comm.c

/*
 * Race for the Galaxy AI
 * 
 * Copyright (C) 2009-2011 Keldon Jones
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "rftg.h"
#include "comm.h"

/*
 * Copy a string from a message.
 *
 * We advance the message pointer past the end of the string.
 */
void get_string(char *dest, char **msg)
{
	/* Copy until we reach the end of the string */
	while (1)
	{
		/* Copy a byte */
		*dest = **msg;

		/* Advance message pointer */
		(*msg)++;

		/* Check for end of string */
		if (!(*dest)) break;

		/* Advance destination pointer */
		dest++;
	}
}

/*
 * Copy an integer from a message.
 *
 * We advance the message pointer past the end of the integer.
 */
int get_integer(char **msg)
{
	int x;

	/* Copy four bytes from message */
	memcpy(&x, *msg, 4);

	/* Advance message pointer */
	(*msg) += 4;

	/* Convert integer to host form */
	return ntohl(x);
}

/*
 * Copy a string to a message.
 *
 * We advance the message pointer past the end of the string.
 */
void put_string(char *ptr, char **msg)
{
	/* Copy bytes */
	while (1)
	{
		/* Copy a byte */
		**msg = *ptr;

		/* Advance message pointer */
		(*msg)++;

		/* Check for end of string */
		if (!(*ptr)) break;

		/* Advance string pointer */
		ptr++;
	}
}

/*
 * Copy an integer to a message.
 *
 * We advance the message pointer past the end of the integer.
 */
void put_integer(int x, char **msg)
{
	/* Translate integer to network form */
	x = htonl(x);

	/* Copy 4 bytes to message */
	memcpy(*msg, &x, 4);

	/* Advance message pointer */
	(*msg) += 4;
}

/*
 * Start creating a message with the given type.
 *
 * We come back and fill in the size later.
 */
void start_msg(char **msg, int type)
{
	/* Start with message type */
	put_integer(type, msg);

	/* Skip past size */
	(*msg) += 4;
}

/*
 * Finish a message by storing the size.
 */
void finish_msg(char *start, char *end)
{
	int size;

	/* Get size */
	size = end - start;

	/* Advance to size area of message */
	start += 4;

	/* Write size */
	put_integer(size, &start);
}

/*
 * Send a formatted message.
 */
void send_msgf(int fd, int type, char *fmt, ...)
{
	char msg[1024], *ptr = msg;
	va_list ap;

	/* Start message */
	start_msg(&ptr, type);

	/* Start processing variable arguments */
	va_start(ap, fmt);

	/* Loop over format characters */
	while (*fmt)
	{
		/* Switch on format type */
		switch (*fmt++)
		{
			/* Integer */
			case 'd':

				/* Add integer to message */
				put_integer(va_arg(ap, int), &ptr);
				break;

			/* String */
			case 's':
			
				/* Add string to message */
				put_string(va_arg(ap, char *), &ptr);
				break;
		}
	}

	/* Stop processing arguments */
	va_end(ap);

	/* Finish message */
	finish_msg(msg, ptr);

	/* Send message */
	send_msg(fd, msg);
}