C code

[indrajit_muk]

Adler-32 here is a code in zlib manual

uLong adler;    //  adler32 value of the uncompressed data 

   uLong adler32 (uLong adler, const Bytef *buf, uInt len); 
Update a running Adler-32 checksum with the bytes buf[0..len-1] and return the updated checksum. If buf is NULL, this function returns the required initial value for the checksum. 
An Adler-32 checksum is almost as reliable as a CRC32 but can be computed much faster. Usage example: 


     uLong adler = adler32(0L, Z_NULL, 0);

     while (read_buffer(buffer, length) != EOF) {
       adler = adler32(adler, buffer, length);
     }
     if (adler != original_adler) error();

how adler32 works and help me to understand the code

[matsp]

Well, without seeing the actual code for "adler32", I have no idea how it works.;

Wikipedia has this article, which may help:
http://en.wikipedia.org/wiki/Adler-32

If you have specific questions, please ask those, not "how does this work", as it would take quite a bit of our time to answer something that you possibly already know, and completely miss the actual point you are asking for.

Also, when you have code-tags, try to either break the lines yourself, or put comments regarding the code OUTSIDE the code-tags, as there is no automatic line-breaks inside code-tags, and it makes the text very hard to read.

--
Mats

[Salem]

Basically a continuation of this - http://cboard.cprogramming.com/showthread.php?t=109402
If all you're going to do is go through the zlib code base, and post snippets of it with "what does this do", then you're in for a surprise.

Start by visiting the home page, read all the documentation, and read up on compression theory.
Then spend a few months learning C, to the point you can reasonably read most code.