint32_t|, but
 // their sum may not. This is bad and poses a security risk. (We're currently
 // saved by the limit on capacity -- the maximum size of the buffer, checked in
 // |DataPipe::ValidateOptions()|, is currently sufficiently small.)
 
@@ skipping 296 matching lines @@
   DCHECK_LE(num_bytes_read, consumer_two_phase_max_num_bytes_read());
   DCHECK_EQ(num_bytes_read % element_num_bytes(), 0u);
   DCHECK_LE(start_index_ + num_bytes_read, capacity_num_bytes());
   MarkDataAsConsumed(num_bytes_read);
   set_consumer_two_phase_max_num_bytes_read(0);
   return MOJO_RESULT_OK;
 }
 
 HandleSignalsState LocalDataPipeImpl::ConsumerGetHandleSignalsState() const {
   HandleSignalsState rv;
-  if (current_num_bytes_ > 0) {
+  // |consumer_read_threshold_num_bytes()| is always at least 1.
+  if (current_num_bytes_ >= consumer_read_threshold_num_bytes()) {
+    if (!consumer_in_two_phase_read()) {
+      rv.satisfied_signals |=
+          MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_READ_THRESHOLD;
+    }
+    rv.satisfiable_signals |=
+        MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_READ_THRESHOLD;
+  } else if (current_num_bytes_ > 0u) {
     if (!consumer_in_two_phase_read())
       rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_READABLE;
     rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_READABLE;
-  } else if (producer_open()) {
-    rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_READABLE;
   }
-  if (!producer_open())
+  if (producer_open()) {
+    rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_READABLE |
+                              MOJO_HANDLE_SIGNAL_PEER_CLOSED |
+                              MOJO_HANDLE_SIGNAL_READ_THRESHOLD;
+  } else {
     rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
-  rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
+    rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
+  }
   return rv;
 }
 
 void LocalDataPipeImpl::ConsumerStartSerialize(Channel* channel,
                                                size_t* max_size,
                                                size_t* max_platform_handles) {
   *max_size = sizeof(SerializedDataPipeConsumerDispatcher) +
               channel->GetSerializedEndpointSize();
   *max_platform_handles = 0;
 }
@@ skipping 96 matching lines @@
 
 void LocalDataPipeImpl::MarkDataAsConsumed(size_t num_bytes) {
   DCHECK_LE(num_bytes, current_num_bytes_);
   start_index_ += num_bytes;
   start_index_ %= capacity_num_bytes();
   current_num_bytes_ -= num_bytes;
 }
 
 }  // namespace system
 }  // namespace mojo