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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "base/object_watcher.h"
#include "base/message_loop.h"
#include "base/logging.h"
namespace base {
//-----------------------------------------------------------------------------
struct ObjectWatcher::Watch : public Task {
ObjectWatcher* watcher; // The associated ObjectWatcher instance
HANDLE object; // The object being watched
HANDLE wait_object; // Returned by RegisterWaitForSingleObject
MessageLoop* origin_loop; // Used to get back to the origin thread
scoped_ptr<Task> task; // Task to notify when signaled
bool did_signal; // DoneWaiting was called
virtual void Run() {
// The watcher may have already been torn down, in which case we need to
// just get out of dodge.
if (!watcher)
return;
// Put this on the stack since CancelWatch deletes task. It is a good
// to call CancelWatch before running the task because we want to allow
// the consumer to call AddWatch again inside Run.
Task* task_to_run = task.release();
watcher->CancelWatch(object);
task_to_run->ResetBirthTime();
task_to_run->Run();
delete task_to_run;
}
};
//-----------------------------------------------------------------------------
ObjectWatcher::ObjectWatcher() {
}
ObjectWatcher::~ObjectWatcher() {
// Cancel any watches that may still exist.
while (!watches_.empty())
CancelWatch(watches_.begin()->first);
}
bool ObjectWatcher::AddWatch(const tracked_objects::Location& from_here,
HANDLE object, Task* task) {
task->SetBirthPlace(from_here);
linked_ptr<Watch>& watch = watches_[object];
CHECK(!watch.get()) << "Already watched!";
watch.reset(new Watch());
watch->watcher = this;
watch->object = object;
watch->origin_loop = MessageLoop::current();
watch->task.reset(task);
watch->did_signal = false;
// Since our job is to just notice when an object is signaled and report the
// result back to this thread, we can just run on a Windows wait thread.
DWORD wait_flags = WT_EXECUTEINWAITTHREAD | WT_EXECUTEONLYONCE;
if (!RegisterWaitForSingleObject(&watch->wait_object, object, DoneWaiting,
watch.get(), INFINITE, wait_flags)) {
NOTREACHED() << "RegisterWaitForSingleObject failed: " << GetLastError();
watches_.erase(object);
return false;
}
return true;
}
bool ObjectWatcher::CancelWatch(HANDLE object) {
WatchMap::iterator i = watches_.find(object);
if (i == watches_.end())
return false;
Watch* watch = i->second.get();
// If DoneWaiting is in progress, we wait for it to finish. We know whether
// DoneWaiting happened or not by inspecting the did_signal flag.
if (!UnregisterWaitEx(watch->wait_object, INVALID_HANDLE_VALUE)) {
NOTREACHED() << "UnregisterWaitEx failed: " << GetLastError();
return false;
}
// If DoneWaiting was called, then the watch would have been posted as a
// task, and will therefore be deleted by the MessageLoop. Otherwise, we
// need to take care to delete it here.
if (watch->did_signal)
i->second.release();
// If the watch has been posted, then we need to make sure it knows not to do
// anything once it is run.
watch->watcher = NULL;
// Delete the task object now so that everything, from the perspective of the
// consumer, is cleaned up once we return from CancelWatch.
watch->task.reset();
watches_.erase(i);
return true;
}
// static
void CALLBACK ObjectWatcher::DoneWaiting(void* param, BOOLEAN timed_out) {
DCHECK(!timed_out);
Watch* watch = static_cast<Watch*>(param);
// Record that we ran this function.
watch->did_signal = true;
watch->origin_loop->PostTask(FROM_HERE, watch);
}
} // namespace base
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