1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
|
% zlib compression module version A.01.02
% Alpha test release.
% Written by A.M. Kuchling (amk@magnet.com)
% Comments are welcomed.
%
% Can you think of a better name than zlib? (The module's purpose isn't
% really obvious from the name)
\section{Built-in Module \sectcode{zlib}}
\bimodindex{zlib}
For applications that require data compression, the functions in this
module allow compression and decompression, using a library based on
GNU zip. The library is available at
\code{ftp://godzilli.cs.sunysb.edu/pub/ngf/zlib-1.00.tar.gz},
and is mirrored at
\code{ftp://ftp.uu.net/graphics/png/src/zlib-1.00.tar.gz}. Version
1.00 is the most recent version as of March 18, 1996; use a later
version if one is available.
The available functions in this module are:
\renewcommand{\indexsubitem}{(in module zlib)}
\begin{funcdesc}{adler32}{string\optional{\, value}}
Computes a Adler-32 checksum of \var{string}. (An Adler-32
checksum is almost as reliable as a CRC32 but can be computed much
more quickly.) If \var{value} is present, it is used as the
starting value of the checksum; otherwise, a fixed default value is
used. This allows computing a running checksum over the
concatenation of several input strings. The algorithm is not
cryptographically strong, and should not be used for
authentication or digital signatures.
\end{funcdesc}
\begin{funcdesc}{compress}{string\optional{\, level}}
Compresses the data in \var{string}, returning a string contained
compressed data. \var{level} is an integer from 1 to 9 controlling
the level of compression; 1 is fastest and produces the least
compression, 9 is slowest and produces the most. The default value is
6, which . Raises the \code{zlib.error} exception if any error occurs.
\end{funcdesc}
\begin{funcdesc}{compressobj}{\optional{level}}
Returns a compression object, to be used for compressing data streams
that won't fit into memory at once. \var{level} is an integer from
1 to 9 controlling the level of compression; 1 is fastest and
produces the least compression, 9 is slowest and produces the most.
The default value is 6.
\end{funcdesc}
\begin{funcdesc}{crc32}{string\optional{\, value}}
Computes a CRC (Cyclic Redundancy Check) sum of \var{string}. If
\var{value} is present, it is used as the starting value of the
checksum; otherwise, a fixed default value is used. This allows
computing a running checksum over the concatenation of several
input strings. The algorithm is not cryptographically strong, and
should not be used for authentication or digital signatures.
\end{funcdesc}
\begin{funcdesc}{decompress}{string}
Decompresses the data in \var{string}, returning a string containing
the uncompressed data. Raises the \code{zlib.error} exception if any
error occurs.
\end{funcdesc}
\begin{funcdesc}{decompressobj}{\optional{wbits}}
Returns a compression object, to be used for decompressing data streams
that won't fit into memory at once. The \var{wbits} parameter controls the size of the window buffer; usually this can be left alone.
\end{funcdesc}
Compression objects support the following methods:
\begin{funcdesc}{compress}{string}
Compress \var{string}, returning a string containing compressed data
for at least part of the data in \var{string}. This data should be
concatenated to the output produced by any preceding calls to the
\code{compress()} method. Some input may be kept in internal buffers
for later processing.
\end{funcdesc}
\begin{funcdesc}{flush}{}
All pending input is processed, and an string containing the remaining
compressed output is returned. After calling \code{flush()}, the
\code{compress()} method cannot be called again; the only realistic
action is to delete the object.
\end{funcdesc}
Decompression objects support the following methods:
\begin{funcdesc}{decompress}{string}
Decompress \var{string}, returning a string containing the
uncompressed data corresponding to at least part of the data in
\var{string}. This data should be concatenated to the output produced
by any preceding calls to the
\code{decompress()} method. Some of the input data may be preserved in internal buffers
for later processing.
\end{funcdesc}
\begin{funcdesc}{flush}{}
All pending input is processed, and a string containing the remaining
uncompressed output is returned. After calling \code{flush()}, the
\code{decompress()} method cannot be called again; the only realistic
action is to delete the object.
\end{funcdesc}
|
