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Faster remainder on bignums without consing.

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Alex Shinn 2013-12-30 10:48:03 +09:00
parent a13e30ce7d
commit ff15d3b850
1 changed files with 15 additions and 2 deletions
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17
bignum.c
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@ -219,6 +219,19 @@ sexp_uint_t sexp_bignum_fxdiv (sexp ctx, sexp a, sexp_uint_t b, int offset) {
return r;
}
sexp sexp_bignum_fxrem (sexp ctx, sexp a, sexp_sint_t b) {
sexp_uint_t len=sexp_bignum_hi(a), *data=sexp_bignum_data(a), q, b0;
int i;
sexp_luint_t n = 0;
b0 = (b >= 0) ? b : -b;
for (i=len-1; i>=0; i--) {
n = (n << sizeof(sexp_uint_t)*8) + data[i];
q = n / b0;
n -= (sexp_luint_t)q * b0;
}
return sexp_make_fixnum(sexp_bignum_sign(a) * (sexp_sint_t)n);
}
sexp sexp_read_bignum (sexp ctx, sexp in, sexp_uint_t init,
signed char sign, sexp_uint_t base) {
int c, digit;
@ -1591,8 +1604,8 @@ sexp sexp_remainder (sexp ctx, sexp a, sexp b) {
r = a;
break;
case SEXP_NUM_BIG_FIX:
b = tmp = sexp_fixnum_to_bignum(ctx, b);
/* ... FALLTHROUGH ... */
r = sexp_bignum_fxrem(ctx, a, sexp_unbox_fixnum(b));
break;
case SEXP_NUM_BIG_BIG:
r = sexp_bignum_normalize(sexp_bignum_remainder(ctx, a, b));
break;