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off by one error in sexp_bignum_mul

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need an extra digit to fit carries
This commit is contained in:
Alex Shinn 2009-07-12 19:06:38 +09:00
parent 821546244a
commit f2e79c3028
1 changed files with 4 additions and 5 deletions
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9
opt/bignum.c
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@ -304,19 +304,18 @@ sexp sexp_bignum_sub (sexp ctx, sexp dst, sexp a, sexp b) {
sexp sexp_bignum_mul (sexp ctx, sexp dst, sexp a, sexp b) {
sexp_uint_t alen=sexp_bignum_hi(a), blen=sexp_bignum_hi(b), i,
*bdata=sexp_bignum_data(b), *ddata;
*bdata=sexp_bignum_data(b);
sexp_gc_var(ctx, c, s_c);
sexp_gc_var(ctx, d, s_d);
if (alen < blen) return sexp_bignum_mul(ctx, dst, b, a);
sexp_gc_preserve(ctx, c, s_c);
sexp_gc_preserve(ctx, d, s_d);
c = (dst ? dst : sexp_make_bignum(ctx, alen+blen+1));
d = sexp_make_bignum(ctx, alen+blen);
ddata = sexp_bignum_data(d);
d = sexp_make_bignum(ctx, alen+blen+1);
for (i=0; i<blen; i++) {
sexp_bignum_fxmul(ctx, d, a, bdata[i], i);
d = sexp_bignum_fxmul(ctx, d, a, bdata[i], i);
c = sexp_bignum_add_digits(ctx, NULL, c, d);
ddata[i] = 0;
sexp_bignum_data(d)[i] = 0;
}
sexp_bignum_sign(c) = sexp_bignum_sign(a) * sexp_bignum_sign(b);
sexp_gc_release(ctx, c, s_c);