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common/random.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_RANDOM_H
+#define COMMON_RANDOM_H
+
+#include "common/scummsys.h"
+
+namespace Common {
+
+/**
+ * @defgroup common_rng RNG
+ * @ingroup common
+ *
+ * @brief Random number generator (RNG) implementation.
+ *
+ * @{
+ */
+
+class String;
+
+/**
+ * Xorshift* random number generator. Although it is definitely not suitable for
+ * cryptographic purposes, it serves our purposes just fine.
+ */
+class RandomSource {
+private:
+	uint32 _randSeed;
+
+public:
+	/**
+	 * Construct a new randomness source with the specific @p name.
+	 * The name used must be globally unique, and is used to
+	 * register the randomness source with the active event recorder,
+	 * if any.
+	 */
+	RandomSource(const String &name);
+
+	/**
+	 * Generates new seed based on the current date/time
+	 */
+	static uint32 generateNewSeed();
+
+	void setSeed(uint32 seed); /*!< Set the seed used to initialize the RNG. */
+
+	uint32 getSeed() const { /*!< Get a random seed that can be used to initialize the RNG. */
+		return _randSeed;
+	}
+
+	/**
+	 * Generate a random unsigned integer in the interval [0, max].
+	 * @param max	The upper bound
+	 * @return	A random number in the interval [0, max].
+	 */
+	uint getRandomNumber(uint max);
+
+	/**
+	 * Generate a random bit, i.e. either 0 or 1.
+	 * Identical to @c getRandomNumber(1), but potentially faster.
+	 * @return	A random bit, either 0 or 1.
+	 */
+	uint getRandomBit();
+
+	/**
+	 * Generate a random unsigned integer in the interval [min, max].
+	 * @param min	The lower bound.
+	 * @param max	The upper bound.
+	 * @return	A random number in the interval [min, max].
+	 */
+	uint getRandomNumberRng(uint min, uint max);
+
+	/**
+	 * Generates a random signed integer in the interval [min, max].
+	 * @param min	the lower bound
+	 * @param max	the upper bound
+	 * @return	a random number in the interval [min, max]
+	 */
+	int getRandomNumberRngSigned(int min, int max);
+
+	/**
+	* Scrambles the seed in order to get a new result.
+	* Code is shared between getRandomNumber and getRandomBit,
+	* so it is split off for clarity.
+	*/
+private:
+	inline void scrambleSeed();
+};
+
+/** @} */
+
+} // End of namespace Common
+
+#endif