littlefs/lfs_crc.c

#include "lfs_util.h"

// Software CRC implementation with small lookup table
void lfs_crc(uint32_t *restrict crc, const void *buffer, size_t size) {
    static const uint32_t rtable[16] = {
        0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
        0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
        0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
        0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
    };

    const uint8_t *data = buffer;

    for (size_t i = 0; i < size; i++) {
        *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 0)) & 0xf];
        *crc = (*crc >> 4) ^ rtable[(*crc ^ (data[i] >> 4)) & 0xf];
    }
}