sfsnprintfappend.c

著名的入侵检测系统snort的最新版本的源码

/****************************************************************************
 *
 * Copyright (C) 2005-2007 Sourcefire, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License Version 2 as
 * published by the Free Software Foundation.  You may not use, modify or
 * distribute this program under any other version of the GNU General
 * Public License.
 *
 * 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.
 *
 ****************************************************************************/
 
/*
*
*  sfsnprintfappend.h
*
*  snprintf that appends to destination buffer
*
*
*  Author: Steven Sturges
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <string.h>
#include "util.h"

/****************************************************************************
 *
 * Function: sfsnprintfappend
 *
 * Purpose: snprintf that appends to destination buffer
 *
 *          Appends the snprintf format string and arguments to dest
 *          without going beyond dsize bounds.  Assumes dest has
 *          been properly allocated, and is of dsize in length.
 *
 * Arguments: dest      ==> pointer to string buffer to append to
 *            dsize     ==> size of buffer dest
 *            format    ==> snprintf format string
 *            ...       ==> arguments for printf
 *
 * Returns: number of characters added to the buffer
 *
 ****************************************************************************/
int sfsnprintfappend(char *dest, int dsize, const char *format, ...)
{
    int currLen, appendLen;
    va_list ap;

    if (!dest || dsize == 0)
        return -1;

    currLen = SnortStrnlen(dest, dsize);
    if (currLen == -1)
        return -1;

    va_start(ap, format);
    appendLen = vsnprintf(dest+currLen, dsize-currLen, format, ap);
    va_end(ap);
 
    dest[dsize-1]=0;/* guarantee a null tremination */
    
    return appendLen;
}