shithub: libmujs

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Issue #85: Use explicit seed in Math.random().

--- a/jsi.h

+++ b/jsi.h

@@ -203,6 +203,8 @@

 	js_Object *TypeError_prototype;

 	js_Object *URIError_prototype;

+	unsigned int seed; /* Math.random seed */

+

 	int nextref; /* for js_ref use */

 	js_Object *R; /* registry of hidden values */

 	js_Object *G; /* the global object */

--- a/jsmath.c

+++ b/jsmath.c

@@ -4,6 +4,32 @@

 #include <time.h>

+#define JS_RAND_MAX (0x7fffffff)

+

+static unsigned int jsM_rand_temper(unsigned int x)

+{

+	x ^= x>>11;

+	x ^= x<<7 & 0x9D2C5680;

+	x ^= x<<15 & 0xEFC60000;

+	x ^= x>>18;

+	return x;

+}

+

+static int jsM_rand_r(unsigned int *seed)

+{

+	return jsM_rand_temper(*seed = *seed * 1103515245 + 12345)/2;

+}

+

+static double jsM_round(double x)

+{

+	if (isnan(x)) return x;

+	if (isinf(x)) return x;

+	if (x == 0) return x;

+	if (x > 0 && x < 0.5) return 0;

+	if (x < 0 && x >= -0.5) return -0;

+	return floor(x + 0.5);

+}

+

 static void Math_abs(js_State *J)

 {

 	js_pushnumber(J, fabs(js_tonumber(J, 1)));

@@ -68,23 +94,13 @@

 static void Math_random(js_State *J)

 {

-	js_pushnumber(J, rand() / (RAND_MAX + 1.0));

+	js_pushnumber(J, jsM_rand_r(&J->seed) / (JS_RAND_MAX + 1.0));

 }

-static double do_round(double x)

-{

-	if (isnan(x)) return x;

-	if (isinf(x)) return x;

-	if (x == 0) return x;

-	if (x > 0 && x < 0.5) return 0;

-	if (x < 0 && x >= -0.5) return -0;

-	return floor(x + 0.5);

-}

-

 static void Math_round(js_State *J)

 {

 	double x = js_tonumber(J, 1);

-	js_pushnumber(J, do_round(x));

+	js_pushnumber(J, jsM_round(x));

 }

 static void Math_sin(js_State *J)

@@ -140,7 +156,7 @@

 void jsB_initmath(js_State *J)

 {

-	srand(time(NULL));

+	J->seed = time(NULL);

 	js_pushobject(J, jsV_newobject(J, JS_CMATH, J->Object_prototype));

 	{