SsrcAttribute.java

/*
 * TeleStax, Open Source Cloud Communications
 * Copyright 2011-2014, Telestax Inc and individual contributors
 * by the @authors tag.
 *
 * This program is free software: you can redistribute it and/or modify
 * under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

package org.restcomm.media.sdp.attributes;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.restcomm.media.sdp.fields.AttributeField;

/**
 * a=ssrc:[ssrc-id] [attribute]<br>
 * a=ssrc:[ssrc-id] [attribute]:[value]
 * 
 * <p>
 * The SDP media attribute "ssrc" indicates a property (known as a
 * "source-level attribute") of a media source (RTP stream) within an RTP
 * session.
 * </p>
 * <p>
 * <b>ssrc-id</b> is the synchronization source (SSRC) ID of the source being
 * described, interpreted as a 32-bit unsigned integer in network byte order and
 * represented in decimal.
 * </p>
 * <p>
 * <b>attribute</b> or <b>attribute:value</b> represents the source-level
 * attribute specific to the given media source.<br>
 * The source-level attribute follows the syntax of the SDP "a=" line. It thus
 * consists of either a single attribute name (a flag) or an attribute name and
 * value, e.g., "cname:user@example.com". No attributes of the former type are
 * defined by this document.
 * </p>
 * <p>
 * Within a media stream, "ssrc" attributes with the same value of <ssrc-id>
 * describe different attributes of the same media sources. Across media
 * streams, <ssrc-id> values are not correlated (unless correlation is indicated
 * by media-stream grouping or some other mechanism) and MAY be repeated.
 * </p>
 * <p>
 * Each "ssrc" media attribute specifies a single source-level attribute for the
 * given <ssrc-id>. For each source mentioned in SDP, the source-level attribute
 * "cname" MUST be provided. Any number of other source-level attributes for the
 * source MAY also be provided.
 * </p>
 * 
 * @author Henrique Rosa (henrique.rosa@telestax.com)
 * 
 * @see <a href="https://tools.ietf.org/html/rfc5576">RFC5576</a>
 */
public class SsrcAttribute extends AttributeField {

	public static final String ATTRIBUTE_TYPE = "ssrc";
	public static final String BEGIN = "a=ssrc:";
	public static final String NEWLINE = "\n";

	private String ssrcId;
	private final Map<String, String> attributes;

	private String lastAttribute;
	private String lastValue;

	public SsrcAttribute(String ssrcId) {
		super(ATTRIBUTE_TYPE);
		this.ssrcId = ssrcId;
		this.attributes = new HashMap<String, String>(3);
		this.lastAttribute = "";
		this.lastValue = "";
	}

	public void setSsrcId(String ssrcId) {
		this.ssrcId = ssrcId;
	}

	public String getSsrcId() {
		return ssrcId;
	}

	public String getAttributeValue(String attribute) {
		return this.attributes.get(attribute);
	}

	public void addAttribute(String attribute, String value) {
		this.lastAttribute = attribute;
		this.lastValue = value;
		this.attributes.put(attribute, value);
	}

	/**
	 * Gets the name of the last inserted attribute.
	 * 
	 * @return the name of the attribute
	 */
	public String getLastAttribute() {
		return lastAttribute;
	}

	/**
	 * Gets the value of the last inserted attribute
	 * 
	 * @return the value of the attribute
	 */
	public String getLastValue() {
		return lastValue;
	}

	public void reset() {
		this.ssrcId = null;
		this.attributes.clear();
	}

	@Override
	public String toString() {
		super.builder.setLength(0);
		for (Entry<String, String> value : this.attributes.entrySet()) {
			super.builder.append(BEGIN).append(this.ssrcId).append(" ")
					.append(value.getKey());
			if (value.getValue() != null && !value.getValue().isEmpty()) {
				super.builder.append(ATTRIBUTE_SEPARATOR)
						.append(value.getValue()).append(NEWLINE);
			}
		}
		super.builder.deleteCharAt(builder.length() - 1);
		return super.builder.toString();
	}
}