lzf.h revision 302408 
1/*
2 * Copyright (c) 2000-2008 Marc Alexander Lehmann <schmorp@schmorp.de>
3 *
4 * Redistribution and use in source and binary forms, with or without modifica-
5 * tion, are permitted provided that the following conditions are met:
6 *
7 *   1.  Redistributions of source code must retain the above copyright notice,
8 *       this list of conditions and the following disclaimer.
9 *
10 *   2.  Redistributions in binary form must reproduce the above copyright
11 *       notice, this list of conditions and the following disclaimer in the
12 *       documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
15 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
16 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO
17 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
18 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
20 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
21 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
22 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
23 * OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * the GNU General Public License ("GPL") version 2 or any later version,
27 * in which case the provisions of the GPL are applicable instead of
28 * the above. If you wish to allow the use of your version of this file
29 * only under the terms of the GPL and not to allow others to use your
30 * version of this file under the BSD license, indicate your decision
31 * by deleting the provisions above and replace them with the notice
32 * and other provisions required by the GPL. If you do not delete the
33 * provisions above, a recipient may use your version of this file under
34 * either the BSD or the GPL.
35 */
36
37#ifndef LZF_H
38#define LZF_H
39
40/***********************************************************************
41**
42**	lzf -- an extremely fast/free compression/decompression-method
43**	http://liblzf.plan9.de/
44**
45**	This algorithm is believed to be patent-free.
46**
47***********************************************************************/
48
49#define LZF_VERSION 0x0105 /* 1.5, API version */
50
51/*
52 * Compress in_len bytes stored at the memory block starting at
53 * in_data and write the result to out_data, up to a maximum length
54 * of out_len bytes.
55 *
56 * If the output buffer is not large enough or any error occurs return 0,
57 * otherwise return the number of bytes used, which might be considerably
58 * more than in_len (but less than 104% of the original size), so it
59 * makes sense to always use out_len == in_len - 1), to ensure _some_
60 * compression, and store the data uncompressed otherwise (with a flag, of
61 * course.
62 *
63 * lzf_compress might use different algorithms on different systems and
64 * even different runs, thus might result in different compressed strings
65 * depending on the phase of the moon or similar factors. However, all
66 * these strings are architecture-independent and will result in the
67 * original data when decompressed using lzf_decompress.
68 *
69 * The buffers must not be overlapping.
70 *
71 * If the option LZF_STATE_ARG is enabled, an extra argument must be
72 * supplied which is not reflected in this header file. Refer to lzfP.h
73 * and lzf_c.c.
74 *
75 */
76unsigned int
77lzf_compress (const void *const in_data,  unsigned int in_len,
78              void             *out_data, unsigned int out_len);
79
80/*
81 * Decompress data compressed with some version of the lzf_compress
82 * function and stored at location in_data and length in_len. The result
83 * will be stored at out_data up to a maximum of out_len characters.
84 *
85 * If the output buffer is not large enough to hold the decompressed
86 * data, a 0 is returned and errno is set to E2BIG. Otherwise the number
87 * of decompressed bytes (i.e. the original length of the data) is
88 * returned.
89 *
90 * If an error in the compressed data is detected, a zero is returned and
91 * errno is set to EINVAL.
92 *
93 * This function is very fast, about as fast as a copying loop.
94 */
95unsigned int
96lzf_decompress (const void *const in_data,  unsigned int in_len,
97                void             *out_data, unsigned int out_len);
98
99/*
100 * Size of hashtable is (1 << HLOG) * sizeof (char *)
101 * decompression is independent of the hash table size
102 * the difference between 15 and 14 is very small
103 * for small blocks (and 14 is usually a bit faster).
104 * For a low-memory/faster configuration, use HLOG == 13;
105 * For best compression, use 15 or 16 (or more, up to 23).
106 */
107#ifndef HLOG
108# define HLOG 16
109#endif
110
111/*
112 * Sacrifice very little compression quality in favour of compression speed.
113 * This gives almost the same compression as the default code, and is
114 * (very roughly) 15% faster. This is the preferred mode of operation.
115 */
116#ifndef VERY_FAST
117# define VERY_FAST 1
118#endif
119
120/*
121 * Sacrifice some more compression quality in favour of compression speed.
122 * (roughly 1-2% worse compression for large blocks and
123 * 9-10% for small, redundant, blocks and >>20% better speed in both cases)
124 * In short: when in need for speed, enable this for binary data,
125 * possibly disable this for text data.
126 */
127#ifndef ULTRA_FAST
128# define ULTRA_FAST 0
129#endif
130
131/*
132 * Unconditionally aligning does not cost very much, so do it if unsure
133 */
134#ifndef STRICT_ALIGN
135# define STRICT_ALIGN !(defined(__i386) || defined (__amd64))
136#endif
137
138/*
139 * You may choose to pre-set the hash table (might be faster on some
140 * modern cpus and large (>>64k) blocks, and also makes compression
141 * deterministic/repeatable when the configuration otherwise is the same).
142 */
143#ifndef INIT_HTAB
144# define INIT_HTAB 1
145#endif
146
147/*
148 * Avoid assigning values to errno variable? for some embedding purposes
149 * (linux kernel for example), this is necessary. NOTE: this breaks
150 * the documentation in lzf.h.
151 */
152#ifndef AVOID_ERRNO
153# define AVOID_ERRNO 0
154#endif
155
156/*
157 * Wether to pass the LZF_STATE variable as argument, or allocate it
158 * on the stack. For small-stack environments, define this to 1.
159 * NOTE: this breaks the prototype in lzf.h.
160 */
161#ifndef LZF_STATE_ARG
162# define LZF_STATE_ARG 0
163#endif
164
165/*
166 * Wether to add extra checks for input validity in lzf_decompress
167 * and return EINVAL if the input stream has been corrupted. This
168 * only shields against overflowing the input buffer and will not
169 * detect most corrupted streams.
170 * This check is not normally noticeable on modern hardware
171 * (<1% slowdown), but might slow down older cpus considerably.
172 */
173#ifndef CHECK_INPUT
174# define CHECK_INPUT 1
175#endif
176
177/*****************************************************************************/
178/* nothing should be changed below */
179
180typedef unsigned char u8;
181
182typedef const u8 *LZF_STATE[1 << (HLOG)];
183
184#if !STRICT_ALIGN
185/* for unaligned accesses we need a 16 bit datatype. */
186# include <limits.h>
187# if USHRT_MAX == 65535
188    typedef unsigned short u16;
189# elif UINT_MAX == 65535
190    typedef unsigned int u16;
191# else
192#  undef STRICT_ALIGN
193#  define STRICT_ALIGN 1
194# endif
195#endif
196
197#if ULTRA_FAST
198# if defined(VERY_FAST)
199#  undef VERY_FAST
200# endif
201#endif
202
203#if INIT_HTAB
204# ifdef __cplusplus
205#  include <cstring>
206# else
207#  include <string.h>
208# endif
209#endif
210
211#endif
212