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

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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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package javax.imageio.metadata;

import org.w3c.dom.Node;

import java.lang.reflect.Method;

import java.security.AccessController;

import java.security.PrivilegedAction;

/**

 * An abstract class to be extended by objects that represent metadata

 * (non-image data) associated with images and streams.  Plug-ins

 * represent metadata using opaque, plug-in specific objects.  These

 * objects, however, provide the ability to access their internal

 * information as a tree of {@code IIOMetadataNode} objects that

 * support the XML DOM interfaces as well as additional interfaces for

 * storing non-textual data and retrieving information about legal

 * data values.  The format of such trees is plug-in dependent, but

 * plug-ins may choose to support a plug-in neutral format described

 * below.  A single plug-in may support multiple metadata formats,

 * whose names maybe determined by calling

 * {@code getMetadataFormatNames}.  The plug-in may also support

 * a single special format, referred to as the "native" format, which

 * is designed to encode its metadata losslessly.  This format will

 * typically be designed specifically to work with a specific file

 * format, so that images may be loaded and saved in the same format

 * with no loss of metadata, but may be less useful for transferring

 * metadata between an {@code ImageReader} and an

 * {@code ImageWriter} for different image formats.  To convert

 * between two native formats as losslessly as the image file formats

 * will allow, an {@code ImageTranscoder} object must be used.

 *

 * @see javax.imageio.ImageReader#getImageMetadata

 * @see javax.imageio.ImageReader#getStreamMetadata

 * @see javax.imageio.ImageReader#readAll

 * @see javax.imageio.ImageWriter#getDefaultStreamMetadata

 * @see javax.imageio.ImageWriter#getDefaultImageMetadata

 * @see javax.imageio.ImageWriter#write

 * @see javax.imageio.ImageWriter#convertImageMetadata

 * @see javax.imageio.ImageWriter#convertStreamMetadata

 * @see javax.imageio.IIOImage

 * @see javax.imageio.ImageTranscoder

 *

 */

public abstract class IIOMetadata {

    /**

     * A boolean indicating whether the concrete subclass supports the

     * standard metadata format, set via the constructor.

     */

    protected boolean standardFormatSupported;

    /**

     * The name of the native metadata format for this object,

     * initialized to {@code null} and set via the constructor.

     */

    protected String nativeMetadataFormatName = null;

    /**

     * The name of the class implementing {@code IIOMetadataFormat}

     * and representing the native metadata format, initialized to

     * {@code null} and set via the constructor.

     */

    protected String nativeMetadataFormatClassName = null;

    /**

     * An array of names of formats, other than the standard and

     * native formats, that are supported by this plug-in,

     * initialized to {@code null} and set via the constructor.

     */

    protected String[] extraMetadataFormatNames = null;

    /**

     * An array of names of classes implementing {@code IIOMetadataFormat}

     * and representing the metadata formats, other than the standard and

     * native formats, that are supported by this plug-in,

     * initialized to {@code null} and set via the constructor.

     */

    protected String[] extraMetadataFormatClassNames = null;

    /**

     * An {@code IIOMetadataController} that is suggested for use

     * as the controller for this {@code IIOMetadata} object.  It

     * may be retrieved via {@code getDefaultController}.  To

     * install the default controller, call

     * {@code setController(getDefaultController())}.  This

     * instance variable should be set by subclasses that choose to

     * provide their own default controller, usually a GUI, for

     * setting parameters.

     *

     * @see IIOMetadataController

     * @see #getDefaultController

     */

    protected IIOMetadataController defaultController = null;

    /**

     * The {@code IIOMetadataController} that will be

     * used to provide settings for this {@code IIOMetadata}

     * object when the {@code activateController} method

     * is called.  This value overrides any default controller,

     * even when {@code null}.

     *

     * @see IIOMetadataController

     * @see #setController(IIOMetadataController)

     * @see #hasController()

     * @see #activateController()

     */

    protected IIOMetadataController controller = null;

    /**

     * Constructs an empty {@code IIOMetadata} object.  The

     * subclass is responsible for supplying values for all protected

     * instance variables that will allow any non-overridden default

     * implementations of methods to satisfy their contracts.  For example,

     * {@code extraMetadataFormatNames} should not have length 0.

     */

    protected IIOMetadata() {}

    /**

     * Constructs an {@code IIOMetadata} object with the given

     * format names and format class names, as well as a boolean

     * indicating whether the standard format is supported.

