FLATE(2)FLATE(2)NAME
deflateinit, deflate, deflatezlib, deflateblock, deflatezlibblock,
inflateinit, inflate, inflatezlib, inflateblock, inflatezlibblock, fla‐
teerr, 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)
DESCRIPTION
These routines compress and decompress data using the deflate compres‐
sion 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 uncom‐
pressed output. Input is retrieved one byte at a time by calling get
with the argument getr. End of input of signaled by returning a nega‐
tive 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 oth‐
erwise 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, Fla‐
teOutputFail, 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 ini‐
tially be zero. Blockcrc pre-conditions and post-conditions crc by
ones complementation.
Adler32 updates the Adler 32-bit checksum of the n butes of data in
buf. The initial value of adler (that is, its value after seeing zero
bytes) should be 1.
SOURCE
/sys/src/libflate
FLATE(2)
