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authorJosh MacDonald <josh.macdonald@gmail.com>2016-02-26 21:44:41 -0800
committerJosh MacDonald <josh.macdonald@gmail.com>2016-02-26 21:44:41 -0800
commit275903904f716ff12d56f8acdc27416d29cf27f9 (patch)
treef10a20d74922ebca7a7109dc93ad8d2be561782b /xdelta1/doc/xdelta.1
parent4b4aed71a959fe11852e45242bb6524be85d3709 (diff)
parentd594fbe514e2a381541a510fe01041e546f56a67 (diff)
Merge branch 'release3_0' into release3_1
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1.ds p \&\s-1Xdelta\s0
2.if n .ds - \%--
3.if t .ds - \(em
4.if !\n(.g \{\
5. if !\w|\*(lq| \{\
6. ds lq ``
7. if \w'\(lq' .ds lq "\(lq
8. \}
9. if !\w|\*(rq| \{\
10. ds rq ''
11. if \w'\(rq' .ds rq "\(rq
12. \}
13.\}
14.de PE
15.sp \\n()Pu
16.ne 2
17.nf
18.IP
19..
20.de EP
21.fi
22.PP
23.sp \\n()Pu
24..
25.TH Xdelta 1
26.SH NAME
27xdelta \- Invoke Xdelta
28.SH SYNOPSIS
29.B xdelta
30.I subcommand
31[
32.IR option ".\|.\|.
33] [
34.IR operand .\|.\|.
35]
36.SH DESCRIPTION
37Xdelta provides the ability to generate deltas between a pair of files
38and later apply those deltas. It operates similar to the
39.B diff
40and
41.B patch
42commands, but works on binary files and does not produce a human
43readable output.
44.PP
45
46Xdelta has three subcommands, delta, patch, and info. Delta accepts
47two file versions and produces a delta, while patch accepts the
48original file version and delta and produces the second version. The
49info command prints useful information about a delta. Each subcommand
50will be detailed seperately.
51
52.SS Gzip processing
53Attempting to compute a delta between compressed input files usually
54results in poor compression. This is because small differences
55between the original contents causes changes in the compression of
56whole blocks of data. To simplify things, Xdelta implements a special
57case for
58.IR gzip (1)
59compressed files. If any version input to the delta command is
60recognized as having gzip compression, it will be automatically
61decompressed into a temporary location prior to comparison. This
62temporary location is either the value of the
63.IR TMPDIR
64environment variable, if set, otherwise "/tmp".
65
66The Xdelta patch header contains a flag indicating that the
67reconstructed version should be recompressed after applying the
68patch. In general, this allows Xdelta to operate transparently on
69gzip compressed inputs.
70
71There is one potential problem when automatically processing gzip
72compressed files, which is that the recompressed content does not
73always match byte-for-byte with the original compressed content. The
74uncompressed content still matches, but if there is an external
75integrity check such as cryptographic signature verification, it may
76fail. To prevent this from happening, the --pristine option disables
77automatic gzip processing.
78
79.SS MD5 integrity check
80By default, Xdelta always verifies the MD5 checksum of the files it
81reconstructs. This prevents you from supplying an incorrect input
82during patch, which would result in corrupt output. Because of this
83feature, you can feel confident that patch has produced valid results.
84The --noverify option disables MD5 verification, but this is only
85recommended for performance testing.
86
87.SS Compressed patch format
88Xdelta uses a fairly simple encoding for its delta, then applies zlib
89compression to the result. You should not have to post-compress an
90Xdelta delta.
91
92.SS Delta
93The delta subcommand has the following synopsis:
94
95.B xdelta
96.I delta
97[
98.IR option ".\|.\|.
99]
100.IR fromfile
101.IR tofile
102.IR patchout
103
104Computes a delta from
105.IR fromfile
106to
107.IR tofile
108and writes it to
109.IR patchout
110
111.SS Patch
112The patch subcommand has the following synopsis:
113
114.B xdelta
115.I patch
116[
117.IR option ".\|.\|.
118]
119.IR patchin
120[
121.IR fromfile
122[
123.IR tofile
124]]
125
126Applies
127.IR patchin
128to
129.IR fromfile
130and produces a reconstructed version of
131.IR tofile.
132
133If fromfile was omitted, Xdelta attempts to use the original fromfile
134name, which is stored in the delta. The from file must be identical
135to the one used to create the delta. If its length or MD5 checksum
136differs, patch will abort with an error message.
137
138If tofile was omitted, Xdelta attempts to use the original tofile
139name, which is also stored in the delta. If the original tofile name
140already exists, a unique filename extension will be added to avoid
141destroying any existing data.
142
143.SS Info
144The info subcommand has the following synopsis:
145
146.B xdelta
147.I info
148.IR patchinfo
149
150Prints information about
151.IR patchinfo
152and the version it reconstructs, including file names, lengths, and
153MD5 checksums.
154
155.SS Options
156
157.IP -0..9
158Set the zlib compression level. Zero indicates no compression. Nine
159indicates maximum compression.
160
161.IP "-h, --help"
162Print a short help message and exit.
163
164.IP "-q, --quiet"
165Quiet. Surpresses several warning messages.
166
167.IP "-v, --version"
168Print the Xdelta version number and exit.
169
170.IP "-V, --verbose"
171Verbose. Prints a bit of extra information.
172
173.IP "-n, --noverify"
174No verify. Turns off MD5 checksum verification of the input and
175output files.
176
177.IP "-m=SIZE, --maxmem=SIZE"
178Set an upper bound on the size of an in-memory page cache. For
179example, --maxmem=32M will use a 32 megabyte page cache.
180
181.IP "-s=BLOCK_SIZE"
182Set the block size, unless it was hard coded (20% speed improvement).
183Should be a power of 2.
184
185.IP "-p, --pristine"
186Disable the automatic decompression of gzipped inputs, to prevent
187unexpected differences in the re-compressed content.
188
189.SH RETURN VALUES
190The delta command exits with status 0 to indicate that no differences
191were found, with status 1 to indicate that some differences were
192found, and with status 2 to indicate an error of some kind. The patch
193and info commands exit with status 0 on success and 2 on failure.
194
195.SH IDENTIFICATION
196Author: Joshua P. MacDonald, jmacd@cs.berkeley.edu
197.br
198.\" $Format: "Manual Page Revision: $Revision$; Release Date: $ProjectDate$."$
199Manual Page Revision: 1.6; Release Date: Sun, 28 Jan 2007 10:02:26 -0800.
200.br
201Copyright \(co 1997, 1998, 1999, 2000, 2001