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LibCrypto: Cache the "trimmed length" of UnsignedBigIntegers

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This avoids repeated traversals of the underlying words and gives a
30% speed-up on "test-crypto -t pk" :^)
This commit is contained in:
Andreas Kling 2020-05-07 12:23:09 +02:00
parent 57f68ac5d7
commit 444b6c8407
2 changed files with 24 additions and 9 deletions
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20
Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
View file

@ -49,7 +49,7 @@ UnsignedBigInteger UnsignedBigInteger::import_data(const u8* ptr, size_t length)
return integer; return integer;
} }
size_t UnsignedBigInteger::export_data(AK::ByteBuffer& data) size_t UnsignedBigInteger::export_data(AK::ByteBuffer& data) const
{ {
UnsignedBigInteger copy { *this }; UnsignedBigInteger copy { *this };
UnsignedBigInteger quotient; UnsignedBigInteger quotient;
@ -105,6 +105,7 @@ void UnsignedBigInteger::set_to_0()
{ {
m_words.clear_with_capacity(); m_words.clear_with_capacity();
m_is_invalid = false; m_is_invalid = false;
m_cached_trimmed_length = {};
} }
void UnsignedBigInteger::set_to(u32 other) void UnsignedBigInteger::set_to(u32 other)
@ -112,6 +113,7 @@ void UnsignedBigInteger::set_to(u32 other)
m_is_invalid = false; m_is_invalid = false;
m_words.resize_and_keep_capacity(1); m_words.resize_and_keep_capacity(1);
m_words[0] = other; m_words[0] = other;
m_cached_trimmed_length = {};
} }
void UnsignedBigInteger::set_to(const UnsignedBigInteger& other) void UnsignedBigInteger::set_to(const UnsignedBigInteger& other)
@ -119,16 +121,20 @@ void UnsignedBigInteger::set_to(const UnsignedBigInteger& other)
m_is_invalid = other.m_is_invalid; m_is_invalid = other.m_is_invalid;
m_words.resize_and_keep_capacity(other.m_words.size()); m_words.resize_and_keep_capacity(other.m_words.size());
__builtin_memcpy(m_words.data(), other.m_words.data(), other.m_words.size() * sizeof(u32)); __builtin_memcpy(m_words.data(), other.m_words.data(), other.m_words.size() * sizeof(u32));
m_cached_trimmed_length = {};
} }
size_t UnsignedBigInteger::trimmed_length() const size_t UnsignedBigInteger::trimmed_length() const
{ {
size_t num_leading_zeroes = 0; if (!m_cached_trimmed_length.has_value()) {
for (int i = length() - 1; i >= 0; --i, ++num_leading_zeroes) { size_t num_leading_zeroes = 0;
if (m_words[i] != 0) for (int i = length() - 1; i >= 0; --i, ++num_leading_zeroes) {
break; if (m_words[i] != 0)
break;
}
m_cached_trimmed_length = length() - num_leading_zeroes;
} }
return length() - num_leading_zeroes; return m_cached_trimmed_length.value();
} }
FLATTEN UnsignedBigInteger UnsignedBigInteger::plus(const UnsignedBigInteger& other) const FLATTEN UnsignedBigInteger UnsignedBigInteger::plus(const UnsignedBigInteger& other) const
@ -206,6 +212,8 @@ void UnsignedBigInteger::set_bit_inplace(size_t bit_index)
m_words.unchecked_append(0); m_words.unchecked_append(0);
} }
m_words[word_index] |= (1 << inner_word_index); m_words[word_index] |= (1 << inner_word_index);
m_cached_trimmed_length = {};
} }
bool UnsignedBigInteger::operator==(const UnsignedBigInteger& other) const bool UnsignedBigInteger::operator==(const UnsignedBigInteger& other) const

13
Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
View file

@ -52,8 +52,8 @@ public:
static UnsignedBigInteger import_data(const AK::StringView& data) { return import_data((const u8*)data.characters_without_null_termination(), data.length()); } static UnsignedBigInteger import_data(const AK::StringView& data) { return import_data((const u8*)data.characters_without_null_termination(), data.length()); }
static UnsignedBigInteger import_data(const u8* ptr, size_t length); static UnsignedBigInteger import_data(const u8* ptr, size_t length);
size_t export_data(AK::ByteBuffer& data); size_t export_data(AK::ByteBuffer& data) const;
size_t export_data(const u8* ptr, size_t length) size_t export_data(const u8* ptr, size_t length) const
{ {
auto buffer = ByteBuffer::wrap(ptr, length); auto buffer = ByteBuffer::wrap(ptr, length);
return export_data(buffer); return export_data(buffer);
@ -67,7 +67,12 @@ public:
void set_to_0(); void set_to_0();
void set_to(u32 other); void set_to(u32 other);
void set_to(const UnsignedBigInteger& other); void set_to(const UnsignedBigInteger& other);
void invalidate() { m_is_invalid = true; }
void invalidate()
{
m_is_invalid = true;
m_cached_trimmed_length = {};
}
bool is_invalid() const { return m_is_invalid; } bool is_invalid() const { return m_is_invalid; }
@ -103,6 +108,8 @@ private:
// Used to indicate a negative result, or a result of an invalid operation // Used to indicate a negative result, or a result of an invalid operation
bool m_is_invalid { false }; bool m_is_invalid { false };
mutable Optional<size_t> m_cached_trimmed_length;
}; };
struct UnsignedDivisionResult { struct UnsignedDivisionResult {