endianutils.java

JAVA 文章管理系统源码

/*
 * Copyright 2001-2004 The 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.commons.io;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * Utility code for dealing with different endian systems.
 * <br>
 * Origin of code: Apache Avalon (Excalibur)
 *
 * @author <a href="mailto:[e-mail]">Peter Donald</a>
 * @version CVS $Revision: 1.13 $ $Date: 2004/02/23 04:35:59 $
 */
public final class EndianUtils
{

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public EndianUtils() { }

    // ========================================== Swapping routines

    /**
     * Converts a "short" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static short swapShort( short value )
    {
        return (short)( ( ( ( value >> 0 ) & 0xff ) << 8 ) +
            ( ( ( value >> 8 ) & 0xff ) << 0 ) );
    }

    /**
     * Converts a "int" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static int swapInteger( int value )
    {
        return
            ( ( ( value >> 0 ) & 0xff ) << 24 ) +
            ( ( ( value >> 8 ) & 0xff ) << 16 ) +
            ( ( ( value >> 16 ) & 0xff ) << 8 ) +
            ( ( ( value >> 24 ) & 0xff ) << 0 );
    }

    /**
     * Converts a "long" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static long swapLong( long value )
    {
        return
            ( ( ( value >> 0 ) & 0xff ) << 56 ) +
            ( ( ( value >> 8 ) & 0xff ) << 48 ) +
            ( ( ( value >> 16 ) & 0xff ) << 40 ) +
            ( ( ( value >> 24 ) & 0xff ) << 32 ) +
            ( ( ( value >> 32 ) & 0xff ) << 24 ) +
            ( ( ( value >> 40 ) & 0xff ) << 16 ) +
            ( ( ( value >> 48 ) & 0xff ) << 8 ) +
            ( ( ( value >> 56 ) & 0xff ) << 0 );
    }

    /**
     * Converts a "float" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static float swapFloat( float value )
    {
        return Float.intBitsToFloat( swapInteger( Float.floatToIntBits( value ) ) );
    }

    /**
     * Converts a "double" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static double swapDouble( double value )
    {
        return Double.longBitsToDouble( swapLong( Double.doubleToLongBits( value ) ) );
    }

    // ========================================== Swapping read/write routines

    /**
     * Writes a "short" value to a byte array at a given offset. The value is
     * converted to the opposed endian system while writing.
     * @param data target byte array
     * @param offset starting offset in the byte array
     * @param value value to write
     */
    public static void writeSwappedShort( byte[] data, int offset, short value )
    {
        data[ offset + 0 ] = (byte)( ( value >> 0 ) & 0xff );
        data[ offset + 1 ] = (byte)( ( value >> 8 ) & 0xff );
    }

    /**
     * Reads a "short" value from a byte array at a given offset. The value is
     * converted to the opposed endian system while reading.
     * @param data source byte array
     * @param offset starting offset in the byte array
     * @return the value read
     */
    public static short readSwappedShort( byte[] data, int offset )
    {
        return (short)( ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 1 ] & 0xff ) << 8 ) );
    }

    /**
     * Reads an unsigned short (16-bit) value from a byte array at a given 
     * offset. The value is converted to the opposed endian system while 
     * reading.
     * @param data source byte array
     * @param offset starting offset in the byte array
     * @return the value read
     */
    public static int readSwappedUnsignedShort( byte[] data, int offset )
    {
        return (int)( ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 1 ] & 0xff ) << 8 ) );
    }

    /**
     * Writes a "int" value to a byte array at a given offset. The value is
     * converted to the opposed endian system while writing.
     * @param data target byte array
     * @param offset starting offset in the byte array
     * @param value value to write
     */
    public static void writeSwappedInteger( byte[] data, int offset, int value )
    {
        data[ offset + 0 ] = (byte)( ( value >> 0 ) & 0xff );
        data[ offset + 1 ] = (byte)( ( value >> 8 ) & 0xff );
        data[ offset + 2 ] = (byte)( ( value >> 16 ) & 0xff );
        data[ offset + 3 ] = (byte)( ( value >> 24 ) & 0xff );
    }

    /**
     * Reads a "int" value from a byte array at a given offset. The value is
     * converted to the opposed endian system while reading.
     * @param data source byte array
     * @param offset starting offset in the byte array
     * @return the value read
     */
    public static int readSwappedInteger( byte[] data, int offset )
    {
        return (int)( ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 1 ] & 0xff ) << 8 ) +
            ( ( data[ offset + 2 ] & 0xff ) << 16 ) +
            ( ( data[ offset + 3 ] & 0xff ) << 24 ) );
    }

    /**
     * Reads an unsigned integer (32-bit) value from a byte array at a given 
     * offset. The value is converted to the opposed endian system while 
     * reading.
     * @param data source byte array
     * @param offset starting offset in the byte array
     * @return the value read
     */
    public static long readSwappedUnsignedInteger( byte[] data, int offset )
    {
        return (long)( ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 1 ] & 0xff ) << 8 ) +
            ( ( data[ offset + 2 ] & 0xff ) << 16 ) +
            ( ( data[ offset + 3 ] & 0xff ) << 24 ) );
    }

    /**
     * Writes a "long" value to a byte array at a given offset. The value is
     * converted to the opposed endian system while writing.
     * @param data target byte array
     * @param offset starting offset in the byte array
     * @param value value to write
     */
    public static void writeSwappedLong( byte[] data, int offset, long value )
    {
        data[ offset + 0 ] = (byte)( ( value >> 0 ) & 0xff );
        data[ offset + 1 ] = (byte)( ( value >> 8 ) & 0xff );
        data[ offset + 2 ] = (byte)( ( value >> 16 ) & 0xff );
        data[ offset + 3 ] = (byte)( ( value >> 24 ) & 0xff );
        data[ offset + 4 ] = (byte)( ( value >> 32 ) & 0xff );
        data[ offset + 5 ] = (byte)( ( value >> 40 ) & 0xff );
        data[ offset + 6 ] = (byte)( ( value >> 48 ) & 0xff );
        data[ offset + 7 ] = (byte)( ( value >> 56 ) & 0xff );
    }

    /**
     * Reads a "long" value from a byte array at a given offset. The value is
     * converted to the opposed endian system while reading.
     * @param data source byte array
     * @param offset starting offset in the byte array
     * @return the value read
     */
    public static long readSwappedLong( byte[] data, int offset )
    {
        long low = (long)( 
            ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 1 ] & 0xff ) << 8 ) +
            ( ( data[ offset + 2 ] & 0xff ) << 16 ) +
            ( ( data[ offset + 3 ] & 0xff ) << 24 ) );
        long high = (long)(
            ( ( data[ offset + 4 ] & 0xff ) << 0 ) +
            ( ( data[ offset + 5 ] & 0xff ) << 8 ) +
            ( ( data[ offset + 6 ] & 0xff ) << 16 ) +
            ( ( data[ offset + 7 ] & 0xff ) << 24 ) );
        return low + (high << 32);
    }

    /**
     * Writes a "float" value to a byte array at a given offset. The value is
     * converted to the opposed endian system while writing.
     * @param data target byte array
     * @param offset starting offset in the byte array
     * @param value value to write
     */
    public static void writeSwappedFloat( byte[] data, int offset, float value )
    {
        writeSwappedInteger( data, offset, Float.floatToIntBits( value ) );