/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 static org.apache.commons.io.IOUtils.EOF;

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

Utility code for dealing with different endian systems.

Different computer architectures adopt different conventions for
byte ordering. In so-called "Little Endian" architectures (eg Intel),
the low-order byte is stored in memory at the lowest address, and
subsequent bytes at higher addresses. For "Big Endian" architectures
(eg Motorola), the situation is reversed.
This class helps you solve this incompatibility.

Origin of code: Excalibur
See Also:
SwappedDataInputStream/**
 * Utility code for dealing with different endian systems.
 * <p>
 * Different computer architectures adopt different conventions for
 * byte ordering. In so-called "Little Endian" architectures (eg Intel),
 * the low-order byte is stored in memory at the lowest address, and
 * subsequent bytes at higher addresses. For "Big Endian" architectures
 * (eg Motorola), the situation is reversed.
 * This class helps you solve this incompatibility.
 * <p>
 * Origin of code: Excalibur
 *
 * @see org.apache.commons.io.input.SwappedDataInputStream
 */
public class EndianUtils {

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

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

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

    
Converts a "int" value between endian systems.
Params:
value – value to convert
Returns:
the converted value/**
     * Converts a "int" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static int swapInteger(final 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.
Params:
value – value to convert
Returns:
the converted value/**
     * Converts a "long" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static long swapLong(final 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.
Params:
value – value to convert
Returns:
the converted value/**
     * Converts a "float" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static float swapFloat(final float value) {
        return Float.intBitsToFloat( swapInteger( Float.floatToIntBits( value ) ) );
    }

    
Converts a "double" value between endian systems.
Params:
value – value to convert
Returns:
the converted value/**
     * Converts a "double" value between endian systems.
     * @param value value to convert
     * @return the converted value
     */
    public static double swapDouble(final 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.
Params:
data – target byte array
offset – starting offset in the byte array
value – value to write/**
     * 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(final byte[] data, final int offset, final 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.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * 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(final byte[] data, final 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.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * 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(final byte[] data, final int offset) {
        return ( ( ( 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.
Params:
data – target byte array
offset – starting offset in the byte array
value – value to write/**
     * 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(final byte[] data, final int offset, final 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.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * 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(final byte[] data, final int offset) {
        return ( ( ( 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.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * 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(final byte[] data, final int offset) {
        final long low = ( ( ( data[ offset + 0 ] & 0xff ) << 0 ) +
                     ( ( data[ offset + 1 ] & 0xff ) << 8 ) +
                     ( ( data[ offset + 2 ] & 0xff ) << 16 ) );

        final long high = data[ offset + 3 ] & 0xff;

        return (high << 24) + (0xffffffffL & low);
    }

    
Writes a "long" value to a byte array at a given offset. The value is
converted to the opposed endian system while writing.
Params:
data – target byte array
offset – starting offset in the byte array
value – value to write/**
     * 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(final byte[] data, final int offset, final 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.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * 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(final byte[] data, final int offset) {
        final long low = readSwappedInteger(data, offset);
        final long high = readSwappedInteger(data, offset + 4);
        return (high << 32) + (0xffffffffL & low);
    }

    
Writes a "float" value to a byte array at a given offset. The value is
converted to the opposed endian system while writing.
Params:
data – target byte array
offset – starting offset in the byte array
value – value to write/**
     * 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(final byte[] data, final int offset, final float value) {
        writeSwappedInteger( data, offset, Float.floatToIntBits( value ) );
    }

    
Reads a "float" value from a byte array at a given offset. The value is
converted to the opposed endian system while reading.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * Reads a "float" 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 float readSwappedFloat(final byte[] data, final int offset) {
        return Float.intBitsToFloat( readSwappedInteger( data, offset ) );
    }

    
Writes a "double" value to a byte array at a given offset. The value is
converted to the opposed endian system while writing.
Params:
data – target byte array
offset – starting offset in the byte array
value – value to write/**
     * Writes a "double" 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 writeSwappedDouble(final byte[] data, final int offset, final double value) {
        writeSwappedLong( data, offset, Double.doubleToLongBits( value ) );
    }

    
Reads a "double" value from a byte array at a given offset. The value is
converted to the opposed endian system while reading.
Params:
data – source byte array
offset – starting offset in the byte array
Returns:
the value read/**
     * Reads a "double" 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 double readSwappedDouble(final byte[] data, final int offset) {
        return Double.longBitsToDouble( readSwappedLong( data, offset ) );
    }

    
Writes a "short" value to an OutputStream. The value is
converted to the opposed endian system while writing.
Params:
output – target OutputStream
value – value to write
Throws:
IOException – in case of an I/O problem/**
     * Writes a "short" value to an OutputStream. The value is
     * converted to the opposed endian system while writing.
     * @param output target OutputStream
     * @param value value to write
     * @throws IOException in case of an I/O problem
     */
    public static void writeSwappedShort(final OutputStream output, final short value)
        throws IOException
    {
        output.write( (byte)( ( value >> 0 ) & 0xff ) );
        output.write( (byte)( ( value >> 8 ) & 0xff ) );
    }

    
Reads a "short" value from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a "short" value from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static short readSwappedShort(final InputStream input)
        throws IOException
    {
        return (short)( ( ( read( input ) & 0xff ) << 0 ) +
            ( ( read( input ) & 0xff ) << 8 ) );
    }

    
Reads a unsigned short (16-bit) from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a unsigned short (16-bit) from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static int readSwappedUnsignedShort(final InputStream input)
        throws IOException
    {
        final int value1 = read( input );
        final int value2 = read( input );

        return ( ( ( value1 & 0xff ) << 0 ) +
            ( ( value2 & 0xff ) << 8 ) );
    }

