Mercurial > hg > sv-dependency-builds
comparison src/bzip2-1.0.6/bzip2.1.preformatted @ 89:8a15ff55d9af
Add bzip2, zlib, liblo, portaudio sources
author | Chris Cannam <cannam@all-day-breakfast.com> |
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date | Wed, 20 Mar 2013 13:59:52 +0000 |
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1 bzip2(1) bzip2(1) | |
2 | |
3 | |
4 | |
5 NNAAMMEE | |
6 bzip2, bunzip2 − a block‐sorting file compressor, v1.0.6 | |
7 bzcat − decompresses files to stdout | |
8 bzip2recover − recovers data from damaged bzip2 files | |
9 | |
10 | |
11 SSYYNNOOPPSSIISS | |
12 bbzziipp22 [ −−ccddffkkqqssttvvzzVVLL112233445566778899 ] [ _f_i_l_e_n_a_m_e_s _._._. ] | |
13 bbuunnzziipp22 [ −−ffkkvvssVVLL ] [ _f_i_l_e_n_a_m_e_s _._._. ] | |
14 bbzzccaatt [ −−ss ] [ _f_i_l_e_n_a_m_e_s _._._. ] | |
15 bbzziipp22rreeccoovveerr _f_i_l_e_n_a_m_e | |
16 | |
17 | |
18 DDEESSCCRRIIPPTTIIOONN | |
19 _b_z_i_p_2 compresses files using the Burrows‐Wheeler block | |
20 sorting text compression algorithm, and Huffman coding. | |
21 Compression is generally considerably better than that | |
22 achieved by more conventional LZ77/LZ78‐based compressors, | |
23 and approaches the performance of the PPM family of sta | |
24 tistical compressors. | |
25 | |
26 The command‐line options are deliberately very similar to | |
27 those of _G_N_U _g_z_i_p_, but they are not identical. | |
28 | |
29 _b_z_i_p_2 expects a list of file names to accompany the com | |
30 mand‐line flags. Each file is replaced by a compressed | |
31 version of itself, with the name "original_name.bz2". | |
32 Each compressed file has the same modification date, per | |
33 missions, and, when possible, ownership as the correspond | |
34 ing original, so that these properties can be correctly | |
35 restored at decompression time. File name handling is | |
36 naive in the sense that there is no mechanism for preserv | |
37 ing original file names, permissions, ownerships or dates | |
38 in filesystems which lack these concepts, or have serious | |
39 file name length restrictions, such as MS‐DOS. | |
40 | |
41 _b_z_i_p_2 and _b_u_n_z_i_p_2 will by default not overwrite existing | |
42 files. If you want this to happen, specify the −f flag. | |
43 | |
44 If no file names are specified, _b_z_i_p_2 compresses from | |
45 standard input to standard output. In this case, _b_z_i_p_2 | |
46 will decline to write compressed output to a terminal, as | |
47 this would be entirely incomprehensible and therefore | |
48 pointless. | |
49 | |
50 _b_u_n_z_i_p_2 (or _b_z_i_p_2 _−_d_) decompresses all specified files. | |
51 Files which were not created by _b_z_i_p_2 will be detected and | |
52 ignored, and a warning issued. _b_z_i_p_2 attempts to guess | |
53 the filename for the decompressed file from that of the | |
54 compressed file as follows: | |
55 | |
56 filename.bz2 becomes filename | |
57 filename.bz becomes filename | |
58 filename.tbz2 becomes filename.tar | |
59 filename.tbz becomes filename.tar | |
60 anyothername becomes anyothername.out | |
61 | |
62 If the file does not end in one of the recognised endings, | |
63 _._b_z_2_, _._b_z_, _._t_b_z_2 or _._t_b_z_, _b_z_i_p_2 complains that it cannot | |
64 guess the name of the original file, and uses the original | |
65 name with _._o_u_t appended. | |
66 | |
67 As with compression, supplying no filenames causes decom | |
68 pression from standard input to standard output. | |
69 | |
70 _b_u_n_z_i_p_2 will correctly decompress a file which is the con | |
71 catenation of two or more compressed files. The result is | |
72 the concatenation of the corresponding uncompressed files. | |
73 Integrity testing (−t) of concatenated compressed files is | |
74 also supported. | |
75 | |
76 You can also compress or decompress files to the standard | |
77 output by giving the −c flag. Multiple files may be com | |
