/*
* mpbrnd_w
* generates a random number in the range 1 < r < b-1
* need workspace of (size) words
*/
void mpbrnd_w(const mpbarrett* b, randomGeneratorContext* rc, mpw* result, mpw* wksp)
{
size_t msz = mpmszcnt(b->size, b->modl);
mpcopy(b->size, wksp, b->modl);
mpsubw(b->size, wksp, 1);
do
{
rc->rng->next(rc->param, (byte*) result, MP_WORDS_TO_BYTES(b->size));
result[0] &= (MP_ALLMASK >> msz);
while (mpge(b->size, result, wksp))
mpsub(b->size, result, wksp);
} while (mpleone(b->size, result));
}
/*
* needs workspace of (size*2) words
*/
static void mpprndbits(mpbarrett* p, size_t bits, size_t lsbset, const mpnumber* min, const mpnumber* max, randomGeneratorContext* rc, mpw* wksp)
{
register size_t size = p->size;
register size_t msbclr = MP_WORDS_TO_BITS(size) - bits;
/* assume that mpbits(max) == bits */
/* calculate k=max-min; generate q such that 0 <= q <= k; then set p = q + min */
/* for the second step, set the appropriate number of bits */
if (max)
{
mpsetx(size, wksp, max->size, max->data);
}
else
{
mpfill(size, wksp, MP_ALLMASK);
wksp[0] &= (MP_ALLMASK >> msbclr);
}
if (min)
{
mpsetx(size, wksp+size, min->size, min->data);
}
else
{
mpzero(size, wksp+size);
wksp[size] |= (MP_MSBMASK >> msbclr);
}
mpsub(size, wksp, wksp+size);
rc->rng->next(rc->param, (byte*) p->modl, MP_WORDS_TO_BYTES(size));
p->modl[0] &= (MP_ALLMASK >> msbclr);
while (mpgt(size, p->modl, wksp))
mpsub(size, p->modl, wksp);
mpadd(size, p->modl, wksp+size);
if (lsbset)
p->modl[size-1] |= (MP_ALLMASK >> (MP_WBITS - lsbset));
}
