ref: d589632207181a7960607a5938f315422386b9cb
dir: /sys/man/2/flate/
.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