COMMON: Move Lua into Common and make it into...

an engine feature

common/lua/double_serialization.cpp

@@ -0,0 +1,68 @@
+/* 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 "common/lua/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(fabs(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;
+}
+
+} // End of namespace Sword25