/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2002 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation" and
* "Apache POI" must not be used to endorse or promote products
* derived from this software without prior written permission. For
* written permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* "Apache POI", nor may "Apache" appear in their name, without
* prior written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* .
*/
package org.apache.poi.util;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
/**
* a utility class for handling little-endian numbers, which the 80x86
* world is replete with. The methods are all static, and input/output
* is from/to byte arrays, or from InputStreams.
*
* @author Marc Johnson (mjohnson at apache dot org)
* @author Andrew Oliver (acoliver at apache dot org)
*
*/
public class LittleEndian
implements LittleEndianConsts
{
// all methods are static, so an accessible constructor makes no
// sense
private LittleEndian()
{
}
/**
* get a short value from a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
*
* @return the short (16-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static short getShort(final byte[] data, final int offset)
{
return (short) getNumber(data, offset, SHORT_SIZE);
}
/**
* get a short array from a byte array.
*/
public static short[] getSimpleShortArray(final byte[] data, final int offset, final int size)
{
short[] results = new short[size];
for (int i = 0; i < size; i++)
{
results[i] = getShort(data, offset + 2 + (i * 2));
}
return results;
}
/**
* get a short array from a byte array. The short array is assumed
* to start with a word describing the length of the array.
*/
public static short[] getShortArray(final byte[] data, final int offset)
{
int size = (short) getNumber(data, offset, SHORT_SIZE);
short[] results = getSimpleShortArray(data, offset, size);
return results;
}
/**
* get a short value from the beginning of a byte array
*
* @param data the byte array
*
* @return the short (16-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static short getShort(final byte[] data)
{
return getShort(data, 0);
}
/**
* get an int value from a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
*
* @return the int (32-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static int getInt(final byte[] data, final int offset)
{
return (int) getNumber(data, offset, INT_SIZE);
}
/**
* get an int value from the beginning of a byte array
*
* @param data the byte array
*
* @return the int (32-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static int getInt(final byte[] data)
{
return getInt(data, 0);
}
/**
* get a long value from a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
*
* @return the long (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static long getLong(final byte[] data, final int offset)
{
return getNumber(data, offset, LONG_SIZE);
}
/**
* get a long value from the beginning of a byte array
*
* @param data the byte array
*
* @return the long (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static long getLong(final byte[] data)
{
return getLong(data, 0);
}
/**
* get a double value from a byte array, reads it in little endian format
* then converts the resulting revolting IEEE 754 (curse them) floating
* point number to a happy java double
*
* @param data the byte array
* @param offset a starting offset into the byte array
*
* @return the double (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static double getDouble(final byte[] data, final int offset)
{
return Double.longBitsToDouble(getNumber(data, offset, DOUBLE_SIZE));
}
/**
* get a double value from the beginning of a byte array
*
* @param data the byte array
*
* @return the double (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static double getDouble(final byte[] data)
{
return getDouble(data, 0);
}
/**
* put a short value into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the short (16-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putShort(final byte[] data, final int offset,
final short value)
{
putNumber(data, offset, value, SHORT_SIZE);
}
/**
* put an unsigned short value into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the short (16-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putUShort(final byte[] data, final int offset,
final int value)
{
putNumber(data, offset, value, SHORT_SIZE);
}
/**
* put a array of shorts into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the short array
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putShortArray(final byte[] data, final int offset, final short[] value)
{
putNumber(data, offset, value.length, SHORT_SIZE);
for (int i = 0; i < value.length; i++)
{
putNumber(data, offset + 2 + (i * 2), value[i], SHORT_SIZE);
}
}
/**
* put a short value into beginning of a byte array
*
* @param data the byte array
* @param value the short (16-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putShort(final byte[] data, final short value)
{
putShort(data, 0, value);
}
/**
* put an int value into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the int (32-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putInt(final byte[] data, final int offset,
final int value)
{
putNumber(data, offset, value, INT_SIZE);
}
/**
* put an int value into beginning of a byte array
*
* @param data the byte array
* @param value the int (32-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putInt(final byte[] data, final int value)
{
putInt(data, 0, value);
}
/**
* put a long value into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the long (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putLong(final byte[] data, final int offset,
final long value)
{
putNumber(data, offset, value, LONG_SIZE);
}
/**
* put a long value into beginning of a byte array
*
* @param data the byte array
* @param value the long (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putLong(final byte[] data, final long value)
{
putLong(data, 0, value);
