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/* ISC license. */
#include <skalibs/biguint.h>
/*
u = u/a mod m. a and m must be relatively prime - otherwise, infinite loop.
a is not immutable.
Original idea: see http://research.sun.com/techrep/2001/abstract-95.html
*/
void bu_divmod_internal (uint32_t *u, uint32_t *a, uint32_t const *m, unsigned int n)
{
uint32_t bb[n] ; uint32_t *b = bb ;
uint32_t vv[n] ; uint32_t *v = vv ;
bu_copy_internal(b, m, n) ;
bu_zero(v, n) ;
/*** XXX: this iterates like mad, should probably be optimized more */
for (;;)
{
while (!(a[0] & 1))
{
bu_srb(a, n) ;
if (u[0] & 1) bu_add(u, n, u, n, m, n) ;
bu_srb(u, n) ;
}
if ((a[0] == 1) && (bu_len(a, n) == 1)) break ;
if (bu_cmp(a, n, b, n) < 0)
{
uint32_t *t = a ; a = b ; b = t ;
t = u ; u = v ; v = t ;
}
bu_add(a, n, a, n, b, n) ;
bu_add(u, n, u, n, v, n) ;
}
}
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