78 pressed and decompressed like this. The resulting outputs | |
79 are fed sequentially to stdout. Compression of multiple | |
80 files in this manner generates a stream containing multi | |
81 ple compressed file representations. Such a stream can be | |
82 decompressed correctly only by _b_z_i_p_2 version 0.9.0 or | |
83 later. Earlier versions of _b_z_i_p_2 will stop after decom | |
84 pressing the first file in the stream. | |
85 | |
86 _b_z_c_a_t (or _b_z_i_p_2 _‐_d_c_) decompresses all specified files to | |
87 the standard output. | |
88 | |
89 _b_z_i_p_2 will read arguments from the environment variables | |
90 _B_Z_I_P_2 and _B_Z_I_P_, in that order, and will process them | |
91 before any arguments read from the command line. This | |
92 gives a convenient way to supply default arguments. | |
93 | |
94 Compression is always performed, even if the compressed | |
95 file is slightly larger than the original. Files of less | |
96 than about one hundred bytes tend to get larger, since the | |
97 compression mechanism has a constant overhead in the | |
98 region of 50 bytes. Random data (including the output of | |
99 most file compressors) is coded at about 8.05 bits per | |
100 byte, giving an expansion of around 0.5%. | |
101 | |
102 As a self‐check for your protection, _b_z_i_p_2 uses 32‐bit | |
103 CRCs to make sure that the decompressed version of a file | |
104 is identical to the original. This guards against corrup | |
105 tion of the compressed data, and against undetected bugs | |
106 in _b_z_i_p_2 (hopefully very unlikely). The chances of data | |
107 corruption going undetected is microscopic, about one | |
108 chance in four billion for each file processed. Be aware, | |
109 though, that the check occurs upon decompression, so it | |
110 can only tell you that something is wrong. It can’t help | |
111 you recover the original uncompressed data. You can use | |
112 _b_z_i_p_2_r_e_c_o_v_e_r to try to recover data from damaged files. | |
113 | |
114 Return values: 0 for a normal exit, 1 for environmental | |
115 problems (file not found, invalid flags, I/O errors, &c), | |
116 2 to indicate a corrupt compressed file, 3 for an internal | |
117 consistency error (eg, bug) which caused _b_z_i_p_2 to panic. | |
118 | |
119 | |
120 OOPPTTIIOONNSS | |
121 −−cc ‐‐‐‐ssttddoouutt | |
122 Compress or decompress to standard output. | |
123 | |
124 −−dd ‐‐‐‐ddeeccoommpprreessss | |
125 Force decompression. _b_z_i_p_2_, _b_u_n_z_i_p_2 and _b_z_c_a_t are | |
126 really the same program, and the decision about | |
127 what actions to take is done on the basis of which | |
128 name is used. This flag overrides that mechanism, | |
129 and forces _b_z_i_p_2 to decompress. | |
130 | |
131 −−zz ‐‐‐‐ccoommpprreessss | |
132 The complement to −d: forces compression, | |
133 regardless of the invocation name. | |
134 | |
135 −−tt ‐‐‐‐tteesstt | |
136 Check integrity of the specified file(s), but don’t | |
137 decompress them. This really performs a trial | |
138 decompression and throws away the result. | |
139 | |
140 −−ff ‐‐‐‐ffoorrccee | |
141 Force overwrite of output files. Normally, _b_z_i_p_2 | |
142 will not overwrite existing output files. Also | |
143 forces _b_z_i_p_2 to break hard links to files, which it | |
144 otherwise wouldn’t do. | |
145 | |
146 bzip2 normally declines to decompress files which | |
147 don’t have the correct magic header bytes. If | |
148 forced (‐f), however, it will pass such files | |
149 through unmodified. This is how GNU gzip behaves. | |
150 | |
151 −−kk ‐‐‐‐kkeeeepp | |
152 Keep (don’t delete) input files during compression | |
153 or decompression. | |
154 | |
155 −−ss ‐‐‐‐ssmmaallll | |
156 Reduce memory usage, for compression, decompression | |
157 and testing. Files are decompressed and tested | |
158 using a modified algorithm which only requires 2.5 | |
