littleendianoutputstream.java

用于Java 组件和通过Windows COM 对象或Windows DLL 来公开的组件之间的互操作

//******************************************************************
// Released under the DevelopMentor OpenSource Software License.
// Please consult the LICENSE file in the project root directory,
// or at http://www.develop.com for details before using this
// software.
//******************************************************************

package com.develop.io;
import java.io.*;

/** 
 * Replica of 
 * {@link java.io.DataOutputStream DataOutputStream}
 * that uses little endian format.  Useful for 
 * dealing with Win32-based formats.
 */
public
class LittleEndianOutputStream extends FilterOutputStream implements DataOutput {
    public static final byte FLAGS_NULL = 0;
    public static final byte FLAGS_NONNULL = 1;
    public static final int SIZEOF_CHAR = 2;
    /**
     * The number of bytes written to the data output stream so far.
     * If this counter overflows, it will be wrapped to Integer.MAX_VALUE.
     */
    protected int written;

    /**
     * Creates a new data output stream to write data to the specified
     * underlying output stream. The counter <code>written</code> is
     * set to zero.
     *
     * @param   out   the underlying output stream, to be saved for later
     *                use.
     * @see     java.io.FilterOutputStream#out
     */
    public LittleEndianOutputStream(OutputStream out) {
    super(out);
    }

    /**
     * Increases the written counter by the specified value
     * until it reaches Integer.MAX_VALUE.
     */
    private void incCount(int value) {
        int temp = written + value;
        if (temp < 0) {
            temp = Integer.MAX_VALUE;
        }
        written = temp;
    }

    /**
     * Writes the specified byte (the low eight bits of the argument
     * <code>b</code>) to the underlying output stream. If no exception
     * is thrown, the counter <code>written</code> is incremented by
     * <code>1</code>.
     * <p>
     * Implements the <code>write</code> method of <code>OutputStream</code>.
     *
     * @param      b   the <code>byte</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public synchronized void write(int b) throws IOException {
    out.write(b);
        incCount(1);
    }

    /**
     * Writes <code>len</code> bytes from the specified byte array
     * starting at offset <code>off</code> to the underlying output stream.
     * If no exception is thrown, the counter <code>written</code> is
     * incremented by <code>len</code>.
     *
     * @param      b     the data.
     * @param      off   the start offset in the data.
     * @param      len   the number of bytes to write.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public synchronized void write(byte b[], int off, int len)
    throws IOException
    {
    out.write(b, off, len);
    incCount(len);
    }

    /**
     * Flushes this data output stream. This forces any buffered output
     * bytes to be written out to the stream.
     * <p>
     * The <code>flush</code> method of <code>DataOuputStream</code>
     * calls the <code>flush</code> method of its underlying output stream.
     *
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.io.OutputStream#flush()
     */
    public void flush() throws IOException {
    out.flush();
    }

    /**
     * Writes a <code>boolean</code> to the underlying output stream as
     * a 1-byte value. The value <code>true</code> is written out as the
     * value <code>(byte)1</code>; the value <code>false</code> is
     * written out as the value <code>(byte)0</code>. If no exception is
     * thrown, the counter <code>written</code> is incremented by
     * <code>1</code>.
     *
     * @param      v   a <code>boolean</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeBoolean(boolean v) throws IOException {
    out.write(v ? 1 : 0);
    incCount(1);
    }

    /**
     * Writes out a <code>byte</code> to the underlying output stream as
     * a 1-byte value. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>1</code>.
     *
     * @param      v   a <code>byte</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeByte(int v) throws IOException {
    out.write(v);
        incCount(1);
    }

    /**
     * Writes a <code>short</code> to the underlying output stream as two
     * bytes, high byte first. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>2</code>.
     *
     * @param      v   a <code>short</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeShort(int v) throws IOException {
    OutputStream out = this.out;
    out.write((v >>> 0) & 0xFF);
    out.write((v >>> 8) & 0xFF);
    incCount(2);
    }

    /**
     * Writes a <code>char</code> to the underlying output stream as a
     * 2-byte value, high byte first. If no exception is thrown, the
     * counter <code>written</code> is incremented by <code>2</code>.
     *
     * @param      v   a <code>char</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeChar(int v) throws IOException {
    OutputStream out = this.out;
    out.write((v >>> 0) & 0xFF);
    out.write((v >>> 8) & 0xFF);
    incCount(SIZEOF_CHAR);
    }

    /**
     * Writes an <code>int</code> to the underlying output stream as four
     * bytes, high byte first. If no exception is thrown, the counter
     * <code>written</code> is incremented by <code>4</code>.
     *
     * @param      v   an <code>int</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeInt(int v) throws IOException {
    OutputStream out = this.out;
    out.write((v >>>  0) & 0xFF);
    out.write((v >>>  8) & 0xFF);
    out.write((v >>> 16) & 0xFF);
    out.write((v >>> 24) & 0xFF);
    incCount(4);
    }

