Hi Stefan
I've posted my algorithm to use the zlib some time age, cause i didn't
find it I'm posting it again.
If youre having some problems with it, just ask...
#define SH(p) ((unsigned short int)(unsigned char)((p)[0]) | ((unsigned
short int)(unsigned char)((p)[1]) << 8))
#define LG(p) ((unsigned long)(SH(p)) | ((unsigned long)(SH((p)+2)) << 16))
#define GZPMAG 0xDA78 /* two-byte zlib
lead-in */
#define BSIZ 2000
/*maxsize of the read-buffer for compression and output-buffer for
decompression*/
#define ZBSIZ (BSIZ/4) /*maxsize
of the compression output-buffer and decompression read-buffer*/
#define CRCVAL_INITIAL 0L /*init value for the crc-generation*/
#define VN_GRUND_LEN 20
/*****a little function to read 1 Character from a file*******/
int FileGetC(FileHand file)
{
unsigned char readchar;
if (1 != FileRead(file, &readchar, 1, 1, NULL))
return -1;
return readchar;
}
/*************************** zipping ********************/
char gzhead[10] = {0x1f , 0x8b, 8 , 0,0,0,0,0,0,3 };//needed header for
the zipped file
int gzip(FileHand inf, FileHand outf)
{
z_stream gzipit;
int readgot, isav;
unsigned long crc32val, itotal, total = 0;
unsigned char ibuf[BSIZ], obuf[ZBSIZ];
/*to use the deflate function the gzipit structure has to be initialised*/
memset(&gzipit, 0, sizeof(gzipit));
FileTell(inf,(long *)&itotal, NULL);
crc32val = CRCVAL_INITIAL;
gzipit.next_out = ibuf;
gzipit.avail_out = BSIZ;
/*initialise all needed structures*/
ZLSetup;
if(deflateInit2(&gzipit, /* level */ 8, 8,/* bits */ 13, /* memlevel
*/ 6, 0) != Z_OK)return -1;
readgot = ZBSIZ;
/*read the file as long as ZBSIZ long pieces can be read*/
while (!FileEOF(inf) && readgot == ZBSIZ)
{
obuf[0]=chrNull;
if (0 >= (readgot = FileRead(inf, obuf,1 , ZBSIZ, NULL)))
break;
crc32val = crc32(crc32val, obuf, readgot);
total += readgot;
/*set the next-in next-out pointer, compress the data and write it into
the outf file*/
gzipit.next_in = obuf;
gzipit.avail_in =readgot;
while (gzipit.avail_in || readgot !=ZBSIZ)
{
isav = deflate(&gzipit, readgot == ZBSIZ ? 0 : Z_FINISH);
if(isav<0)
{
deflateEnd(&gzipit);
return -1;
}
if( gzipit.avail_out == BSIZ ) /* no bytes added */
break;
FileWrite(outf, ibuf, 1, BSIZ - gzipit.avail_out, NULL);
gzipit.next_out = ibuf;
gzipit.avail_out = BSIZ;
}
}
/*the rest of the data that is smaller as ZBSIZ has to be compressed*/
isav = deflate(&gzipit, Z_FINISH);
FileWrite(outf, ibuf, 1, BSIZ - gzipit.avail_out, NULL);
if(isav<0)
{
deflateEnd(&gzipit);
return -1;
}
/*if any error occured the function exits immediately*/
isav = deflateEnd(&gzipit);
if(isav<0)
return -1;
memcpy(ibuf,&crc32val,4);
itotal = LG(ibuf);
FileWrite(outf, &itotal, 1, 4, NULL);
memcpy(ibuf,&total,4);
itotal = LG(ibuf);
FileWrite(outf, &itotal, 1, 4, NULL);
return 0;
}
/*******************unzipping***************************/
int unzip(FileHand ifd,FileHand ofd)
{
int k;
UInt16 cardno = 0;
UInt32 got;
z_stream pgpz;
unsigned char ibuf[ZBSIZ], obuf[BSIZ];
FileRewind(ifd);
/*initialise the z_stream structure*/
memset(&pgpz, 0, sizeof(pgpz));
ZLSetup;
k = inflateInit2(&pgpz, 15);
if(k!=0)
return -1;
while (!FileEOF(ifd) )
{
/*reset the whole input and output buffer*/
if(k<0)break;
memset(ibuf, 0, ZBSIZ);
memset(obuf, 0, BSIZ - pgpz.avail_out);
got = FileRead(ifd, ibuf, 1, ZBSIZ/4, NULL);
/*show the uncompressing algorithm where to start and where to write the
data*/
pgpz.next_in = ibuf;
pgpz.avail_in = got;
while (pgpz.avail_in || FileEOF(ifd))
{
pgpz.next_out = obuf;
pgpz.avail_out = BSIZ;
/*uncompress the dataand write the output into the ofd-File*/
k = inflate(&pgpz, FileEOF(ifd) ? Z_FULL_FLUSH : 0);
FileWrite(ofd, obuf, 1, BSIZ - pgpz.avail_out, NULL);
/*if the outputbuffer wasn't big enough or the output buffer wasn
touched or the file is at an end - then continue*/
if (k == Z_BUF_ERROR && pgpz.avail_out != BSIZ && FileEOF(ifd))
continue;
/*if the inflate didn't work the break the while-cycle*/
if (k != Z_OK)
break;
}
}
if(k<0)
{
k = inflateEnd(&pgpz);
return -1;
}
/*tell the decompress algorithm that it's time has come*/
k = inflateEnd(&pgpz);
/* if the ending failed return an errorcode */
if(k<0)
{
k = inflateEnd(&pgpz);
return -1;
}
else
return 0;
}
/**********************************************************************************/
Stefan Kolb wrote:
Hello,
my application receives data via tcp/IP over gsm. bacause of the low
transmission rate i would like to uses zip compression. Where can I fing any
examples how to use zlib?
Thanks
Stefan
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email
______________________________________________________________________
--
For information on using the PalmSource Developer Forums, or to unsubscribe,
please see http://www.palmos.com/dev/support/forums/
