001/* ImageInputStreamSpi.java -- Service provider for image input streams.
002   Copyright (C) 2004, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.imageio.spi;
040
041import java.io.File;
042import java.io.IOException;
043
044import javax.imageio.stream.ImageInputStream;
045
046/**
047 * An abstract superclass for service providers that create
048 * {@linkplain javax.imageio.stream.ImageInputStream image input
049 * streams} for a file, URL, byte array or any other source.
050 *
051 * @since 1.4
052 *
053 * @author Sascha Brawer (brawer@dandelis.ch)
054 */
055public abstract class ImageInputStreamSpi
056  extends IIOServiceProvider
057{
058  /**
059   * Indicates which kind of input is processable by the streams
060   * created by {@link #createInputStreamInstance(Object)}.
061   */
062  protected Class<?> inputClass;
063
064
065  /**
066   * Constructs a service provider for image input streams, given no
067   * parameters. It is up to the sub-class to set {@link #vendorName},
068   * {@link #version} and {@link #inputClass} to non-null values.
069   */
070  protected ImageInputStreamSpi()
071  {
072  }
073
074
075  /**
076   * Constructs a service provider for image input streams, given the
077   * vendor name and a version string.
078   *
079   * @throws IllegalArgumentException if <code>vendorName</code>
080   * or <code>version</code> is <code>null</code>.
081   */
082  public ImageInputStreamSpi(String vendorName, String version,
083                             Class<?> inputClass)
084  {
085    super(vendorName, version);
086    this.inputClass = inputClass;
087  }
088
089
090  /**
091   * Determines which kind of input is processable by the streams
092   * created by {@link #createInputStreamInstance(Object)}.
093   */
094  public Class<?> getInputClass()
095  {
096    return inputClass;
097  }
098
099
100  /**
101   * Determines whether <code>ImageInputStreams</code> created
102   * by this service provider benefit from using a cache file.
103   *
104   * <p>The default behavior is to return <code>false</code>.
105   *
106   * @return <code>true</code> if the created streams are faster or
107   * need less memory when a cache file is being used;
108   * <code>false</code> if no positive effect results from the cache
109   * file.
110   */
111  public boolean canUseCacheFile()
112  {
113    return false;
114  }
115
116
117  /**
118   * Determines whether <code>ImageInputStreams</code> created
119   * by this service provider require the use of a cache file.
120   *
121   * <p>The default behavior is to return <code>false</code>.
122   *
123   * @return <code>true</code> if the created streams can only work
124   * when a cache file is being used; <code>false</code> if no cache
125   * file is needed.
126   */
127  public boolean needsCacheFile()
128  {
129    return false;
130  }
131
132
133  public abstract ImageInputStream createInputStreamInstance(Object input,
134                                                             boolean useCache,
135                                                             File cacheDir)
136    throws IOException;
137
138
139  public ImageInputStream createInputStreamInstance(Object input)
140    throws IOException
141  {
142    return createInputStreamInstance(input, canUseCacheFile(), null);
143  }
144}