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eb0f1450ad
This uses it for CRC table initializations when using --disable-small. It avoids mythread_once() overhead. It also means that then --disable-small --disable-threads is thread-safe if this attribute is supported.
69 lines
1.2 KiB
C
69 lines
1.2 KiB
C
///////////////////////////////////////////////////////////////////////////////
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//
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/// \file crc32_small.c
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/// \brief CRC32 calculation (size-optimized)
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//
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// Author: Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "check.h"
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uint32_t lzma_crc32_table[1][256];
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#ifdef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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__attribute__((__constructor__))
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#endif
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static void
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crc32_init(void)
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{
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static const uint32_t poly32 = UINT32_C(0xEDB88320);
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for (size_t b = 0; b < 256; ++b) {
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uint32_t r = b;
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for (size_t i = 0; i < 8; ++i) {
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if (r & 1)
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r = (r >> 1) ^ poly32;
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else
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r >>= 1;
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}
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lzma_crc32_table[0][b] = r;
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}
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return;
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}
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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extern void
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lzma_crc32_init(void)
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{
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mythread_once(crc32_init);
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return;
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}
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#endif
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extern LZMA_API(uint32_t)
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lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
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{
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#ifndef HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR
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lzma_crc32_init();
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#endif
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crc = ~crc;
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while (size != 0) {
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crc = lzma_crc32_table[0][*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
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--size;
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}
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return ~crc;
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}
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