URLStreamHandler.java   [plain text]

// URLStreamHandler.java - Superclass of all stream protocol handlers.

/* Copyright (C) 1999, 2002  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

package java.net;

/**
 * @author Warren Levy <warrenl@cygnus.com>
 * @date March 4, 1999.
 */

/**
 * Written using on-line Java Platform 1.2 API Specification, as well
 * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
 * Status:  Believed complete and correct.
 */

public abstract class URLStreamHandler
{
  protected abstract URLConnection openConnection(URL u)
    throws java.io.IOException;

  protected void parseURL(URL u, String spec, int start, int limit)
  {
    String host = u.getHost();
    int port = u.getPort();
    String file = u.getFile();
    
    /* TBD: The JDK 1.2 doc specifically says that limit is the position
     * to stop parsing at and that it will be either the end of the string
     * or the position of '#'; thus the doc infers that this method does
     * not set the ref.
     */
    if (spec.regionMatches (start, "//", 0, 2))
      {
	int hostEnd;
	int colon;

	start += 2;
	int slash = spec.indexOf('/', start);
	if (slash >= 0) 
	  hostEnd = slash;
        else
	  hostEnd = limit;

	host = spec.substring (start, hostEnd);
	
	// Look for optional port number.  It is valid for the non-port
	// part of the host name to be null (e.g. a URL "http://:80").
	// TBD: JDK 1.2 in this case sets host to null rather than "";
	// this is undocumented and likely an unintended side effect in 1.2
	// so we'll be simple here and stick with "". Note that
	// "http://" or "http:///" produce a "" host in JDK 1.2.
	if ((colon = host.indexOf(':')) >= 0)
	  {
	    try
	      {
		port = Integer.parseInt(host.substring(colon + 1));
	      }
	    catch (NumberFormatException e)
	      {
		; // Ignore invalid port values; port is already set to u's
		  // port.
	      }
	    host = host.substring(0, colon);
	  }
	file = null;
	start = hostEnd;
      } 
    else if (host == null) 
      host = "";

    if (start < limit && spec.charAt(start) == '/') 
      {
	// This is an absolute path name; ignore any file context.
	file = spec.substring(start, limit);
      } 
    else if (file == null || file.length() <= 0)
      {
	// No file context available; just spec for file.
	file = spec.substring(start, limit);
      }
    else if (start < limit)
      {
	// Context is available, but only override it if there is a new file.
	file = file.substring(0, file.lastIndexOf('/'))
		+ '/' + spec.substring(start, limit);
      }

    u.set(u.getProtocol(), host, port, file, u.getRef());
  }
  
  private static String canonicalizeFilename(String file)
  {
    int index;

    // Replace "/./" with "/".  This probably isn't very efficient in
    // the general case, but it's probably not bad most of the time.
    while ((index = file.indexOf("/./")) >= 0)
      file = file.substring(0, index) + file.substring(index + 2);

    // Process "/../" correctly.  This probably isn't very efficient in
    // the general case, but it's probably not bad most of the time.
    while ((index = file.indexOf("/../")) >= 0)
      {
	// Strip of the previous directory - if it exists.
	int previous = file.lastIndexOf('/', index - 1);
	if (previous >= 0)
	  file = file.substring(0, previous) + file.substring(index + 3);
	else
	  break;
      }
    return file; 
  }

  public boolean sameFile(URL url1, URL url2)
  {
    if (url1 == url2)
      return true;
    // This comparison is very conservative.  It assumes that any
    // field can be null.
    if (url1 == null || url2 == null || url1.getPort() != url2.getPort())
      return false;
    String s1, s2;
    s1 = url1.getProtocol();
    s2 = url2.getProtocol();
    if (s1 != s2 && (s1 == null || ! s1.equals(s2)))
      return false;
    s1 = url1.getHost();
    s2 = url2.getHost();
    if (s1 != s2 && (s1 == null || ! s1.equals(s2)))
      return false;
    s1 = canonicalizeFilename(url1.getFile());
    s2 = canonicalizeFilename(url2.getFile());
    if (s1 != s2 && (s1 == null || ! s1.equals(s2)))
      return false;
    return true;
  }

  protected void setURL(URL u, String protocol, String host, int port,
			String file, String ref)
  {
    u.set(protocol, host, port, file, ref);
  }

  protected String toExternalForm(URL u)
  {
    String resStr, host, file, ref;
    int port;

    resStr = u.getProtocol() + ":";
    host = u.getHost();
    port = u.getPort();
    file = u.getFile();
    ref = u.getRef();

    // JDK 1.2 online doc infers that host could be null because it
    // explicitly states that file cannot be null, but is silent on host.
    //
    // Note that this produces different results from JDK 1.2 as JDK 1.2
    // ignores a non-default port if host is null or "".  That is inconsistent
    // with the spec since the result of this method is spec'ed so it can be
    // used to construct a new URL that is equivalent to the original.
    if (host == null)
      host = "";
    if (port >= 0 || ! (host.length() == 0))
      resStr = resStr + "//" + host + (port < 0 ? "" : ":" + port);

    resStr = resStr + file;

    if (ref != null)
      resStr = resStr + "#" + ref;

    return resStr;
  }
}