Mojo: Armed Watchers

mojo/edk/system/data_pipe_consumer_dispatcher.cc

Index: mojo/edk/system/data_pipe_consumer_dispatcher.cc
diff --git a/mojo/edk/system/data_pipe_consumer_dispatcher.cc b/mojo/edk/system/data_pipe_consumer_dispatcher.cc
index c908e3ae8bf7d4f9668d9fa3836d1e8b79f8f97b..474e99d4955fc3c0e6cdc98f045af90e9d44e988 100644
--- a/mojo/edk/system/data_pipe_consumer_dispatcher.cc
+++ b/mojo/edk/system/data_pipe_consumer_dispatcher.cc
@@ -80,6 +80,7 @@ DataPipeConsumerDispatcher::DataPipeConsumerDispatcher(
       node_controller_(node_controller),
       control_port_(control_port),
       pipe_id_(pipe_id),
+      watchers_(this),
       shared_ring_buffer_(shared_ring_buffer) {
   if (initialized) {
     base::AutoLock lock(lock_);
@@ -97,34 +98,10 @@ MojoResult DataPipeConsumerDispatcher::Close() {
   return CloseNoLock();
 }
 
-
-MojoResult DataPipeConsumerDispatcher::Watch(
-    MojoHandleSignals signals,
-    const Watcher::WatchCallback& callback,
-    uintptr_t context) {
-  base::AutoLock lock(lock_);
-
-  if (is_closed_ || in_transit_)
-    return MOJO_RESULT_INVALID_ARGUMENT;
-
-  return awakable_list_.AddWatcher(
-      signals, callback, context, GetHandleSignalsStateNoLock());
-}
-
-MojoResult DataPipeConsumerDispatcher::CancelWatch(uintptr_t context) {
-  base::AutoLock lock(lock_);
-
-  if (is_closed_ || in_transit_)
-    return MOJO_RESULT_INVALID_ARGUMENT;
-
-  return awakable_list_.RemoveWatcher(context);
-}
-
 MojoResult DataPipeConsumerDispatcher::ReadData(void* elements,
                                                 uint32_t* num_bytes,
                                                 MojoReadDataFlags flags) {
   base::AutoLock lock(lock_);
-  new_data_available_ = false;
 
   if (!shared_ring_buffer_ || in_transit_)
     return MOJO_RESULT_INVALID_ARGUMENT;
@@ -132,6 +109,9 @@ MojoResult DataPipeConsumerDispatcher::ReadData(void* elements,
   if (in_two_phase_read_)
     return MOJO_RESULT_BUSY;
 
+  const bool had_new_data = new_data_available_;
+  new_data_available_ = false;
+
   if ((flags & MOJO_READ_DATA_FLAG_QUERY)) {
     if ((flags & MOJO_READ_DATA_FLAG_PEEK) ||
         (flags & MOJO_READ_DATA_FLAG_DISCARD))
@@ -140,6 +120,9 @@ MojoResult DataPipeConsumerDispatcher::ReadData(void* elements,
     DVLOG_IF(2, elements)
         << "Query mode: ignoring non-null |elements|";
     *num_bytes = static_cast<uint32_t>(bytes_available_);
+
+    if (had_new_data)
+      watchers_.NotifyState(GetHandleSignalsStateNoLock());
     return MOJO_RESULT_OK;
   }
 
@@ -162,12 +145,16 @@ MojoResult DataPipeConsumerDispatcher::ReadData(void* elements,
       all_or_none ? max_num_bytes_to_read : 0;
 
   if (min_num_bytes_to_read > bytes_available_) {
+    if (had_new_data)
+      watchers_.NotifyState(GetHandleSignalsStateNoLock());
     return peer_closed_ ? MOJO_RESULT_FAILED_PRECONDITION
                         : MOJO_RESULT_OUT_OF_RANGE;
   }
 
   uint32_t bytes_to_read = std::min(max_num_bytes_to_read, bytes_available_);
   if (bytes_to_read == 0) {
+    if (had_new_data)
+      watchers_.NotifyState(GetHandleSignalsStateNoLock());
     return peer_closed_ ? MOJO_RESULT_FAILED_PRECONDITION
                         : MOJO_RESULT_SHOULD_WAIT;
   }
@@ -199,6 +186,10 @@ MojoResult DataPipeConsumerDispatcher::ReadData(void* elements,
     NotifyRead(bytes_to_read);
   }
 
