6b56b3c14e
LittleFS requires a `lfs_crc()` function, however the basic crc function provided by LittleFS gets disabled when a custom configuration header is used. To ensure identical crc behavior let Zephyr have a copy of the basic lfs_crc. This allows to ensure identical behavior when moving glue code into Zephyr repo, and allow us to change to an existing crc implementation provided natively by Zephyr at a later time. Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
32 lines
831 B
C
32 lines
831 B
C
/*
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* lfs util functions
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*
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* Copyright (c) 2017, Arm Limited. All rights reserved.
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include "lfs_util.h"
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/* Use the LFS naive CRC implementation until it has been decided which CRC to
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* use for LittleFS.
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*/
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/* Software CRC implementation with small lookup table */
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uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size)
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{
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static const uint32_t rtable[16] = {
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0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
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0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
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0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
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0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
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};
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const uint8_t *data = buffer;
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for (size_t i = 0; i < size; i++) {
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crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 0)) & 0xf];
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crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 4)) & 0xf];
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}
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return crc;
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}
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