poi/src/java/org/apache/poi/hpsf/Property.java

/* ====================================================================
   Copyright 2002-2004   Apache Software Foundation

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================== */
        
package org.apache.poi.hpsf;

import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Map;

import org.apache.poi.util.HexDump;
import org.apache.poi.util.LittleEndian;

/**
 * <p>A property in a {@link Section} of a {@link PropertySet}.</p>
 *
 * <p>The property's <strong>ID</strong> gives the property a meaning
 * in the context of its {@link Section}. Each {@link Section} spans
 * its own name space of property IDs.</p>
 *
 * <p>The property's <strong>type</strong> determines how its
 * <strong>value </strong> is interpreted. For example, if the type is
 * {@link Variant#VT_LPSTR} (byte string), the value consists of a
 * DWord telling how many bytes the string contains. The bytes follow
 * immediately, including any null bytes that terminate the
 * string. The type {@link Variant#VT_I4} denotes a four-byte integer
 * value, {@link Variant#VT_FILETIME} some date and time (of a
 * file).</p>
 *
 * <p>Please note that not all {@link Variant} types yet. This might change
 * over time but largely depends on your feedback so that the POI team knows
 * which variant types are really needed. So please feel free to submit error
 * reports or patches for the types you need.</p>
 *
 * @author Rainer Klute <a
 * href="mailto:klute@rainer-klute.de">&lt;klute@rainer-klute.de&gt;</a>
 * @author Drew Varner (Drew.Varner InAndAround sc.edu)
 * @see Section
 * @see Variant
 * @version $Id$
 * @since 2002-02-09
 */
public class Property
{

    /** <p>Codepage 1200 denotes Unicode.</p> */
    public static final int CP_UNICODE = 1200;

    /** <p>The property's ID.</p> */
    protected long id;


    /**
     * <p>Returns the property's ID.</p>
     *
     * @return The ID value
     */
    public long getID()
    {
        return id;
    }



    /** <p>The property's type.</p> */
    protected long type;


    /**
     * <p>Returns the property's type.</p>
     *
     * @return The type value
     */
    public long getType()
    {
        return type;
    }



    /** <p>The property's value.</p> */
    protected Object value;


    /**
     * <p>Returns the property's value.</p>
     *
     * @return The property's value
     */
    public Object getValue()
    {
        return value;
    }



    /**
     * <p>Creates a {@link Property} instance by reading its bytes
     * from the property set stream.</p>
     *
     * @param id The property's ID.
     * @param src The bytes the property set stream consists of.
     * @param offset The property's type/value pair's offset in the
     * section.
     * @param length The property's type/value pair's length in bytes.
     * @param codepage The section's and thus the property's
     * codepage. It is needed only when reading string values.
     * 
     * @exception UnsupportedEncodingException if the specified codepage is not
     * supported
     */
    public Property(final long id, final byte[] src, final long offset,
                    final int length, final int codepage)
    throws UnsupportedEncodingException
    {
        this.id = id;

        /*
         * ID 0 is a special case since it specifies a dictionary of
         * property IDs and property names.
         */
        if (id == 0)
        {
            value = readDictionary(src, offset, length, codepage);
            return;
        }

        int o = (int) offset;
        type = LittleEndian.getUInt(src, o);
        o += LittleEndian.INT_SIZE;

        try
        {
            value = VariantSupport.read(src, o, length, (int) type, codepage);
        }
        catch (UnsupportedVariantTypeException ex)
        {
            VariantSupport.writeUnsupportedTypeMessage(ex);
            value = ex.getValue();
        }
    }



    /**
     * <p>Creates an empty property. It must be filled using the set method to
     * be usable.</p>
     */
    protected Property()
    { }



    /**
     * <p>Reads a dictionary.</p>
     *
     * @param src The byte array containing the bytes making out the
     * dictionary.
     * @param offset At this offset within <var>src</var> the
     * dictionary starts.
     * @param length The dictionary contains at most this many bytes.
     * @param codepage The codepage of the string values.
     * @return The dictonary
     */
    protected Map readDictionary(final byte[] src, final long offset,
                                 final int length, final int codepage)
    {
        /* Check whether "offset" points into the "src" array". */
        if (offset < 0 || offset > src.length)
            throw new HPSFRuntimeException
                ("Illegal offset " + offset + " while HPSF stream contains " +
                 length + " bytes.");
        int o = (int) offset;

        /*
         * Read the number of dictionary entries.
         */
        final long nrEntries = LittleEndian.getUInt(src, o);
        o += LittleEndian.INT_SIZE;

        final Map m = new HashMap((int) nrEntries, (float) 1.0);
        for (int i = 0; i < nrEntries; i++)
        {
            /* The key. */
            final Long id = new Long(LittleEndian.getUInt(src, o));
            o += LittleEndian.INT_SIZE;

