Determine Array Length Before Compiling

Question

I try to setup a simple access control mechanism in Arduino and C++. The single password for access is known at compilation time and looks something like this

const unsigned int PASSWORD[] = {1, 2, 3, 4, 5};

To compare the user input with PASSWORD, I need several other arrays (not all of them with the same data type) that have the same number of elements as PASSWORD.

At the moment, the only way I can think of to achieve this is to have a second constant variable

const unsigned int PASSWORD_LENGTH = 5;

However, having the user enter a password and the same password's length in the settings seems like an unnecessary redundancy to me.

Therefore, my question is, if there is a way to inform the compiler about PASSWORD's length and to use this length as a variable in the code, without having the user counting the elements herself?

Simple `const unsigned int PASSWORD_LENGTH = sizeof(PASSWORD) / sizeof(int);` — πάντα ῥεῖ, Mar 02 '19 at 09:46
`sizeof(PASSWORD) / sizeof(*PASSWORD)` is a bit more generic. Since we're talking about arduino you could even make a macro out of that. — john, Mar 02 '19 at 09:49
would a second array `unsigned long COMP_ARRAY[sizeof(PASSWORD) / sizeof(int)];` even compile? — speendo, Mar 02 '19 at 09:50
okay, in that case I understand this question is considered stupid ;) — speendo, Mar 02 '19 at 09:52
actually it was not ment to be stupid, because it is a bit difficult for me to share this information with different classes in my code. However, I have to admit this was not part of my question — speendo, Mar 02 '19 at 09:54
It's likely you'd want a header then that has your `const unsigned password_length` in it — Tas, Mar 02 '19 at 10:18

score 0 · Answer 1 · answered Mar 02 '19 at 10:22

0

You can use std::size().

This will help : https://en.cppreference.com/w/cpp/iterator/size

answered Mar 02 '19 at 10:22

RammerChoi

99
6

May not be available with OP's compiler. – Matthieu Brucher Mar 02 '19 at 10:24

Determine Array Length Before Compiling

1 Answers1