HostList.java

/*
 * Title:        CloudSim Toolkit
 * Description:  CloudSim (Cloud Simulation) Toolkit for Modeling and Simulation of Clouds
 * Licence:      GPL - http://www.gnu.org/copyleft/gpl.html
 *
 * Copyright (c) 2009-2012, The University of Melbourne, Australia
 */

package org.cloudbus.cloudsim.lists;

import java.util.List;

import org.cloudbus.cloudsim.Host;

/**
 * HostList is a collection of operations on lists of hosts (PMs).
 * 
 * @author Anton Beloglazov
 * @since CloudSim Toolkit 2.0
 */
public class HostList {

	/**
	 * Gets a {@link Host} with a given id.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @param id the host ID
	 * @return a Host with the given ID or $null if not found
         * 
	 * @pre id >= 0
	 * @post $none
	 */
	public static <T extends Host> T getById(List<T> hostList, int id) {
		for (T host : hostList) {
			if (host.getId() == id) {
				return host;
			}
		}
		return null;
	}

	/**
	 * Gets the total number of PEs for all Hosts.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @return total number of PEs for all PMs
	 * @pre $none
	 * @post $result >= 0
	 */
	public static <T extends Host> int getNumberOfPes(List<T> hostList) {
		int numberOfPes = 0;
		for (T host : hostList) {
			numberOfPes += host.getPeList().size();
		}
		return numberOfPes;
	}

	/**
	 * Gets the total number of <tt>FREE</tt> (non-busy) PEs for all Hosts.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @return total number of free PEs
	 * @pre $none
	 * @post $result >= 0
	 */
	public static <T extends Host> int getNumberOfFreePes(List<T> hostList) {
		int numberOfFreePes = 0;
		for (T host : hostList) {
			numberOfFreePes += PeList.getNumberOfFreePes(host.getPeList());
		}
		return numberOfFreePes;
	}

	/**
	 * Gets the total number of <tt>BUSY</tt> PEs for all Hosts.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @return total number of busy PEs
	 * @pre $none
	 * @post $result >= 0
	 */
	public static <T extends Host> int getNumberOfBusyPes(List<T> hostList) {
		int numberOfBusyPes = 0;
		for (T host : hostList) {
			numberOfBusyPes += PeList.getNumberOfBusyPes(host.getPeList());
		}
		return numberOfBusyPes;
	}

	/**
	 * Gets the first host with free PEs.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @return a Host object or <tt>null</tt> if not found
	 * @pre $none
	 * @post $none
	 */
	public static <T extends Host> T getHostWithFreePe(List<T> hostList) {
		return getHostWithFreePe(hostList, 1);
	}

	/**
	 * Gets the first Host with a specified number of free PEs.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @param pesNumber the pes number
	 * @return a Host object or <tt>null</tt> if not found
	 * @pre $none
	 * @post $none
	 */
	public static <T extends Host> T getHostWithFreePe(List<T> hostList, int pesNumber) {
		for (T host : hostList) {
			if (PeList.getNumberOfFreePes(host.getPeList()) >= pesNumber) {
				return host;
			}
		}
		return null;
	}

	/**
	 * Sets the status of a particular PE on a given Host.
	 * 
	 * @param <T> the generic type
	 * @param hostList the list of existing hosts
	 * @param status the PE status, either <tt>Pe.FREE</tt> or <tt>Pe.BUSY</tt>
	 * @param hostId the host id
	 * @param peId the id of the PE to set the status
	 * @return <tt>true</tt> if the PE status has changed, <tt>false</tt> otherwise (host id or
	 *         PE id might not be exist)
	 * @pre hostId >= 0
	 * @pre peId >= 0
	 * @post $none
	 */
	public static <T extends Host> boolean setPeStatus(List<T> hostList, int status, int hostId, int peId) {
		T host = getById(hostList, hostId);
		if (host == null) {
			return false;
		}
		return host.setPeStatus(peId, status);
	}

}