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Math::BigInt does floored divs, BN_div does truncated div, compensate

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According to documentation, perl's Math::BigInt does floored division,
i.e. the bdiv function does 1 / -4 = -1.  OpenSSL's BN_div, as well as
bc, do truncated division, i.e. 1 / -4 = 0.

We need to compensate for that difference in test/recipes/bc.pl to
make sure to verify the bntest results under its own conditions, by
dividing the absolute values of the given numbers and fixup the
result's negativity afterwards.

Closes RT#4485

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
This commit is contained in:
Richard Levitte 2016-03-26 00:07:50 +01:00
parent c828cd7cd0
commit ce84456ddf
1 changed files with 9 additions and 0 deletions
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9
test/recipes/bc.pl
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@ -46,7 +46,16 @@ sub __multiplier {
if ($operator eq "*") {
$operand1->bmul($operand2);
} elsif ($operator eq "/") {
# Math::BigInt->bdiv() is documented to do floored division,
# i.e. 1 / -4 = -1, while bc and OpenSSL BN_div do truncated
# division, i.e. 1 / -4 = 0. We need to make the operation
# work like OpenSSL's BN_div to be able to verify.
my $neg = ($operand1->is_neg()
? !$operand2->is_neg() : $operand2->is_neg());
$operand1->babs();
$operand2->babs();
$operand1->bdiv($operand2);
if ($neg) { $operand1->bneg(); }
} elsif ($operator eq "%") {
# Here's a bit of a quirk...
# With OpenSSL's BN, as well as bc, the result of -10 % 3 is -1