variantsupport.java

来自「EXCEL read and write」· Java 代码 · 共 589 行 · 第 1/2 页

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   this work for additional information regarding copyright ownership.
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   (the "License"); you may not use this file except in compliance with
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       http://www.apache.org/licenses/LICENSE-2.0

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   distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.poi.hpsf;

import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.Date;
import java.util.LinkedList;
import java.util.List;

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

/**
 * <p>Supports reading and writing of variant data.</p>
 * 
 * <p><strong>FIXME (3):</strong> Reading and writing should be made more
 * uniform than it is now. The following items should be resolved:
 * 
 * <ul>
 *
 * <li><p>Reading requires a length parameter that is 4 byte greater than the
 * actual data, because the variant type field is included. </p></li>
 *
 * <li><p>Reading reads from a byte array while writing writes to an byte array
 * output stream.</p></li>
 *
 * </ul>
 *
 * @author Rainer Klute <a
 * href="mailto:[e-mail]">&lt;[e-mail]&gt;</a>
 * @since 2003-08-08
 * @version $Id: VariantSupport.java 619848 2008-02-08 11:55:43Z klute $
 */
public class VariantSupport extends Variant
{

    private static boolean logUnsupportedTypes = false;

    /**
     * <p>Specifies whether warnings about unsupported variant types are to be
     * written to <code>System.err</code> or not.</p>
     *
     * @param logUnsupportedTypes If <code>true</code> warnings will be written,
     * if <code>false</code> they won't.
     */
    public static void setLogUnsupportedTypes(final boolean logUnsupportedTypes)
    {
        VariantSupport.logUnsupportedTypes = logUnsupportedTypes;
    }

    /**
     * <p>Checks whether logging of unsupported variant types warning is turned
     * on or off.</p>
     *
     * @return <code>true</code> if logging is turned on, else
     * <code>false</code>. 
     */
    public static boolean isLogUnsupportedTypes()
    {
        return logUnsupportedTypes;
    }



    /**
     * <p>Keeps a list of the variant types an "unsupported" message has already
     * been issued for.</p>
     */
    protected static List unsupportedMessage;

    /**
     * <p>Writes a warning to <code>System.err</code> that a variant type is
     * unsupported by HPSF. Such a warning is written only once for each variant
     * type. Log messages can be turned on or off by </p>
     *
     * @param ex The exception to log
     */
    protected static void writeUnsupportedTypeMessage
        (final UnsupportedVariantTypeException ex)
    {
        if (isLogUnsupportedTypes())
        {
            if (unsupportedMessage == null)
                unsupportedMessage = new LinkedList();
            Long vt = new Long(ex.getVariantType());
            if (!unsupportedMessage.contains(vt))
            {
                System.err.println(ex.getMessage());
                unsupportedMessage.add(vt);
            }
        }
    }


    /**
     * <p>HPSF is able to read these {@link Variant} types.</p>
     */
    final static public int[] SUPPORTED_TYPES = { Variant.VT_EMPTY,
            Variant.VT_I2, Variant.VT_I4, Variant.VT_I8, Variant.VT_R8,
            Variant.VT_FILETIME, Variant.VT_LPSTR, Variant.VT_LPWSTR,
            Variant.VT_CF, Variant.VT_BOOL };



    /**
     * <p>Checks whether HPSF supports the specified variant type. Unsupported
     * types should be implemented included in the {@link #SUPPORTED_TYPES}
     * array.</p>
     * 
     * @see Variant
     * @param variantType the variant type to check
     * @return <code>true</code> if HPFS supports this type, else
     *         <code>false</code>
     */
    public boolean isSupportedType(final int variantType)
    {
        for (int i = 0; i < SUPPORTED_TYPES.length; i++)
            if (variantType == SUPPORTED_TYPES[i])
                return true;
        return false;
    }



    /**
     * <p>Reads a variant type from a byte array.</p>
     * 
     * @param src The byte array
     * @param offset The offset in the byte array where the variant starts
     * @param length The length of the variant including the variant type field
     * @param type The variant type to read
     * @param codepage The codepage to use for non-wide strings
     * @return A Java object that corresponds best to the variant field. For
     *         example, a VT_I4 is returned as a {@link Long}, a VT_LPSTR as a
     *         {@link String}.
     * @exception ReadingNotSupportedException if a property is to be written
     *            who's variant type HPSF does not yet support
     * @exception UnsupportedEncodingException if the specified codepage is not
     *            supported.
     * @see Variant
     */
    public static Object read(final byte[] src, final int offset,
                              final int length, final long type,
                              final int codepage)
    throws ReadingNotSupportedException, UnsupportedEncodingException
    {
        Object value;
        int o1 = offset;
        int l1 = length - LittleEndian.INT_SIZE;
        long lType = type;