            /* The value (a string). The length is the either the
             * number of characters if the character set is Unicode or
             * else the number of bytes. The length includes
             * terminating 0x00 bytes which we have to strip off to
             * create a Java string. */
            long sLength = LittleEndian.getUInt(src, o);
            o += LittleEndian.INT_SIZE;

            /* Read the bytes or characters depending on whether the
             * character set is Unicode or not. */
            StringBuffer b = new StringBuffer((int) sLength);
            for (int j = 0; j < sLength; j++)
                if (codepage == CP_UNICODE)
                {
                    final int i1 = o + (j * 2);
                    final int i2 = i1 + 1;
                    b.append((char) ((src[i2] << 8) + src[i1]));
                }
                else
                    b.append((char) src[o + j]);

            /* Strip 0x00 characters from the end of the string: */
            while (b.length() > 0 && b.charAt(b.length() - 1) == 0x00)
                b.setLength(b.length() - 1);
            if (codepage == CP_UNICODE)
            {
                if (sLength % 2 == 1)
                    sLength++;
                o += (sLength + sLength);
            }
            else
                o += sLength;
            m.put(id, b.toString());
        }
        return m;
    }



    /**
     * <p>Returns the property's size in bytes. This is always a multiple of
     * 4.</p>
     *
     * @return the property's size in bytes
     * 
     * @exception WritingNotSupportedException if HPSF does not yet support the
     * property's variant type.
     */
    protected int getSize() throws WritingNotSupportedException
    {
        int length = VariantSupport.getVariantLength(type);
        if (length >= 0)
            return length; /* Fixed length */
        if (length == -2)
            /* Unknown length */
            throw new WritingNotSupportedException(type, null);

        /* Variable length: */
        final int PADDING = 4; /* Pad to multiples of 4. */
        switch ((int) type)
        {
            case Variant.VT_LPSTR:
            {
                int l = ((String) value).length() + 1;
                int r = l % PADDING;
                if (r > 0)
                    l += PADDING - r;
                length += l;
                break;
            }
            case Variant.VT_EMPTY:
                break;
            default:
                throw new WritingNotSupportedException(type, value);
        }
        return length;
    }



    /**
     * <p>Compares two properties. Please beware that a property with ID == 0 is
     * a special case: It does not have a type, and its value is the section's
     * dictionary.</p>
     * 
     * @see Object#equals(java.lang.Object)
     */
    public boolean equals(final Object o)
    {
        if (!(o instanceof Property))
            return false;
        final Property p = (Property) o;
        final Object pValue = p.getValue();
        final long pId = p.getID();
        if (id != pId || (id != 0 && type != p.getType()))
            return false;
        if (value == null && pValue == null)
            return true;
        if (value == null || pValue == null)
            return false;

        /* It's clear now that both values are non-null. */
        final Class valueClass = value.getClass();
        final Class pValueClass = pValue.getClass();
        if (!(valueClass.isAssignableFrom(pValueClass)) &&
            !(pValueClass.isAssignableFrom(valueClass)))
            return false;

        if (value instanceof byte[])
            return Util.equal((byte[]) value, (byte[]) pValue);

        return value.equals(pValue);
    }



    /**
     * @see Object#hashCode()
     */
    public int hashCode()
    {
        long hashCode = 0;
        hashCode += id;
        hashCode += type;
        if (value != null)
            hashCode += value.hashCode();
        final int returnHashCode = (int) (hashCode & 0x0ffffffffL );
        return returnHashCode;

    }



    /**
     * @see Object#toString()
     */
    public String toString()
    {
        final StringBuffer b = new StringBuffer();
        b.append(getClass().getName());
        b.append('[');
        b.append("id: ");
        b.append(getID());
        b.append(", type: ");
        b.append(getType());
        final Object value = getValue();
        b.append(", value: ");
        b.append(value.toString());
        if (value instanceof String)
        {
            final String s = (String) value;
            final int l = s.length();
            final byte[] bytes = new byte[l * 2];
            for (int i = 0; i < l; i++)
            {
                final char c = s.charAt(i);
                final byte high = (byte) ((c & 0x00ff00) >> 8);
                final byte low  = (byte) ((c & 0x0000ff) >> 0);
                bytes[i * 2]     = high;
                bytes[i * 2 + 1] = low;
            }
            final String hex = HexDump.dump(bytes, 0L, 0);
            b.append(" [");
            b.append(hex);
            b.append("]");
        }
        b.append(']');
        return b.toString();
    }

}