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Comparing liblzf/lzf_c.c (file contents):
Revision 1.44 by root, Tue Jun 1 09:11:33 2010 UTC vs.
Revision 1.47 by root, Sun Feb 26 03:17:50 2012 UTC

1/* 1/*
2 * Copyright (c) 2000-2010 Marc Alexander Lehmann <schmorp@schmorp.de> 2 * Copyright (c) 2000-2010,2012 Marc Alexander Lehmann <schmorp@schmorp.de>
3 * 3 *
4 * Redistribution and use in source and binary forms, with or without modifica- 4 * Redistribution and use in source and binary forms, with or without modifica-
5 * tion, are permitted provided that the following conditions are met: 5 * tion, are permitted provided that the following conditions are met:
6 * 6 *
7 * 1. Redistributions of source code must retain the above copyright notice, 7 * 1. Redistributions of source code must retain the above copyright notice,
… …
45 * it works ;) 45 * it works ;)
46 */ 46 */
47#ifndef FRST 47#ifndef FRST
48# define FRST(p) (((p[0]) << 8) | p[1]) 48# define FRST(p) (((p[0]) << 8) | p[1])
49# define NEXT(v,p) (((v) << 8) | p[2]) 49# define NEXT(v,p) (((v) << 8) | p[2])
50# if MULTIPLICATION_IS_SLOW
50# if ULTRA_FAST 51# if ULTRA_FAST
51# define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1)) 52# define IDX(h) ((( h >> (3*8 - HLOG)) - h ) & (HSIZE - 1))
52# elif VERY_FAST 53# elif VERY_FAST
53# define IDX(h) ((( h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 54# define IDX(h) ((( h >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
55# else
56# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1))
57# endif
54# else 58# else
59/* this one was developed with sesse,
60 * and is very similar to the one in snappy.
61 * it does need a modern enough cpu with a fast multiplication.
62 */
55# define IDX(h) ((((h ^ (h << 5)) >> (3*8 - HLOG)) - h*5) & (HSIZE - 1)) 63# define IDX(h) (((h * 0x1e35a7bdU) >> (32 - HLOG - 8)) & (HSIZE - 1))
56# endif 64# endif
57#endif 65#endif
58/*
59 * IDX works because it is very similar to a multiplicative hash, e.g.
60 * ((h * 57321 >> (3*8 - HLOG)) & (HSIZE - 1))
61 * the latter is also quite fast on newer CPUs, and compresses similarly.
62 *
63 * the next one is also quite good, albeit slow ;)
64 * (int)(cos(h & 0xffffff) * 1e6)
65 */
66 66
67#if 0 67#if 0
68/* original lzv-like hash function, much worse and thus slower */ 68/* original lzv-like hash function, much worse and thus slower */
69# define FRST(p) (p[0] << 5) ^ p[1] 69# define FRST(p) (p[0] << 5) ^ p[1]
70# define NEXT(v,p) ((v) << 5) ^ p[2] 70# define NEXT(v,p) ((v) << 5) ^ p[2]
… …
112 u8 *out_end = op + out_len; 112 u8 *out_end = op + out_len;
113 const u8 *ref; 113 const u8 *ref;
114 114
115 /* off requires a type wide enough to hold a general pointer difference. 115 /* off requires a type wide enough to hold a general pointer difference.
116 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only 116 * ISO C doesn't have that (size_t might not be enough and ptrdiff_t only
117 * works for differences within a single object). We also assume that no 117 * works for differences within a single object). We also assume that
118 * no bit pattern traps. Since the only platform that is both non-POSIX 118 * no bit pattern traps. Since the only platform that is both non-POSIX
119 * and fails to support both assumptions is windows 64 bit, we make a 119 * and fails to support both assumptions is windows 64 bit, we make a
120 * special workaround for it. 120 * special workaround for it.
121 */ 121 */
122#if defined (WIN32) && defined (_M_X64) 122#if defined (_WIN32) && defined (_M_X64)
123 unsigned _int64 off; /* workaround for missing POSIX compliance */ 123 /* workaround for missing POSIX compliance */
124 #if #if __GNUC__
125 unsigned long long off;
126 #else
127 unsigned __int64 off;
128 #endif
124#else 129#else
125 unsigned long off; 130 unsigned long off;
126#endif 131#endif
127 unsigned int hval; 132 unsigned int hval;
128 int lit; 133 int lit;

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