/*
*------------------------------------------------------------------------------
* Copyright (C) 2006-2007 University of Dundee. All rights reserved.
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*------------------------------------------------------------------------------
*/
package training.util;
/**
* Packs a sequence of bytes representing a big-endian float into
* a <code>double</code> value of appropriate integer type.
* <p>This class handles the conversion of float of <code>4</code>-byte length
* (bytes are assumed to be <code>8</code>-bit long).
* </p>
*
* @author Jean-Marie Burel
* <a href="mailto:j.burel@dundee.ac.uk">j.burel@dundee.ac.uk</a>
* @author Donald MacDonald
* <a href="mailto:donald@lifesci.dundee.ac.uk">donald@lifesci.dundee.ac.uk</a>
* @since Beta4.3.2
*/
public class FloatConverter
extends BytesConverter
{
/**
* Implemented as specified by {@link BytesConverter}
* @see BytesConverter#pack(ReadOnlyByteArray, int, int)
*/
public double pack(ReadOnlyByteArray data, int offset, int length)
{
int r = 0, tmp;
for (int k = 0; k < length; ++k) {
//Get k-byte starting from MSB, that is LSB[length-k-1].
tmp = data.get(offset+k)&0xFF;
//Add LSB[j]*(2^8)^j to r, where j=length-k-1.
r |= tmp<<(length-k-1)*8;
/*
* This probably deserves a quick explanation.
* We consider every byte value as a digit in base 2^8=B.
* This means that the numeric value is given by
* LSB[0]*B^0 + LSB[1]*B^1 + ... + LSB[n]*B^n.
* So, if we know where the LSB in the input bytes is (that is, the
* endianness), we can calculate the numeric value regardless of the
* endianness of the platform we're running on.
* We use a left shift to calculate LSB[k]*B^k because this operator
* shifts from LSB to MSB, regardless of endianness.
*/
}
return Float.intBitsToFloat(r);
}
}