path: root/src/libmdsserver/util.h

/**
 * mds — A micro-display server
 * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef MDS_LIBMDSSERVER_UTIL_H
#define MDS_LIBMDSSERVER_UTIL_H


#include <stddef.h>


/**
 * Read an environment variable, but handle it as undefined if empty
 * 
 * @param   var  The environment variable's name
 * @return       The environment variable's value, `NULL` if empty or not defined
 */
char* getenv_nonempty(const char* var);

/**
 * Re-exec the server.
 * This function only returns on failure.
 * 
 * @param  argc      The number of elements in `argv`
 * @param  argv      The command line arguments
 * @param  reexeced  Whether the server has previously been re-exec:ed
 */
void reexec_server(int argc, char** argv, int reexeced);

/**
 * Set up a signal trap.
 * This function should only be used for common mds
 * signals, and this function may choose to add
 * additional behaviour depending on the signal, such
 * as blocking other signals.
 * 
 * @param   signo     The signal to trap
 * @param   function  The function to run when the signal is caught
 * @return            Zero on success, -1 on error
 */
int xsigaction(int signo, void (*function)(int signo));

/**
 * Send a message over a socket
 * 
 * @param   socket   The file descriptor of the socket
 * @param   message  The message to send
 * @param   length   The length of the message
 * @return           The number of bytes that have been sent (even on error)
 */
size_t send_message(int socket, const char* message, size_t length);


#endif