Question

I have been trying to figure out how installers work and how they bundle everything into one executable file and how to create my own. I have tried using a hex editor called HxD which allows you to export the current hex-dump of a file into a .c source file with an array containing the hex dump that looks like the below.

Excited, I tried to write the file using some simple C++ code:

ofstream newbin("test.exe", ios::binary);
newbin << hex << rawData;
newbin.close();

… and then tried to run it.

After some further research it turns out that my little program is only writing the MZ. header which PE files use in windows and excluding the rest of the code. The executable that is created has a hex-dump of 4D 5A 90 or in ASCII MZ.. Is this a fault in my coding? Why won’t it write the hex data? Would I need to use some lower-level writing tool or assembly? If so, are there any C/C++ libraries that allow me to write at such a level? Thanks!

Answer 1

rawData is a char* and is interpreted as a character string by the streaming operator, which is terminated by the first 0x00 byte it encounters.

For binary writing, you are best off using the

ostream& write(const char*, int);

method, leading to

newbin.write(rawData, 65536);

Assuming 65536 is the actual used size of the buffer.

Hope this helps 🙂