I'm able to successfully read the file list in zip files but when trying to uncompress the file it returns -3. unsigned long actualLen = uncompressedSize; BYTE *pActualData = NULL; pActualData = (BYTE*)malloc(uncompressedSize); int i = uncompress(pActualData,&actualLen,FileData,compressedSize); it return -3. Interally the error is returned from inflate method.