#define _XOPEN_SOURCE 600
#define _DEFAULT_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <pthread.h>
#include <unistd.h>
#include <errno.h>
#include <termios.h>
#include <assert.h>

static int pty_make_raw(int ptym)
{
    struct termios t;
    int err;

    err = tcgetattr(ptym, &t);
    if (err)
	return err;

    cfmakeraw(&t);
    return tcsetattr(ptym, TCSANOW, &t);
}

unsigned char data[65536];
unsigned char readbuf[65536];
int slavefd, slaveerr;
size_t readsize;

int
cmp_mem(unsigned char *buf, unsigned char *buf2, size_t len, size_t pos)
{
    size_t i;
    int rv = 0;

    for (i = 0; i < len; i++) {
	if (buf[i] != buf2[i]) {
	    printf("Mismatch on byte %lu, expected 0x%2.2x, got 0x%2.2x\n",
		   (long) (i + pos), buf[i], buf2[i]);
	    fflush(stdout);
	    rv = -1;
	    break;
	}
    }
    return rv;
}

static void *read_thread(void *dummy)
{
    ssize_t i;

    do {
	i = read(slavefd, readbuf + readsize, sizeof(readbuf) - readsize);
	if (i <= -1) {
	    if (errno == EAGAIN)
		continue;
	    if (errno == EIO)
		/* Remote close causes an EIO. */
		return NULL;
	    perror("read");
	    slaveerr = errno;
	    return NULL;
	}
	if (i + readsize > sizeof(data)) {
	    slaveerr = E2BIG;
	    return NULL;
	}
	if (i && cmp_mem(data + readsize, readbuf + readsize, i, readsize)) {
	    fprintf(stderr, "Data mismatch, starting at %ld, %ld bytes\n",
		    (long) readsize, (long) i);
	    assert(0);
	    slaveerr = EBADMSG;
	    return NULL;
	}
	readsize += i;
    } while (i != 0);

    return NULL;
}

int main(int argc, char *argv[])
{
    int ptym, err;
    char *slave;
    ssize_t i;
    pthread_t slavethr;

    for (i = 0; i < sizeof(data); i += 2) {
	data[i] = (i / 2) >> 8;
	data[i + 1] = i / 2;
    }

    ptym = posix_openpt(O_RDWR | O_NOCTTY);
    if (ptym == -1) {
	perror("posix_openpt");
	exit(1);
    }

    if (fcntl(ptym, F_SETFL, O_NONBLOCK) == -1) {
	perror("fcntl ptym");
	exit(1);
    }

    if (pty_make_raw(ptym)) {
	perror("pty_make_raw");
	exit(1);
    }

    if (unlockpt(ptym) < 0) {
	perror("unlockpt");
	exit(1);
    }

    slave = ptsname(ptym);
    slavefd = open(slave, O_RDWR);
    if (slavefd == -1) {
	perror("open");
	exit(1);
    }

    err = pthread_create(&slavethr, NULL, read_thread, NULL);
    if (err) {
	fprintf(stderr, "pthread_create: %s\n", strerror(err));
	exit(1);
    }

    i = write(ptym, data, sizeof(data));
    if (i == -1) {
	perror("write");
	exit(1);
    }
    close(ptym);

    pthread_join(slavethr, NULL);

    exit(0);
}