construct/include/ircd/mods.h

/*
 * Copyright (C) 2016 Charybdis Development Team
 * Copyright (C) 2016 Jason Volk <jason@zemos.net>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once
#define HAVE_IRCD_MODS_H

/// Modules system
namespace ircd::mods
{
	IRCD_EXCEPTION(ircd::error, error)
	IRCD_EXCEPTION(error, filesystem_error)
	IRCD_EXCEPTION(error, invalid_export)
	IRCD_EXCEPTION(error, expired_symbol)
	IRCD_EXCEPTION(error, undefined_symbol)

	struct mod;
	struct module;
	struct sym_ptr;
	template<class T> struct import;
	template<class T> struct import_shared;
	struct paths extern paths;

	std::string postfixed(const std::string &name);
	std::string unpostfixed(const std::string &name);

	std::vector<std::string> symbols(const std::string &fullpath, const std::string &section);
	std::vector<std::string> symbols(const std::string &fullpath);
	std::vector<std::string> sections(const std::string &fullpath);

	// Find module names where symbol resides
	bool has_symbol(const std::string &name, const std::string &symbol);
	std::vector<std::string> find_symbol(const std::string &symbol);

	// returns dir/name of first dir containing 'name' (and this will be a loadable module)
	// Unlike libltdl, the reason each individual candidate failed is presented in a vector.
	std::string search(const std::string &name, std::vector<std::string> &why);
	std::string search(const std::string &name);

	// Potential modules available to load
	std::forward_list<std::string> available();
	bool available(const std::string &name);
	bool loaded(const std::string &name);
}

// Bring struct module into main ircd::
namespace ircd
{
	using mods::module;
	using mods::import;
	using mods::import_shared;
}

struct ircd::mods::paths
:std::vector<std::string>
{
	bool added(const std::string &dir) const;

	bool del(const std::string &dir);
	bool add(const std::string &dir, std::nothrow_t);
	bool add(const std::string &dir);

	paths();
};

struct ircd::mods::module
:std::shared_ptr<mod>
{
	std::string name() const;
	std::string path() const;

	bool has(const std::string &name) const;

	template<class T = uint8_t> const T *ptr(const std::string &name) const;
	template<class T = uint8_t> T *ptr(const std::string &name);

	template<class T> const T &get(const std::string &name) const;
	template<class T> T &get(const std::string &name);

	module(std::shared_ptr<mod> ptr = {})
	:std::shared_ptr<mod>{std::move(ptr)}
	{}

	module(const std::string &name);
	~module() noexcept;
};

namespace ircd::mods
{
	template<> const uint8_t *module::ptr<const uint8_t>(const std::string &name) const;
	template<> uint8_t *module::ptr<uint8_t>(const std::string &name);
}

class ircd::mods::sym_ptr
:std::weak_ptr<mod>
{
	void *ptr;

  public:
	operator bool() const                        { return !expired();                              }
	bool operator!() const                       { return expired();                               }

	template<class T> const T *get() const;
	template<class T> const T *operator->() const;
	template<class T> const T &operator*() const;
	template<class T, class... args> auto operator()(args&&... a) const;

	template<class T> T *get();
	template<class T> T *operator->();
	template<class T> T &operator*();

	sym_ptr(const std::string &modname, const std::string &symname);
	~sym_ptr() noexcept;
};

template<class T>
struct ircd::mods::import
:sym_ptr
{
	template<class... args>
	auto operator()(args&&... a) const
	{
		return sym_ptr::operator()<T>(std::forward<args>(a)...);
	}

	const T *operator->() const                  { return sym_ptr::operator-><T>();                }
	const T &operator*() const                   { return sym_ptr::operator*<T>();                 }
	operator const T &() const                   { return sym_ptr::operator*<T>();                 }

	T *operator->()                              { return sym_ptr::operator-><T>();                }
	T &operator*()                               { return sym_ptr::operator*<T>();                 }
	operator T &()                               { return sym_ptr::operator*<T>();                 }

	using sym_ptr::sym_ptr;
};

template<class T>
struct ircd::mods::import_shared
:import<std::shared_ptr<T>>
,std::shared_ptr<T>
{
	using std::shared_ptr<T>::get;
	using std::shared_ptr<T>::operator bool;
	using std::shared_ptr<T>::operator->;
	using std::shared_ptr<T>::operator*;

	operator const T &() const                   { return std::shared_ptr<T>::operator*();         }
	operator T &()                               { return std::shared_ptr<T>::operator*();         }

	import_shared(const std::string &modname, const std::string &symname);
};

template<class T>
ircd::mods::import_shared<T>::import_shared(const std::string &modname,
                                            const std::string &symname)
:import<std::shared_ptr<T>>
{
	modname, symname
}
,std::shared_ptr<T>
{
	import<std::shared_ptr<T>>::operator*()
}{}

template<class T>
T &
ircd::mods::sym_ptr::operator*()
{
	if(unlikely(expired()))
		throw expired_symbol("The reference to a symbol in another module is no longer valid");

	return *get<T>();
}

template<class T>
T *
ircd::mods::sym_ptr::operator->()
{
	return get<T>();
}

template<class T>
T *
ircd::mods::sym_ptr::get()
{
	return reinterpret_cast<T *>(ptr);
}

template<class T,
         class... args>
auto
ircd::mods::sym_ptr::operator()(args&&... a)
const
{
	return (*get<T>())(std::forward<args>(a)...);
}

template<class T>
const T &
ircd::mods::sym_ptr::operator*()
const
{
	if(unlikely(expired()))
		throw expired_symbol("The const reference to a symbol in another module is no longer valid");

	return *get<T>();
}

template<class T>
const T *
ircd::mods::sym_ptr::operator->()
const
{
	return get<T>();
}

template<class T>
const T *
ircd::mods::sym_ptr::get()
const
{
	return reinterpret_cast<const T *>(ptr);
}

template<class T>
T &
ircd::mods::module::get(const std::string &name)
{
	return *ptr<T>(name);
}

template<class T>
const T &
ircd::mods::module::get(const std::string &name)
const
{
	return *ptr<T>(name);
}

template<class T>
T *
ircd::mods::module::ptr(const std::string &name)
{
	return reinterpret_cast<T *>(ptr<uint8_t>(name));
}

template<class T>
const T *
ircd::mods::module::ptr(const std::string &name)
const
{
	return reinterpret_cast<const T *>(ptr<const uint8_t>(name));
}