/*
 * canon_switch2.c
 *
 * Test read() after non-canon -> canon switch
 *  w/ EOL push immediately after
 *
 *    gcc -Wall -o canon_switch canon_switch.c
 *
 * Based on orginal code by Ilya Zykov <ilya@ilyx.ru>
 */

#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <poll.h>
#include <sys/wait.h>

static int fd;

static void error_exit(char *f, ...) {
	va_list va;

	va_start(va, f);
	vprintf(f, va);
	if (errno)
		printf(": %s (code: %d)\n", strerror(errno), errno);
	else
		printf("\n");
	va_end(va);

	if (fd >= 0)
		close(fd);

	exit(EXIT_FAILURE);
}

static void fill_pattern(char *pattern, size_t len) {
	size_t i, n;
	const char test[] = "1234567890";

	n = strlen(test);
	for (i = 0; i <= len - n; i += n)
		strncpy(&pattern[i], test, n);
	strncpy(&pattern[i], test, len % n);
}

int main(int argc, char *argv[]) {
	int child_id;
	char pts_name[24];
	int ptn, unlock = 0;
	struct termios termios, save;

	setbuf(stdout, NULL);

	fd = open("/dev/ptmx", O_RDWR);
	if (fd < 0)
		error_exit("opening pty master");
	if (ioctl(fd, TIOCGPTN, &ptn) < 0)
		error_exit("getting pty #");
	if (ioctl(fd, TIOCSPTLCK, &unlock) < 0)
                error_exit("unlocking pty pair");
        snprintf(pts_name, sizeof(pts_name), "/dev/pts/%d", ptn);

	if (tcgetattr(fd, &termios) < 0)
		error_exit("tcgetattr");
	save = termios;
	termios.c_lflag &= ~(ICANON | ECHO | ISIG);
	termios.c_iflag &= ~(IXON | IXOFF | ICRNL | INLCR);
	if ((termios.c_cflag & CSIZE) == CS8)
		termios.c_cflag &= ~(ISTRIP | INPCK);
	termios.c_cc[VMIN] = 1;
	termios.c_cc[VTIME] = 0;
	termios.c_cc[VLNEXT] = _POSIX_VDISABLE;
	termios.c_oflag &= ~OPOST;
	if (tcsetattr(fd, TCSAFLUSH, &termios) < 0)
		error_exit("tcsetattr master");

	child_id = fork();
	switch (child_id) {
	case -1: error_exit("forking child");

	case 0:	{ /* child */
		printf("Child [%ld] on slave pty %s\n", (long)getpid(), pts_name);

		close(fd);	/* master pty no longer needed */

		fd = open(pts_name, O_RDWR);
		if (fd < 0)
			error_exit("opening pty slave");

		/* wait for master write in non-canon mode */
		{
			struct pollfd pollfds[1] = { { fd, POLLIN },
						   };
			poll(pollfds, 1, -1);
		}

		sleep(1);

		if (tcsetattr(fd, TCSANOW, &save))
			error_exit("tcsetattr restore");

		{
			char buf[8192];
			int n;

			n = read(fd, buf, sizeof(buf));
			if (n < 0)
				error_exit("slave reading");
			printf("read: %d\n", n);
			printf("%.*s", n, buf);

			n = read(fd, buf, sizeof(buf));
			if (n < 0)
				error_exit("slave reading");
			printf("read: %d\n", n);
			if (n == 0)
				error_exit("unexpected EOF");
			printf("%.*s", n, buf);

			n = read(fd, buf, sizeof(buf));
			if (n < 0)
				error_exit("slave reading");
			printf("read: %d\n", n);
			printf("%.*s", n, buf);
		}

		close(fd);
		}
		return 0;

	default: { /* parent */
		int n, id, status, c;

		char pattern[4096];
		char pattern2[] = "The quick brown fox jumped over the lazy dog.\r";

		/* Simulate an input pattern that was supposed to be
		 * all 4096 chars of pattern (which terminates in an EOF push)
		 * but was received as 4095 (because that's the maximum raw mode
		 * allows in the input buffer at once).
		 */
		fill_pattern(pattern, sizeof(pattern));
		pattern[4095] = termios.c_cc[VEOF];
		c = 4096;
		n = write(fd, pattern, c);
		if (n < 0)
			error_exit("master writing");
		printf("write: %d, wrote: %d\n", c, n);

		c = strlen(pattern2);
		n = write(fd, pattern2, c);
		if (n < 0)
			error_exit("master writing");
		printf("write: %d, wrote: %d\n", c, n);

		id = waitpid(child_id, &status, 0);
		if (id < 0 || id != child_id)
			error_exit("waiting for child");
		printf("[%ld] exited status: %d\n", (long) child_id, status);
		}
		return 0;
	}
}