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/**********************************************************************
* $Id: CommonBits.cpp 1820 2006-09-06 16:54:23Z mloskot $
*
* GEOS - Geometry Engine Open Source
* http://geos.refractions.net
*
* Copyright (C) 2005-2006 Refractions Research Inc.
* Copyright (C) 2001-2002 Vivid Solutions Inc.
*
* This is free software; you can redistribute and/or modify it under
* the terms of the GNU Lesser General Public Licence as published
* by the Free Software Foundation.
* See the COPYING file for more information.
*
**********************************************************************/
#include <geos/platform.h> // for int64
#include <geos/precision/CommonBits.h>
namespace geos {
namespace precision { // geos.precision
/*static public*/
int64
CommonBits::signExpBits(int64 num)
{
return num >> 52;
}
/*static public*/
int
CommonBits::numCommonMostSigMantissaBits(int64 num1, int64 num2)
{
int count = 0;
for (int i = 52; i >= 0; i--){
if (getBit(num1, i) != getBit(num2, i))
return count;
count++;
}
return 52;
}
/*static public*/
int64
CommonBits::zeroLowerBits(int64 bits, int nBits)
{
int64 invMask = (1<< nBits)-1;
int64 mask = ~ invMask;
int64 zeroed = bits & mask;
return zeroed;
}
/*static public*/
int
CommonBits::getBit(int64 bits, int i)
{
int64 mask = (1 << i);
return (bits & mask) != 0 ? 1 : 0;
}
/*public*/
CommonBits::CommonBits() {
isFirst = true;
commonMantissaBitsCount = 53;
commonBits = 0;
}
/*public*/
void
CommonBits::add(double num)
{
int64 numBits=(int64)num;
if (isFirst) {
commonBits = numBits;
commonSignExp = signExpBits(commonBits);
isFirst = false;
return;
}
int64 numSignExp = signExpBits(numBits);
if (numSignExp != commonSignExp) {
commonBits = 0;
return;
}
// System.out.println(toString(commonBits));
// System.out.println(toString(numBits));
commonMantissaBitsCount = numCommonMostSigMantissaBits(commonBits, numBits);
commonBits = zeroLowerBits(commonBits, 64 - (12 + commonMantissaBitsCount));
// System.out.println(toString(commonBits));
}
/*public*/
double
CommonBits::getCommon()
{
return (double)commonBits;
}
///**
//* A representation of the Double bits formatted for easy readability
//*/
//String toString(int64 bits)
//{
//double x = Double.int64BitsToDouble(bits);
//String numStr = int64.toBinaryString(bits);
//String padStr = "0000000000000000000000000000000000000000000000000000000000000000" + numStr;
//String bitStr = padStr.substring(padStr.length() - 64);
//String str = bitStr.substring(0, 1) + " "
//+ bitStr.substring(1, 12) + "(exp) "
//+ bitStr.substring(12)
//+ " [ " + x + " ]";
//return str;
//}
} // namespace geos.precision
} // namespace geos
/**********************************************************************
* $Log$
* Revision 1.4 2006/03/23 09:17:19 strk
* precision.h header split, minor optimizations
*
**********************************************************************/
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