C++ #define that gets a string

Question

I want to create a VERY basic obfuscation method, basically I just wanna xor every string so calling

printf("%s\n", OBF("Test"));

Will generate something like

printf("%s\n", unxor("\x65\x54\x42\x45"));

I xored the string with 1 in this case

I don't think there's any way to loop over a string in the preprocessor. — Barmar, Nov 02 '17 at 15:35
Might be able to pull something off with [preprocessor metaprogramming](http://www.boost.org/libs/preprocessor), but I'm not sure. — Fred Larson, Nov 02 '17 at 15:40
no idea why people saying it can't be done: https://stackoverflow.com/a/34981003/8874953 — Lucifer M, Nov 02 '17 at 15:52
so, then: Possible duplicate of [C++: How to encrypt strings at compile time?](https://stackoverflow.com/questions/4102320/c-how-to-encrypt-strings-at-compile-time) — underscore_d, Nov 02 '17 at 16:03

score 1 · Answer 1 · answered Nov 02 '17 at 15:53

Using modern C++ you can write it without any macros like this:

#include <iostream>
#include <array>
#include <utility>
#include <cstddef>

constexpr const char key_byte{'1'};

template<::std::size_t VArrayItemsCount, ::std::size_t... Is> constexpr auto
obf_impl
(
    ::std::index_sequence<Is...>
,   char const ( & sz_text )[VArrayItemsCount]
)
-> ::std::array<char, VArrayItemsCount>
{
    return(::std::array<char, VArrayItemsCount>{static_cast<char>(sz_text[Is] ^ key_byte)..., '\0'});
}

template<::std::size_t VArrayItemsCount> constexpr auto
obf
(
    char const ( & sz_text )[VArrayItemsCount]
)
-> ::std::array<char, VArrayItemsCount>
{
    return
    (
        obf_impl<VArrayItemsCount>
        (
            ::std::make_index_sequence<VArrayItemsCount - ::std::size_t{1}>()
        ,   sz_text
        )
    );
}

int main()
{
    constexpr const auto hello{obf("hello")};
    ::std::cout << hello.data() << ::std::endl;
    return 0;
}

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C++ #define that gets a string

1 Answers1