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/*
* Copyright (C) 2013 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authored by: Jussi Pakkanen <jussi.pakkanen@canonical.com>
*/
#pragma once
#include <stdexcept>
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wold-style-cast"
#pragma GCC diagnostic ignored "-Wcast-qual"
#include <glib-object.h>
namespace lomiri
{
namespace thumbnailer
{
namespace internal
{
/**
* This class is meant for automatically managing the lifetime of C objects derived
* from gobject. Its API perfectly mirrors the API of unique_ptr except that you
* can't define your own deleter function as it is always g_object_unref.
*
* API/ABI stability is not guaranteed. If you need to pass the object across an ABI
* boundary, pass the plain gobject.
*
* This is how you would use gobj_ptr 99% of the time:
*
* gobj_ptr<GSomeType> o(g_some_type_new(...));
*
* More specifically, the object will decrement the gobject reference count
* of the object it points to when it goes out of scope. It will never increment it.
* Thus you should only assign to it when already holding a reference. gobj_ptr
* will then take ownership of that particular reference.
*
* Floating gobjects can not be put in this container as they are meant to be put
* into native gobject aware containers immediately upon construction. Trying to insert
* a floating gobject into a gobj_ptr will throw an invalid_argument exception. To
* prevent accidental memory leaks, the floating gobject is unreffed in this case.
*/
template <typename T>
class gobj_ptr final
{
private:
T* u;
void validate_float(T* t)
{
if (t != nullptr && g_object_is_floating(G_OBJECT(t)))
{
// LCOV_EXCL_START // False negative from gcovr.
throw std::invalid_argument("Tried to add a floating gobject into a gobj_ptr.");
// LCOV_EXCL_STOP
}
}
public:
typedef T element_type;
typedef T* pointer;
typedef decltype(g_object_unref) deleter_type;
constexpr gobj_ptr() noexcept : u(nullptr)
{
}
explicit gobj_ptr(T* t)
: u(t)
{
// What should we do if validate throws? Unreffing unknown objs
// is dodgy but not unreffing runs the risk of
// memory leaks. Currently unrefs as u is destroyed
// when this exception is thrown.
validate_float(t);
}
constexpr gobj_ptr(std::nullptr_t) noexcept : u(nullptr){};
gobj_ptr(gobj_ptr&& o) noexcept
{
u = o.u;
o.u = nullptr;
}
gobj_ptr(const gobj_ptr& o)
: u(nullptr)
{
*this = o;
}
gobj_ptr& operator=(const gobj_ptr& o)
{
if (o.u != nullptr)
{
g_object_ref(o.u);
}
reset(o.u);
return *this;
}
~gobj_ptr()
{
reset();
}
deleter_type& get_deleter() noexcept
{
return g_object_unref;
}
deleter_type& get_deleter() const noexcept
{
return g_object_unref;
}
void swap(gobj_ptr<T>& o) noexcept
{
T* tmp = u;
u = o.u;
o.u = tmp;
}
void reset(pointer p = pointer())
{
if (u != nullptr)
{
g_object_unref(G_OBJECT(u));
u = nullptr;
}
// Same throw dilemma as in pointer constructor.
u = p;
validate_float(p);
}
T* release() noexcept
{
T* r = u;
u = nullptr;
return r;
}
T* get() const noexcept
{
return u;
}
T& operator*() const
{
return *u;
}
T* operator->() const noexcept
{
return u;
}
explicit operator bool() const noexcept
{
return u != nullptr;
}
gobj_ptr& operator=(gobj_ptr&& o) noexcept
{
reset();
u = o.u;
o.u = nullptr;
return *this;
}
gobj_ptr& operator=(std::nullptr_t) noexcept
{
reset();
return *this;
}
bool operator==(const gobj_ptr<T>& o) const noexcept
{
return u == o.u;
}
bool operator!=(const gobj_ptr<T>& o) const noexcept
{
return u != o.u;
}
bool operator<(const gobj_ptr<T>& o) const noexcept
{
return u < o.u;
}
bool operator<=(const gobj_ptr<T>& o) const noexcept
{
return u <= o.u;
}
bool operator>(const gobj_ptr<T>& o) const noexcept
{
return u > o.u;
}
bool operator>=(const gobj_ptr<T>& o) const noexcept
{
return u >= o.u;
}
};
} // namespace internal
} // namespace thumbnailer
} // namespace lomiri
#pragma GCC diagnostic pop
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