#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <getopt.h>
#include <errno.h>

/* pipe file descriptors */
static int fd[2];

/* send/write size */
static size_t size;

/* options */
static struct option long_opts[] = {
	{ "size", required_argument, NULL, 's' },
	{ NULL,   0,                 NULL,  0  },
};

static void *reader(void *arg)
{
	unsigned char buf[size];
	ssize_t read_ = 0;

	while (read_ < size) {
		ssize_t ret;

		ret = read(fd[0], buf + read_, size - read_);
		if (ret < 0) {
			perror("read() failed");
			exit(EXIT_FAILURE);
		}
		read_ += ret;
	}

	printf("Reader: got data\n");
	return NULL;
}

static void *writer(void *arg)
{
	unsigned char buf[size];
	ssize_t written = 0;

	sleep(1);

	while (written < size) {
		ssize_t ret;

		ret = write(fd[1], buf + written, size - written);
		if (ret < 0) {
			perror("write() failed");
			exit(EXIT_FAILURE);
		}

		written += ret;
	}

	printf("Writer: sent data\n");

	sleep(1);

	return NULL;
}

static inline void print_usage_and_die(void)
{
	fprintf(stderr, "usage: pipedemo [-s <size>]\n");
	exit(EXIT_FAILURE);
}

int main(int argc, char **argv)
{
	pthread_t tid1, tid2;
	char *end;
	int c;

	size = 4 << 10;
	while ((c = getopt_long(argc, argv, "s:", long_opts, NULL)) != -1) {
		switch (c) {
		case 's':
			size = strtoull(optarg, &end, 10);
			if (end == optarg || *end != '\0' || errno == ERANGE) {
				fprintf(stderr, "given size is not valid\n");
				return EXIT_FAILURE;
			}
			break;
		default:
			print_usage_and_die();
		}
	}

	if (pipe(fd) < 0) {
		perror("pipe() failed");
		return EXIT_FAILURE;
	}

	if (pthread_create(&tid1, NULL, reader, NULL) ||
	    pthread_create(&tid2, NULL, writer, NULL)) {
		fprintf(stderr, "pthread_create() failed\n");
		return EXIT_FAILURE;
	}

	if (pthread_setname_np(tid1, "pipedemo-reader") ||
	    pthread_setname_np(tid2, "pipedemo-writer")) {
		fprintf(stderr, "pthread_create() failed\n");
		return EXIT_FAILURE;
	}

	pthread_join(tid1, NULL);
	pthread_join(tid2, NULL);

	return EXIT_SUCCESS;
}