Maze Parsing

16x16 maze

 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
|    _ _   _ _  |  _   _ _ _ _  |
| |_|_  |_|_   _|  _|_ _   _|   |
|   |_   _|_  | |_| |_   _ _| |_|
|_| |_   _ _|_ _       _| |_   _|
| | |_   _    | |_|_|_  |  _|_  |
|    _| | |_|_     _| |_ _  |   |
| |   |    _| |_| |_     _ _| | |
| |_| |_|_ _    | |_ _|_ _|_  | |
|_|  _|  _ _ _| | | |  _ _  | |_|
|_   _|_ _   _|_|_|_  |_ _ _  | |
|   | |  _| |   |_   _| | |  _| |
| |_|  _ _ _     _ _|_    | | | |
| | |_  |  _|  _| |_    |_|_ _  |
| |_ _   _| |_| | |_  |_ _ _| | |
|  _|        _   _ _  | |  _ _  |
|_ _ _|_ _ _|_ _ _|_ _ _ _ _ _|_|

gistfile1.c

static bool space(char cur) { return cur == ' ' || cur == '\t'; }
static bool underscore(char cur) { return cur == '_'; }
static bool newline(char cur) { return cur == '\n'; }
static bool pipe_char(char cur) { return cur == '|'; }
static bool underscore_or_space(char cur) {
    return underscore(cur) || space(cur);
}
static bool pipe_char_or_space(char cur) { return pipe_char(cur) || space(cur); }

static void accept(bool (*accept_f)(char), char* name, char* dest, char cur) {
    assert(cur != EOF && "Error: End of file was reached while still parsing.");
    if (accept_f(cur)) {
        *dest = cur;
        return;
    }
    fprintf(stderr, "Error: expected %s, but found '%c'\n", name, cur);
    exit(1);
}

static void ignore_trailing_whitespace(FILE* stream) {
    int8_t cur = fgetc(stream);
    while (space(cur)) {
        cur = fgetc(stream);
    }
    char _;
    accept(newline, "a newline", &_, cur);
}

static void parse_maze_file(char chars[CHAR_WIDTH][CHAR_HEIGHT], FILE* stream) {
    int8_t col = 0;
    int8_t row = HEIGHT;
    int8_t k = 0;

    // parse top line
    accept(space, "a space", &chars[col][row], fgetc(stream)); col++;
    for (k = 0; k < WIDTH-1; k++) {
        accept(underscore, "an underscore", &chars[col][row], fgetc(stream)); col++;
        accept(space, "a space", &chars[col][row], fgetc(stream)); col++;
    }
    accept(underscore, "an underscore", &chars[col][row], fgetc(stream)); col++;
    ignore_trailing_whitespace(stream);  col = 0; row--;

    // parse body
    for (k = 0; k < HEIGHT; k++) {
        accept(pipe_char, "a pipe_char", &chars[col][row], fgetc(stream)); col++;
        int8_t l = 0;
        for (l = 0; l < WIDTH-1; l++) {
            accept(underscore_or_space, "an underscore or space",
                   &chars[col][row], fgetc(stream)); col++;
            accept(pipe_char_or_space, "a pipe_char or space", &chars[col][row],
                   fgetc(stream)); col++;
        }
        accept(underscore_or_space, "an underscore or space", &chars[col][row],
                fgetc(stream)); col++;
        accept(pipe_char, "a pipe_char", &chars[col][row], fgetc(stream)); col++;
        ignore_trailing_whitespace(stream); col = 0; row--;
    }
}