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'math.randomseed()' sets a somewhat random seed

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When called with no arguments, 'math.randomseed' uses time and ASLR
to generate a somewhat random seed. the initial seed when Lua starts
is generated this way.
This commit is contained in:
Roberto Ierusalimschy
2019-03-13 14:47:48 -03:00
parent c5feac2b5e
commit 9eca305e75
3 changed files with 36 additions and 20 deletions
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31
lmathlib.c
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@@ -301,7 +301,7 @@ static int math_type (lua_State *L) {
/* rotate left 'x' by 'n' bits */
static Rand64 rotl (Rand64 x, int n) {
return (x << n) | (trim64(x) >> (64 - n));
return (x << n) | (trim64(x) >> (64 - n));
}
static Rand64 nextrand (Rand64 *state) {
@@ -597,11 +597,27 @@ static void setseed (Rand64 *state, lua_Unsigned n1, lua_Unsigned n2) {
}
/*
** Set a "random" seed. To get some randomness, use the current time
** and the address of 'L' (in case the machine does address space layout
** randomization).
*/
static void randseed (lua_State *L, RanState *state) {
lua_Unsigned seed1 = (lua_Unsigned)time(NULL);
lua_Unsigned seed2 = (lua_Unsigned)(size_t)L;
setseed(state->s, seed1, seed2);
}
static int math_randomseed (lua_State *L) {
RanState *state = (RanState *)lua_touserdata(L, lua_upvalueindex(1));
lua_Integer n1 = luaL_checkinteger(L, 1);
lua_Integer n2 = luaL_optinteger(L, 2, 0);
setseed(state->s, n1, n2);
if (lua_isnone(L, 1))
randseed(L, state);
else {
lua_Integer n1 = luaL_checkinteger(L, 1);
lua_Integer n2 = luaL_optinteger(L, 2, 0);
setseed(state->s, n1, n2);
}
return 0;
}
@@ -615,15 +631,10 @@ static const luaL_Reg randfuncs[] = {
/*
** Register the random functions and initialize their state.
** To give some "randomness" to the initial seed, use the current time
** and the address of 'L' (in case the machine does address space layout
** randomization).
*/
static void setrandfunc (lua_State *L) {
RanState *state = (RanState *)lua_newuserdatauv(L, sizeof(RanState), 0);
lua_Unsigned seed1 = (lua_Unsigned)time(NULL);
lua_Unsigned seed2 = (lua_Unsigned)(size_t)L;
setseed(state->s, seed1, seed2);
randseed(L, state); /* initialize with a "random" seed */
luaL_setfuncs(L, randfuncs, 1);
}