207 lines
4 KiB
Text
207 lines
4 KiB
Text
.TH FLATE 2
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.SH NAME
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deflateinit, deflate, deflatezlib, deflateblock, deflatezlibblock, inflateinit, inflate, inflatezlib, inflateblock, inflatezlibblock, flateerr, mkcrctab, blockcrc, adler32 \- deflate compression
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <flate.h>
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.PP
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.ta \w'ulongmm'u
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.PP
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.B
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int deflateinit(void)
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.PP
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.B
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int deflate(void *wr, int (*w)(void*,void*,int),
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.br
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.B
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void *rr, int (*r)(void*,void*,int),
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.br
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.B
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int level, int debug)
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.PP
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.B
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int deflatezlib(void *wr, int (*w)(void*,void*,int),
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.br
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.B
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void *rr, int (*r)(void*,void*,int),
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.br
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.B
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int level, int debug)
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.PP
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.B
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int deflateblock(uchar *dst, int dsize,
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.br
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.B
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uchar *src, int ssize,
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.br
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.B
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int level, int debug)
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.PP
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.B
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int deflatezlibblock(uchar *dst, int dsize,
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.br
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.B
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uchar *src, int ssize,
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.br
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.B
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int level, int debug)
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.PP
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.B
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int inflateinit(void)
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.PP
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.B
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int inflate(void *wr, int (*w)(void*, void*, int),
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.br
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.B
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void *getr, int (*get)(void*))
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.PP
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.B
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int inflatezlib(void *wr, int (*w)(void*, void*, int),
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.br
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.B
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void *getr, int (*get)(void*))
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.PP
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.B
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int inflateblock(uchar *dst, int dsize,
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.br
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.B
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uchar *src, int ssize)
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.PP
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.B
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int inflatezlibblock(uchar *dst, int dsize,
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.br
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.B
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uchar *src, int ssize)
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.PP
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.B
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char *flateerr(int error)
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.PP
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.B
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ulong *mkcrctab(ulong poly)
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.PP
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.B
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ulong blockcrc(ulong *tab, ulong crc, void *buf, int n)
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.PP
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.B
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ulong adler32(ulong adler, void *buf, int n)
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.SH DESCRIPTION
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These routines compress and decompress data using the deflate compression algorithm,
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which is used for most gzip, zip, and zlib files.
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.PP
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.I Deflate
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compresses input data retrieved by calls to
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.I r
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with arguments
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.IR rr ,
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an input buffer, and a count of bytes to read.
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.I R
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should return the number of bytes read;
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end of input is signaled by returning zero, an input error by
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returning a negative number.
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The compressed output is written to
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.I w
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with arguments
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.IR wr ,
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the output data, and the number of bytes to write.
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.I W
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should return the number of bytes written;
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writing fewer than the requested number of bytes is an error.
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.I Level
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indicates the amount of computation deflate should do while compressing the data.
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Higher
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.I levels
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usually take more time and produce smaller outputs.
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Valid values are 1 to 9, inclusive; 6 is a good compromise.
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If
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.I debug
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is non-zero, cryptic debugging information is produced on standard error.
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.PP
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.I Inflate
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reverses the process, converting compressed data into uncompressed output.
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Input is retrieved one byte at a time by calling
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.I get
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with the argument
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.IR getr .
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End of input is signaled by returning a negative value.
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The uncompressed output is written to
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.IR w ,
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which has the same interface as for
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.IR deflate .
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.PP
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.I
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Deflateblock
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and
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.I inflateblock
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operate on blocks of memory but are otherwise similar to
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.I deflate
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and
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.IR inflate .
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.PP
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The zlib functions are similar, but operate on files with a zlib header and trailer.
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.PP
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.I Deflateinit
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or
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.I inflateinit
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must be called once before any call to the corresponding routines.
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.PP
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If the above routines fail,
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they return a negative number indicating the problem.
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The possible values are
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.IR FlateNoMem ,
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.IR FlateInputFail ,
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.IR FlateOutputFail ,
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.IR FlateCorrupted ,
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and
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.IR FlateInternal .
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.I Flateerr
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converts the number into a printable message.
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.I FlateOk
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is defined to be zero,
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the successful return value for
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.IR deflateinit ,
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.IR deflate ,
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.IR deflatezlib ,
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.IR inflateinit ,
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.IR inflate ,
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and
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.IR inflatezlib .
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The block functions return the number of bytes produced when they succeed.
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.PP
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.I Mkcrctab
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allocates
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(using
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.IR malloc (2)),
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initializes, and returns a table for rapid computation of 32 bit CRC values using the polynomial
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.IR poly .
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.I Blockcrc
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uses
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.IR tab ,
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a table returned by
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.IR mkcrctab ,
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to update
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.I crc
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for the
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.I n
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bytes of data in
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.IR buf ,
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and returns the new value.
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.I Crc
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should initially be zero.
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.I Blockcrc
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pre-conditions and post-conditions
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.I crc
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by ones complementation.
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.PP
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.I Adler32
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updates the Adler 32-bit checksum of the
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.I n
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bytes of data in
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.IR buf.
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The initial value of
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.I adler
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(that is, its value after seeing zero bytes) should be 1.
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.SH SOURCE
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.B /sys/src/libflate
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