        /* Instead of trying to read 8-bit characters from a Unicode string,
         * read 16-bit characters. */
        if (codepage == Constants.CP_UNICODE && type == Variant.VT_LPSTR)
            lType = Variant.VT_LPWSTR;

        switch ((int) lType)
        {
            case Variant.VT_EMPTY:
            {
                value = null;
                break;
            }
            case Variant.VT_I2:
            {
                /*
                 * Read a short. In Java it is represented as an
                 * Integer object.
                 */
                value = new Integer(LittleEndian.getShort(src, o1));
                break;
            }
            case Variant.VT_I4:
            {
                /*
                 * Read a word. In Java it is represented as an
                 * Integer object.
                 */
                value = new Integer(LittleEndian.getInt(src, o1));
                break;
            }
            case Variant.VT_I8:
            {
                /*
                 * Read a double word. In Java it is represented as a
                 * Long object.
                 */
                value = new Long(LittleEndian.getLong(src, o1));
                break;
            }
            case Variant.VT_R8:
            {
                /*
                 * Read an eight-byte double value. In Java it is represented as
                 * a Double object.
                 */
                value = new Double(LittleEndian.getDouble(src, o1));
                break;
            }
            case Variant.VT_FILETIME:
            {
                /*
                 * Read a FILETIME object. In Java it is represented
                 * as a Date object.
                 */
                final long low = LittleEndian.getUInt(src, o1);
                o1 += LittleEndian.INT_SIZE;
                final long high = LittleEndian.getUInt(src, o1);
                value = Util.filetimeToDate((int) high, (int) low);
                break;
            }
            case Variant.VT_LPSTR:
            {
                /*
                 * Read a byte string. In Java it is represented as a
                 * String object. The 0x00 bytes at the end must be
                 * stripped.
                 */
                final int first = o1 + LittleEndian.INT_SIZE;
                long last = first + LittleEndian.getUInt(src, o1) - 1;
                o1 += LittleEndian.INT_SIZE;
                while (src[(int) last] == 0 && first <= last)
                    last--;
                final int l = (int) (last - first + 1);
                value = codepage != -1 ?
                    new String(src, first, l,
                               codepageToEncoding(codepage)) :
                    new String(src, first, l);
                break;
            }
            case Variant.VT_LPWSTR:
            {
                /*
                 * Read a Unicode string. In Java it is represented as
                 * a String object. The 0x00 bytes at the end must be
                 * stripped.
                 */
                final int first = o1 + LittleEndian.INT_SIZE;
                long last = first + LittleEndian.getUInt(src, o1) - 1;
                long l = last - first;
                o1 += LittleEndian.INT_SIZE;
                StringBuffer b = new StringBuffer((int) (last - first));
                for (int i = 0; i <= l; i++)
                {
                    final int i1 = o1 + (i * 2);
                    final int i2 = i1 + 1;
                    final int high = src[i2] << 8;
                    final int low = src[i1] & 0x00ff;
                    final char c = (char) (high | low);
                    b.append(c);
                }
                /* Strip 0x00 characters from the end of the string: */
                while (b.length() > 0 && b.charAt(b.length() - 1) == 0x00)
                    b.setLength(b.length() - 1);
                value = b.toString();
                break;
            }
            case Variant.VT_CF:
            {
                final byte[] v = new byte[l1];
                for (int i = 0; i < l1; i++)
                    v[i] = src[(o1 + i)];
                value = v;
                break;
            }
            case Variant.VT_BOOL:
            {
                /*
                 * The first four bytes in src, from src[offset] to
                 * src[offset + 3] contain the DWord for VT_BOOL, so
                 * skip it, we don't need it.
                 */
                // final int first = offset + LittleEndian.INT_SIZE;
                long bool = LittleEndian.getUInt(src, o1);
                if (bool != 0)
                    value = Boolean.TRUE;
                else
                    value = Boolean.FALSE;