ZLIB for Visual Basic

Download ZLIB for Visual Basic (26kB 24-8-97)

ZLIB

    ZLIB has been ported to an .OCX by Mark Nelson. If you don't want the overhead of an .ocx, you can use this zlibvb.bas file (module) to give you access to the basic routines. In order to use it, you're going to need one of the ZLIB.DLL files from the ZLIB page; I've included one of them in the .zip file. Here is the API.
 

Name	Returns	Params	Desc
compress	zlib error code	dest pointer to empty buffer for compressed data dest_len pre-compression size of the dest buffer src pointer to the buffer containing the raw data src_len size of the source data	compresses raw data  on return, dest_len  contains the size of the data in  the dest buffer  make sure you allow enough room in the destination buffer; the recommended size is (source_len)*1001/1000+12  don't forget to truncate the dest buffer down to the size returned to you in dest_len
uncompress	zlib error code	dest pointer to empty buffer for uncompressed data dest_len pointer to the pre-uncompression size of the dest buffer src pointer to the buffer containing the compressed data src_len size of the source data	uncompresses the data back to its original form  on return, dest_len  contains the size of the data in the dest buffer  you'll have to know how big the reconstruction buffer is going to need to be before you make this call
gzopen	zlib file handle	path file name mode either "rb" or "wb"	open the named file for compression read or write  if you read from a non-zlib-compressed file, the reads will just pass the data right through
gzread	number of uncompressed bytes actually read  0 for eof  -1 on error	file the handle from the gzopen call buf pointer to a buffer len size of buf
gzwrite	the number of uncompressed bytes actually written  0 on error	file the handle from the gzopen call buf pointer to a buffer len size of buf
gzflush	zlib error number	file the handle from the gzopen call mode flush mode	use a flush mode of 4 if you want to flush at the end of the file; gzclose() does the same thing  use a flush mode of 3 to force a flush and "segment" a file; segments can be decompressed individually/independently
gclose	zlib error number	file the handle from the gzopen call
addler32	running adler32 number	adler the running adler number buf pointer to a buffer len size of buf	calculates a running Adler32 checksum  call with buf set to 0 to start the checksum
crc32	running crc32	crc the running adler number buf pointer to a buffer len size of buf	calculates a running crc32 checksum  includes one's complement code  call with buf set to 0 to start the checksum

 
The .zip file includes a .BAS file which you can include in your VB project. This will give you access to the above API. There are three versions of the API included in the .BAS file:

1. If you want to work with strings, you can use Basic strings as your buffers
2. If you wish, you can use Basic byte arrays as your buffers
3. If you have a problem with the generic names "compress" and "uncompress" and "crc32", you can expose a different naming system, like ZlibCompress, ZlibUncompress and ZlibCrc32

The .zip file contains Basic test code, which serves as an illustration.