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// Copyright 2024 Marc A. Lehmann |
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// Copyright 2008,2009,2010 Massachusetts Institute of Technology. |
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// All rights reserved. Use of this source code is governed by a |
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// BSD-style license that can be found in the LICENSE file. |
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#include "crc32ctables.c" |
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// Implementations adapted from Intel's Slicing By 8 Sourceforge Project |
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// http://sourceforge.net/projects/slicing-by-8/ |
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/*++ |
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* |
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* Copyright (c) 2004-2006 Intel Corporation - All Rights Reserved |
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* |
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* This software program is licensed subject to the BSD License, |
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* available at http://www.opensource.org/licenses/bsd-license.html |
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* |
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* Abstract: The main routine |
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* |
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--*/ |
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static uint32_t crc32cSlicingBy8(uint32_t crc, const void* data, size_t length) { |
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size_t li; |
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const char* p_buf = (const char*) data; |
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// Handle leading misaligned bytes |
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size_t initial_bytes = (sizeof(int32_t) - (intptr_t)p_buf) & (sizeof(int32_t) - 1); |
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if (length < initial_bytes) initial_bytes = length; |
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for (li = 0; li < initial_bytes; li++) { |
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crc = crc_tableil8_o32[(crc ^ *p_buf++) & 0x000000FF] ^ (crc >> 8); |
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} |
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length -= initial_bytes; |
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size_t running_length = length & ~(sizeof(uint64_t) - 1); |
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size_t end_bytes = length - running_length; |
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for (li = 0; li < running_length/8; li++) { |
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crc ^= *(uint32_t*) p_buf; |
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p_buf += 4; |
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uint32_t term1 = crc_tableil8_o88[crc & 0x000000FF] ^ |
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crc_tableil8_o80[(crc >> 8) & 0x000000FF]; |
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uint32_t term2 = crc >> 16; |
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crc = term1 ^ |
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crc_tableil8_o72[term2 & 0x000000FF] ^ |
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crc_tableil8_o64[(term2 >> 8) & 0x000000FF]; |
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term1 = crc_tableil8_o56[(*(uint32_t *)p_buf) & 0x000000FF] ^ |
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crc_tableil8_o48[((*(uint32_t *)p_buf) >> 8) & 0x000000FF]; |
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term2 = (*(uint32_t *)p_buf) >> 16; |
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crc = crc ^ term1 ^ |
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crc_tableil8_o40[term2 & 0x000000FF] ^ |
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crc_tableil8_o32[(term2 >> 8) & 0x000000FF]; |
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p_buf += 4; |
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} |
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for (li=0; li < end_bytes; li++) { |
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crc = crc_tableil8_o32[(crc ^ *p_buf++) & 0x000000FF] ^ (crc >> 8); |
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} |
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return crc; |
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} |
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