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LibCrypto: Implement a (mostly) proper to_double for UnsignedBigInteger

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SignedBigInteger can immediately use this by just negating the double if
the sign bit is set.
For simple cases (below 2^53) we can just convert via an u64, however
above that we need to extract the top 53 bits and use those as the
mantissa.

This function currently does not behave exactly as the JS spec specifies
however it is much less naive than the previous implementation.
This commit is contained in:
davidot 2022-08-24 10:13:16 +02:00 • committed by Linus Groh
parent 2290fbc2a0
commit 8b8cee3172
3 changed files with 241 additions and 71 deletions
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2
Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
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@ -70,6 +70,8 @@ double SignedBigInteger::to_double() const
double unsigned_value = m_unsigned_data.to_double();
if (!m_sign)
return unsigned_value;
VERIFY(!is_zero());
return -unsigned_value;
}