Fibonacci growth example

read_puzzle.c

static struct puzzle *
read_puzzles(size_t *n_puzzle, FILE *puzzlefile)
{
        struct puzzle *puzzles;
        size_t cap = 64, n_linebuf;
        char *linebuf = NULL;

        *n_puzzle = 0;
        puzzles = malloc(cap * sizeof *puzzles);
        if (puzzles == NULL) {
                perror("malloc");
                exit(EXIT_FAILURE);
        }

        while (getline(&linebuf, &n_linebuf, puzzlefile) != -1) {
                if (*n_puzzle >= cap) {
                        /* Fibonacci growth */
                        cap = cap * 13 / 8;
                        assert(cap > *n_puzzle);
                        puzzles = realloc(puzzles, cap * sizeof *puzzles);
                        if (puzzles == NULL) {
                                perror("realloc");
                                exit(EXIT_FAILURE);
                        }
                }

                if (puzzle_parse(puzzles + (*n_puzzle)++, linebuf) != 0) {
                        fprintf(stderr, "Invalid puzzle: %s", linebuf);
                        exit(EXIT_FAILURE);
                }

                assert(puzzle_valid(puzzles + *n_puzzle - 1));
        }

        if (ferror(puzzlefile)) {
                perror("getline");
                exit(EXIT_FAILURE);
        }

        free(linebuf);

        return (puzzles);
}