159 bytes per block byte. This means any file can be | |
160 decompressed in 2300k of memory, albeit at about | |
161 half the normal speed. | |
162 | |
163 During compression, −s selects a block size of | |
164 200k, which limits memory use to around the same | |
165 figure, at the expense of your compression ratio. | |
166 In short, if your machine is low on memory (8 | |
167 megabytes or less), use −s for everything. See | |
168 MEMORY MANAGEMENT below. | |
169 | |
170 −−qq ‐‐‐‐qquuiieett | |
171 Suppress non‐essential warning messages. Messages | |
172 pertaining to I/O errors and other critical events | |
173 will not be suppressed. | |
174 | |
175 −−vv ‐‐‐‐vveerrbboossee | |
176 Verbose mode ‐‐ show the compression ratio for each | |
177 file processed. Further −v’s increase the ver | |
178 bosity level, spewing out lots of information which | |
179 is primarily of interest for diagnostic purposes. | |
180 | |
181 −−LL ‐‐‐‐lliicceennssee ‐‐VV ‐‐‐‐vveerrssiioonn | |
182 Display the software version, license terms and | |
183 conditions. | |
184 | |
185 −−11 ((oorr −−−−ffaasstt)) ttoo −−99 ((oorr −−−−bbeesstt)) | |
186 Set the block size to 100 k, 200 k .. 900 k when | |
187 compressing. Has no effect when decompressing. | |
188 See MEMORY MANAGEMENT below. The −−fast and −−best | |
189 aliases are primarily for GNU gzip compatibility. | |
190 In particular, −−fast doesn’t make things signifi | |
191 cantly faster. And −−best merely selects the | |
192 default behaviour. | |
193 | |
194 −−‐‐ Treats all subsequent arguments as file names, even | |
195 if they start with a dash. This is so you can han | |
196 dle files with names beginning with a dash, for | |
197 example: bzip2 −‐ −myfilename. | |
198 | |
199 −−‐‐rreeppeettiittiivvee‐‐ffaasstt ‐‐‐‐rreeppeettiittiivvee‐‐bbeesstt | |
200 These flags are redundant in versions 0.9.5 and | |
201 above. They provided some coarse control over the | |
202 behaviour of the sorting algorithm in earlier ver | |
203 sions, which was sometimes useful. 0.9.5 and above | |
204 have an improved algorithm which renders these | |
205 flags irrelevant. | |
206 | |
207 | |
208 MMEEMMOORRYY MMAANNAAGGEEMMEENNTT | |
209 _b_z_i_p_2 compresses large files in blocks. The block size | |
210 affects both the compression ratio achieved, and the | |
211 amount of memory needed for compression and decompression. | |
212 The flags −1 through −9 specify the block size to be | |
213 100,000 bytes through 900,000 bytes (the default) respec | |
214 tively. At decompression time, the block size used for | |
215 compression is read from the header of the compressed | |
216 file, and _b_u_n_z_i_p_2 then allocates itself just enough memory | |
217 to decompress the file. Since block sizes are stored in | |
218 compressed files, it follows that the flags −1 to −9 are | |
219 irrelevant to and so ignored during decompression. | |
220 | |
221 Compression and decompression requirements, in bytes, can | |
222 be estimated as: | |
223 | |
224 Compression: 400k + ( 8 x block size ) | |
225 | |
226 Decompression: 100k + ( 4 x block size ), or | |
227 100k + ( 2.5 x block size ) | |
228 | |
229 Larger block sizes give rapidly diminishing marginal | |
230 returns. Most of the compression comes from the first two | |
231 or three hundred k of block size, a fact worth bearing in | |
232 mind when using _b_z_i_p_2 on small machines. It is also | |
233 important to appreciate that the decompression memory | |
234 requirement is set at compression time by the choice of | |
235 block size. | |
236 | |
237 For files compressed with the default 900k block size, | |
238 _b_u_n_z_i_p_2 will require about 3700 kbytes to decompress. To | |
239 support decompression of any file on a 4 megabyte machine, | |
240 _b_u_n_z_i_p_2 has an option to decompress using approximately | |
241 half this amount of memory, about 2300 kbytes. Decompres | |
