/*
 * \brief  POSIX thread header
 * \author Christian Prochaska
 * \author Alexander Boettcher
 * \date   2012-03-12
 *
 */

/*
 * Copyright (C) 2012-2017 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU Affero General Public License version 3.
 */

#ifndef _LIBC__INTERNAL__PTHREAD_H_
#define _LIBC__INTERNAL__PTHREAD_H_

/* Genode includes */
#include <libc/component.h>
#include <util/reconstructible.h>

/* libc includes */
#include <pthread.h>

/*
 * Used by 'pthread_self()' to find out if the current thread is an alien
 * thread.
 */
class Pthread_registry
{
	private:

		enum { MAX_NUM_PTHREADS = 128 };

		pthread_t _array[MAX_NUM_PTHREADS] = { 0 };

	public:

		void insert(pthread_t thread);

		void remove(pthread_t thread);

		bool contains(pthread_t thread);
};


Pthread_registry &pthread_registry();


extern "C" {

	struct pthread_attr
	{
		void   *stack_addr { nullptr };
		size_t  stack_size { Libc::Component::stack_size() };
	};

	/*
	 * This class is named 'struct pthread' because the 'pthread_t' type is
	 * defined as 'struct pthread*' in '_pthreadtypes.h'
	 */
	struct pthread;
}


struct Genode::Thread::Tls::Base
{
	/**
	 * Register thread-local-storage object at Genode thread
	 */
	static void tls(Genode::Thread &thread, Tls::Base &tls)
	{
		thread._tls = Tls { &tls };
	}

	struct Undefined : Exception { };

	/**
	 * Obtain thread-local-storage object for the calling thread
	 *
	 * \throw Undefined
	 */
	static Tls::Base &tls()
	{
		Thread &myself = *Thread::myself();

		if (!myself._tls.ptr)
			throw Undefined();

		return *myself._tls.ptr;
	}
};


struct pthread : Genode::Noncopyable, Genode::Thread::Tls::Base
{
	typedef void *(*start_routine_t) (void *);

	private:

		struct Thread_object : Genode::Thread
		{
			start_routine_t _start_routine;
			void           *_arg;

			void          *&_stack_addr;
			size_t         &_stack_size;

			enum { WEIGHT = Genode::Cpu_session::Weight::DEFAULT_WEIGHT };

			/* 'stack_addr_out' and 'stack_size_out' are written when the thread starts */
			Thread_object(char const *name, size_t stack_size,
			              Genode::Cpu_session *cpu,
			              Genode::Affinity::Location location,
			              start_routine_t start_routine, void *arg,
			              void *&stack_addr_out, size_t &stack_size_out)
			:
				Genode::Thread(WEIGHT, name, stack_size, Type::NORMAL, cpu, location),
				_start_routine(start_routine), _arg(arg),
				_stack_addr(stack_addr_out), _stack_size(stack_size_out)
			{ }

			void entry() override;
		};

		Genode::Constructible<Thread_object> _thread_object;

		/*
		 * Helper to construct '_thread_object' in class initializer
		 */
		template <typename... ARGS>
		Genode::Thread &_construct_thread_object(ARGS &&... args)
		{
			_thread_object.construct(args...);
			return *_thread_object;
		}

		/*
		 * Refers to '_thread_object' or an external 'Genode::Thread' object
		 */
		Genode::Thread &_thread;

		void _associate_thread_with_pthread()
		{
			Genode::Thread::Tls::Base::tls(_thread, *this);
			pthread_registry().insert(this);
		}

		bool _exiting = false;

		/*
		 * The join lock is needed because 'Libc::resume_all()' uses a
		 * 'Signal_transmitter' which holds a reference to a signal context
		 * capability, which needs to be released before the thread can be
		 * destroyed.
		 *
		 * Also, we cannot use 'Genode::Thread::join()', because it only
		 * returns when the thread entry function returns, which does not
		 * happen with 'pthread_cancel()'.
		 */
		Genode::Lock _join_lock { Genode::Lock::LOCKED };

		/* return value for 'pthread_join()' */
		void *_retval = PTHREAD_CANCELED;

		/* attributes for 'pthread_attr_get_np()' */
		void   *_stack_addr = nullptr;
		size_t  _stack_size = 0;

	public:

		/**
		 * Constructor for threads created via 'pthread_create'
		 */
		pthread(start_routine_t start_routine,
		        void *arg, size_t stack_size, char const * name,
		        Genode::Cpu_session * cpu, Genode::Affinity::Location location)
		:
			_thread(_construct_thread_object(name, stack_size, cpu, location,
			                                 start_routine, arg,
			                                 _stack_addr, _stack_size))
		{
			_associate_thread_with_pthread();
		}

		/**
		 * Constructor to create pthread object out of existing thread,
		 * i.e., the main thread
		 */
		pthread(Genode::Thread &existing_thread)
		:
			_thread(existing_thread)
		{
			/* obtain stack attributes of main thread */
			Genode::Thread::Stack_info info = Genode::Thread::mystack();
			_stack_addr = (void *)info.base;
			_stack_size = info.top - info.base;

			_associate_thread_with_pthread();
		}

		~pthread()
		{
			pthread_registry().remove(this);
		}

		void start() { _thread.start(); }

		void join(void **retval);

		/*
		 * Inform the thread calling 'pthread_join()' that this thread can be
		 * destroyed.
		 */
		void cancel();

		void exit(void *retval)
		{
			_retval = retval;
			cancel();
		}

		void   *stack_addr() const { return _stack_addr; }
		size_t  stack_size() const { return _stack_size; }
};


namespace Libc { void init_pthread_support(Env &env); }

#endif /* _LIBC__INTERNAL__PTHREAD_H_ */