moth/include/isaac.c

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/*
------------------------------------------------------------------------------
rand.c: By Bob Jenkins. My random number generator, ISAAC. Public Domain.
MODIFIED:
960327: Creation (addition of randinit, really)
970719: use context, not global variables, for internal state
980324: added main (ifdef'ed out), also rearranged randinit()
010626: Note that this is public domain
------------------------------------------------------------------------------
*/
#include <stdint.h>
#include "rand.h"
#define ind(mm,x) (*(uint32_t *)((uint8_t *)(mm) + ((x) & ((RANDSIZ-1)<<2))))
#define rngstep(mix,a,b,mm,m,m2,r,x) \
{ \
x = *m; \
a = (a^(mix)) + *(m2++); \
*(m++) = y = ind(mm,x) + a + b; \
*(r++) = b = ind(mm,y>>RANDSIZL) + x; \
}
void isaac(struct randctx *ctx)
{
register uint32_t a, b, x, y, *m, *mm, *m2, *r, *mend;
mm = ctx->randmem;
r = ctx->randrsl;
a = ctx->randa;
b = ctx->randb + (++ctx->randc);
for (m = mm, mend = m2 = m + (RANDSIZ / 2); m < mend;) {
rngstep(a << 13, a, b, mm, m, m2, r, x);
rngstep(a >> 6, a, b, mm, m, m2, r, x);
rngstep(a << 2, a, b, mm, m, m2, r, x);
rngstep(a >> 16, a, b, mm, m, m2, r, x);
}
for (m2 = mm; m2 < mend;) {
rngstep(a << 13, a, b, mm, m, m2, r, x);
rngstep(a >> 6, a, b, mm, m, m2, r, x);
rngstep(a << 2, a, b, mm, m, m2, r, x);
rngstep(a >> 16, a, b, mm, m, m2, r, x);
}
ctx->randb = b;
ctx->randa = a;
}
#define mix(a,b,c,d,e,f,g,h) \
{ \
a^=b<<11; d+=a; b+=c; \
b^=c>>2; e+=b; c+=d; \
c^=d<<8; f+=c; d+=e; \
d^=e>>16; g+=d; e+=f; \
e^=f<<10; h+=e; f+=g; \
f^=g>>4; a+=f; g+=h; \
g^=h<<8; b+=g; h+=a; \
h^=a>>9; c+=h; a+=b; \
}
/* if (flag==TRUE), then use the contents of randrsl[] to initialize mm[]. */
void randinit(struct randctx *ctx, uint_fast8_t flag)
{
uint_fast32_t i;
uint32_t a, b, c, d, e, f, g, h;
uint32_t *m, *r;
ctx->randa = ctx->randb = ctx->randc = 0;
m = ctx->randmem;
r = ctx->randrsl;
a = b = c = d = e = f = g = h = 0x9e3779b9; /* the golden ratio */
for (i = 0; i < 4; ++i) { /* scramble it */
mix(a, b, c, d, e, f, g, h);
}
if (flag) {
/* initialize using the contents of r[] as the seed */
for (i = 0; i < RANDSIZ; i += 8) {
a += r[i];
b += r[i + 1];
c += r[i + 2];
d += r[i + 3];
e += r[i + 4];
f += r[i + 5];
g += r[i + 6];
h += r[i + 7];
mix(a, b, c, d, e, f, g, h);
m[i] = a;
m[i + 1] = b;
m[i + 2] = c;
m[i + 3] = d;
m[i + 4] = e;
m[i + 5] = f;
m[i + 6] = g;
m[i + 7] = h;
}
/* do a second pass to make all of the seed affect all of m */
for (i = 0; i < RANDSIZ; i += 8) {
a += m[i];
b += m[i + 1];
c += m[i + 2];
d += m[i + 3];
e += m[i + 4];
f += m[i + 5];
g += m[i + 6];
h += m[i + 7];
mix(a, b, c, d, e, f, g, h);
m[i] = a;
m[i + 1] = b;
m[i + 2] = c;
m[i + 3] = d;
m[i + 4] = e;
m[i + 5] = f;
m[i + 6] = g;
m[i + 7] = h;
}
} else {
/* fill in m[] with messy stuff */
for (i = 0; i < RANDSIZ; i += 8) {
mix(a, b, c, d, e, f, g, h);
m[i] = a;
m[i + 1] = b;
m[i + 2] = c;
m[i + 3] = d;
m[i + 4] = e;
m[i + 5] = f;
m[i + 6] = g;
m[i + 7] = h;
}
}
isaac(ctx); /* fill in the first set of results */
ctx->randcnt = RANDSIZ; /* prepare to use the first set of results */
}
#ifdef NEVER
#include <stdio.h>
int main()
{
uint32_t i, j;
struct randctx ctx;
ctx.randa = ctx.randb = ctx.randc = (uint32_t) 0;
for (i = 0; i < 256; ++i)
ctx.randrsl[i] = (uint32_t) 0;
randinit(&ctx, 1);
for (i = 0; i < 2; ++i) {
isaac(&ctx);
for (j = 0; j < 256; ++j) {
printf("%.8x", ctx.randrsl[j]);
if ((j & 7) == 7)
printf("\n");
}
}
}
#endif