crc32.cpp

/*
 crc32.cpp

 Copyright (c) 2015 Ivan Grokhotkov. All rights reserved.
 This file is part of the esp8266 core for Arduino environment.

 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.

 This library 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
 Lesser General Public License for more details.

 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "coredecls.h"

// moved from core_esp8266_eboot_command.cpp
uint32_t crc32 (const void* data, size_t length, uint32_t crc /*= 0xffffffff*/)
{
    const uint8_t* ldata = (const uint8_t*)data;
    while (length--)
    {
        uint8_t c = *ldata++;
        for (uint32_t i = 0x80; i > 0; i >>= 1)
        {
            bool bit = crc & 0x80000000;
            if (c & i)
                bit = !bit;
            crc <<= 1;
            if (bit)
                crc ^= 0x04c11db7;
        }
    }
    return crc;
}