ssd_bus.cpp

/* Copyright 2009, 2010 Brendan Tauras */

/* ssd_bus.cpp is part of FlashSim. */

/* FlashSim is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version. */

/* FlashSim is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details. */

/* You should have received a copy of the GNU General Public License
 * along with FlashSim.  If not, see <http://www.gnu.org/licenses/>. */

/****************************************************************************/

/* Bus class
 * Brendan Tauras 2009-04-06
 *
 * Multi-channel bus comprised of Channel class objects
 * Simulates control and data delays by allowing variable channel lock
 * durations.  The sender (controller class) should specify the delay (control,
 * data, or both) for events (i.e. read = ctrl, ctrl+data; write = ctrl+data;
 * erase or merge = ctrl).  The hardware enable signals are implicitly
 * simulated by the sender locking the appropriate bus channel through the lock
 * method, then sending to multiple devices by calling the appropriate method
 * in the Package class. */

#include <new>
#include <assert.h>
#include <stdio.h>
#include "ssd.h"

using namespace ssd;

/* a multi-channel bus: multiple independent channels that operate in parallel
 * allocate channels and pass parameters to channels via the lock method
 * the table size is synonymous to the queue size for each separate channel
 * it is not necessary to use the max connections properly, but it is provided
 * 	to help ensure correctness */
Bus::Bus(uint num_channels, double ctrl_delay, double data_delay, uint table_size, uint max_connections):
	num_channels(num_channels),

	/* use a const pointer (Channel * const channels) to use as an array
	 * but like a reference, we cannot reseat the pointer */
	channels((Channel *) malloc(num_channels * sizeof(Channel)))
{
	assert(table_size > 0);
	if(ctrl_delay < 0.0){
		fprintf(stderr, "Bus warning: %s: constructor received negative control delay value\n\tsetting control delay to 0.0\n", __func__);
		ctrl_delay = 0.0;
	}
	if(data_delay < 0.0){
		fprintf(stderr, "Bus warning: %s: constructor received negative data delay value\n\tsetting data delay to 0.0\n", __func__);
		data_delay = 0.0;
	}
	uint i;

	/* allocate channels */
	/* new cannot initialize an array with constructor args
	 *    malloc the array
	 *    then use placement new to call the constructor for each element
	 * chose an array over container class so we don't have to rely on anything
	 *    i.e. STL's std::vector */
	/* array allocated in initializer list:
	 * channels = (Channel *) malloc(num_channels * sizeof(Channel)); */
	if(channels == NULL)
	{
		fprintf(stderr, "Bus error: %s: constructor unable to allocate Channels\n", __func__);
		exit(MEM_ERR);
	}
	for(i = 0; i < num_channels; i++)
		(void) new (&channels[i]) Channel(ctrl_delay, data_delay, table_size, max_connections);

	return;
}

/* deallocate channels */
Bus::~Bus(void)
{
	assert(channels != NULL);
	uint i;
	for(i = 0; i < num_channels; i++)
		channels[i].~Channel();
	free(channels);
	return;
}

/* not required before calling lock()
 * but should be used to help ensure correctness
 * controller that talks on all channels should not connect/disconnect
 * 	only devices that use a channel should connect/disconnect */
enum status Bus::connect(uint channel)
{
	assert(channels != NULL && channel < num_channels);
	return channels[channel].connect();
}

/* not required when finished
 * but should be used to help ensure correctness
 * controller that talks on all channels should not connect/disconnect
 * 	only devices that use a channel should connect/disconnect */
enum status Bus::disconnect(uint channel)
{
	assert(channels != NULL && channel < num_channels);
	return channels[channel].disconnect();
}

/* lock bus channel for event
 * updates event with bus delay and bus wait time if there is wait time
 * channel will automatically unlock after event is finished using bus
 * assumes event is sent across channel as soon as bus is available
 * event may fail if channel is saturated so check return value
 */
enum status Bus::lock(uint channel, double start_time, double duration, Event &event)
{
	assert(channels != NULL && start_time >= 0.0 && duration > 0.0);
	return channels[channel].lock(start_time, duration, event);
}

Channel &Bus::get_channel(uint channel)
{
	assert(channels != NULL && channel < num_channels);
	return channels[channel];
}