    
Writes a "int" value to an OutputStream. The value is
converted to the opposed endian system while writing.
Params:
output – target OutputStream
value – value to write
Throws:
IOException – in case of an I/O problem/**
     * Writes a "int" value to an OutputStream. The value is
     * converted to the opposed endian system while writing.
     * @param output target OutputStream
     * @param value value to write
     * @throws IOException in case of an I/O problem
     */
    public static void writeSwappedInteger(final OutputStream output, final int value)
        throws IOException
    {
        output.write( (byte)( ( value >> 0 ) & 0xff ) );
        output.write( (byte)( ( value >> 8 ) & 0xff ) );
        output.write( (byte)( ( value >> 16 ) & 0xff ) );
        output.write( (byte)( ( value >> 24 ) & 0xff ) );
    }

    
Reads a "int" value from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a "int" value from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static int readSwappedInteger(final InputStream input)
        throws IOException
    {
        final int value1 = read( input );
        final int value2 = read( input );
        final int value3 = read( input );
        final int value4 = read( input );

        return ( ( value1 & 0xff ) << 0 ) +
            ( ( value2 & 0xff ) << 8 ) +
            ( ( value3 & 0xff ) << 16 ) +
            ( ( value4 & 0xff ) << 24 );
    }

    
Reads a unsigned integer (32-bit) from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a unsigned integer (32-bit) from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static long readSwappedUnsignedInteger(final InputStream input)
        throws IOException
    {
        final int value1 = read( input );
        final int value2 = read( input );
        final int value3 = read( input );
        final int value4 = read( input );

        final long low = ( ( ( value1 & 0xff ) << 0 ) +
                     ( ( value2 & 0xff ) << 8 ) +
                     ( ( value3 & 0xff ) << 16 ) );

        final long high = value4 & 0xff;

        return (high << 24) + (0xffffffffL & low);
    }

    
Writes a "long" value to an OutputStream. The value is
converted to the opposed endian system while writing.
Params:
output – target OutputStream
value – value to write
Throws:
IOException – in case of an I/O problem/**
     * Writes a "long" value to an OutputStream. The value is
     * converted to the opposed endian system while writing.
     * @param output target OutputStream
     * @param value value to write
     * @throws IOException in case of an I/O problem
     */
    public static void writeSwappedLong(final OutputStream output, final long value)
        throws IOException
    {
        output.write( (byte)( ( value >> 0 ) & 0xff ) );
        output.write( (byte)( ( value >> 8 ) & 0xff ) );
        output.write( (byte)( ( value >> 16 ) & 0xff ) );
        output.write( (byte)( ( value >> 24 ) & 0xff ) );
        output.write( (byte)( ( value >> 32 ) & 0xff ) );
        output.write( (byte)( ( value >> 40 ) & 0xff ) );
        output.write( (byte)( ( value >> 48 ) & 0xff ) );
        output.write( (byte)( ( value >> 56 ) & 0xff ) );
    }

    
Reads a "long" value from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a "long" value from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static long readSwappedLong(final InputStream input)
        throws IOException
    {
        final byte[] bytes = new byte[8];
        for ( int i=0; i<8; i++ ) {
            bytes[i] = (byte) read( input );
        }
        return readSwappedLong( bytes, 0 );
    }

    
Writes a "float" value to an OutputStream. The value is
converted to the opposed endian system while writing.
Params:
output – target OutputStream
value – value to write
Throws:
IOException – in case of an I/O problem/**
     * Writes a "float" value to an OutputStream. The value is
     * converted to the opposed endian system while writing.
     * @param output target OutputStream
     * @param value value to write
     * @throws IOException in case of an I/O problem
     */
    public static void writeSwappedFloat(final OutputStream output, final float value)
        throws IOException
    {
        writeSwappedInteger( output, Float.floatToIntBits( value ) );
    }

    
Reads a "float" value from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a "float" value from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static float readSwappedFloat(final InputStream input)
        throws IOException
    {
        return Float.intBitsToFloat( readSwappedInteger( input ) );
    }

    
Writes a "double" value to an OutputStream. The value is
converted to the opposed endian system while writing.
Params:
output – target OutputStream
value – value to write
Throws:
IOException – in case of an I/O problem/**
     * Writes a "double" value to an OutputStream. The value is
     * converted to the opposed endian system while writing.
     * @param output target OutputStream
     * @param value value to write
     * @throws IOException in case of an I/O problem
     */
    public static void writeSwappedDouble(final OutputStream output, final double value)
        throws IOException
    {
        writeSwappedLong( output, Double.doubleToLongBits( value ) );
    }

    
Reads a "double" value from an InputStream. The value is
converted to the opposed endian system while reading.
Params:
input – source InputStream
Throws:
IOException – in case of an I/O problem
Returns:
the value just read/**
     * Reads a "double" value from an InputStream. The value is
     * converted to the opposed endian system while reading.
     * @param input source InputStream
     * @return the value just read
     * @throws IOException in case of an I/O problem
     */
    public static double readSwappedDouble(final InputStream input)
        throws IOException
    {
        return Double.longBitsToDouble( readSwappedLong( input ) );
    }

    
Reads the next byte from the input stream.
Params:
input –  the stream
Throws:
IOException – if the end of file is reached
Returns:
the byte/**
     * Reads the next byte from the input stream.
     * @param input  the stream
     * @return the byte
     * @throws IOException if the end of file is reached
     */
    private static int read(final InputStream input)
        throws IOException
    {
        final int value = input.read();

        if( EOF == value ) {
            throw new EOFException( "Unexpected EOF reached" );
        }

        return value;
    }
}