How to calculate the exact size of a piece of code?

Originally Posted by zaratustra

I need to calculate the exact number of bytes occupies Func() so I can pass this information to the writeprocessmemory.
How can i do that?

For example this way:

void __declspec(naked) BeginOfCode() {}

void __stdcall Wrapper()
{
   [...your code... ]
}

void __declspec(naked) EndOfCode() {}

void Inject()
{
   WriteProcess(
     ...
     Wrapper,
     EndOfCode - BeginOfCode,
     ...
}

Naked attribute used to strip any dummy code in output object