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