1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       crc32_small.c
4/// \brief      CRC32 calculation (size-optimized)
5//
6//  Author:     Lasse Collin
7//
8//  This file has been put into the public domain.
9//  You can do whatever you want with this file.
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#include "check.h"
14
15
16uint32_t lzma_crc32_table[1][256];
17
18
19static void
20crc32_init(void)
21{
22	static const uint32_t poly32 = UINT32_C(0xEDB88320);
23
24	for (size_t b = 0; b < 256; ++b) {
25		uint32_t r = b;
26		for (size_t i = 0; i < 8; ++i) {
27			if (r & 1)
28				r = (r >> 1) ^ poly32;
29			else
30				r >>= 1;
31		}
32
33		lzma_crc32_table[0][b] = r;
34	}
35
36	return;
37}
38
39
40extern void
41lzma_crc32_init(void)
42{
43	mythread_once(crc32_init);
44	return;
45}
46
47
48extern LZMA_API(uint32_t)
49lzma_crc32(const uint8_t *buf, size_t size, uint32_t crc)
50{
51	lzma_crc32_init();
52
53	crc = ~crc;
54
55	while (size != 0) {
56		crc = lzma_crc32_table[0][*buf++ ^ (crc & 0xFF)] ^ (crc >> 8);
57		--size;
58	}
59
60	return ~crc;
61}
62