242 sion speed is also halved, so you should use this option | |
243 only where necessary. The relevant flag is ‐s. | |
244 | |
245 In general, try and use the largest block size memory con | |
246 straints allow, since that maximises the compression | |
247 achieved. Compression and decompression speed are virtu | |
248 ally unaffected by block size. | |
249 | |
250 Another significant point applies to files which fit in a | |
251 single block ‐‐ that means most files you’d encounter | |
252 using a large block size. The amount of real memory | |
253 touched is proportional to the size of the file, since the | |
254 file is smaller than a block. For example, compressing a | |
255 file 20,000 bytes long with the flag ‐9 will cause the | |
256 compressor to allocate around 7600k of memory, but only | |
257 touch 400k + 20000 * 8 = 560 kbytes of it. Similarly, the | |
258 decompressor will allocate 3700k but only touch 100k + | |
259 20000 * 4 = 180 kbytes. | |
260 | |
261 Here is a table which summarises the maximum memory usage | |
262 for different block sizes. Also recorded is the total | |
263 compressed size for 14 files of the Calgary Text Compres | |
264 sion Corpus totalling 3,141,622 bytes. This column gives | |
265 some feel for how compression varies with block size. | |
266 These figures tend to understate the advantage of larger | |
267 block sizes for larger files, since the Corpus is domi | |
268 nated by smaller files. | |
269 | |
270 Compress Decompress Decompress Corpus | |
271 Flag usage usage ‐s usage Size | |
272 | |
273 ‐1 1200k 500k 350k 914704 | |
274 ‐2 2000k 900k 600k 877703 | |
275 ‐3 2800k 1300k 850k 860338 | |
276 ‐4 3600k 1700k 1100k 846899 | |
277 ‐5 4400k 2100k 1350k 845160 | |
278 ‐6 5200k 2500k 1600k 838626 | |
279 ‐7 6100k 2900k 1850k 834096 | |
280 ‐8 6800k 3300k 2100k 828642 | |
281 ‐9 7600k 3700k 2350k 828642 | |
282 | |
283 | |
284 RREECCOOVVEERRIINNGG DDAATTAA FFRROOMM DDAAMMAAGGEEDD FFIILLEESS | |
285 _b_z_i_p_2 compresses files in blocks, usually 900kbytes long. | |
286 Each block is handled independently. If a media or trans | |
287 mission error causes a multi‐block .bz2 file to become | |
288 damaged, it may be possible to recover data from the | |
289 undamaged blocks in the file. | |
290 | |
291 The compressed representation of each block is delimited | |
292 by a 48‐bit pattern, which makes it possible to find the | |
293 block boundaries with reasonable certainty. Each block | |
294 also carries its own 32‐bit CRC, so damaged blocks can be | |
295 distinguished from undamaged ones. | |
296 | |
297 _b_z_i_p_2_r_e_c_o_v_e_r is a simple program whose purpose is to | |
298 search for blocks in .bz2 files, and write each block out | |
299 into its own .bz2 file. You can then use _b_z_i_p_2 −t to test | |
300 the integrity of the resulting files, and decompress those | |
301 which are undamaged. | |
302 | |
303 _b_z_i_p_2_r_e_c_o_v_e_r takes a single argument, the name of the dam | |
304 aged file, and writes a number of files | |
305 "rec00001file.bz2", "rec00002file.bz2", etc, containing | |
306 the extracted blocks. The output filenames are | |
307 designed so that the use of wildcards in subsequent pro | |
308 cessing ‐‐ for example, "bzip2 ‐dc rec*file.bz2 > recov | |
309 ered_data" ‐‐ processes the files in the correct order. | |
310 | |
311 _b_z_i_p_2_r_e_c_o_v_e_r should be of most use dealing with large .bz2 | |
312 files, as these will contain many blocks. It is clearly | |
313 futile to use it on damaged single‐block files, since a | |
314 damaged block cannot be recovered. If you wish to min | |
315 imise any potential data loss through media or transmis | |
316 sion errors, you might consider compressing with a smaller | |
317 block size. | |
318 | |
319 | |
320 PPEERRFFOORRMMAANNCCEE NNOOTTEESS | |
321 The sorting phase of compression gathers together similar | |
