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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}s.  For more information on service
 * provider interfaces, see the class comment for the
 * {@code IIORegistry} class.
 *
 * <p> This interface allows arbitrary objects to be "wrapped" by
 * instances of {@code ImageInputStream}.  For example,
 * a particular {@code ImageInputStreamSpi} might allow
 * a generic {@code InputStream} to be used as an input source;
 * another might take input from a {@code URL}.
 *
 * <p> By treating the creation of {@code ImageInputStream}s as a
 * pluggable service, it becomes possible to handle future input
 * sources without changing the API.  Also, high-performance
 * implementations of {@code ImageInputStream} (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} object indicating the legal object type
     * for use by the {@code createInputStreamInstance} 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}.  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} with a given set
     * of values.
     *
     * @param vendorName the vendor name.
     * @param version a version identifier.
     * @param inputClass a {@code Class} object indicating the
     * legal object type for use by the
     * {@code createInputStreamInstance} method.
     *
     * @exception IllegalArgumentException if {@code vendorName}
     * is {@code null}.
     * @exception IllegalArgumentException if {@code version}
     * is {@code null}.
     */
    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} object representing the class or
     * interface type that must be implemented by an input source in
     * order to be "wrapped" in an {@code ImageInputStream} via
     * the {@code createInputStreamInstance} method.
     *
     * <p> Typical return values might include
     * {@code InputStream.class} or {@code URL.class}, but
     * any class may be used.
     *
     * @return a {@code Class} 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} if the {@code ImageInputStream}
     * implementation associated with this service provider can
     * optionally make use of a cache file for improved performance
     * and/or memory footrprint.  If {@code false}, the value of
     * the {@code useCache} argument to
     * {@code createInputStreamInstance} will be ignored.
     *
     * <p> The default implementation returns {@code false}.
     *
     * @return {@code true} 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} if the {@code ImageInputStream}
     * implementation associated with this service provider requires
     * the use of a cache {@code File}.  If {@code true},
     * the value of the {@code useCache} argument to
     * {@code createInputStreamInstance} will be ignored.
     *
     * <p> The default implementation returns {@code false}.
     *
     * @return {@code true} 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}
     * implementation associated with this service provider.  If the
     * use of a cache file is optional, the {@code useCache}
     * parameter will be consulted.  Where a cache is required, or
     * not applicable, the value of {@code useCache} will be ignored.
     *
     * @param input an object of the class type returned by
     * {@code getInputClass}.
     * @param useCache a {@code boolean} indicating whether a
     * cache file should be used, in cases where it is optional.
     * @param cacheDir a {@code File} indicating where the
     * cache file should be created, or {@code null} to use the
     * system directory.
     *
     * @return an {@code ImageInputStream} instance.
     *
     * @exception IllegalArgumentException if {@code input} is
     * not an instance of the correct class or is {@code null}.
     * @exception IllegalArgumentException if a cache file is needed
     * but {@code cacheDir} is non-{@code null} 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}
     * 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}.
     *
     * @return an {@code ImageInputStream} instance.
     *
     * @exception IllegalArgumentException if {@code input} is
     * not an instance of the correct class or is {@code null}.
     * @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);
    }
}