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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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.
*
*/
#include "sword25/util/double_serialization.h"
#include "common/scummsys.h"
namespace Util {
SerializedDouble encodeDouble(double value) {
// Split the value into its significand and exponent
int exponent;
double significand = frexp(value, &exponent);
// Shift the the first part of the significand into the integer range
double shiftedsignificandPart = ldexp(abs(significand), 32);
uint32 significandOne = uint32(floor(shiftedsignificandPart));
// Shift the remainder of the significand into the integer range
shiftedsignificandPart -= significandOne;
uint32 significandTwo = (uint32)(ldexp(shiftedsignificandPart, 31));
SerializedDouble returnValue;
returnValue.significandOne = significandOne; // SignificandOne
returnValue.signAndSignificandTwo = ((uint32)(value < 0 ? 1 : 0) << 31) | // Sign
significandTwo; // SignificandTwo
returnValue.exponent = (int16)exponent;
return returnValue;
}
double decodeDouble(SerializedDouble value) {
// Expand the exponent and the parts of the significand
int exponent = (int)value.exponent;
double expandedsignificandOne = (double)value.significandOne;
double expandedsignificandTwo = (double)(value.signAndSignificandTwo & 0x7FFFFFFF);
// Deflate the significand
double shiftedsignificand = ldexp(expandedsignificandTwo, -21);
double significand = ldexp(expandedsignificandOne + shiftedsignificand, -32);
// Re-calculate the actual double
double returnValue = ldexp(significand, exponent);
// Check the sign bit and return
return ((value.signAndSignificandTwo & 0x80000000) == 0x80000000) ? -returnValue : returnValue;
}
#if 0
// Why these are needed?
uint64 encodeDouble_64(double value) {
// Split the value into its significand and exponent
int exponent;
double significand = frexp(value, &exponent);
// Shift the significand into the integer range
double shiftedsignificand = ldexp(abs(significand), 53);
// Combine everything using the IEEE standard
uint64 uintsignificand = (uint64)shiftedsignificand;
return ((uint64)(value < 0 ? 1 : 0) << 63) | // Sign
((uint64)(exponent + 1023) << 52) | // Exponent stored as an offset to 1023
(uintsignificand & 0x000FFFFFFFFFFFFFLL); // significand with MSB inferred
}
double decodeDouble_64(uint64 value) {
// Expand the exponent and significand
int exponent = (int)((value >> 52) & 0x7FF) - 1023;
double expandedsignificand = (double)(0x10000000000000LL /* Inferred MSB */ | (value & 0x000FFFFFFFFFFFFFLL));
// Deflate the significand
int temp;
double significand = frexp(expandedsignificand, &temp);
// Re-calculate the actual double
double returnValue = ldexp(significand, exponent);
// Check the sign bit and return
return ((value & 0x8000000000000000LL) == 0x8000000000000000LL) ? -returnValue : returnValue;
}
CompactSerializedDouble encodeDouble_Compact(double value) {
// Split the value into its significand and exponent
int exponent;
double significand = frexp(value, &exponent);
// Shift the the first part of the significand into the integer range
double shiftedsignificandPart = ldexp(abs(significand), 32);
uint32 significandOne = uint32(floor(shiftedsignificandPart));
// Shift the remainder of the significand into the integer range
shiftedsignificandPart -= significandOne;
uint32 significandTwo = (uint32)(ldexp(shiftedsignificandPart, 21));
CompactSerializedDouble returnValue;
returnValue.signAndSignificandOne = ((uint32)(value < 0 ? 1 : 0) << 31) | // Sign
(significandOne & 0x7FFFFFFF); // significandOne with MSB inferred
// Exponent stored as an offset to 1023
returnValue.exponentAndSignificandTwo = ((uint32)(exponent + 1023) << 21) | significandTwo;
return returnValue;
}
double decodeDouble_Compact(CompactSerializedDouble value) {
// Expand the exponent and the parts of the significand
int exponent = (int)(value.exponentAndSignificandTwo >> 21) - 1023;
double expandedsignificandOne = (double)(0x80000000 /* Inferred MSB */ | (value.signAndSignificandOne & 0x7FFFFFFF));
double expandedsignificandTwo = (double)(value.exponentAndSignificandTwo & 0x1FFFFF);
// Deflate the significand
double shiftedsignificand = ldexp(expandedsignificandTwo, -21);
double significand = ldexp(expandedsignificandOne + shiftedsignificand, -32);
// Re-calculate the actual double
double returnValue = ldexp(significand, exponent);
// Check the sign bit and return
return ((value.signAndSignificandOne & 0x80000000) == 0x80000000) ? -returnValue : returnValue;
}
#endif
} // End of namespace Sword25
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