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using some weak "randomness" (time and memory address) to initialize 

seeds for the PRNG
This commit is contained in:
Roberto Ierusalimschy 2018-05-16 08:27:59 -03:00
parent 80bd4a8940
commit de53c2ec7e
1 changed files with 21 additions and 10 deletions
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31
lmathlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lmathlib.c,v 1.132 2018/05/04 20:01:45 roberto Exp roberto $
** $Id: lmathlib.c,v 1.133 2018/05/09 14:54:37 roberto Exp roberto $
** Standard mathematical library
** See Copyright Notice in lua.h
*/
@ -14,6 +14,7 @@
#include <limits.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include "lua.h"
@ -304,14 +305,15 @@ static Rand64 rotl (Rand64 x, int n) {
}
static Rand64 nextrand (Rand64 *state) {
Rand64 res = rotl(state[1] * 5, 7) * 9;
Rand64 t = state[1] << 17;
state[2] ^= state[0];
state[3] ^= state[1];
state[1] ^= state[2];
state[0] ^= state[3];
state[2] ^= t;
state[3] = rotl(state[3], 45);
Rand64 state0 = state[0];
Rand64 state1 = state[1];
Rand64 state2 = state[2] ^ state0;
Rand64 state3 = state[3] ^ state1;
Rand64 res = rotl(state1 * 5, 7) * 9;
state[0] = state0 ^ state3;
state[1] = state1 ^ state2;
state[2] = state2 ^ (state1 << 17);
state[3] = rotl(state3, 45);
return res;
}
@ -591,9 +593,18 @@ static const luaL_Reg randfuncs[] = {
{NULL, NULL}
};
/*
** 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);
setseed(state->s, 0, 0);
lua_Unsigned seed1 = (lua_Unsigned)time(NULL);
lua_Unsigned seed2 = (lua_Unsigned)(size_t)L;
setseed(state->s, seed1, seed2);
luaL_setfuncs(L, randfuncs, 1);
}