init

common/GameUI/Random.cpp

@@ -0,0 +1,131 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: Basic random number generator
+//
+// $NoKeywords: $
+//===========================================================================//
+
+
+#include <time.h>
+#include "Random.h"
+
+// memdbgon must be the last include file in a .cpp file!!!
+#include "tier0/memdbgon.h"
+
+#define IA 16807
+#define IM 2147483647
+#define IQ 127773
+#define IR 2836
+#define NTAB 32
+#define NDIV (1+(IM-1)/NTAB)
+
+static long idum = 0;
+
+void SeedRandomNumberGenerator(long lSeed)
+{
+	if (lSeed)
+	{
+		idum = lSeed;
+	}
+	else
+	{
+		idum = -time(NULL);
+	}
+	if (1000 < idum)
+	{
+		idum = -idum;
+	}
+	else if (-1000 < idum)
+	{
+		idum -= 22261048;
+	}
+}
+
+long ran1(void)
+{
+	int j;
+	long k;
+	static long iy=0;
+	static long iv[NTAB];
+	
+	if (idum <= 0 || !iy)
+	{
+		if (-(idum) < 1) idum=1;
+		else idum = -(idum);
+		for (j=NTAB+7;j>=0;j--)
+		{
+			k=(idum)/IQ;
+			idum=IA*(idum-k*IQ)-IR*k;
+			if (idum < 0) idum += IM;
+			if (j < NTAB) iv[j] = idum;
+		}
+		iy=iv[0];
+	}
+	k=(idum)/IQ;
+	idum=IA*(idum-k*IQ)-IR*k;
+	if (idum < 0) idum += IM;
+	j=iy/NDIV;
+	iy=iv[j];
+	iv[j] = idum;
+
+	return iy;
+}
+
+// fran1 -- return a random floating-point number on the interval [0,1)
+//
+#define AM (1.0/IM)
+#define EPS 1.2e-7
+#define RNMX (1.0-EPS)
+float fran1(void)
+{
+	float temp = (float)AM*ran1();
+	if (temp > RNMX) return (float)RNMX;
+	else return temp;
+}
+
+#ifndef _XBOX
+float RandomFloat( float flLow, float flHigh )
+{
+	if (idum == 0)
+	{
+		SeedRandomNumberGenerator(0);
+	}
+
+	float fl = fran1(); // float in [0,1)
+	return (fl * (flHigh-flLow)) + flLow; // float in [low,high)
+}
+#endif
+
+long RandomLong( long lLow, long lHigh )
+{
+	if (idum == 0)
+	{
+		SeedRandomNumberGenerator(0);
+	}
+
+	unsigned long maxAcceptable;
+	unsigned long x = lHigh-lLow+1;
+	unsigned long n;
+	if (x <= 0 || MAX_RANDOM_RANGE < x-1)
+	{
+		return lLow;
+	}
+
+	// The following maps a uniform distribution on the interval [0,MAX_RANDOM_RANGE]
+	// to a smaller, client-specified range of [0,x-1] in a way that doesn't bias
+	// the uniform distribution unfavorably. Even for a worst case x, the loop is
+	// guaranteed to be taken no more than half the time, so for that worst case x,
+	// the average number of times through the loop is 2. For cases where x is
+	// much smaller than MAX_RANDOM_RANGE, the average number of times through the
+	// loop is very close to 1.
+	//
+	maxAcceptable = MAX_RANDOM_RANGE - ((MAX_RANDOM_RANGE+1) % x );
+	do
+	{
+		n = ran1();
+	} while (n > maxAcceptable);
+
+	return lLow + (n % x);
+}
+
+