     *

     * <p> This constructor does not attempt to check the class names

     * for validity.  Invalid class names may cause exceptions in

     * subsequent calls to {@code getMetadataFormat}.

     *

     * @param standardMetadataFormatSupported {@code true} if

     * this object can return or accept a DOM tree using the standard

     * metadata format.

     * @param nativeMetadataFormatName the name of the native metadata

     * format, as a {@code String}, or {@code null} if there

     * is no native format.

     * @param nativeMetadataFormatClassName the name of the class of

     * the native metadata format, or {@code null} if there is

     * no native format.

     * @param extraMetadataFormatNames an array of {@code String}s

     * indicating additional formats supported by this object, or

     * {@code null} if there are none.

     * @param extraMetadataFormatClassNames an array of {@code String}s

     * indicating the class names of any additional formats supported by

     * this object, or {@code null} if there are none.

     *

     * @exception IllegalArgumentException if

     * {@code extraMetadataFormatNames} has length 0.

     * @exception IllegalArgumentException if

     * {@code extraMetadataFormatNames} and

     * {@code extraMetadataFormatClassNames} are neither both

     * {@code null}, nor of the same length.

     */

    protected IIOMetadata(boolean standardMetadataFormatSupported,

                          String nativeMetadataFormatName,

                          String nativeMetadataFormatClassName,

                          String[] extraMetadataFormatNames,

                          String[] extraMetadataFormatClassNames) {

        this.standardFormatSupported = standardMetadataFormatSupported;

        this.nativeMetadataFormatName = nativeMetadataFormatName;

        this.nativeMetadataFormatClassName = nativeMetadataFormatClassName;

        if (extraMetadataFormatNames != null) {

            if (extraMetadataFormatNames.length == 0) {

                throw new IllegalArgumentException

                    ("extraMetadataFormatNames.length == 0!");

            }

            if (extraMetadataFormatClassNames == null) {

                throw new IllegalArgumentException

                    ("extraMetadataFormatNames != null && extraMetadataFormatClassNames == null!");

            }

            if (extraMetadataFormatClassNames.length !=

                extraMetadataFormatNames.length) {

                throw new IllegalArgumentException

                    ("extraMetadataFormatClassNames.length != extraMetadataFormatNames.length!");

            }

            this.extraMetadataFormatNames = extraMetadataFormatNames.clone();

            this.extraMetadataFormatClassNames = extraMetadataFormatClassNames.clone();

        } else {

            if (extraMetadataFormatClassNames != null) {

                throw new IllegalArgumentException

                    ("extraMetadataFormatNames == null && extraMetadataFormatClassNames != null!");

            }

        }

    }

    /**

     * Returns {@code true} if the standard metadata format is

     * supported by {@code getMetadataFormat},

     * {@code getAsTree}, {@code setFromTree}, and

     * {@code mergeTree}.

     *

     * <p> The default implementation returns the value of the

     * {@code standardFormatSupported} instance variable.

     *

     * @return {@code true} if the standard metadata format

     * is supported.

     *

     * @see #getAsTree

     * @see #setFromTree

     * @see #mergeTree

     * @see #getMetadataFormat

     */

    public boolean isStandardMetadataFormatSupported() {

        return standardFormatSupported;

    }

    /**

     * Returns {@code true} if this object does not support the

     * {@code mergeTree}, {@code setFromTree}, and

     * {@code reset} methods.

     *

     * @return true if this {@code IIOMetadata} object cannot be

     * modified.

     */

    public abstract boolean isReadOnly();

    /**

     * Returns the name of the "native" metadata format for this

     * plug-in, which typically allows for lossless encoding and

     * transmission of the metadata stored in the format handled by

     * this plug-in.  If no such format is supported,

     * {@code null} will be returned.

     *

     * <p> The structure and contents of the "native" metadata format

     * are defined by the plug-in that created this

     * {@code IIOMetadata} object.  Plug-ins for simple formats

     * will usually create a dummy node for the root, and then a

     * series of child nodes representing individual tags, chunks, or

     * keyword/value pairs.  A plug-in may choose whether or not to

     * document its native format.

     *

     * <p> The default implementation returns the value of the

     * {@code nativeMetadataFormatName} instance variable.

     *

     * @return the name of the native format, or {@code null}.