    /**
     * Writes a <code>long</code> to the underlying output stream as eight
     * bytes, high byte first. In no exception is thrown, the counter
     * <code>written</code> is incremented by <code>8</code>.
     *
     * @param      v   a <code>long</code> to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeLong(long v) throws IOException {
    OutputStream out = this.out;
    out.write((int)(v >>>  0) & 0xFF);
    out.write((int)(v >>>  8) & 0xFF);
    out.write((int)(v >>> 16) & 0xFF);
    out.write((int)(v >>> 24) & 0xFF);
    out.write((int)(v >>> 32) & 0xFF);
    out.write((int)(v >>> 40) & 0xFF);
    out.write((int)(v >>> 48) & 0xFF);
    out.write((int)(v >>> 56) & 0xFF);
    incCount(8);
    }

    /**
     * Converts the float argument to an <code>int</code> using the
     * <code>floatToIntBits</code> method in class <code>Float</code>,
     * and then writes that <code>int</code> value to the underlying
     * output stream as a 4-byte quantity, high byte first. If no
     * exception is thrown, the counter <code>written</code> is
     * incremented by <code>4</code>.
     *
     * @param      v   a <code>float</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.lang.Float#floatToIntBits(float)
     */
    public final void writeFloat(float v) throws IOException {
    writeInt(Float.floatToIntBits(v));
    }

    /**
     * Converts the double argument to a <code>long</code> using the
     * <code>doubleToLongBits</code> method in class <code>Double</code>,
     * and then writes that <code>long</code> value to the underlying
     * output stream as an 8-byte quantity, high byte first. If no
     * exception is thrown, the counter <code>written</code> is
     * incremented by <code>8</code>.
     *
     * @param      v   a <code>double</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     * @see        java.lang.Double#doubleToLongBits(double)
     */
    public final void writeDouble(double v) throws IOException {
    writeLong(Double.doubleToLongBits(v));
    }

    /**
     * Writes out the string to the underlying output stream as a
     * sequence of bytes. Each character in the string is written out, in
     * sequence, by discarding its high eight bits. If no exception is
     * thrown, the counter <code>written</code> is incremented by the
     * length of <code>s</code>.
     *
     * @param      s   a string of bytes to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeBytes(String s) throws IOException {
    OutputStream out = this.out;
    int len = s.length();
    for (int i = 0 ; i < len ; i++) {
        out.write((byte)s.charAt(i));
    }
    incCount(len);
    }

    /**
     * Writes a string to the underlying output stream as a sequence of
     * characters. Each character is written to the data output stream as
     * if by the <code>writeChar</code> method. If no exception is
     * thrown, the counter <code>written</code> is incremented by twice
     * the length of <code>s</code>.
     *
     * @param      s   a <code>String</code> value to be written.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.DataOutputStream#writeChar(int)
     * @see        java.io.FilterOutputStream#out
     */
    public final void writeChars(String s) throws IOException {
    OutputStream out = this.out;
    int len = s.length();
    for (int i = 0 ; i < len ; i++) {
        int v = s.charAt(i);
        out.write((v >>> 0) & 0xFF);
        out.write((v >>> 8) & 0xFF);
    }
    incCount(len * SIZEOF_CHAR);
    }

    public void writeStringUnicode(String str)
            throws IOException
    {
        if (str == null) {
            writeByte(FLAGS_NULL);
            return;
        }
        writeByte(FLAGS_NONNULL);
        int length = str.length();
        writeInt(length);
        for (int n=0; n<length; n++)
        {
            writeChar(str.charAt(n));
        }
    }


    public final void writeStringANSI(String str) throws IOException {
        if (str == null) {
            writeByte(FLAGS_NULL);
            return;
        }
        writeByte(FLAGS_NONNULL);
        int length = str.length();
        writeInt(length);
        for (int n=0; n<length; n++)
        {
            write((byte)str.charAt(n));
        }
    }

    public final void writeUTF(String str) throws IOException {
        throw new IllegalStateException("No support for LittleEndian UTF");
    }

    static int writeUTF(String str, DataOutput out) throws IOException {
        throw new IllegalStateException("No support for LittleEndian UTF");
    }

    /**
     * Returns the current value of the counter <code>written</code>,
     * the number of bytes written to this data output stream so far.
     * If the counter overflows, it will be wrapped to Integer.MAX_VALUE.
     *
     * @return  the value of the <code>written</code> field.
     * @see     java.io.DataOutputStream#written
     */
    public final int size() {
    return written;
    }

    static byte[] bytes256 = new byte[256];
    
    public void writeZeroBytes(int count) 
                        throws IOException
        {
        while (count >= 256) {
            write(bytes256, 0, 256);
            count -= 256;
        }
        write(bytes256, 0, count);
    }

}