Subversion Repositories planix.SVN

.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 of 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

butes 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