/*
* ====================================================================
* 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
/**
* Constructor for the LittleEndian object
*/
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
*/
public static short getShort(final byte[] data, final int offset) {
return (short) getNumber(data, offset, SHORT_SIZE);
}
/**
* get an unsigned short value from a byte array
*
*@param data the byte array
*@param offset a starting offset into the byte array
*@return the unsigned short (16-bit) value in an integer
*/
public static int getUShort(final byte[] data, final int offset) {
short num = (short) getNumber(data, offset, SHORT_SIZE);
int retNum;
if (num < 0) {
retNum = ((int) Short.MAX_VALUE + 1) * 2 + (int) num;
} else {
retNum = (int) num;
}
return retNum;
}
/**
* get a short array from a byte array.
*
*@param data Description of the Parameter
*@param offset Description of the Parameter
*@param size Description of the Parameter
*@return The simpleShortArray value
*/
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.
*
*@param data Description of the Parameter
*@param offset Description of the Parameter
*@return The shortArray value
*/
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
*/
public static short getShort(final byte[] data) {
return getShort(data, 0);
}
/**
* get an unsigned short value from the beginning of a byte array
*
*@param data the byte array
*@return the unsigned short (16-bit) value in an int
*/
public static int getUShort(final byte[] data) {
return getUShort(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
*/
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
*/
public static int getInt(final byte[] data) {
return getInt(data, 0);
}
/**
* get an unsigned int value from a byte array
*
*@param data the byte array
*@param offset a starting offset into the byte array
*@return the unsigned int (32-bit) value in a long
*/
public static long getUInt(final byte[] data, final int offset) {
int num = (int) getNumber(data, offset, INT_SIZE);
long retNum;
if (num < 0) {
retNum = ((long) Integer.MAX_VALUE + 1) * 2 + (long) num;
} else {
retNum = (int) num;
}
return retNum;
}
/**
* get an unsigned int value from a byte array
*
*@param data the byte array
*@return the unsigned int (32-bit) value in a long
*/
public static long getUInt(final byte[] data) {
return getUInt(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
*/
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
*/
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
*/
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
*/
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
*/
public static void putShort(final byte[] data, final int offset,
final short 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
*/
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 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 short value into beginning of a byte array
*
*@param data the byte array
*@param value the short (16-bit) value
*/
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
*/
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
*/
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
*/
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
*/
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
*/
public static void putDouble(final byte[] data, final int offset,
final double value) {
// Excel likes NaN to be a specific value.
if (Double.isNaN(value))
putNumber(data, offset, -276939487313920L, DOUBLE_SIZE);
else
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
*/
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 final static byte[] _short_buffer = new byte[SHORT_SIZE];
private final static byte[] _int_buffer = new byte[INT_SIZE];
private final static 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;
}
/**
* Gets the number attribute of the LittleEndian class
*
*@param data Description of the Parameter
*@param offset Description of the Parameter
*@param size Description of the Parameter
*@return The number value
*/
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;
}
/**
* Description of the Method
*
*@param data Description of the Parameter
*@param offset Description of the Parameter
*@param value Description of the Parameter
*@param size Description of the Parameter
*/
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.
*
*@param b Description of the Parameter
*@return Description of the Return Value
*/
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
*/
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
*/
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.
*@return The byteArray value
*@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;
}
}