Initial commit

engines/glk/glulx/float.cpp

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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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "glk/glulx/glulx.h"
+
+namespace Glk {
+namespace Glulx {
+
+uint Glulx::encode_float(gfloat32 val) {
+	gfloat32 absval;
+	uint sign;
+	int expo;
+	gfloat32 mant;
+	uint fbits;
+
+	if (signbit(val)) {
+		sign = 0x80000000;
+		absval = -val;
+	} else {
+		sign = 0x0;
+		absval = val;
+	}
+
+	if (isinf(val)) {
+		return sign | 0x7f800000; /* infinity */
+	}
+
+	if (isnan(val)) {
+		return sign | 0x7fc00000;
+	}
+
+	mant = frexpf(absval, &expo);
+
+	/* Normalize mantissa to be in the range [1.0, 2.0) */
+	if (0.5 <= mant && mant < 1.0) {
+		mant *= 2.0;
+		expo--;
+	} else if (mant == 0.0) {
+		expo = 0;
+	} else {
+		return sign | 0x7f800000; /* infinity */
+	}
+
+	if (expo >= 128) {
+		return sign | 0x7f800000; /* infinity */
+	} else if (expo < -126) {
+		/* Denormalized (very small) number */
+		mant = ldexpf(mant, 126 + expo);
+		expo = 0;
+	} else if (!(expo == 0 && mant == 0.0)) {
+		expo += 127;
+		mant -= 1.0; /* Get rid of leading 1 */
+	}
+
+	mant *= 8388608.0; /* 2^23 */
+	fbits = (uint)(mant + 0.5); /* round mant to nearest int */
+	if (fbits >> 23) {
+		/* The carry propagated out of a string of 23 1 bits. */
+		fbits = 0;
+		expo++;
+		if (expo >= 255) {
+			return sign | 0x7f800000; /* infinity */
+		}
+	}
+
+	return (sign) | ((uint)(expo << 23)) | (fbits);
+}
+
+gfloat32 Glulx::decode_float(uint val) {
+	int sign;
+	int expo;
+	uint mant;
+	gfloat32 res;
+
+	/* First byte */
+	sign = ((val & 0x80000000) != 0);
+	expo = (val >> 23) & 0xFF;
+	mant = val & 0x7FFFFF;
+
+	if (expo == 255) {
+		if (mant == 0) {
+			/* Infinity */
+			return (sign ? (-INFINITY) : (INFINITY));
+		} else {
+			/* Not a number */
+			return (sign ? (-NAN) : (NAN));
+		}
+	}
+
+	res = (gfloat32)mant / 8388608.0;
+
+	if (expo == 0) {
+		expo = -126;
+	} else {
+		res += 1.0;
+		expo -= 127;
+	}
+	res = ldexpf(res, expo);
+
+	return (sign ? (-res) : (res));
+}
+
+} // End of namespace Glulx
+} // End of namespace Glk