How to compress a buffer with zlib?

Question

There is a usage example at the zlib website: http://www.zlib.net/zlib_how.html

However in the example they are compressing a file. I would like to compress a binary data stored in a buffer in memory. I don't want to save the compressed buffer to disk either.

Basically here is my buffer:

fIplImageHeader->imageData = (char*)imageIn->getFrame();

How can I compress it with zlib?

I would appreciate some code example of how to do that.

Answer 1

zlib.h has all the functions you need: compress (or compress2) and uncompress. See the source code of zlib for an answer.

ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen));
/*
         Compresses the source buffer into the destination buffer.  sourceLen is
     the byte length of the source buffer.  Upon entry, destLen is the total size
     of the destination buffer, which must be at least the value returned by
     compressBound(sourceLen).  Upon exit, destLen is the actual size of the
     compressed buffer.

         compress returns Z_OK if success, Z_MEM_ERROR if there was not
     enough memory, Z_BUF_ERROR if there was not enough room in the output
     buffer.
*/

ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen));
/*
         Decompresses the source buffer into the destination buffer.  sourceLen is
     the byte length of the source buffer.  Upon entry, destLen is the total size
     of the destination buffer, which must be large enough to hold the entire
     uncompressed data.  (The size of the uncompressed data must have been saved
     previously by the compressor and transmitted to the decompressor by some
     mechanism outside the scope of this compression library.) Upon exit, destLen
     is the actual size of the uncompressed buffer.

         uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
     enough memory, Z_BUF_ERROR if there was not enough room in the output
     buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.  In
     the case where there is not enough room, uncompress() will fill the output
     buffer with the uncompressed data up to that point.
*/