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// Copyright 2016 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_PLATFORM_HEAP_SELF_KEEP_ALIVE_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_SELF_KEEP_ALIVE_H_
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/persistent.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/gc_plugin.h"
namespace blink {
// SelfKeepAlive<Object> is the idiom to use for objects that have to keep
// themselves temporarily alive and cannot rely on there being some
// external reference in that interval:
//
// class Opener : public GarbageCollected<Opener> {
// public:
// ...
// void Open() {
// // Retain a self-reference while in an opened state:
// keep_alive_ = this;
// ....
// }
//
// void Close() {
// // Clear self-reference that ensured we were kept alive while opened.
// keep_alive_.Clear();
// ....
// }
//
// private:
// ...
// SelfKeepAlive<Opener> keep_alive_;
// };
//
// The responsibility to call Clear() in a timely fashion resides with the
// implementation of the object.
template <typename Self>
class SelfKeepAlive final {
DISALLOW_NEW();
public:
explicit SelfKeepAlive(
const PersistentLocation& loc = PERSISTENT_LOCATION_FROM_HERE)
: keep_alive_(loc) {}
explicit SelfKeepAlive(
Self* self,
const PersistentLocation& loc = PERSISTENT_LOCATION_FROM_HERE)
: keep_alive_(self, loc) {}
SelfKeepAlive& operator=(Self* self) {
DCHECK(!keep_alive_ || keep_alive_.Get() == self);
keep_alive_ = self;
return *this;
}
void Clear() { keep_alive_.Clear(); }
explicit operator bool() const { return keep_alive_; }
private:
GC_PLUGIN_IGNORE("Allowed to temporarily introduce non reclaimable memory.")
Persistent<Self> keep_alive_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_HEAP_SELF_KEEP_ALIVE_H_
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