#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <errno.h>

FILE *f1;
FILE *f2;
FILE *f3;
FILE *f4;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t condA_B = PTHREAD_COND_INITIALIZER;
pthread_cond_t condB_C = PTHREAD_COND_INITIALIZER;
pthread_cond_t condC_D = PTHREAD_COND_INITIALIZER;
pthread_cond_t condD_A = PTHREAD_COND_INITIALIZER;

int flaga,flagb,flagc,flagd;

void *th_fun_a(void *arg)
{
	int i = 0;

	while(i < 10)
	{
		pthread_mutex_lock(&mutex);
		flaga = 1;
		pthread_cond_wait(&condD_A,&mutex);
		flaga = 0;

		f1 = fopen("A.txt","a+");
		//fseek(f1,0,SEEK_END);
		fputc('1',f1);
		fclose(f1);
		
		f2 = fopen("B.txt","a+");
		//fseek(f2,0,SEEK_END);
		fputc('2',f2);
		fclose(f2);

		f3 = fopen("C.txt","a+");
		//fseek(f3,0,SEEK_END);
		fputc('3',f3);
		fclose(f3);

		f4 = fopen("D.txt","a+");
		//fseek(f4,0,SEEK_END);
		fputc('4',f4);
		fclose(f4);

		while(!flagb)
		{
			pthread_mutex_unlock(&mutex);
			usleep(50);
			pthread_mutex_lock(&mutex);
		}

		pthread_cond_broadcast(&condA_B);
		pthread_mutex_unlock(&mutex);
		
		i++;
		usleep(50);

	}
	flaga = 1;
}

void *th_fun_b(void *arg)
{
	int i = 0;

	while(i < 10)
	{
		pthread_mutex_lock(&mutex);
		flagb = 1;
		pthread_cond_wait(&condA_B,&mutex);
		flagb = 0;

		f1 = fopen("A.txt","a+");
		//fseek(f1,0,SEEK_END);
		fputc('2',f1);
		fclose(f1);
		
		f2 = fopen("B.txt","a+");
		//fseek(f2,0,SEEK_END);
		fputc('3',f2);
		fclose(f2);

		f3 = fopen("C.txt","a+");
		//fseek(f3,0,SEEK_END);
		fputc('4',f3);
		fclose(f3);

		f4 = fopen("D.txt","a+");
		//fseek(f4,0,SEEK_END);
		fputc('1',f4);
		fclose(f4);

		while(!flagc)
		{
			pthread_mutex_unlock(&mutex);
			usleep(50);
			pthread_mutex_lock(&mutex);
		}

		pthread_cond_broadcast(&condB_C);
		pthread_mutex_unlock(&mutex);
		
		i++;
		usleep(50);

	}
}

void *th_fun_c(void *arg)
{
	int i = 0;

	while(i < 10)
	{
		pthread_mutex_lock(&mutex);
		flagc = 1;
		pthread_cond_wait(&condB_C,&mutex);
		flagc = 0;

		f1 = fopen("A.txt","a+");
		//fseek(f1,0,SEEK_END);
		fputc('3',f1);
		fclose(f1);
		
		f2 = fopen("B.txt","a+");
		//fseek(f2,0,SEEK_END);
		fputc('4',f2);
		fclose(f2);

		f3 = fopen("C.txt","a+");
		fseek(f3,0,SEEK_END);
		fputc('1',f3);
		fclose(f3);

		f4 = fopen("D.txt","a+");
		//fseek(f4,0,SEEK_END);
		fputc('2',f4);
		fclose(f4);

		while(!flagd)
		{
			pthread_mutex_unlock(&mutex);
			usleep(50);
			pthread_mutex_lock(&mutex);
		}

		pthread_cond_broadcast(&condC_D);
		pthread_mutex_unlock(&mutex);
		
		i++;
		usleep(50);

	}
}

void *th_fun_d(void *arg)
{
	int i = 0;

	while(i < 10)
	{
		pthread_mutex_lock(&mutex);
		flagd = 1;
		pthread_cond_wait(&condC_D,&mutex);
		flagd = 0;

		f1 = fopen("A.txt","a+");
		//fseek(f1,0,SEEK_END);
		fputc('4',f1);
		fclose(f1);
		
		f2 = fopen("B.txt","a+");
		//fseek(f2,0,SEEK_END);
		fputc('1',f2);
		fclose(f2);

		f3 = fopen("C.txt","a+");
		//fseek(f3,0,SEEK_END);
		fputc('2',f3);
		fclose(f3);

		f4 = fopen("D.txt","a+");
		//fseek(f4,0,SEEK_END);
		fputc('3',f4);
		fclose(f4);

		while(!flaga)
		{
			pthread_mutex_unlock(&mutex);
			usleep(50);
			pthread_mutex_lock(&mutex);
		}

		pthread_cond_broadcast(&condD_A);
		pthread_mutex_unlock(&mutex);
		
		i++;
		usleep(50);

	}
}

int main()
{
	pthread_t th[4];

	void *(*th_funs[])(void *) = 
	{
		th_fun_a,
		th_fun_b,
		th_fun_c,
		th_fun_d,
	};

	int i;

	for(i = 0; i < 4; i++)
	{
		if(pthread_create(th+i,NULL,th_funs[i],(void *)i) < 0)
		{
			fprintf(stderr,"creat:%s\n",strerror(errno));
			exit(-1);
		}
	}

	pthread_mutex_lock(&mutex);
	while(!flagd)
	{
		pthread_mutex_unlock(&mutex);
		usleep(50);
		pthread_mutex_lock(&mutex);
	}
	printf("hi\n");
	pthread_cond_broadcast(&condD_A);
	pthread_mutex_unlock(&mutex);

	for(i = 0; i < 4; i++)
	{
		pthread_join(th[i],NULL);
		printf("process %d finished!\n",i);
	}

    return 0;
}