Data went missing when converting const char * to std::string

In this example,

*just giving the const char * value as an input(ie::test one)

*converting const char * to std::string

*passed the value of std::string to compress the string

*string compressed and can able to see the value of the compressed String

*eg::compressed String::x�+I-.Q��Ko#

*Now converting the std::string of compressed data to const char *...

*when i 'm doing this step ,getting only 75% of the data.few data's went missing.

Eg:: x�+I-.Q��K

*what shall i need to do inorder to get the whole data?

*Can someone help me in this regard?

      int main ( int argc,char *argv[] )

    {

        const char *str = "test one";
        int length = 0;

        std::string compressionString(str);//converting char * to std::string
        cout << "compressionString::" << compressionString<< endl;

        while(*(str+length))
        length++; //length of char *

        cout << "Length of entered string:: " <<length << endl;

        std::string compStr = compress_string(compressionString);//Compress the string using compress_string()

        cout << "compressed String::"<<compStr << endl;

        const char* m_pcompCharptr = compStr.c_str();

        cout << "Compressed string char* length::"<< sizeof(m_pcompCharptr) <<endl;
        cout << "Compressed value which is present in char * is :: " <<m_pcompCharptr << endl;

        cout << "Compressed String length:: " << compStr.length() << endl;
       int iCompLen = compStr.length();

        cout << "iCompLen::" << iCompLen << endl;

        std::string decompressionString(m_pcompCharptr);//converting const char* to std::string

        std::string decompStr = decompress_string(decompressionString);

        cout << "decompStr::" << decompStr << endl;
        return 0;
}

Output::

compressionString::test one

Length of entered string:: 8

compressed String::x�+I-.Q��Ko#

Compressed string char* levgth::8

Compressed value which is present in char * is :: x�+I-.Q��K

Compressed String length:: 16

iCompLen::16

terminate called after throwing an instance of 'std::runtime_error' what(): Exception during zlib decompression: (-5) Aborted (core dumped)