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LibCrypto: Added static non-allocating UnsignedBigInteger operators

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This changes the plus, minus, etc... operators from UnsignedBigInteger to use a
static helper method. The static methods do not allocate any variables, instead
all the required BigInteger output and temporary variables are required on call
as parameters.

This change already optimizes the number of allocations in complex operations
such as multiply or divide, by having a single allocation per call (instead of
one per loop).

This new API also provides a way to limit the number of allocations for complex
computations in other parts of the code. This is done by using these helpers in
any place that currently makes use of the standard operators.
This commit is contained in:
DexesTTP 2020-05-03 10:57:00 +02:00 • committed by Andreas Kling
parent d008a38f93
commit 28ea347e55
2 changed files with 270 additions and 144 deletions
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12
Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
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@ -64,6 +64,8 @@ public:
const AK::Vector<u32, STARTING_WORD_SIZE>& words() const { return m_words; }
void set_to_0();
void set_to(const UnsignedBigInteger& other);
void invalidate() { m_is_invalid = true; }
bool is_invalid() const { return m_is_invalid; }
@ -80,13 +82,19 @@ public:
void set_bit_inplace(size_t bit_index);
static void add_without_allocation(const UnsignedBigInteger& left, const UnsignedBigInteger& right, UnsignedBigInteger& output);
static void subtract_without_allocation(const UnsignedBigInteger& left, const UnsignedBigInteger& right, UnsignedBigInteger& output);
static void shift_left_without_allocation(const UnsignedBigInteger& number, size_t bits_to_shift_by, UnsignedBigInteger& temp_result, UnsignedBigInteger& temp_plus, UnsignedBigInteger& output);
static void multiply_without_allocation(const UnsignedBigInteger& left, const UnsignedBigInteger& right, UnsignedBigInteger& temp_shift_result, UnsignedBigInteger& temp_shift_plus, UnsignedBigInteger& temp_shift, UnsignedBigInteger& temp_plus, UnsignedBigInteger& output);
static void divide_without_allocation(const UnsignedBigInteger& numerator, const UnsignedBigInteger& denominator, UnsignedBigInteger& temp_shift_result, UnsignedBigInteger& temp_shift_plus, UnsignedBigInteger& temp_shift, UnsignedBigInteger& temp_minus, UnsignedBigInteger& quotient, UnsignedBigInteger& remainder);
bool operator==(const UnsignedBigInteger& other) const;
bool operator!=(const UnsignedBigInteger& other) const;
bool operator<(const UnsignedBigInteger& other) const;
private:
ALWAYS_INLINE UnsignedBigInteger shift_left_by_n_words(const size_t number_of_words) const;
ALWAYS_INLINE u32 shift_left_get_one_word(const size_t num_bits, const size_t result_word_index) const;
ALWAYS_INLINE static void shift_left_by_n_words(const UnsignedBigInteger& number, size_t number_of_words, UnsignedBigInteger& output);
ALWAYS_INLINE static u32 shift_left_get_one_word(const UnsignedBigInteger& number, size_t num_bits, size_t result_word_index);
static constexpr size_t BITS_IN_WORD = 32;
AK::Vector<u32, STARTING_WORD_SIZE> m_words;