nuttx/fs/littlefs/lfs_util.c

/****************************************************************************
 * fs/littlefs/lfs_util.c
 *
 * This file is a part of NuttX:
 *
 *   Copyright (C) 2019 Gregory Nutt. All rights reserved.
 *
 * Ported by:
 *
 *   Copyright (C) 2019 Pinecone Inc. All rights reserved.
 *   Author: lihaichen <li8303@163.com>
 *
 * This port derives from ARM mbed logic which has a compatible 3-clause
 * BSD license:
 *
 *   Copyright (c) 2017, Arm Limited. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the names ARM, NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include "lfs.h"
#include "lfs_util.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/* Only compile if user does not provide custom config */

#ifndef LFS_CONFIG

/* Software CRC implementation with small lookup table */

void lfs_crc(FAR uint32_t *crc, FAR 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,
  };

  FAR const uint8_t *data = buffer;
  size_t i;

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

#endif