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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_WEBCODECS_CODEC_PRESSURE_GAUGE_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_WEBCODECS_CODEC_PRESSURE_GAUGE_H_
#include <utility>
#include "base/functional/callback.h"
#include "base/sequence_checker.h"
#include "base/synchronization/lock.h"
#include "third_party/blink/renderer/modules/modules_export.h"
#include "third_party/blink/renderer/modules/webcodecs/reclaimable_codec.h"
#include "third_party/blink/renderer/platform/wtf/hash_map.h"
namespace blink {
// Per-renderer-process singleton which keeps track of total codec pressure,
// across many ExecutionContexts (e.g different CodecPressureManagers).
class MODULES_EXPORT CodecPressureGauge {
public:
using PressureCallbackId = size_t;
// Callback to receive the global pressure exceeded flag.
using PressureThresholdChangedCallback = base::RepeatingCallback<void(bool)>;
// Return result comprised of a callback's ID and the status of the global
// pressure exceeded flag at the time of the callback's registration.
using RegistrationResult = std::pair<PressureCallbackId, bool>;
static CodecPressureGauge& GetInstance(ReclaimableCodec::CodecType);
// Disable copy and assign.
CodecPressureGauge(const CodecPressureGauge&) = delete;
CodecPressureGauge& operator=(const CodecPressureGauge&) = delete;
// Adds a new callback, which listens for changes to global pressure levels.
// Returns the callback's ID (for unregistering) and whether we are currently
// exceeding global pressure levels. Callbacks can be run from any thread, and
// should post to the right sequences accordingly.
// Can be called on any thread.
RegistrationResult RegisterPressureCallback(PressureThresholdChangedCallback);
// Removes a callback from getting pressure threshold notifications.
// Callers can use |pressure_released| to release a block of pressure, rather
// than calling Decrement() many times.
// Can be called on any thread.
void UnregisterPressureCallback(PressureCallbackId, size_t pressure_released);
// Increments/decrements global pressure. Can be called from any thread.
void Increment();
void Decrement();
void set_pressure_threshold_for_testing(size_t threshold) {
base::AutoLock locker(lock_);
pressure_threshold_ = threshold;
}
size_t global_pressure_for_testing() {
base::AutoLock locker(lock_);
return global_pressure_;
}
bool is_global_pressure_exceeded_for_testing() {
base::AutoLock locker(lock_);
return global_pressure_exceeded_;
}
private:
using PressureCallbacks =
WTF::HashMap<PressureCallbackId, PressureThresholdChangedCallback>;
// Used on platforms with a pressure limit shared by encoders and decoders.
static CodecPressureGauge& SharedInstance();
// Used on platforms with a different limit for encoders and decoders.
static CodecPressureGauge& DecoderInstance();
static CodecPressureGauge& EncoderInstance();
explicit CodecPressureGauge(size_t pressure_threshold);
void CheckForThresholdChanges_Locked();
base::Lock lock_;
bool global_pressure_exceeded_ GUARDED_BY(lock_) = false;
size_t global_pressure_ GUARDED_BY(lock_) = 0u;
size_t pressure_threshold_ GUARDED_BY(lock_);
// Start at 1, because WTF::HashMap uses 0 to denote deleted elements.
PressureCallbackId next_pressure_callback_id_ GUARDED_BY(lock_) = 1u;
PressureCallbacks pressure_callbacks_ GUARDED_BY(lock_);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_MODULES_WEBCODECS_CODEC_PRESSURE_GAUGE_H_
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