libjava/javax/imageio/spi/ImageInputStreamSpi.java

   1 /* ImageInputStreamSpi.java -- Service provider for image input streams.
   2    Copyright (C) 2004, 2005  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package javax.imageio.spi;
  40
  41 import java.io.File;
  42 import java.io.IOException;
  43
  44 import javax.imageio.stream.ImageInputStream;
  45
  46 /**
  47  * An abstract superclass for service providers that create
  48  * {@linkplain javax.imageio.stream.ImageInputStream image input
  49  * streams} for a file, URL, byte array or any other source.
  50  *
  51  * @since 1.4
  52  *
  53  * @author Sascha Brawer (brawer@dandelis.ch)
  54  */
  55 public abstract class ImageInputStreamSpi
  56   extends IIOServiceProvider
  57 {
  58   /**
  59    * Indicates which kind of input is processable by the streams
  60    * created by {@link #createInputStreamInstance(Object)}.
  61    */
  62   protected Class inputClass;
  63
  64
  65   /**
  66    * Constructs a service provider for image input streams, given no
  67    * parameters. It is up to the sub-class to set {@link #vendorName},
  68    * {@link #version} and {@link #inputClass} to non-null values.
  69    */
  70   protected ImageInputStreamSpi()
  71   {
  72   }
  73
  74
  75   /**
  76    * Constructs a service provider for image input streams, given the
  77    * vendor name and a version string.
  78    *
  79    * @throws IllegalArgumentException if <code>vendorName</code>
  80    * or <code>version</code> is <code>null</code>.
  81    */
  82   public ImageInputStreamSpi(String vendorName, String version,
  83                              Class inputClass)
  84   {
  85     super(vendorName, version);
  86     this.inputClass = inputClass;
  87   }
  88
  89
  90   /**
  91    * Determines which kind of input is processable by the streams
  92    * created by {@link #createInputStreamInstance(Object)}.
  93    */
  94   public Class getInputClass()
  95   {
  96     return inputClass;
  97   }
  98
  99
 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 }