+  // We may have just read the last available data and thus changed the signals
+  // state.
+  watchers_.NotifyState(GetHandleSignalsStateNoLock());
+
   return MOJO_RESULT_OK;
 }
 
@@ -206,7 +197,6 @@ MojoResult DataPipeConsumerDispatcher::BeginReadData(const void** buffer,
                                                      uint32_t* buffer_num_bytes,
                                                      MojoReadDataFlags flags) {
   base::AutoLock lock(lock_);
-  new_data_available_ = false;
   if (!shared_ring_buffer_ || in_transit_)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
@@ -219,7 +209,12 @@ MojoResult DataPipeConsumerDispatcher::BeginReadData(const void** buffer,
       (flags & MOJO_READ_DATA_FLAG_PEEK))
     return MOJO_RESULT_INVALID_ARGUMENT;
 
+  const bool had_new_data = new_data_available_;
+  new_data_available_ = false;
+
   if (bytes_available_ == 0) {
+    if (had_new_data)
+      watchers_.NotifyState(GetHandleSignalsStateNoLock());
     return peer_closed_ ? MOJO_RESULT_FAILED_PRECONDITION
                         : MOJO_RESULT_SHOULD_WAIT;
   }
@@ -237,6 +232,9 @@ MojoResult DataPipeConsumerDispatcher::BeginReadData(const void** buffer,
   *buffer_num_bytes = bytes_to_read;
   two_phase_max_bytes_read_ = bytes_to_read;
 
+  if (had_new_data)
+    watchers_.NotifyState(GetHandleSignalsStateNoLock());
+
   return MOJO_RESULT_OK;
 }
 
@@ -273,6 +271,7 @@ MojoResult DataPipeConsumerDispatcher::EndReadData(uint32_t num_bytes_read) {
   HandleSignalsState new_state = GetHandleSignalsStateNoLock();
   if (!new_state.equals(old_state))
     awakable_list_.AwakeForStateChange(new_state);
+  watchers_.NotifyState(new_state);
 
   return rv;
 }
@@ -282,6 +281,24 @@ HandleSignalsState DataPipeConsumerDispatcher::GetHandleSignalsState() const {
   return GetHandleSignalsStateNoLock();
 }
 
+MojoResult DataPipeConsumerDispatcher::AddWatcherRef(
+    const scoped_refptr<WatcherDispatcher>& watcher,
+    uintptr_t context) {
+  base::AutoLock lock(lock_);
+  if (is_closed_ || in_transit_)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  return watchers_.Add(watcher, context, GetHandleSignalsStateNoLock());
+}
+
+MojoResult DataPipeConsumerDispatcher::RemoveWatcherRef(
+    WatcherDispatcher* watcher,
+    uintptr_t context) {
+  base::AutoLock lock(lock_);
+  if (is_closed_ || in_transit_)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  return watchers_.Remove(watcher, context);
+}
+
 MojoResult DataPipeConsumerDispatcher::AddAwakable(
     Awakable* awakable,
     MojoHandleSignals signals,
@@ -464,6 +481,7 @@ MojoResult DataPipeConsumerDispatcher::CloseNoLock() {
   shared_ring_buffer_ = nullptr;
 
   awakable_list_.CancelAll();
+  watchers_.NotifyClosed();
   if (!transferred_) {
     base::AutoUnlock unlock(lock_);
     node_controller_->ClosePort(control_port_);
@@ -581,7 +599,9 @@ void DataPipeConsumerDispatcher::UpdateSignalsStateNoLock() {
     new_data_available_ = true;
 
   if (peer_closed_ != was_peer_closed || has_new_data) {
-    awakable_list_.AwakeForStateChange(GetHandleSignalsStateNoLock());
+    HandleSignalsState state = GetHandleSignalsStateNoLock();
+    awakable_list_.AwakeForStateChange(state);
+    watchers_.NotifyState(state);
   }
 }