blob: 32c7a26a2c572d9d334dc7e4422b4a599847f05b [file] [log] [blame]
// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <lib/async/cpp/task.h>
#include <lib/async/default.h>
#include <lib/async/dispatcher.h>
#include <lib/fit/defer.h>
#include <lib/fit/function.h>
#include <zircon/assert.h>
namespace camera {
// The SharedToken class associates an owned object with a thread-safe copyable deferred callback.
// This can be used to tie an object to its associated release or cleanup methods. When all copies
// of an instance are destroyed, the specified callback is invoked.
template <typename T>
class SharedToken {
// Creates a new SharedToken. Upon destruction of the last copy of an instance, the callback is
// executed immediately.
explicit SharedToken(T object, fit::closure callback)
: object_{new T(std::forward<T>(object)), [callback = std::move(callback)](auto ptr) {
}} {}
// Creates a new SharedToken. Upon destruction of the last copy of an instance, the callback is
// posted as a task on the specified dispatcher. If dispatcher is null, the default dispatcher for
// the caller's thread is used.
explicit SharedToken(T object, fit::closure callback, async_dispatcher_t* dispatcher)
: object_{new T(std::forward<T>(object)),
[callback = std::move(callback),
dispatcher =
dispatcher ? dispatcher : async_get_default_dispatcher()](auto ptr) mutable {
async::PostTask(dispatcher, [callback = std::move(callback),
ptr = std::unique_ptr<T>(ptr)]() mutable {
ptr = nullptr;
}} {
ZX_ASSERT_MSG(dispatcher || async_get_default_dispatcher(),
"default dispatcher for thread is not set");
// These methods return a reference/pointer to the shared owned object, which remains valid for
// the lifetime of the linked token. This method is itself thread-safe, however the underlying
// object that it returns may not be.
T& operator*() const { return *object_; }
T* operator->() const { return object_.get(); }
std::shared_ptr<T> object_;
} // namespace camera