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https://github.com/eledio-devices/thirdparty-littlefs.git
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1476181bd1
Suggested by sn00pster, LFS_CONFIG is an opt-in user provided configuration file that will override the util implementation in lfs_util.h. This is useful for allowing system-specific overrides without needing to rely on git merges or other forms of patching for updates.
43 lines
1.3 KiB
C
43 lines
1.3 KiB
C
/*
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* lfs util functions
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*
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* Copyright (c) 2017 ARM Limited
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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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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void lfs_crc(uint32_t *restrict 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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}
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#endif
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