#pragma once

#include <stdint.h>


struct prot_msg {
	uint8_t *data;  // malloc'd buffer, should be free'd by recipient
	size_t length;  // length of data
};


// The interface exposed here is NOT thread-safe. Having multiple
// threads in in the same process working with prot is unsafe, since
// internal communication assumes one calling thread.


// This is a channel, a "connection", to another party.
struct prot;

// Returns a file descriptor that becomes readable in select(2) if
// there may be a new event on the channel. Do not actually read data
// from this file descriptor.
int prot_get_select_fd(struct prot *ch);

// Terminates the connection, blocks until acknowledged. Then channel
// is closed and freed.
void prot_terminate(struct prot *ch);


// Create channel on which the server can accept new connections using
// prot_accept(). Only one accept channel can be made in one process.
struct prot* prot_create_accept_channel();

// Returns a new connection with a client if such an establishment
// request is ready; an acknowledgement is replied to the request. If
// no new connection is ready at the moment, the function returns
// NULL. (This is a non-blocking function.)
struct prot* prot_accept(struct prot *ach);


// Creates a client connection to a server with the specified address.
// Blocks until the establishment request is acknowledged.
struct prot* prot_connect(uint32_t server_addr);


// Receives a waiting message; returns {.data=NULL} on error, in which
// case errno is set: EAGAIN = no message ready; ECONNRESET = peer
// closed connection; other values: internal errors.
// Channel should not be an accept channel. This is a non-blocking
// function.
struct prot_msg prot_recv(struct prot *ch);

// Sends the given data on the given channel. Channel should not be an
// accept channel. Returns 0 on success and -1 on error, in which case
// errno is set: ECONNRESET = peer closed connection; other values:
// internal errors.
int prot_send(struct prot *ch, const void *data, size_t length);