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cstringpointersdynamic-allocation

Appending individual characters from string onto a char pointer

I'm writing a parser in C, and I've got some code that looks like this:

char *consume_while(parser *self, int(*test)(char)) {
    char *result;
    while (eof(self) && (*test)(next_char(self))) {
         // append the return value from the function consumed_char(self)
         // onto the "result" string defined above.
    }
    return result;
}

But I'm kinda new to the whole string manipulation aspect of C, so how would I append the character returned from the function consumed_char(self) to the result char pointer? I've seen people using the strcat function, but that wont work as it takes two constant char pointers, but I'm dealing with a char* and a char. In java it would be something like this:

result += consumed_char(self);

What's the equivalent in C? Thanks :)

Solution

  • In C, strings do not exist as a type, they are just char arrays with a null-terminating character. This means, assuming your buffers are big enough and filled with zeroes, it can be as simple as:

    result[(strlen(result)] = consumed_char(self);

    if not, your best bet is to use strcat and change your consumed_self function to return a char *.

    That being said, writing a parser without basic understanding of C-style strings, is, to say the least, quite ambitious.