#include <sys/io.h> /* ioperm(), inb(), outb() */
#include <stdio.h> /* printf(), fprintf() */
#include <stdlib.h> /* exit(), EXIT_FAILURE */

#define status (base + 1)
#define control (base + 2)

/* DOS scans these 3 downwards to detect parallel ports, so do we. */
int scanp[4] = { 0x3BC, 0x378, 0x278, -1 };

int ports[4];
int nports;

int lp_test(int base) {
        int c, d;
        if (ioperm(base, 4, 1)) {
                fprintf(stderr, "warning: cannot probe port %i\n", base);
        } else {
                c = inb(base);
                c++;
                outb(c, base);
                d = inb(base);
                outb(--c, base);
                ioperm(base, 4, 0);
                if (d == c)
                        return 1;
        }
        return 0;
}

int lp_detect(void) {
        int i, nports = 0;
        for (i = 0; scanp[i] != -1; ++i)
                if (lp_test(scanp[i]))
                        ports[nports++] = scanp[i];
        ports[nports] = -1;
        return nports;
}

void printb(char b) {
        int bit = 7;
        printf("0x%X ", b);
        next:
        printf("%i", (b & (1 << bit)) >> bit);
        if (bit > 0) {
                putchar(' ');
                --bit;
                goto next;
        }
        putchar('\n');
}

int main(int argc, char *argv[]) {
        int base, c;

        if (!lp_detect()) {
                fprintf(stderr, "error: no parallel port found\n");
                exit(EXIT_FAILURE);
        }

        base = ports[0];
        if (ioperm(base, 4, 1)) {
                fprintf(stderr, "error: failed to claim port %i\n");
                exit(EXIT_FAILURE);
        }
        c = inb(control);
        printb(c);

        return EXIT_SUCCESS;
}