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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
ImageInputStreams.  For more information on service
provider interfaces, see the class comment for the
IIORegistry class.
 This interface allows arbitrary objects to be "wrapped" by
instances of ImageInputStream.  For example,
a particular ImageInputStreamSpi might allow
a generic InputStream to be used as an input source;
another might take input from a URL.
 By treating the creation of ImageInputStreams as a
pluggable service, it becomes possible to handle future input
sources without changing the API.  Also, high-performance
implementations of ImageInputStream (for example,
native implementations for a particular platform) can be installed
and used transparently by applications.
See Also:
IIORegistry
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 Class object indicating the legal object type
for use by the createInputStreamInstance method.
/**
     * A <code>Class</code> object indicating the legal object type
     * for use by the <code>createInputStreamInstance</code> method.
     */
    protected Class<?> inputClass;

    
Constructs a blank ImageInputStreamSpi.  It is up
to the subclass to initialize instance variables and/or
override method implementations in order to provide working
versions of all methods.
/**
     * 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 ImageInputStreamSpi with a given set
of values.
Params:
vendorName – the vendor name.
version – a version identifier.
inputClass – a Class object indicating the
legal object type for use by the
createInputStreamInstance method.
Throws:
IllegalArgumentException – if vendorName
is null.
IllegalArgumentException – if version
is null./**
     * 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 Class object representing the class or
interface type that must be implemented by an input source in
order to be "wrapped" in an ImageInputStream via
the createInputStreamInstance method.
 Typical return values might include
InputStream.class or URL.class, but
any class may be used.
See Also:
createInputStreamInstance(Object, boolean, File)
Returns:
a Class variable./**
     * 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 true if the ImageInputStream
implementation associated with this service provider can
optionally make use of a cache file for improved performance
and/or memory footrprint.  If false, the value of
the useCache argument to
createInputStreamInstance will be ignored.
 The default implementation returns false.
Returns:
true if a cache file can be used by the
input streams created by this service provider./**
     * 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 true if the ImageInputStream
implementation associated with this service provider requires
the use of a cache File.  If true,
the value of the useCache argument to
createInputStreamInstance will be ignored.
 The default implementation returns false.
Returns:
true if a cache file is needed by the
input streams created by this service provider./**
     * 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 ImageInputStream
implementation associated with this service provider.  If the
use of a cache file is optional, the useCache
parameter will be consulted.  Where a cache is required, or
not applicable, the value of useCache will be ignored.
Params:
input – an object of the class type returned by
getInputClass.
useCache – a boolean indicating whether a
cache file should be used, in cases where it is optional.
cacheDir – a File indicating where the
cache file should be created, or null to use the
system directory.
Throws:
IllegalArgumentException – if input is
not an instance of the correct class or is null.
IllegalArgumentException – if a cache file is needed
but cacheDir is non-null and is not a
directory.
IOException – if a cache file is needed but cannot be
created.
See Also:
getInputClass
canUseCacheFile
needsCacheFile
Returns:
an ImageInputStream instance./**
     * 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 ImageInputStream
implementation associated with this service provider.  A cache
file will be created in the system-dependent default
temporary-file directory, if needed.
Params:
input – an object of the class type returned by
getInputClass.
Throws:
IllegalArgumentException – if input is
not an instance of the correct class or is null.
IOException – if a cache file is needed but cannot be
created.
See Also:
getInputClass()
Returns:
an ImageInputStream instance./**
     * 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);
    }
}