From bb6ac9c6781e2639da8957ccf08957974d6ce697 Mon Sep 17 00:00:00 2001
From: cherierm <cherierm@48e7efb5-ca39-0410-a469-dd3cf9ba447f>
Date: Wed, 25 Jun 2008 14:47:58 +0000
Subject: [PATCH] Windows version of rand_r() and drand48()functions.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@5808 48e7efb5-ca39-0410-a469-dd3cf9ba447f
---
 src/surf/random_mgr.c | 184 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 178 insertions(+), 6 deletions(-)

diff --git a/src/surf/random_mgr.c b/src/surf/random_mgr.c
index bae7a68ca5..90d0b93ef3 100644
--- a/src/surf/random_mgr.c
+++ b/src/surf/random_mgr.c
@@ -2,17 +2,189 @@
 #include "xbt/sysdep.h"
 
 #ifdef WIN32
-static double drand48(void)
+
+static unsigned int _seed = 2147483647;
+
+typedef unsigned __int64 uint64_t;
+typedef unsigned int uint32_t;
+
+struct drand48_data
+{
+	unsigned short int __x[3];  /* Current state.  */
+	unsigned short int __old_x[3]; /* Old state.  */
+	unsigned short int __c;     /* Additive const. in congruential formula.  */
+	unsigned short int __init;  /* Flag for initializing.  */
+	unsigned long long int __a; /* Factor in congruential formula.  */
+};
+
+static struct drand48_data __libc_drand48_data = {0}; 
+
+union ieee754_double
+  {
+	double d;
+	
+	/* This is the IEEE 754 double-precision format.  */
+	struct
+	{
+		/* Together these comprise the mantissa.  */
+		unsigned int mantissa1:32;
+		unsigned int mantissa0:20;
+		unsigned int exponent:11;
+		unsigned int negative:1;
+		/* Little endian.  */
+	} ieee;
+	
+	/* This format makes it easier to see if a NaN is a signalling NaN.  */
+	struct
+	{
+		/* Together these comprise the mantissa.  */
+		unsigned int mantissa1:32;
+		unsigned int mantissa0:19;
+		unsigned int quiet_nan:1;
+		unsigned int exponent:11;
+		unsigned int negative:1;
+	
+	} ieee_nan;
+};
+
+#define IEEE754_DOUBLE_BIAS	0x3ff 					/* Added to exponent.  */
+
+double
+drand48 (void);
+
+int
+_drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer);
+
+int
+_erand48_r (unsigned short int xsubi[3], struct drand48_data *buffer, double *result);
+
+
+int
+_erand48_r (unsigned short int xsubi[3], struct drand48_data *buffer, double *result)
+{
+	union ieee754_double temp;
+	
+	/* Compute next state.  */
+	if (_drand48_iterate(xsubi, buffer) < 0)
+		return -1;
+	
+	/* Construct a positive double with the 48 random bits distributed over
+	its fractional part so the resulting FP number is [0.0,1.0).  */
+	
+	temp.ieee.negative = 0;
+	temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
+	temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
+	temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
+	
+	/* Please note the lower 4 bits of mantissa1 are always 0.  */
+	*result = temp.d - 1.0;
+	
+	return 0;
+}
+
+int
+_drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer)
+{
+	uint64_t X;
+	uint64_t result;
+	
+	/* Initialize buffer, if not yet done.  */
+	
+	if(buffer->__init == 0)
+	{
+		buffer->__a = 0x5deece66dull;
+		buffer->__c = 0xb;
+		buffer->__init = 1;
+	}
+	
+	/* Do the real work.  We choose a data type which contains at least
+	48 bits.  Because we compute the modulus it does not care how
+	many bits really are computed.  */
+	
+	X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
+	
+	result = X * buffer->__a + buffer->__c;
+
+	
+	xsubi[0] = result & 0xffff;
+	xsubi[1] = (result >> 16) & 0xffff;
+	xsubi[2] = (result >> 32) & 0xffff;
+	
+	return 0;
+}
+
+
+double
+_drand48 (void)
+{
+	double result;
+	
+	(void) _erand48_r (__libc_drand48_data.__x, &__libc_drand48_data, &result);
+	
+	 return result;
+ }
+
+void
+_srand(unsigned int seed)
+{
+	_seed = seed;
+}
+
+int 
+_rand(void)
 {
-   THROW_UNIMPLEMENTED;
-   return -1;
+	const long a = 16807;
+	const long m = 2147483647;
+	const long q = 127773; /* (m/a) */
+	const long r = 2836; /* (m%a) */
+	
+	long lo, k, s;
+	
+	s = (long)_seed;
+	
+	k = (long)(s/q);
+	
+	lo = (s - q * k);
+	
+	s = a * lo -r * k;
+	
+	if(s <= 0)
+		s += m;
+		
+	_seed = (int)(s & RAND_MAX);
+	
+	return _seed;
 }
 
-static double rand_r(unsigned int* seed)
+int 
+_rand_r(unsigned int* pseed)
 {
-   THROW_UNIMPLEMENTED;
-   return -1;
+	const long a = 16807;
+	const long m = 2147483647;
+	const long q = 127773; 			/* (m/a) */
+	const long r = 2836; 			/* (m%a) */
+	
+	long lo, k, s;
+	
+	s = (long)*pseed;
+	
+	k = (long)(s/q);
+	
+	lo = (s - q * k);
+	
+	s = a * lo -r * k;
+	
+	if(s <= 0)
+		s += m;
+		
+	return (int)(s & RAND_MAX); 
+	
 }
+
+
+#define rand_r _rand_r
+#define drand48 _drand48
+
 #endif
 
 static double custom_random(Generator generator, long int *seed){
-- 
2.20.1