//
// Copyright 2016 Garrett D'Amore <garrett@damore.org>
//
// This software is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

#ifndef CORE_PROTOCOL_H
#define CORE_PROTOCOL_H

// Protocol implementation details.  Protocols must implement the
// interfaces in this file.  Note that implementing new protocols is
// not necessarily intended to be a trivial task.  The protocol developer
// must understand the nature of nng, as they are responsible for handling
// most of the logic.  The protocol generally does most of the work for
// locking, and calls into the transport's pipe functions to do actual
// work, and the pipe functions generally assume no locking is needed.
// As a consequence, most of the concurrency in nng exists in the protocol
// implementations.
struct nni_protocol {
	uint16_t	proto_self;             // our 16-bit protocol ID
	uint16_t	proto_peer;             // who we peer with (ID)
	const char *	proto_name;             // string version of our name
	size_t		proto_pipe_size;        // pipe private data size

	//Create protocol instance, which will be stored on the socket.
	int		(*proto_create)(void **, nni_sock *);

	// Destroy the protocol instance.
	void		(*proto_destroy)(void *);

	// Add and remove pipes.  These are called as connections are
	// created or destroyed.
	int		(*proto_add_pipe)(void *, nni_pipe *, void *);
	void		(*proto_rem_pipe)(void *, void *);

	// Thread functions for processing send & receive sides of
	// protocol pipes.  Send may be NULL, but recv should should not.
	// (Recv needs to detect a closed pipe, if nothing else.)
	void		(*proto_pipe_send)(void *);
	void		(*proto_pipe_recv)(void *);

	// Option manipulation.  These may be NULL.
	int		(*proto_setopt)(void *, int, const void *, size_t);
	int		(*proto_getopt)(void *, int, void *, size_t *);

	// Receive filter.  This may be NULL, but if it isn't, then
	// messages coming into the system are routed here just before being
	// delivered to the application.  To drop the message, the prtocol
	// should return NULL, otherwise the message (possibly modified).
	nni_msg *	(*proto_recv_filter)(void *, nni_msg *);

	// Send filter.  This may be NULL, but if it isn't, then messages
	// here are filtered just after they come from the application.
	nni_msg *	(*proto_send_filter)(void *, nni_msg *);
};

// These functions are not used by protocols, but rather by the socket
// core implementation. The lookups can be used by transports as well.
extern nni_protocol *nni_protocol_find(uint16_t);
extern const char *nni_protocol_name(uint16_t);
extern uint16_t nni_protocol_number(const char *);

#endif // CORE_PROTOCOL_H