// SAX locator interface for document events.
// http://www.saxproject.org
// No warranty; no copyright -- use this as you will.
// $Id: Locator.java,v 1.8 2002/01/30 21:13:47 dbrownell Exp $

package org.xml.sax;


/**
 * Interface for associating a SAX event with a document location.
 *
 * <blockquote>
 * <em>This module, both source code and documentation, is in the
 * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
 * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
 * for further information.
 * </blockquote>
 *
 * <p>If a SAX parser provides location information to the SAX
 * application, it does so by implementing this interface and then
 * passing an instance to the application using the content
 * handler's {@link org.xml.sax.ContentHandler#setDocumentLocator
 * setDocumentLocator} method.  The application can use the
 * object to obtain the location of any other SAX event
 * in the XML source document.</p>
 *
 * <p>Note that the results returned by the object will be valid only
 * during the scope of each callback method: the application
 * will receive unpredictable results if it attempts to use the
 * locator at any other time, or after parsing completes.</p>
 *
 * <p>SAX parsers are not required to supply a locator, but they are
 * very strongly encouraged to do so.  If the parser supplies a
 * locator, it must do so before reporting any other document events.
 * If no locator has been set by the time the application receives
 * the {@link org.xml.sax.ContentHandler#startDocument startDocument}
 * event, the application should assume that a locator is not 
 * available.</p>
 *
 * @since SAX 1.0
 * @author David Megginson
 * @version 2.0.1 (sax2r2)
 * @see org.xml.sax.ContentHandler#setDocumentLocator 
 */
public interface Locator {
    
    
    /**
     * Return the public identifier for the current document event.
     *
     * <p>The return value is the public identifier of the document
     * entity or of the external parsed entity in which the markup
     * triggering the event appears.</p>
     *
     * @return A string containing the public identifier, or
     *         null if none is available.
     * @see #getSystemId
     */
    public abstract String getPublicId ();
    
    
    /**
     * Return the system identifier for the current document event.
     *
     * <p>The return value is the system identifier of the document
     * entity or of the external parsed entity in which the markup
     * triggering the event appears.</p>
     *
     * <p>If the system identifier is a URL, the parser must resolve it
     * fully before passing it to the application.  For example, a file
     * name must always be provided as a <em>file:...</em> URL, and other
     * kinds of relative URI are also resolved against their bases.</p>
     *
     * @return A string containing the system identifier, or null
     *         if none is available.
     * @see #getPublicId
     */
    public abstract String getSystemId ();
    
    
    /**
     * Return the line number where the current document event ends.
     * Lines are delimited by line ends, which are defined in
     * the XML specification.
     *
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of diagnostics;
     * it is not intended to provide sufficient information
     * to edit the character content of the original XML document.
     * In some cases, these "line" numbers match what would be displayed
     * as columns, and in others they may not match the source text
     * due to internal entity expansion.  </p>
     *
     * <p>The return value is an approximation of the line number
     * in the document entity or external parsed entity where the
     * markup triggering the event appears.</p>
     *
     * <p>If possible, the SAX driver should provide the line position 
     * of the first character after the text associated with the document 
     * event.  The first line is line 1.</p>
     *
     * @return The line number, or -1 if none is available.
     * @see #getColumnNumber
     */
    public abstract int getLineNumber ();
    
    
    /**
     * Return the column number where the current document event ends.
     * This is one-based number of Java <code>char</code> values since
     * the last line end.
     *
     * <p><strong>Warning:</strong> The return value from the method
     * is intended only as an approximation for the sake of diagnostics;
     * it is not intended to provide sufficient information
     * to edit the character content of the original XML document.
     * For example, when lines contain combining character sequences, wide
     * characters, surrogate pairs, or bi-directional text, the value may
     * not correspond to the column in a text editor's display. </p>
     *
     * <p>The return value is an approximation of the column number
     * in the document entity or external parsed entity where the
     * markup triggering the event appears.</p>
     *
     * <p>If possible, the SAX driver should provide the line position 
     * of the first character after the text associated with the document 
     * event.  The first column in each line is column 1.</p>
     *
     * @return The column number, or -1 if none is available.
     * @see #getLineNumber
     */
    public abstract int getColumnNumber ();
    
}

// end of Locator.java
