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LibCrypto: Avoid overly big allocs in intermediate ModularPower results
If we don't limit the sizes of the intermediate results, they will grow indefinitely, causing each iteration to take longer and longer (in both memcpy time, and algorithm runtime). While calculating the trimmed length is fairly expensive, it's a small cost to pay for uniform iteration times.
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2020176f0f
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3 changed files with 17 additions and 1 deletions
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@ -156,6 +156,13 @@ size_t UnsignedBigInteger::trimmed_length() const
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return m_cached_trimmed_length.value();
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}
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void UnsignedBigInteger::clamp_to_trimmed_length()
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{
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auto length = trimmed_length();
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if (m_words.size() > length)
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m_words.resize(length);
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}
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FLATTEN UnsignedBigInteger UnsignedBigInteger::plus(const UnsignedBigInteger& other) const
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{
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UnsignedBigInteger result;
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@ -578,7 +585,7 @@ FLATTEN void UnsignedBigInteger::shift_left_without_allocation(
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// output += (carry_word << temp_result.length())
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// FIXME : Using temp_plus this way to transform carry_word into a bigint is not
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// efficient nor pretty. Maybe we should have an "add_with_shift" method ?
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// efficient nor pretty. Maybe we should have an "add_with_shift" method ?
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temp_plus.set_to_0();
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temp_plus.m_words.append(carry_word);
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shift_left_by_n_words(temp_plus, temp_result.length(), temp_result);
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