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vm: make bignum-bitnot faster.

db4
John Benediktsson 2012-08-31 15:22:07 -07:00
parent 3836d57321
commit afdaff3059
1 changed files with 53 additions and 1 deletions
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54
vm/bignum.cpp
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@ -1380,7 +1380,59 @@ void factor_vm::bignum_destructive_copy(bignum * source, bignum * target)
/* allocates memory */ /* allocates memory */
bignum *factor_vm::bignum_bitwise_not(bignum * x) bignum *factor_vm::bignum_bitwise_not(bignum * x)
{ {
return bignum_subtract(BIGNUM_ONE(1), x); GC_BIGNUM (x);
bignum_length_type size = BIGNUM_LENGTH (x);
bignum_digit_type *scan_x, *end_x, *scan_y;
bignum *y;
int carry = 1;
if (BIGNUM_NEGATIVE_P (x)) {
y = allot_bignum (size, 0);
scan_x = BIGNUM_START_PTR (x);
end_x = scan_x + size;
scan_y = BIGNUM_START_PTR (y);
while (scan_x < end_x) {
if (*scan_x == 0) {
*scan_y++ = BIGNUM_RADIX - 1;
scan_x++;
} else {
*scan_y++ = *scan_x++ - 1;
carry = 0;
break;
}
}
} else {
y = allot_bignum (size, 1);
scan_x = BIGNUM_START_PTR (x);
end_x = scan_x + size;
scan_y = BIGNUM_START_PTR (y);
while (scan_x < end_x) {
if (*scan_x == (BIGNUM_RADIX - 1)) {
*scan_y++ = 0;
scan_x++;
} else {
*scan_y++ = *scan_x++ + 1;
carry = 0;
break;
}
}
}
while (scan_x < end_x) {
*scan_y++ = *scan_x++;
}
if (carry) {
GC_BIGNUM (y);
x = allot_bignum (size + 1, BIGNUM_NEGATIVE_P (y));
bignum_destructive_copy (y, x);
scan_x = BIGNUM_START_PTR (x);
*(scan_x + size) = 1;
return x;
} else {
return bignum_trim (y);
}
} }
/* allocates memory */ /* allocates memory */