     *

     * @see #getExtraMetadataFormatNames

     * @see #getMetadataFormatNames

     */

    public String getNativeMetadataFormatName() {

        return nativeMetadataFormatName;

    }

    /**

     * Returns an array of {@code String}s containing the names

     * of additional metadata formats, other than the native and standard

     * formats, recognized by this plug-in's

     * {@code getAsTree}, {@code setFromTree}, and

     * {@code mergeTree} methods.  If there are no such additional

     * formats, {@code null} is returned.

     *

     * <p> The default implementation returns a clone of the

     * {@code extraMetadataFormatNames} instance variable.

     *

     * @return an array of {@code String}s with length at least

     * 1, or {@code null}.

     *

     * @see #getAsTree

     * @see #setFromTree

     * @see #mergeTree

     * @see #getNativeMetadataFormatName

     * @see #getMetadataFormatNames

     */

    public String[] getExtraMetadataFormatNames() {

        if (extraMetadataFormatNames == null) {

            return null;

        }

        return extraMetadataFormatNames.clone();

    }

    /**

     * Returns an array of {@code String}s containing the names

     * of all metadata formats, including the native and standard

     * formats, recognized by this plug-in's {@code getAsTree},

     * {@code setFromTree}, and {@code mergeTree} methods.

     * If there are no such formats, {@code null} is returned.

     *

     * <p> The default implementation calls

     * {@code getNativeMetadataFormatName},

     * {@code isStandardMetadataFormatSupported}, and

     * {@code getExtraMetadataFormatNames} and returns the

     * combined results.

     *

     * @return an array of {@code String}s.

     *

     * @see #getNativeMetadataFormatName

     * @see #isStandardMetadataFormatSupported

     * @see #getExtraMetadataFormatNames

     */

    public String[] getMetadataFormatNames() {

        String nativeName = getNativeMetadataFormatName();

        String standardName = isStandardMetadataFormatSupported() ?

            IIOMetadataFormatImpl.standardMetadataFormatName : null;

        String[] extraNames = getExtraMetadataFormatNames();

        int numFormats = 0;

        if (nativeName != null) {

            ++numFormats;

        }

        if (standardName != null) {

            ++numFormats;

        }

        if (extraNames != null) {

            numFormats += extraNames.length;

        }

        if (numFormats == 0) {

            return null;

        }

        String[] formats = new String[numFormats];

        int index = 0;

        if (nativeName != null) {

            formats[index++] = nativeName;

        }

        if (standardName != null) {

            formats[index++] = standardName;

        }

        if (extraNames != null) {

            for (int i = 0; i < extraNames.length; i++) {

                formats[index++] = extraNames[i];

            }

        }

        return formats;

    }

    /**

     * Returns an {@code IIOMetadataFormat} object describing the

     * given metadata format, or {@code null} if no description

     * is available.  The supplied name must be one of those returned

     * by {@code getMetadataFormatNames} (<i>i.e.</i>, either the

     * native format name, the standard format name, or one of those

     * returned by {@code getExtraMetadataFormatNames}).

     *

     * <p> The default implementation checks the name against the

     * global standard metadata format name, and returns that format

     * if it is supported.  Otherwise, it checks against the native

     * format names followed by any additional format names.  If a

     * match is found, it retrieves the name of the

     * {@code IIOMetadataFormat} class from

     * {@code nativeMetadataFormatClassName} or

     * {@code extraMetadataFormatClassNames} as appropriate, and

     * constructs an instance of that class using its

     * {@code getInstance} method.

     *

     * @param formatName the desired metadata format.

     *

     * @return an {@code IIOMetadataFormat} object.

     *

     * @exception IllegalArgumentException if {@code formatName}

     * is {@code null} or is not one of the names recognized by

     * the plug-in.

     * @exception IllegalStateException if the class corresponding to

     * the format name cannot be loaded.

