/* ==================================================================== | |
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.poi.ss.util; | |
import java.math.BigInteger; | |
import static org.apache.poi.ss.util.IEEEDouble.*; | |
/** | |
* Represents a 64 bit IEEE double quantity expressed with both decimal and binary exponents | |
* Does not handle negative numbers or zero | |
* <p/> | |
* The value of a {@link ExpandedDouble} is given by<br/> | |
* <tt> a × 2<sup>b</sup></tt> | |
* <br/> | |
* where:<br/> | |
* | |
* <tt>a</tt> = <i>significand</i><br/> | |
* <tt>b</tt> = <i>binaryExponent</i> - bitLength(significand) + 1<br/> | |
* | |
* @author Josh Micich | |
*/ | |
final class ExpandedDouble { | |
private static final BigInteger BI_FRAC_MASK = BigInteger.valueOf(FRAC_MASK); | |
private static final BigInteger BI_IMPLIED_FRAC_MSB = BigInteger.valueOf(FRAC_ASSUMED_HIGH_BIT); | |
private static BigInteger getFrac(long rawBits) { | |
return BigInteger.valueOf(rawBits).and(BI_FRAC_MASK).or(BI_IMPLIED_FRAC_MSB).shiftLeft(11); | |
} | |
public static ExpandedDouble fromRawBitsAndExponent(long rawBits, int exp) { | |
return new ExpandedDouble(getFrac(rawBits), exp); | |
} | |
/** | |
* Always 64 bits long (MSB, bit-63 is '1') | |
*/ | |
private final BigInteger _significand; | |
private final int _binaryExponent; | |
public ExpandedDouble(long rawBits) { | |
int biasedExp = (int) (rawBits >> 52); | |
if (biasedExp == 0) { | |
// sub-normal numbers | |
BigInteger frac = BigInteger.valueOf(rawBits).and(BI_FRAC_MASK); | |
int expAdj = 64 - frac.bitLength(); | |
_significand = frac.shiftLeft(expAdj); | |
_binaryExponent = (biasedExp & 0x07FF) - 1023 - expAdj; | |
} else { | |
BigInteger frac = getFrac(rawBits); | |
_significand = frac; | |
_binaryExponent = (biasedExp & 0x07FF) - 1023; | |
} | |
} | |
ExpandedDouble(BigInteger frac, int binaryExp) { | |
if (frac.bitLength() != 64) { | |
throw new IllegalArgumentException("bad bit length"); | |
} | |
_significand = frac; | |
_binaryExponent = binaryExp; | |
} | |
/** | |
* Convert to an equivalent {@link NormalisedDecimal} representation having 15 decimal digits of precision in the | |
* non-fractional bits of the significand. | |
*/ | |
public NormalisedDecimal normaliseBaseTen() { | |
return NormalisedDecimal.create(_significand, _binaryExponent); | |
} | |
/** | |
* @return the number of non-fractional bits after the MSB of the significand | |
*/ | |
public int getBinaryExponent() { | |
return _binaryExponent; | |
} | |
public BigInteger getSignificand() { | |
return _significand; | |
} | |
} |