// This program is Operation System's first project.
// This proejct's name is producer-consumer relationship problem.
// °ú  ¸ñ : Operation System
// ±³¼ö´Ô : ±è Á¤±¹ ±³¼ö´Ô
// ÇÐ  °ú : ÄÄÇ»ÅÍ °øÇаú
// ÇÐ  ³â : 4 Çгâ
// ÇÐ  ¹ø : 19980220
// ÀÌ  ¸§ : ÀÌ ½Â ÀÍ


#include <stdio.h>
#include <pthread.h>
#define MAX 10
#define MIN 0

void Initialize(void); // function declaration
void c_push(int push_data); // function declaration
void c_pop(); // function declaration

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t buffer_has_space = PTHREAD_COND_INITIALIZER;
pthread_cond_t buffer_has_data = PTHREAD_COND_INITIALIZER;

typedef struct Circular_queue circular_queue;
typedef struct Data_type  data_type;

struct Circular_queue {
	data_type* pFirst;
	data_type* pEnd;
	int max;
};

struct Data_type {
	int data;
	data_type* pNext;
};

circular_queue c_queue; // Shared variables

void* producer(void* p_id) 
{
	int i;
	for(i=0; i<5000; i++)
	{
		printf("Go in the Critical Section by pid=%d == ", &p_id);
		fflush(stdout);

		pthread_mutex_lock(&mutex); // Critical Section
		while (c_queue.max >= MAX)
		{
			printf("pid=%d | c_queue.max =%d == ", &p_id, c_queue.max);
			fflush(stdout);
			printf("pid=%d now sleeping! \n", &p_id);
			fflush(stdout);
		
			if (pthread_cond_wait(&buffer_has_space, &mutex) == -1 )
			{
				printf("cond_wait error\n");
				fflush(stdout);
			}

		printf("pid=%d  wake up == ",&p_id);
			fflush(stdout);
			printf("c_queue.max=%d == ", c_queue.max);
			fflush(stdout);
		}

		printf("pid=%d == ", &p_id);
		fflush(stdout);
		c_push(i);
		
		pthread_cond_signal(&buffer_has_data);
		pthread_mutex_unlock(&mutex);
		printf("pid=%d loop count %d\n", &p_id, i);
		fflush(stdout);
	}	
	printf("pid=%d pthread exit == loop count %d\n", &p_id, i);
	fflush(stdout);
	pthread_exit(NULL);

}

void* consumer(void* c_id) 
{
	int i;
	for(i=0; i<10000; i++)
	{
		printf("Go in the Critical Section by cid=%d == ", &c_id);
		fflush(stdout);

		pthread_mutex_lock(&mutex); //Critical Section

		while(c_queue.max <= MIN)
		{
			printf("cid=%d | c_queue.max =%d == ", &c_id, c_queue.max);
			fflush(stdout);
			printf(" cid=%d now sleeping! \n", &c_id);
			fflush(stdout);

			if(pthread_cond_wait(&buffer_has_data, &mutex) == -1 )
			{
				printf("cond_wait_error\n");
				fflush(stdout);
			}

			printf("cid=%d  wake up == ",&c_id);
			fflush(stdout);
			printf("c_queue.max=%d == ", c_queue.max);
			fflush(stdout);

		}

		printf("cid=%d == ", &c_id);
		fflush(stdout);

		c_pop();

		printf("consumer c_queue.max = %d", c_queue.max);
		fflush(stdout);
		
		pthread_cond_signal(&buffer_has_space);
//		pthread_cond_broadcast(&buffer_has_space);
		pthread_mutex_unlock(&mutex);

		printf("cid=%d loop count %d \n", &c_id, i);
		fflush(stdout);
	}
	printf("cid=%d pthread exit == loop count %d\n", &c_id, i);
	fflush(stdout);
	pthread_exit(NULL);

}


int main()
{

	int i=0;
	int process_id[3];

	Initialize(); // Initialize c_queue

	pthread_t threads[3];
	pthread_create(&threads[0], NULL, producer, (void *)&process_id[0]);
	pthread_create(&threads[1], NULL, producer, (void *)&process_id[1]);
	pthread_create(&threads[2], NULL, consumer, (void *)&process_id[2]);
	
	for(i=0; i<3; i++) {
		pthread_join(threads[i], NULL);
	}
	
}

// c_queue's initializing function
void Initialize()
{
	c_queue.pFirst = NULL;
	c_queue.pEnd = NULL;
	c_queue.max = MIN;
}

void c_push(int push_data)
{
	if( c_queue.max < MAX ) {
		
		if( c_queue.pFirst == NULL ) { // first push
			data_type* temp;
			temp = (data_type* )malloc(sizeof(data_type));
			temp->data = push_data;
			c_queue.pFirst = temp;
			temp->pNext = c_queue.pEnd;
			c_queue.pEnd = temp;
		}
		else
		{
			data_type* temp;
			data_type* position = c_queue.pFirst;
			temp = (data_type* )malloc(sizeof(data_type));
			temp->data = push_data;
			
			temp->pNext = position->pNext;
			position->pNext = temp;
			c_queue.pFirst = temp;
		}
		printf("** push %d ***", push_data);
		c_queue.max++;
	}
	else // if c_queue.max is true 
	{
		printf("can't push data in queue because this queue is full! : max is %d \n", c_queue.max);
	}
}

void c_pop()
{
	if( c_queue.max == MIN ) {
		printf("can't pop data in queue because this queue is empty!\n");
	}
	else {
		data_type* temp;

//		if( c_queue.max == 1 ) // when this queue have one data
		if( c_queue.pFirst == c_queue.pEnd)
		{
			temp = c_queue.pFirst;
			
			c_queue.pFirst = NULL;
			c_queue.pEnd = NULL;
		}
		else { // when this queue have data more than one
			data_type* temp2;
			temp = c_queue.pEnd;
			temp2 = c_queue.pEnd->pNext;
			c_queue.pEnd = temp2;
		}
		printf("*** pop %d ***", temp->data);
		c_queue.max--;

		free(temp);
	}
}