322 strings in the file. Because of this, files containing | |
323 very long runs of repeated symbols, like "aabaabaabaab | |
324 ..." (repeated several hundred times) may compress more | |
325 slowly than normal. Versions 0.9.5 and above fare much | |
326 better than previous versions in this respect. The ratio | |
327 between worst‐case and average‐case compression time is in | |
328 the region of 10:1. For previous versions, this figure | |
329 was more like 100:1. You can use the −vvvv option to mon | |
330 itor progress in great detail, if you want. | |
331 | |
332 Decompression speed is unaffected by these phenomena. | |
333 | |
334 _b_z_i_p_2 usually allocates several megabytes of memory to | |
335 operate in, and then charges all over it in a fairly ran | |
336 dom fashion. This means that performance, both for com | |
337 pressing and decompressing, is largely determined by the | |
338 speed at which your machine can service cache misses. | |
339 Because of this, small changes to the code to reduce the | |
340 miss rate have been observed to give disproportionately | |
341 large performance improvements. I imagine _b_z_i_p_2 will per | |
342 form best on machines with very large caches. | |
343 | |
344 | |
345 CCAAVVEEAATTSS | |
346 I/O error messages are not as helpful as they could be. | |
347 _b_z_i_p_2 tries hard to detect I/O errors and exit cleanly, | |
348 but the details of what the problem is sometimes seem | |
349 rather misleading. | |
350 | |
351 This manual page pertains to version 1.0.6 of _b_z_i_p_2_. Com | |
352 pressed data created by this version is entirely forwards | |
353 and backwards compatible with the previous public | |
354 releases, versions 0.1pl2, 0.9.0, 0.9.5, 1.0.0, 1.0.1, | |
355 1.0.2 and above, but with the following exception: 0.9.0 | |
356 and above can correctly decompress multiple concatenated | |
357 compressed files. 0.1pl2 cannot do this; it will stop | |
358 after decompressing just the first file in the stream. | |
359 | |
360 _b_z_i_p_2_r_e_c_o_v_e_r versions prior to 1.0.2 used 32‐bit integers | |
361 to represent bit positions in compressed files, so they | |
362 could not handle compressed files more than 512 megabytes | |
363 long. Versions 1.0.2 and above use 64‐bit ints on some | |
364 platforms which support them (GNU supported targets, and | |
365 Windows). To establish whether or not bzip2recover was | |
366 built with such a limitation, run it without arguments. | |
367 In any event you can build yourself an unlimited version | |
368 if you can recompile it with MaybeUInt64 set to be an | |
369 unsigned 64‐bit integer. | |
370 | |
371 | |
372 | |
373 | |
374 AAUUTTHHOORR | |
375 Julian Seward, jsewardbzip.org. | |
376 | |
377 http://www.bzip.org | |
378 | |
379 The ideas embodied in _b_z_i_p_2 are due to (at least) the fol | |
380 lowing people: Michael Burrows and David Wheeler (for the | |
381 block sorting transformation), David Wheeler (again, for | |
382 the Huffman coder), Peter Fenwick (for the structured cod | |
383 ing model in the original _b_z_i_p_, and many refinements), and | |
384 Alistair Moffat, Radford Neal and Ian Witten (for the | |
385 arithmetic coder in the original _b_z_i_p_)_. I am much | |
386 indebted for their help, support and advice. See the man | |
387 ual in the source distribution for pointers to sources of | |
388 documentation. Christian von Roques encouraged me to look | |
389 for faster sorting algorithms, so as to speed up compres | |
390 sion. Bela Lubkin encouraged me to improve the worst‐case | |
391 compression performance. Donna Robinson XMLised the docu | |
392 mentation. The bz* scripts are derived from those of GNU | |
393 gzip. Many people sent patches, helped with portability | |
394 problems, lent machines, gave advice and were generally | |
395 helpful. | |
396 | |
397 | |
398 | |
399 bzip2(1) |