static error bignum_monty_reduce(bignum *A, const bignum *T, const bignum *m,
const monty_ctx *monty)
{
size_t n = bignum_len_words(m);
BIGNUM_TMP(tmp);
/* 1. A <- T */
ER(bignum_dup(A, T));
/* 2. For i from 0 to (n - 1) do the following: */
for (size_t i = 0; i < n; i++)
{
/* 2.1 u_i <- a_i m' mod b */
uint32_t u = word(A, i) * monty->mprime;
/* 2.2 A <- A + u_i m b^i */
ER(bignum_mulw(&tmp, m, u));
ER(bignum_shl(&tmp, i * BIGNUM_BITS));
ER(bignum_addl(A, &tmp));
}
/* 3. A <- A / b^n */
bignum_dump(" A-pre-div", A);
ER(bignum_shr(A, monty->R_shift));
/* 4. If A >= m then A <- A - m. */
if (bignum_gte(A, m))
ER(bignum_subl(A, m));
return OK;
}
error monty_normalise_n(bignum *xR, const bignum *x, const bignum *m, size_t R_shift)
{
BIGNUM_TMP(tmp);
ER(bignum_dup(&tmp, x));
ER(bignum_shl(&tmp, R_shift));
ER(bignum_mod(xR, &tmp, m));
return OK;
}
static obj long_lshl(INT_64 a, INT_32 b)
{
int am;
if((am = search_one_sub(a, 0)) < 0)
return ZERO;
if(am + b <= 63)
return int_64_compact(int_64_shl(a, b));
return bignum_shl(int64_to_bignum_u(a), b);
}
static obj int_lshl(INT_32 a, INT_32 b)
{
int am;
if(!a)
return int2fx(0);
if(b > 63 || (am = (b + search_one32(a))) > 63)
return bignum_shl(int_32_to_bignum_u(a), b);
if(am > 30)
return int_64_compact(int_64_shl(int_32_to_int_64(a), b));
return int2fx(a<<b);
}
