source: nscp/include/utils.cpp @ c391984

/**************************************************************************
*   Copyright (C) 2004-2007 by Michael Medin <michael@medin.name>         *
*                                                                         *
*   This code is part of NSClient++ - http://trac.nakednuns.org/nscp      *
*                                                                         *
*   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 <utils.h>

static unsigned long crc32_table[256];
static bool hascrc32 = false;
void generate_crc32_table(void){
        unsigned long crc, poly;
        int i, j;
        poly=0xEDB88320L;
        for(i=0;i<256;i++){
                crc=i;
                for(j=8;j>0;j--){
                        if(crc & 1)
                                crc=(crc>>1)^poly;
                        else
                                crc>>=1;
                }
                crc32_table[i]=crc;
        }
        hascrc32 = true;
}
unsigned long calculate_crc32(const char *buffer, int buffer_size){
        if (!hascrc32)
                generate_crc32_table();
        register unsigned long crc;
        int this_char;
        int current_index;

        crc=0xFFFFFFFF;

        for(current_index=0;current_index<buffer_size;current_index++){
                this_char=(int)buffer[current_index];
                crc=((crc>>8) & 0x00FFFFFF) ^ crc32_table[(crc ^ this_char) & 0xFF];
        }

        return (crc ^ 0xFFFFFFFF);
}

unsigned long calculate_crc32(const unsigned char *buffer, int buffer_size){
        if (!hascrc32)
                generate_crc32_table();
        register unsigned long crc;
        int this_char;
        int current_index;

        crc=0xFFFFFFFF;

        for(current_index=0;current_index<buffer_size;current_index++){
                this_char=(int)buffer[current_index];
                crc=((crc>>8) & 0x00FFFFFF) ^ crc32_table[(crc ^ this_char) & 0xFF];
        }

        return (crc ^ 0xFFFFFFFF);
}