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47 lines
1.7 KiB
C
47 lines
1.7 KiB
C
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/* crc32.c -- compute the CRC-32 of a data stream
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* Copyright (C) 1995-2006, 2010, 2011, 2012 Mark Adler
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* Adapted by Jonas 'Sortie' Termansen for Sortix libmount in 2015.
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#include <stddef.h>
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#include <unistd.h>
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#include <mount/gpt.h>
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uint32_t gpt_crc32(const void* buffer_ptr, size_t size)
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{
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/* generate a crc for every 8-bit value */
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uint32_t poly = 0xedb88320UL;
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uint32_t crc_table[256];
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for ( unsigned int n = 0; n < 256; n++ )
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{
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uint32_t c = n;
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for ( unsigned int k = 0; k < 8; k++ )
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c = c & 1 ? poly ^ (c >> 1) : c >> 1;
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crc_table[n] = c;
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}
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/* calculate bytewise crc of input buffer */
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const unsigned char* buffer = (const unsigned char*) buffer_ptr;
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uint32_t crc = 0xffffffffUL;
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for ( size_t i = 0; i < size; i++ )
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crc = crc_table[(crc ^ buffer[i]) & 0xff] ^ (crc >> 8);
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return crc ^ 0xffffffffUL;
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}
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