chromium/third_party/blink/renderer/platform/bindings/parkable_string.h

// Copyright 2018 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_BINDINGS_PARKABLE_STRING_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_PARKABLE_STRING_H_

#include <memory>
#include <utility>

#include "base/check_op.h"
#include "base/dcheck_is_on.h"
#include "base/gtest_prod_util.h"
#include "base/memory/scoped_refptr.h"
#include "base/synchronization/lock.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "third_party/blink/renderer/platform/bindings/buildflags.h"
#include "third_party/blink/renderer/platform/disk_data_metadata.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
#include "third_party/blink/renderer/platform/wtf/size_assertions.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
#include "third_party/blink/renderer/platform/wtf/thread_safe_ref_counted.h"
#include "third_party/blink/renderer/platform/wtf/threading.h"

// ParkableString represents a string that may be parked in memory, that it its
// underlying memory address may change. Its content can be retrieved with the
// |ToString()| method.
// As a consequence, the inner pointer should never be cached, and only touched
// through a string returned by the |ToString()| method.
// It is safe to call `ToString()` and destroy ParkableStrings from any thread,
// although the interactions with the ParkableStringManager must always be
// performed on the main thread.
namespace blink {

class DiskDataAllocator;
class WebProcessMemoryDump;
struct BackgroundTaskParams;

// A parked string is parked by calling |Park()|, and unparked by calling
// |ToString()| on a parked string.
// |Lock()| does *not* unpark a string.
class PLATFORM_EXPORT ParkableStringImpl
    : public WTF::ThreadSafeRefCounted<ParkableStringImpl> { … };

#if !DCHECK_IS_ON()
// 3 pointers:
// - vtable (from RefCounted)
// - string_.Impl()
// - metadata_
ASSERT_SIZE(ParkableStringImpl, void* [3]);
#endif

class PLATFORM_EXPORT ParkableString final { … };

static_assert …;

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_PARKABLE_STRING_H_