/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdint.h>

/* Calculate CRC32 how the STM32F4xx family does */

static unsigned int crc_table[] =
{
    0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
    0x130476DC ,0x17C56B6B ,0x1A864DB2 ,0x1E475005,
    0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
    0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD
};

static uint32_t crc32_word(uint32_t crc, uint32_t data)
{
    crc = crc ^ data;

    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];
    crc = (crc << 4) ^ crc_table[crc >> 28];

    return crc;
}

uint32_t stm32f4_crc32(uint8_t *buffer, int length)
{
    uint32_t *data = (uint32_t *)buffer;
    uint32_t word;
    uint32_t crc = ~0;
    int i;

    /* word by word crc32 */
    for (i=0; i<(length>>2); i++) {
        crc = crc32_word(crc, data[i]);
    }

    /* zero pad last word if required */
    if (length & 0x3) {
        for (i*=4, word=0; i<length; i++)
            word |= buffer[i] << ((i & 0x3) * 8);
        crc = crc32_word(crc, word);
    }

    return crc;
}