FLATE(2) FLATE(2)
NAME
deflateinit, deflate, deflatezlib, deflateblock,
deflatezlibblock, inflateinit, inflate, inflatezlib,
inflateblock, inflatezlibblock, flateerr, mkcrctab,
blockcrc, adler32 - deflate compression
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <flate.h>
int deflateinit(void)
int deflate(void *wr, int (*w)(void*,void*,int),
void *rr, int (*r)(void*,void*,int),
int level, int debug)
int deflatezlib(void *wr, int (*w)(void*,void*,int),
void *rr, int (*r)(void*,void*,int),
int level, int debug)
int deflateblock(uchar *dst, int dsize,
uchar *src, int ssize,
int level, int debug)
int deflatezlibblock(uchar *dst, int dsize,
uchar *src, int ssize,
int level, int debug)
int inflateinit(void)
int inflate(void *wr, int (*w)(void*, void*, int),
void *getr, int (*get)(void*))
int inflatezlib(void *wr, int (*w)(void*, void*, int),
void *getr, int (*get)(void*))
int inflateblock(uchar *dst, int dsize,
uchar *src, int ssize)
int inflatezlibblock(uchar *dst, int dsize,
uchar *src, int ssize)
char *flateerr(int error)
ulong *mkcrctab(ulong poly)
ulong blockcrc(ulong *tab, ulong crc, void *buf, int n)
ulong adler32(ulong adler, void *buf, int n)
Page 1 Plan 9 (printed 12/23/24)
FLATE(2) FLATE(2)
DESCRIPTION
These routines compress and decompress data using the
deflate compression algorithm, which is used for most gzip,
zip, and zlib files.
Deflate compresses input data retrieved by calls to r with
arguments rr, an input buffer, and a count of bytes to read.
R should return the number of bytes read; end of input is
signaled by returning zero, an input error by returning a
negative number. The compressed output is written to w with
arguments wr, the output data, and the number of bytes to
write. W should return the number of bytes written; writing
fewer than the requested number of bytes is an error. Level
indicates the amount of computation deflate should do while
compressing the data. Higher levels usually take more time
and produce smaller outputs. Valid values are 1 to 9,
inclusive; 6 is a good compromise. If debug is non-zero,
cryptic debugging information is produced on standard error.
Inflate reverses the process, converting compressed data
into uncompressed output. Input is retrieved one byte at a
time by calling get with the argument getr. End of input is
signaled by returning a negative value. The uncompressed
output is written to w, which has the same interface as for
deflate.
Deflateblock and inflateblock operate on blocks of memory
but are otherwise similar to deflate and inflate.
The zlib functions are similar, but operate on files with a
zlib header and trailer.
Deflateinit or inflateinit must be called once before any
call to the corresponding routines.
If the above routines fail, they return a negative number
indicating the problem. The possible values are FlateNoMem,
FlateInputFail, FlateOutputFail, FlateCorrupted, and
FlateInternal. Flateerr converts the number into a printable
message. FlateOk is defined to be zero, the successful
return value for deflateinit, deflate, deflatezlib,
inflateinit, inflate, and inflatezlib. The block functions
return the number of bytes produced when they succeed.
Mkcrctab allocates (using malloc(2)), initializes, and
returns a table for rapid computation of 32 bit CRC values
using the polynomial poly. Blockcrc uses tab, a table
returned by mkcrctab, to update crc for the n bytes of data
in buf, and returns the new value. Crc should initially be
zero. Blockcrc pre-conditions and post-conditions crc by
ones complementation.
Page 2 Plan 9 (printed 12/23/24)
FLATE(2) FLATE(2)
Adler32 updates the Adler 32-bit checksum of the n bytes of
data in buf. The initial value of adler (that is, its value
after seeing zero bytes) should be 1.
SOURCE
/sys/src/libflate
Page 3 Plan 9 (printed 12/23/24)