pH/sommelier/weak-resource-ptr.h

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// Copyright 2022 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef VM_TOOLS_SOMMELIER_WEAK_RESOURCE_PTR_H_
#define VM_TOOLS_SOMMELIER_WEAK_RESOURCE_PTR_H_
#include "sommelier.h" // NOLINT(build/include_directory)
#include <algorithm>
#include <functional>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
// WeakResourcePtr is a weak pointer for a proxy object (sl_host_foo). It can
// be useful for objects with events like enter/leave, to keep track of an
// object provided in the enter event and ensure that it is not used if the
// client destroys it.
template <typename SlHostType>
class WeakResourcePtr {
public:
WeakResourcePtr() {
wl_list_init(&destroy_listener_.link);
destroy_listener_.notify = ResourceDestroyed;
}
~WeakResourcePtr() { wl_list_remove(&destroy_listener_.link); }
WeakResourcePtr& operator=(SlHostType* host) {
if (host == host_)
return *this;
Reset();
if (host) {
host_ = host;
wl_resource_add_destroy_listener(host_->resource, &destroy_listener_);
}
return *this;
}
operator bool() const { return host_; }
SlHostType* operator->() const { return host_; }
SlHostType* get() const { return host_; }
void Reset() {
host_ = nullptr;
// Remove the listener
wl_list_remove(&destroy_listener_.link);
wl_list_init(&destroy_listener_.link);
}
private:
SlHostType* host_ = nullptr;
// This is always in an initialized state
wl_listener destroy_listener_;
static void ResourceDestroyed(wl_listener* listener, void* data) {
WeakResourcePtr* ptr;
ptr = wl_container_of(listener, ptr, destroy_listener_);
ptr->Reset();
}
};
#endif // VM_TOOLS_SOMMELIER_WEAK_RESOURCE_PTR_H_