I'm working on this project where I need to parse a text file that contains a two-column table consisting of names on the left and values on the right.
Now, I need to write those to specific places in a control table, which are identified using hexadecimal addresses; in a header file that I can't edit, they have been defined as such:
#define HARRY_POTTER 0x3A
There's then a writing function that takes an address and a value and writes it into a storage place (this function is also out of my control). So, calling this
write(0x3A, 7);
Would have the same result as calling this
write(HARRY_POTTER, 7);
Because of that definition in the header file.
Now, I've got the parsing down, which basically gives me the left column, the name, as a string (so, "HARRY_POTTER", for example), and the right column, the value, as an integer.
What I'm wondering is if there's any way to use this string, "HARRY_POTTER" as the identifier in the write function; essentially converting the string into an identifier, so that I could just loop through my entire array of parsed values and it would automatically write them to the address that matches the string/ the name in the left column.
Is this possible? If yes, how?
No, it's not possible as you ask. The reason is because the string that you read from the file is only known at run-time, while preprocessing occurs at compile-time, so HARRY_POTTER must already have been replaced. In fact, no identifiers at all exist after the program has been compiled.
What you may want it to introduce a mapping from std::strings to the constants that you have defined. For example:
std::unordered_map<std::string, int> mapping = {{"HARRY_POTTER", HARRY_POTTER},
{"RON_WEASLEY", RON_WEASLEY}};
The constants will be replaced at compile-time, of course, so this is just equivalent to:
std::unordered_map<std::string, int> mapping = {{"HARRY_POTTER", 0x3A},
{"RON_WEASLEY", 0x7C}};
Then you can call write with:
write(mapping.at(key), 7);
Where key is a string with a value like "HARRY_POTTER".