Add Mersenne Twister random number generator

input/input_state.h

@@ -30,7 +30,6 @@ enum {
 	PAD_BUTTON_LEFT_THUMB = 1 << 18,   // Click left thumb stick on X360
 	PAD_BUTTON_RIGHT_THUMB = 1 << 19,   // Click right thumb stick on X360
 	PAD_BUTTON_UNTHROTTLE = 1 << 20, // Click Tab to unthrottle
-
 };
 
 #ifndef MAX_POINTERS

util/random/rng.h

@@ -1,4 +1,4 @@
-#pragma once
+#pragma once
 
 #include "base/basictypes.h"
 
@@ -24,7 +24,48 @@ public:
 		return (float)R32() / (float)(0xFFFFFFFF);
 	}
 
-private:
+	// public for easy save/load. Yes a bit ugly but better than moving DoState into native.
 	uint32 m_w;
 	uint32 m_z;
 };
+
+
+// Data must consist only of the index and the twister array. This matches the PSP
+// MT context exactly.
+class MersenneTwister {
+public:
+	MersenneTwister(uint32_t seed) : index_(0) {
+		mt_[0] = seed;
+		for (uint32_t i = 1; i < MT_SIZE; i++)
+			mt_[i] = (1812433253 * (mt_[i - 1] ^ (mt_[i - 1] >> 30)) + i);
+	}
+
+	uint32_t R32() {
+		if (index_ == 0)
+			gen();
+		uint32_t y = mt_[index_];
+		y ^=  y >> 11;
+		y ^= (y <<  7) & 2636928640;
+		y ^= (y << 15) & 4022730752;
+		y ^=  y >> 18;
+		index_ = (index_ + 1) % MT_SIZE;
+		return y;
+	}
+
+private:
+	enum {
+		MT_SIZE = 624,
+	};
+
+	uint32_t index_;
+	uint32_t mt_[MT_SIZE];
+
+	void gen() {
+		for(uint32_t i = 0; i < MT_SIZE; i++){
+			uint32_t y = (mt_[i] & 0x80000000) + (mt_[(i + 1) % MT_SIZE] & 0x80000000);
+			mt_[i] = mt_[(i + 397) % MT_SIZE] ^ (y >> 1);
+			if (y % 2) mt_[i] ^= 2567483615;
+		}
+		return;
+	}
+};