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/* Copyright (c) 2010 by Michael J. Roberts. All Rights Reserved. */
/*
Name
vmisaac.cpp - T3 VM ISAAC random number generator implementation
Function
Notes
Modified
04/11/10 MJRoberts - Creation
*/
#include "vmisaac.h"
/* service macros for ISAAC random number generator */
#define isaac_ind(mm,x) ((mm)[(x>>2)&(ISAAC_RANDSIZ-1)])
#define isaac_step(mix,a,b,mm,m,m2,r,x) \
{ \
x = *m; \
a = ((a^(mix)) + *(m2++)) & 0xffffffff; \
*(m++) = y = (isaac_ind(mm,x) + a + b) & 0xffffffff; \
*(r++) = b = (isaac_ind(mm,y>>ISAAC_RANDSIZL) + x) & 0xffffffff; \
}
#define isaac_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; \
}
/* generate the group of numbers */
void isaac_gen_group(isaacctx *ctx)
{
uint32_t a;
uint32_t b;
uint32_t x;
uint32_t y;
uint32_t *m;
uint32_t *mm;
uint32_t *m2;
uint32_t *r;
uint32_t *mend;
mm = ctx->mem;
r = ctx->rsl;
a = ctx->a;
b = (ctx->b + (++ctx->c)) & 0xffffffff;
for (m = mm, mend = m2 = m + (ISAAC_RANDSIZ/2) ; m<mend ; )
{
isaac_step(a<<13, a, b, mm, m, m2, r, x);
isaac_step(a>>6, a, b, mm, m, m2, r, x);
isaac_step(a<<2, a, b, mm, m, m2, r, x);
isaac_step(a>>16, a, b, mm, m, m2, r, x);
}
for (m2 = mm; m2<mend; )
{
isaac_step(a<<13, a, b, mm, m, m2, r, x);
isaac_step(a>>6, a, b, mm, m, m2, r, x);
isaac_step(a<<2, a, b, mm, m, m2, r, x);
isaac_step(a>>16, a, b, mm, m, m2, r, x);
}
ctx->b = b;
ctx->a = a;
}
/*
* Initialize. If flag is true, then use the contents of ctx->rsl[] to
* initialize ctx->mm[]; otherwise, we'll use a fixed starting
* configuration.
*/
void isaac_init(isaacctx *ctx, int flag)
{
int i;
uint32_t a;
uint32_t b;
uint32_t c;
uint32_t d;
uint32_t e;
uint32_t f;
uint32_t g;
uint32_t h;
uint32_t *m;
uint32_t *r;
ctx->a = ctx->b = ctx->c = 0;
m = ctx->mem;
r = ctx->rsl;
a = b = c = d = e = f = g = h = 0x9e3779b9; /* the golden ratio */
/* scramble the initial settings */
for (i = 0 ; i < 4 ; ++i)
{
isaac_mix(a, b, c, d, e, f, g, h);
}
if (flag)
{
/* initialize using the contents of ctx->rsl[] as the seed */
for (i = 0 ; i < ISAAC_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];
isaac_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 < ISAAC_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];
isaac_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
{
/* initialize using fixed initial settings */
for (i = 0 ; i < ISAAC_RANDSIZ ; i += 8)
{
isaac_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;
}
}
/* fill in the first set of results */
isaac_gen_group(ctx);
/* prepare to use the first set of results */
ctx->cnt = ISAAC_RANDSIZ;
}
/*
* Get the internal state
*/
size_t isaac_get_state(isaacctx *ctx, char *buf)
{
/* if the didn't provide a buffer, it's a size-needed query */
const size_t sz = 4 * (4 + ISAAC_RANDSIZ + ISAAC_RANDSIZ);
if (buf == 0)
return sz;
/* copy the scalar members */
oswp4(buf, ctx->cnt); buf += 4;
oswp4(buf, ctx->a); buf += 4;
oswp4(buf, ctx->b); buf += 4;
oswp4(buf, ctx->c); buf += 4;
/* copy the array members */
for (int i = 0 ; i < ISAAC_RANDSIZ ; ++i, buf += 8)
{
oswp4(buf, ctx->rsl[i]);
oswp4(buf+4, ctx->mem[i]);
}
return sz;
}
/*
* Set the internal state
*/
void isaac_set_state(isaacctx *ctx, const char *buf)
{
/* decode the buffer into our context */
ctx->cnt = osrp4(buf); buf += 4;
ctx->a = osrp4(buf); buf += 4;
ctx->b = osrp4(buf); buf += 4;
ctx->c = osrp4(buf); buf += 4;
for (int i = 0 ; i < ISAAC_RANDSIZ ; ++i, buf += 8)
{
ctx->rsl[i] = osrp4(buf);
ctx->mem[i] = osrp4(buf+4);
}
/* sanity check the result: make sure 'cnt' is in range */
if (ctx->cnt > ISAAC_RANDSIZ)
ctx->cnt = 0;
}
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