#define READLINE_VALID_CHAR(C) (((u8)(C) >= 0x20 && (u8)(C) < 0x7F) || (C) == '\n')

StringView
read_line(FILE *fd, char delimiter) {
    #define RL_BUF_SIZE KB(64)
    static char readline_buf[RL_BUF_SIZE];

    // Clear buffer.
    for (size_t i = 0; i < RL_BUF_SIZE; i++) {
        readline_buf[i] = 0;
    }

    // Barebones readline implementation.
    size_t n = 0;
    char c;
    while ((c = getc(fd)) != delimiter) {
        if (c == '\b') {
            readline_buf[n] = '\0';
            n--;
        } else if (READLINE_VALID_CHAR(c) && n < RL_BUF_SIZE) {
            readline_buf[n] = c;
            n++;
        }
    }

    return (StringView){.start = (char *)&readline_buf, .n = n};
}