#ifdef Posix_compile
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/mman.h>
#include <sys/sem.h>
#include <semaphore.h>
#include <fcntl.h>
#else
#include <windows.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define data_slice 5


int N, sem, *fd, num_cycles;
char buffer[data_slice];



void error_handler(char *message) {
	fprintf(stderr, "%s\n", message);
	perror("ERROR");
	exit(EXIT_FAILURE);
}


void *thread(void *my_index) {
	int ret;
	struct sembuf oper;

	oper.sem_flg = SEM_UNDO;

	while (1) {
		oper.sem_num = (long)my_index;
		oper.sem_op = -1;

	stepA:	ret = semop(sem, &oper, 1);
		if (ret == -1 && errno != EINTR)
			error_handler("semop has failed");
		if (ret == -1)
			goto stepA;

	stepB:	ret = write(fd[(long)my_index], buffer, data_slice);
		if (ret == -1 && errno != EINTR)
			error_handler("write has failed");
		if (ret == -1)
			goto stepB;

		oper.sem_num = N;
		oper.sem_op = 1;

	stepC:	ret = semop(sem, &oper, 1);
		if (ret == -1 && errno == EINTR)
			error_handler("semop has failed");
		if (ret == -1)
			goto stepC;
	}
}


void SIGINT_handler(int signo, siginfo_t *a, void *b) {
	int i, j, index = 0;
	char c;

	for(i = 0; i < N; i++) {
		lseek(fd[i], 0, SEEK_SET);
	}
	for(i = 0; i < num_cycles; i++) {
		for(j = 0; j < data_slice; j++) {
			read(fd[index], &c, 1);
			printf("%c",c);
		}
		index = (index + 1) % N;
	}
	printf("\n");
}



int main(int argc, char *argv[]) {
	int ret, res, j;
	long i;
	pthread_t tid;
	sigset_t set;
	struct sembuf oper;
	struct sigaction act;

	if (argc < 2) {
		printf("Usage: pathname [pathname] ... [pathname]\n");
		exit(-1);
	}
	N = argc - 1;

	sem = semget(IPC_PRIVATE, N + 1, IPC_CREAT|0666);
	if (sem == -1)
		error_handler("semget has failed");

	fd =(int *)malloc(N*sizeof(int));
	if (fd == NULL)
		error_handler("malloc has failed");

	for(i = 0; i < N; i++) {
		ret = semctl(sem, i, SETVAL, 0);
		if (ret == -1)
			error_handler("semctl has failed");

		fd[i] = open(argv[i+1], O_CREAT|O_RDWR|O_TRUNC, 0666);
		if (fd[i] == -1)
			error_handler("Unable to open the file");
	}
	ret = semctl(sem, N, SETVAL, 1);
	if (ret == -1)
		error_handler("semctl has failed");

	for (i = 0; i < N; i++) {
		ret = pthread_create(&tid, NULL, thread, (void *)i);
		if (ret != 0)
			error_handler("pthread_create has failed");
	}
	sigfillset(&set);
	act.sa_sigaction = SIGINT_handler;
	act.sa_mask = set;
	act.sa_flags = 0;

	ret = sigaction(SIGINT, &act, NULL);
	if (ret == -1)
		error_handler("sigaction has failed");

	oper.sem_flg = SEM_UNDO;
	num_cycles = 0;
	i = 0;

	while (1) {
		res = 5;

		oper.sem_num = N;
		oper.sem_op = -1;

	step1:	ret = semop(sem, &oper, 1);
		if (ret == -1 && errno != EINTR)
			error_handler("semop has failed");
		if (ret == -1)
			goto step1;
		j = 0;
		while (res > 0) {
	step2:		buffer[j] = getchar();
			if (buffer[j] == EOF && errno != EINTR)
				error_handler("getchar has failed");
			if (buffer[j] == EOF || buffer[j] == '\n')
				goto step2;
			res--;
			j++;
		}

		oper.sem_num = i;
		oper.sem_op = 1;

	step3:	ret = semop(sem, &oper, 1);
		if (ret == -1 && errno != EINTR)
			error_handler("semop has failed");
		if (ret == -1)
			goto step3;

		i = (i + 1) % N;
		num_cycles++;
	}
}