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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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package javax.imageio.spi;

import java.io.File;

import java.io.IOException;

import javax.imageio.stream.ImageInputStream;

/**

 * The service provider interface (SPI) for

 * <code>ImageInputStream</code>s.  For more information on service

 * provider interfaces, see the class comment for the

 * <code>IIORegistry</code> class.

 *

 * <p> This interface allows arbitrary objects to be "wrapped" by

 * instances of <code>ImageInputStream</code>.  For example,

 * a particular <code>ImageInputStreamSpi</code> might allow

 * a generic <code>InputStream</code> to be used as an input source;

 * another might take input from a <code>URL</code>.

 *

 * <p> By treating the creation of <code>ImageInputStream</code>s as a

 * pluggable service, it becomes possible to handle future input

 * sources without changing the API.  Also, high-performance

 * implementations of <code>ImageInputStream</code> (for example,

 * native implementations for a particular platform) can be installed

 * and used transparently by applications.

 *

 * @see IIORegistry

 * @see javax.imageio.stream.ImageInputStream

 *

 */

public abstract class ImageInputStreamSpi extends IIOServiceProvider {

    /**

     * A <code>Class</code> object indicating the legal object type

     * for use by the <code>createInputStreamInstance</code> method.

     */

    protected Class<?> inputClass;

    /**

     * Constructs a blank <code>ImageInputStreamSpi</code>.  It is up

     * to the subclass to initialize instance variables and/or

     * override method implementations in order to provide working

     * versions of all methods.

     */

    protected ImageInputStreamSpi() {

    }

    /**

     * Constructs an <code>ImageInputStreamSpi</code> with a given set

     * of values.

     *

     * @param vendorName the vendor name.

     * @param version a version identifier.

     * @param inputClass a <code>Class</code> object indicating the

     * legal object type for use by the

     * <code>createInputStreamInstance</code> method.

     *

     * @exception IllegalArgumentException if <code>vendorName</code>

     * is <code>null</code>.

     * @exception IllegalArgumentException if <code>version</code>

     * is <code>null</code>.

     */

    public ImageInputStreamSpi(String vendorName,

                               String version,

                               Class<?> inputClass) {

        super(vendorName, version);

        this.inputClass = inputClass;

    }

    /**

     * Returns a <code>Class</code> object representing the class or

     * interface type that must be implemented by an input source in

     * order to be "wrapped" in an <code>ImageInputStream</code> via

     * the <code>createInputStreamInstance</code> method.

     *

     * <p> Typical return values might include

     * <code>InputStream.class</code> or <code>URL.class</code>, but

     * any class may be used.

     *

     * @return a <code>Class</code> variable.

     *

     * @see #createInputStreamInstance(Object, boolean, File)

     */

    public Class<?> getInputClass() {

        return inputClass;

    }

    /**

     * Returns <code>true</code> if the <code>ImageInputStream</code>

     * implementation associated with this service provider can

     * optionally make use of a cache file for improved performance

     * and/or memory footrprint.  If <code>false</code>, the value of

     * the <code>useCache</code> argument to

     * <code>createInputStreamInstance</code> will be ignored.

     *

     * <p> The default implementation returns <code>false</code>.

     *

     * @return <code>true</code> if a cache file can be used by the

     * input streams created by this service provider.

     */

    public boolean canUseCacheFile() {

        return false;

    }

    /**

     * Returns <code>true</code> if the <code>ImageInputStream</code>

     * implementation associated with this service provider requires

     * the use of a cache <code>File</code>.  If <code>true</code>,

     * the value of the <code>useCache</code> argument to

     * <code>createInputStreamInstance</code> will be ignored.

     *

     * <p> The default implementation returns <code>false</code>.

     *

     * @return <code>true</code> if a cache file is needed by the

     * input streams created by this service provider.

     */

    public boolean needsCacheFile() {

        return false;

    }

    /**

     * Returns an instance of the <code>ImageInputStream</code>

     * implementation associated with this service provider.  If the

     * use of a cache file is optional, the <code>useCache</code>

     * parameter will be consulted.  Where a cache is required, or

     * not applicable, the value of <code>useCache</code> will be ignored.

     *

     * @param input an object of the class type returned by

     * <code>getInputClass</code>.

     * @param useCache a <code>boolean</code> indicating whether a

     * cache file should be used, in cases where it is optional.

     * @param cacheDir a <code>File</code> indicating where the

     * cache file should be created, or <code>null</code> to use the

     * system directory.

     *

     * @return an <code>ImageInputStream</code> instance.

     *

     * @exception IllegalArgumentException if <code>input</code> is

     * not an instance of the correct class or is <code>null</code>.

     * @exception IllegalArgumentException if a cache file is needed

     * but <code>cacheDir</code> is non-<code>null</code> and is not a

     * directory.

     * @exception IOException if a cache file is needed but cannot be

     * created.

     *

     * @see #getInputClass

     * @see #canUseCacheFile

     * @see #needsCacheFile

     */

    public abstract ImageInputStream

        createInputStreamInstance(Object input,

                                  boolean useCache,

                                  File cacheDir) throws IOException;

    /**

     * Returns an instance of the <code>ImageInputStream</code>

     * implementation associated with this service provider.  A cache

     * file will be created in the system-dependent default

     * temporary-file directory, if needed.

     *

     * @param input an object of the class type returned by

     * <code>getInputClass</code>.

     *

     * @return an <code>ImageInputStream</code> instance.

     *

     * @exception IllegalArgumentException if <code>input</code> is

     * not an instance of the correct class or is <code>null</code>.

     * @exception IOException if a cache file is needed but cannot be

     * created.

     *

     * @see #getInputClass()

     */

    public ImageInputStream createInputStreamInstance(Object input)

        throws IOException {

        return createInputStreamInstance(input, true, null);

    }

}