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

/* Non standard include */
#include <commtech.h>
#include <specific_comm.h>


void *create_comm_channel(void)
{
	struct channel *channel;

	if (!posix_memalign((void *) &channel, CACHE_LINE_SIZE, sizeof(struct channel)))
	{
		if (!posix_memalign((void *) &channel->shared_space, CACHE_LINE_SIZE, SHARED_SPACE_SIZE))
		{
			int i;

			channel->head = 0;
			channel->tail = 0;
			for (i = 0; i < SHARED_SPACE_VOIDPTR; i++)
				channel->shared_space[i] = NULL;
			return channel;
		}
		else
			free(channel);
	}
	return NULL;
}

int destroy_comm_channel(void *channel)
{
	free((void *) ((struct channel *) channel)->shared_space);
	free(channel);
	return 0;
}

int adjust_slip(struct channel *channel)
{
	int dist, dist_old, unused;

	puts("adjust_slip is called"); /* Must be removed after calibration */
	unused = 0;
	dist = (channel->head + SHARED_SPACE_VOIDPTR - channel->tail) % SHARED_SPACE_VOIDPTR;
	if (dist < DANGER)
	{
		dist_old = 0;
		do
		{
			int i;

			dist_old = dist;

			/* 
			 * I consider 20 as being the number of ++ which could
			 * be done while one data is sent by the producer
			 */
			for (i = 0; i < 20 * ((GOOD + 1) - dist); i++)
				unused++;
			dist = (channel->head + SHARED_SPACE_VOIDPTR - channel->tail) % SHARED_SPACE_VOIDPTR;
		} while (dist < GOOD && dist_old < dist);
	}
	return unused;
}

void *recv_one_data(struct channel *channel)
{
	void *result;
	static __thread int nb_iter = 0;

	if (nb_iter == ADJUST_FREQ)
	{
		adjust_slip(channel);
		nb_iter = 0;
	}
	while (1)
	{
		result = channel->shared_space[channel->tail];
		if (NULL == result)
			continue;
		channel->shared_space[channel->tail] = NULL;
		channel->tail = (channel->tail + 1) % SHARED_SPACE_VOIDPTR;
		break;
	}
	return result;
}

ssize_t recv_some_data(struct channel *channel, void **buf, size_t count)
{
	int n, next_adjust;
	static __thread int nb_iter = 0;

	next_adjust = ADJUST_FREQ - nb_iter;
	for(n = 0; n < count; n++)
	{
		/* if ((nb_iter + n) % ADJUST_FREQ == 0) */
		if (n && (n % next_adjust == ADJUST_FREQ))
		{
			adjust_slip(channel);
			nb_iter = 0;
		}
		/*
		 * The behaviour of this is not documented but we know
		 * the values inside buf won't change during this affectation
		 */
		*buf = channel->shared_space[channel->tail];
		if (NULL == *buf)
			break;
		buf++;
		channel->shared_space[channel->tail] = NULL;
		channel->tail = (channel->tail + 1) % SHARED_SPACE_VOIDPTR;
	}
	nb_iter = (nb_iter + n) % ADJUST_FREQ;
	return n;
}