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

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 *  Portions of this software are based upon public domain software
 *  originally written at the National Center for Supercomputing Applications,
 *  University of Illinois, Urbana-Champaign.
 *
 *  Portions of this software are based upon public domain software
 *  originally written at the National Center for Supercomputing Applications,
 *  University of Illinois, Urbana-Champaign.
 */
package org.apache.poi.hpsf;

import org.apache.poi.util.LittleEndian;

/**
 * <p>Reader for specific data types.</p>
 *
 * @author Rainer Klute (klute@rainer-klute.de)
 * @see Property
 * @see Variant
 * @version $Id$
 * @since 2002-12-09
 */
public class TypeReader
{

    /**
     * <p>Reads a variant data 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
     * @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}.
     *
     * @see Variant
     */
    public static Object read(final byte[] src, int offset, int length,
                              final int type)
    {
        /*
         * FIXME: Support reading more types and clean up this code!
         */
        Object value;
        length = length - LittleEndian.INT_SIZE;
        switch (type)
        {
            case Variant.VT_EMPTY:
            {
                /*
                 * FIXME: The value returned by this case relies on the
                 * assumption that the value VT_EMPTY denotes consists of zero 
                 * bytes. I'd be glad if some could confirm or correct this. 
                 */
                value = null;
                break;
            }
            case Variant.VT_I2:
            {
                /*
                 * Read a short. In Java it is represented as an
                 * Integer object.
                 */
                value = new Integer(LittleEndian.getUShort(src, offset));
                break;
            }
            case Variant.VT_I4:
            {
                /*
                 * Read a word. In Java it is represented as a
                 * Long object.
                 */
                value = new Long(LittleEndian.getUInt(src, offset));
                break;
            }
            case Variant.VT_FILETIME:
            {
                /*
                 * Read a FILETIME object. In Java it is represented
                 * as a Date object.
                 */
                final long low = LittleEndian.getUInt(src, offset);
                offset += LittleEndian.INT_SIZE;
                final long high = LittleEndian.getUInt(src, offset);
                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.
                 *
                 * FIXME: Reading an 8-bit string should pay attention
                 * to the codepage. Currently the byte making out the
                 * property's value are interpreted according to the
                 * platform's default character set.
                 */
                final int first = offset + LittleEndian.INT_SIZE;
                long last = first + LittleEndian.getUInt(src, offset) - 1;
                offset += LittleEndian.INT_SIZE;
                while (src[(int) last] == 0 && first <= last)
                    last--;
                value = new String(src, (int) first, (int) (last - first + 1));
                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 = offset + LittleEndian.INT_SIZE;
                long last = first + LittleEndian.getUInt(src, offset) - 1;
                long l = last - first;
                offset += LittleEndian.INT_SIZE;
                StringBuffer b = new StringBuffer((int) (last - first));
                for (int i = 0; i <= l; i++)
                {
                    final int i1 = offset + (i * 2);
                    final int i2 = i1 + 1;
                    b.append((char) ((src[i2] << 8) + src[i1]));
                }
                /* Strip 0x00 characters from the end of the string: */
                while (b.charAt(b.length() - 1) == 0x00)
                    b.setLength(b.length() - 1);
                value = b.toString();
                break;
            }
            case Variant.VT_CF:
            {
                final byte[] v = new byte[length];
                for (int i = 0; i < length; i++)
                    v[i] = src[(int) (offset + 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, offset);
                if (bool != 0)
                    value = new Boolean(true);
                else
                    value = new Boolean(false);
                break;
            }
            default:
            {
                final byte[] v = new byte[length];
                for (int i = 0; i < length; i++)
                    v[i] = src[(int) (offset + i)];
                value = v;
                break;
            }
        }
        return value;
    }

}