}
/**
* put a double value into a byte array
*
* @param data the byte array
* @param offset a starting offset into the byte array
* @param value the double (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putDouble(final byte[] data, final int offset,
final double value)
{
putNumber(data, offset, Double.doubleToLongBits(value), DOUBLE_SIZE);
}
/**
* put a double value into beginning of a byte array
*
* @param data the byte array
* @param value the double (64-bit) value
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static void putDouble(final byte[] data, final double value)
{
putDouble(data, 0, value);
}
/**
* Exception to handle buffer underruns
*
* @author Marc Johnson (mjohnson at apache dot org)
*/
public static class BufferUnderrunException
extends IOException
{
/**
* simple constructor
*/
BufferUnderrunException()
{
super("buffer underrun");
}
}
/**
* get a short value from an InputStream
*
* @param stream the InputStream from which the short is to be
* read
*
* @return the short (16-bit) value
*
* @exception IOException will be propagated back to the caller
* @exception BufferUnderrunException if the stream cannot provide
* enough bytes
*/
public static short readShort(final InputStream stream)
throws IOException, BufferUnderrunException
{
return getShort(readFromStream(stream, SHORT_SIZE));
}
/**
* get an int value from an InputStream
*
* @param stream the InputStream from which the int is to be read
*
* @return the int (32-bit) value
*
* @exception IOException will be propagated back to the caller
* @exception BufferUnderrunException if the stream cannot provide
* enough bytes
*/
public static int readInt(final InputStream stream)
throws IOException, BufferUnderrunException
{
return getInt(readFromStream(stream, INT_SIZE));
}
/**
* get a long value from an InputStream
*
* @param stream the InputStream from which the long is to be read
*
* @return the long (64-bit) value
*
* @exception IOException will be propagated back to the caller
* @exception BufferUnderrunException if the stream cannot provide
* enough bytes
*/
public static long readLong(final InputStream stream)
throws IOException, BufferUnderrunException
{
return getLong(readFromStream(stream, LONG_SIZE));
}
private static final byte[] _short_buffer = new byte[SHORT_SIZE];
private static final byte[] _int_buffer = new byte[INT_SIZE];
private static final byte[] _long_buffer = new byte[LONG_SIZE];
/**
* Read the appropriate number of bytes from the stream and return
* them to the caller.
*
* It should be noted that, in an attempt to improve system
* performance and to prevent a transient explosion of discarded
* byte arrays to be garbage collected, static byte arrays are
* employed for the standard cases of reading a short, an int, or
* a long.
*
* THIS INTRODUCES A RISK FOR THREADED OPERATIONS!
*
* However, for the purposes of the POI project, this risk is
* deemed negligible. It is, however, so noted.
*
* @param stream the InputStream we're reading from
* @param size the number of bytes to read; in 99.99% of cases,
* this will be SHORT_SIZE, INT_SIZE, or LONG_SIZE --
* but it doesn't have to be.
*
* @return the byte array containing the required number of
* bytes. The array will contain all zero's on end of
* stream
*
* @exception IOException will be propagated back to the caller
* @exception BufferUnderrunException if the stream cannot provide
* enough bytes
*/
public static byte[] readFromStream(final InputStream stream,
final int size)
throws IOException, BufferUnderrunException
{
byte[] buffer = null;
switch (size)
{
case SHORT_SIZE:
buffer = _short_buffer;
break;
case INT_SIZE:
buffer = _int_buffer;
break;
case LONG_SIZE:
buffer = _long_buffer;
break;
default :
buffer = new byte[size];
break;
}
int count = stream.read(buffer);
if (count == -1)
{
// return a zero-filled buffer
Arrays.fill(buffer, (byte) 0);
} else if (count != size)
{
throw new BufferUnderrunException();
}
return buffer;
}
private static long getNumber(final byte[] data, final int offset,
final int size)
{
long result = 0;
for (int j = offset + size - 1; j >= offset; j--)
{
result <<= 8;
result |= 0xff & data[j];
}
return result;
}
private static void putNumber(final byte[] data, final int offset,
final long value, final int size)
{
int limit = size + offset;
long v = value;
for (int j = offset; j < limit; j++)
{
data[j] = (byte) (v & 0xFF);
v >>= 8;
}
}
/**
* Convert an 'unsigned' byte to an integer. ie, don't carry across the sign.
*/
public static int ubyteToInt(byte b)
{
return ((b & 0x80) == 0 ? (int) b : (int) (b & (byte) 0x7f) + 0x80);
}
/**
* get the unsigned value of a byte.
*
* @param data the byte array.
* @param offset a starting offset into the byte array.
*
* @return the unsigned value of the byte as a 32 bit integer
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static int getUnsignedByte(final byte[] data, final int offset)
{
return (int) getNumber(data, offset, BYTE_SIZE);
}
/**
* get the unsigned value of a byte.
*
* @param data the byte array
*
* @return the unsigned value of the byte as a 32 bit integer
*
* @exception ArrayIndexOutOfBoundsException may be thrown
*/
public static int getUnsignedByte(final byte[] data)
{
return getUnsignedByte(data, 0);
}
/**
* Copy a portion of a byte array
*
* @param data the original byte array
* @param offset Where to start copying from.
* @param size Number of bytes to copy.
*
* @throws IndexOutOfBoundsException - if copying would cause access of data
* outside array bounds.
*/
public static byte[] getByteArray(final byte[] data, int offset, int size)
{
byte[] copy = new byte[size];
System.arraycopy(data, offset, copy, 0, size);
return copy;
}
/**
* Retrieves and unsigned short. This is converted UP to a int
* so it can fit.
*
* @param data The data to read
* @param offset The offset to read the short from
* @return An integer representation of the short.
*/
public static int getUShort( byte[] data, int offset )
{
return (int)getNumber(data, offset, SHORT_SIZE);
}
}