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

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This commit is contained in:
Tor Andersson
2019-02-25 12:15:56 +01:00
parent 43c844510b
commit d3feec4365
2 changed files with 31 additions and 13 deletions
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2
jsi.h
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@@ -203,6 +203,8 @@ struct js_State
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 */

42
jsmath.c
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@@ -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_pow(js_State *J)
static void Math_random(js_State *J)
{
js_pushnumber(J, rand() / (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);
js_pushnumber(J, jsM_rand_r(&J->seed) / (JS_RAND_MAX + 1.0));
}
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 @@ static void Math_min(js_State *J)
void jsB_initmath(js_State *J)
{
srand(time(NULL));
J->seed = time(NULL);
js_pushobject(J, jsV_newobject(J, JS_CMATH, J->Object_prototype));
{