mirror of
https://gitee.com/openharmony/third_party_littlefs
synced 2024-11-23 06:50:37 +00:00
10f45ac02f
In looking at the common CRC APIs out there, this seemed the most common. At least more common than the current modified-in-place pointer API. It also seems to have a slightly better code footprint. I'm blaming pointer optimization issues. One downside is that lfs_crc can't report errors, however it was already assumed that lfs_crc can not error.
34 lines
862 B
C
34 lines
862 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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// Only compile if user does not provide custom config
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#ifndef LFS_CONFIG
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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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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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#endif
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