Using zlib in C programming

g++ -Wall -Wextra comp.cpp -lz -o comp

#include <iostream>

#include <cstring>

#include <zlib.h>

using namespace std;

/*

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.

     This function can be used to compress a whole file at once if the

   input file is mmap'ed.

     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 compressed buffer.

     This function can be used to decompress a whole file at once if the

   input file is mmap'ed.

     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.

*/

int main()

{

    char d[] =

    "QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm";

    cout << "sizeof(d): " << sizeof(d) << endl;

    const unsigned int DESTLEN = 256;

    char dest[DESTLEN];

    if (sizeof(d) > DESTLEN) {

        cerr << "Dest size " << DESTLEN << " too small : " << sizeof(d) << endl;

        return 0;

    }

    uLongf destlen = DESTLEN;

    unsigned int compress_bound = compressBound(sizeof(d));

    cout << "Source len: " << sizeof(d) << ", size of compress bound: " << compress_bound << ", size of destlen: " <<

    DESTLEN << endl;

    if (compress_bound > DESTLEN) {

        cerr << "Dest size " << DESTLEN << " too small for compress_bound: " << compress_bound << endl;

        return 0;

    }

    int rtn = compress((Bytef*)dest, &destlen, (Bytef*)d, sizeof(d));

    if (rtn != Z_OK) {

        cerr << "Compress failed" << rtn << endl;

    } else {

        cout << "Compress suceeded: destlen: " << destlen << endl;

        //cout << "Compressed: " << dest << endl;

    }

    char dest2[DESTLEN] = {0};

    uLongf destlen2 = DESTLEN;

    rtn = uncompress((Bytef*)dest2, &destlen2, (Bytef*)dest, destlen);

    if (rtn != Z_OK) {

        cerr << "Decompress failed" << rtn << endl;

    } else {

        cout << "Decompress suceeded: destlen: " << destlen2 << endl;

        cout << "Decompressed: " << dest2 << endl;

    }

    rtn = memcmp(d, dest2, sizeof(d));

    cout << "Comparison: " << rtn << endl;

    return 0;

}