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author | Guido van Rossum <guido@python.org> | 1997-04-30 18:12:27 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1997-04-30 18:12:27 (GMT) |
commit | 04bc9d6e67016d0968d86744fd4379870f5a6c6e (patch) | |
tree | 075d48538da4b2d30dd825ab572e778e27668bde /Doc/lib/libzlib.tex | |
parent | 1526219431c3db4fcdc54cc207d99459f886249d (diff) | |
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zlib by AMK
Diffstat (limited to 'Doc/lib/libzlib.tex')
-rw-r--r-- | Doc/lib/libzlib.tex | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/Doc/lib/libzlib.tex b/Doc/lib/libzlib.tex new file mode 100644 index 0000000..c0ab117 --- /dev/null +++ b/Doc/lib/libzlib.tex @@ -0,0 +1,107 @@ +% 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} + + + |