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common/frac.h

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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/>.
+ *
+ */
+
+#ifndef COMMON_FRAC_H
+#define COMMON_FRAC_H
+
+#include "common/scummsys.h"
+
+/**
+ * @defgroup common_frac Fixed-point fractions
+ * @ingroup common
+ *
+ * @brief  API for fixed-point fractions.
+ *
+ * @{
+ */
+
+/**
+ * The precision of the fractional (fixed-point) type that is defined below.
+ * Normally, you should never need to modify this value.
+ */
+enum {
+	FRAC_BITS = 16,
+	FRAC_LO_MASK = ((1L << FRAC_BITS) - 1),
+	FRAC_HI_MASK = ((1L << FRAC_BITS) - 1) << FRAC_BITS,
+
+	FRAC_ONE = (1L << FRAC_BITS),		// 1.0
+	FRAC_HALF = (1L << (FRAC_BITS-1))	// 0.5
+};
+
+/**
+ * Fixed-point fractions, used by the sound rate converter and other code.
+ */
+typedef int32 frac_t;
+
+inline frac_t doubleToFrac(double value) { return (frac_t)(value * FRAC_ONE); }
+inline double fracToDouble(frac_t value) { return ((double)value) / FRAC_ONE; }
+
+inline frac_t intToFrac(int16 value) { return value * (1 << FRAC_BITS); }
+inline int16 fracToInt(frac_t value) { return value / (1 << FRAC_BITS); }
+
+/** @} */
+
+#endif