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vm: additional fix in bignum_gcd.

db4
John Benediktsson 2012-08-03 21:50:48 -07:00
parent bd957cb3b4
commit f7bb7c6a32
1 changed files with 21 additions and 15 deletions
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36
vm/bignum.cpp
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@ -1768,10 +1768,10 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
{ {
GC_BIGNUM(a); GC_BIGNUM(a);
GC_BIGNUM(b); GC_BIGNUM(b);
bignum *c, *d, *e; bignum *c, *d, *e, *f;
bignum_twodigit_type x, y, q, s, t, A, B, C, D; bignum_twodigit_type x, y, q, s, t, A, B, C, D;
int nbits, k; int nbits, k;
bignum_length_type size_a, size_b, size_d; bignum_length_type size_a, size_b, size_c;
bignum_digit_type *scan_a, *scan_b, *scan_c, *scan_d, *a_end, *b_end; bignum_digit_type *scan_a, *scan_b, *scan_c, *scan_d, *a_end, *b_end;
/* clone the bignums so we can modify them in-place */ /* clone the bignums so we can modify them in-place */
@ -1796,12 +1796,12 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
/* Initial reduction: make sure that 0 <= b <= a. */ /* Initial reduction: make sure that 0 <= b <= a. */
if (bignum_compare(a, b) == bignum_comparison_less) { if (bignum_compare(a, b) == bignum_comparison_less) {
d = a; c = a;
size_d = size_a; size_c = size_a;
a = b; a = b;
size_a = size_b; size_a = size_b;
b = d; b = c;
size_b = size_d; size_b = size_c;
} }
while (size_a > 1) { while (size_a > 1) {
@ -1839,14 +1839,14 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
return a; return a;
} }
e = bignum_remainder (a, b); e = bignum_remainder (a, b);
GC_BIGNUM(e); GC_BIGNUM (e);
if (e == BIGNUM_OUT_OF_BAND) { if (e == BIGNUM_OUT_OF_BAND) {
return e; return e;
} }
a = b; a = b;
size_a = size_b; size_a = size_b;
b = e; b = e;
size_b = BIGNUM_LENGTH (b); size_b = BIGNUM_LENGTH (e);
continue; continue;
} }
@ -1856,8 +1856,8 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
*/ */
scan_a = BIGNUM_START_PTR (a); scan_a = BIGNUM_START_PTR (a);
scan_b = BIGNUM_START_PTR (b); scan_b = BIGNUM_START_PTR (b);
scan_c = BIGNUM_START_PTR (a); scan_c = scan_a;
scan_d = BIGNUM_START_PTR (b); scan_d = scan_b;
a_end = scan_a + size_a; a_end = scan_a + size_a;
b_end = scan_b + size_b; b_end = scan_b + size_b;
s = 0; s = 0;
@ -1875,7 +1875,7 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
s -= (B * *scan_a); s -= (B * *scan_a);
t += (D * *scan_a++); t += (D * *scan_a++);
*scan_c++ = (bignum_digit_type) (s & BIGNUM_DIGIT_MASK); *scan_c++ = (bignum_digit_type) (s & BIGNUM_DIGIT_MASK);
*scan_d++ = (bignum_digit_type) (t & BIGNUM_DIGIT_MASK); //*scan_d++ = (bignum_digit_type) (t & BIGNUM_DIGIT_MASK);
s >>= BIGNUM_DIGIT_LENGTH; s >>= BIGNUM_DIGIT_LENGTH;
t >>= BIGNUM_DIGIT_LENGTH; t >>= BIGNUM_DIGIT_LENGTH;
} }
@ -1893,7 +1893,7 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
s += (A * *scan_a); s += (A * *scan_a);
t -= (C * *scan_a++); t -= (C * *scan_a++);
*scan_c++ = (bignum_digit_type) (s & BIGNUM_DIGIT_MASK); *scan_c++ = (bignum_digit_type) (s & BIGNUM_DIGIT_MASK);
*scan_d++ = (bignum_digit_type) (t & BIGNUM_DIGIT_MASK); //*scan_d++ = (bignum_digit_type) (t & BIGNUM_DIGIT_MASK);
s >>= BIGNUM_DIGIT_LENGTH; s >>= BIGNUM_DIGIT_LENGTH;
t >>= BIGNUM_DIGIT_LENGTH; t >>= BIGNUM_DIGIT_LENGTH;
} }
@ -1901,9 +1901,15 @@ bignum * factor_vm::bignum_gcd(bignum * a, bignum * b)
BIGNUM_ASSERT (s == 0); BIGNUM_ASSERT (s == 0);
BIGNUM_ASSERT (t == 0); BIGNUM_ASSERT (t == 0);
// update size_a and size_b to remove any zeros at end e = bignum_trim (a);
while (size_a > 0 && *(--scan_a) == 0) size_a--; GC_BIGNUM(e);
while (size_b > 0 && *(--scan_b) == 0) size_b--; a = e;
size_a = BIGNUM_LENGTH (a);
f = bignum_trim (b);
GC_BIGNUM(f);
b = f;
size_b = BIGNUM_LENGTH (b);
BIGNUM_ASSERT (size_a >= size_b);
} }
/* a fits into a fixnum, so b must too */ /* a fits into a fixnum, so b must too */