     */

    public IIOMetadataFormat getMetadataFormat(String formatName) {

        if (formatName == null) {

            throw new IllegalArgumentException("formatName == null!");

        }

        if (standardFormatSupported

            && formatName.equals

                (IIOMetadataFormatImpl.standardMetadataFormatName)) {

            return IIOMetadataFormatImpl.getStandardFormatInstance();

        }

        String formatClassName = null;

        if (formatName.equals(nativeMetadataFormatName)) {

            formatClassName = nativeMetadataFormatClassName;

        } else if (extraMetadataFormatNames != null) {

            for (int i = 0; i < extraMetadataFormatNames.length; i++) {

                if (formatName.equals(extraMetadataFormatNames[i])) {

                    formatClassName = extraMetadataFormatClassNames[i];

                    break;  // out of for

                }

            }

        }

        if (formatClassName == null) {

            throw new IllegalArgumentException("Unsupported format name");

        }

        try {

            final String className = formatClassName;

            // Try to load from the module of the IIOMetadata implementation

            // for this plugin since the IIOMetadataImpl is part of the plugin

            PrivilegedAction<Class<?>> pa = () -> { return getMetadataFormatClass(className); };

            Class<?> cls = AccessController.doPrivileged(pa);

            Method meth = cls.getMethod("getInstance");

            return (IIOMetadataFormat) meth.invoke(null);

        } catch (Exception e) {

            RuntimeException ex =

                new IllegalStateException ("Can't obtain format");

            ex.initCause(e);

            throw ex;

        }

    }

    // If updating this method also see the same in ImageReaderWriterSpi.java

    private Class<?> getMetadataFormatClass(String formatClassName) {

        Module thisModule = IIOMetadata.class.getModule();

        Module targetModule = this.getClass().getModule();

        Class<?> c = null;

        try {

            ClassLoader cl = this.getClass().getClassLoader();

            c = Class.forName(formatClassName, false, cl);

            if (!IIOMetadataFormat.class.isAssignableFrom(c)) {

                return null;

            }

        } catch (ClassNotFoundException e) {

        }

        if (thisModule.equals(targetModule) || c == null) {

            return c;

        }

        if (targetModule.isNamed()) {

            int i = formatClassName.lastIndexOf(".");

            String pn = i > 0 ? formatClassName.substring(0, i) : "";

            if (!targetModule.isExported(pn, thisModule)) {

                throw new IllegalStateException("Class " + formatClassName +

                   " in named module must be exported to java.desktop module.");

            }

        }

        return c;

    }

    /**

     * Returns an XML DOM {@code Node} object that represents the

     * root of a tree of metadata contained within this object

     * according to the conventions defined by a given metadata

     * format.

     *

     * <p> The names of the available metadata formats may be queried

     * using the {@code getMetadataFormatNames} method.

     *

     * @param formatName the desired metadata format.

     *

     * @return an XML DOM {@code Node} object forming the

     * root of a tree.

     *

     * @exception IllegalArgumentException if {@code formatName}

     * is {@code null} or is not one of the names returned by

     * {@code getMetadataFormatNames}.

     *

     * @see #getMetadataFormatNames

     * @see #setFromTree

     * @see #mergeTree

     */

    public abstract Node getAsTree(String formatName);

    /**

     * Alters the internal state of this {@code IIOMetadata}

     * object from a tree of XML DOM {@code Node}s whose syntax

     * is defined by the given metadata format.  The previous state is

     * altered only as necessary to accommodate the nodes that are

     * present in the given tree.  If the tree structure or contents

     * are invalid, an {@code IIOInvalidTreeException} will be

     * thrown.

     *

     * <p> As the semantics of how a tree or subtree may be merged with

     * another tree are completely format-specific, plug-in authors may

     * implement this method in whatever manner is most appropriate for

     * the format, including simply replacing all existing state with the

     * contents of the given tree.

     *

     * @param formatName the desired metadata format.

     * @param root an XML DOM {@code Node} object forming the

     * root of a tree.

     *

     * @exception IllegalStateException if this object is read-only.

     * @exception IllegalArgumentException if {@code formatName}

     * is {@code null} or is not one of the names returned by

     * {@code getMetadataFormatNames}.

     * @exception IllegalArgumentException if {@code root} is

     * {@code null}.

     * @exception IIOInvalidTreeException if the tree cannot be parsed

     * successfully using the rules of the given format.

     *

     * @see #getMetadataFormatNames

     * @see #getAsTree

     * @see #setFromTree

     */

    public abstract void mergeTree(String formatName, Node root)

        throws IIOInvalidTreeException;

    /**

     * Returns an {@code IIOMetadataNode} representing the chroma

     * information of the standard {@code javax_imageio_1.0}

     * metadata format, or {@code null} if no such information is

     * available.  This method is intended to be called by the utility

     * routine {@code getStandardTree}.

     *

     * <p> The default implementation returns {@code null}.