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// Copyright 2015 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 CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_
#define CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_
#include <stdint.h>
#include <deque>
#include "base/macros.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "content/common/content_export.h"
#include "ipc/ipc_sender.h"
namespace scheduler {
class RendererScheduler;
}
namespace content {
// Utility class for throttling a stream of resource requests targetted to a
// specific IPC sender. The throttling itself is very basic:
// * When there is no high-priority work imminent to the main thread, as
// indicated by the RendererScheduler, throttling is disabled.
// * When >= N requests have been sent in a given time window, requests are
// throttled. A timer periodically flushes a portion of the queued requests
// until all such requests have been flushed.
// TODO(jdduke): Remove this class after resource requests become sufficiently
// cheap on the IO thread, crbug.com/440037.
class CONTENT_EXPORT ResourceDispatchThrottler : public IPC::Sender {
public:
// |flush_period| and |max_requests_per_flush| must be strictly positive
// in duration/value.
ResourceDispatchThrottler(IPC::Sender* proxied_sender,
scheduler::RendererScheduler* scheduler,
base::TimeDelta flush_period,
uint32_t max_requests_per_flush);
~ResourceDispatchThrottler() override;
// IPC::Sender implementation:
bool Send(IPC::Message* msg) override;
private:
friend class ResourceDispatchThrottlerForTest;
// Virtual for testing.
virtual base::TimeTicks Now() const;
virtual void ScheduleFlush();
void Flush();
void FlushAll();
bool ForwardMessage(IPC::Message* msg);
base::ThreadChecker thread_checker_;
IPC::Sender* const proxied_sender_;
scheduler::RendererScheduler* const scheduler_;
const base::TimeDelta flush_period_;
const uint32_t max_requests_per_flush_;
base::Timer flush_timer_;
base::TimeTicks last_sent_request_time_;
uint32_t sent_requests_since_last_flush_;
std::deque<IPC::Message*> throttled_messages_;
DISALLOW_COPY_AND_ASSIGN(ResourceDispatchThrottler);
};
} // namespace content
#endif // CONTENT_RENDERER_SCHEDULER_RESOURCE_DISPATCH_THROTTLER_H_
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