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LibCrypto+LibJS: Better bigint bitwise_or binop

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Similar to the bitwise_and change, but we have to be careful to
sign-extend two's complement numbers only up to the highest set bit
in the positive number.
This commit is contained in:
Nico Weber 2022-01-18 08:46:42 -05:00 committed by Ali Mohammad Pur
parent 1f98639396
commit 013799a4dd
Notes: sideshowbarker 2024-07-17 20:40:12 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/013799a4dd3
Pull-request: https://github.com/SerenityOS/serenity/pull/11996
Reviewed-by: https://github.com/alimpfard
8 changed files with 77 additions and 23 deletions
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26
Tests/LibCrypto/TestBigInteger.cpp
View file

@ -427,6 +427,26 @@ TEST_CASE(test_bigint_big_endian_export)
EXPECT(memcmp(exported + 3, "hello", 5) == 0);
}
TEST_CASE(test_bigint_one_based_index_of_highest_set_bit)
{
auto num1 = "1234567"_bigint;
auto num2 = "1234567"_bigint;
EXPECT_EQ("0"_bigint.one_based_index_of_highest_set_bit(), 0u);
EXPECT_EQ("1"_bigint.one_based_index_of_highest_set_bit(), 1u);
EXPECT_EQ("7"_bigint.one_based_index_of_highest_set_bit(), 3u);
EXPECT_EQ("4294967296"_bigint.one_based_index_of_highest_set_bit(), 33u);
}
TEST_CASE(test_signed_bigint_bitwise_not_fill_to_one_based_index)
{
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(0), "0"_bigint);
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(1), "1"_bigint);
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(2), "3"_bigint);
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(4), "15"_bigint);
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(32), "4294967295"_bigint);
EXPECT_EQ("0"_bigint.bitwise_not_fill_to_one_based_index(33), "8589934591"_bigint);
}
TEST_CASE(test_bigint_bitwise_or)
{
auto num1 = "1234567"_bigint;
@ -448,9 +468,11 @@ TEST_CASE(test_signed_bigint_bitwise_or)
auto num1 = "-1234567"_sbigint;
auto num2 = "1234567"_sbigint;
EXPECT_EQ(num1.bitwise_or(num1), num1);
EXPECT_EQ(num1.bitwise_or(num2), num1);
EXPECT_EQ(num2.bitwise_or(num1), num1);
EXPECT_EQ(num1.bitwise_or(num2), "-1"_sbigint);
EXPECT_EQ(num2.bitwise_or(num1), "-1"_sbigint);
EXPECT_EQ(num2.bitwise_or(num2), num2);
EXPECT_EQ("0"_sbigint.bitwise_or("-1"_sbigint), "-1"_sbigint);
}
TEST_CASE(test_bigint_bitwise_and)

22
Userland/Libraries/LibCrypto/BigInt/Algorithms/BitwiseOperations.cpp
View file

@ -131,9 +131,9 @@ FLATTEN void UnsignedBigIntegerAlgorithms::bitwise_xor_without_allocation(
/**
* Complexity: O(N) where N is the number of words
*/
FLATTEN void UnsignedBigIntegerAlgorithms::bitwise_not_fill_to_size_without_allocation(
FLATTEN void UnsignedBigIntegerAlgorithms::bitwise_not_fill_to_one_based_index_without_allocation(
UnsignedBigInteger const& right,
size_t size,
size_t index,
UnsignedBigInteger& output)
{
// If the value is invalid, the output value is invalid as well.
@ -141,17 +141,23 @@ FLATTEN void UnsignedBigIntegerAlgorithms::bitwise_not_fill_to_size_without_allo
output.invalidate();
return;
}
if (size == 0) {
if (index == 0) {
output.set_to_0();
return;
}
size_t size = (index + UnsignedBigInteger::BITS_IN_WORD - 1) / UnsignedBigInteger::BITS_IN_WORD;
output.m_words.resize_and_keep_capacity(size);
size_t i;
for (i = 0; i < min(size, right.length()); ++i)
output.m_words[i] = ~right.words()[i];
for (; i < size; ++i)
output.m_words[i] = NumericLimits<UnsignedBigInteger::Word>::max();
VERIFY(size > 0);
for (size_t i = 0; i < size - 1; ++i)
output.m_words[i] = ~(i < right.length() ? right.words()[i] : 0);
index -= (size - 1) * UnsignedBigInteger::BITS_IN_WORD;
auto last_word_index = size - 1;
auto last_word = last_word_index < right.length() ? right.words()[last_word_index] : 0;
output.m_words[last_word_index] = (NumericLimits<UnsignedBigInteger::Word>::max() >> (UnsignedBigInteger::BITS_IN_WORD - index)) & ~last_word;
}
/**

2
Userland/Libraries/LibCrypto/BigInt/Algorithms/UnsignedBigIntegerAlgorithms.h
View file

@ -18,7 +18,7 @@ public:
static void bitwise_or_without_allocation(UnsignedBigInteger const& left, UnsignedBigInteger const& right, UnsignedBigInteger& output);
static void bitwise_and_without_allocation(UnsignedBigInteger const& left, UnsignedBigInteger const& right, UnsignedBigInteger& output);
static void bitwise_xor_without_allocation(UnsignedBigInteger const& left, UnsignedBigInteger const& right, UnsignedBigInteger& output);
static void bitwise_not_fill_to_size_without_allocation(UnsignedBigInteger const& left, size_t, UnsignedBigInteger& output);
static void bitwise_not_fill_to_one_based_index_without_allocation(UnsignedBigInteger const& left, size_t, UnsignedBigInteger& output);
static void shift_left_without_allocation(UnsignedBigInteger const& number, size_t bits_to_shift_by, UnsignedBigInteger& temp_result, UnsignedBigInteger& temp_plus, UnsignedBigInteger& output);
static void multiply_without_allocation(UnsignedBigInteger const& left, UnsignedBigInteger const& right, UnsignedBigInteger& temp_shift_result, UnsignedBigInteger& temp_shift_plus, UnsignedBigInteger& temp_shift, UnsignedBigInteger& output);
static void divide_without_allocation(UnsignedBigInteger const& numerator, UnsignedBigInteger const& denominator, UnsignedBigInteger& temp_shift_result, UnsignedBigInteger& temp_shift_plus, UnsignedBigInteger& temp_shift, UnsignedBigInteger& temp_minus, UnsignedBigInteger& quotient, UnsignedBigInteger& remainder);

26
Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.cpp
View file

@ -184,12 +184,18 @@ FLATTEN SignedDivisionResult SignedBigInteger::divided_by(UnsignedBigInteger con
FLATTEN SignedBigInteger SignedBigInteger::bitwise_or(const SignedBigInteger& other) const
{
auto result = bitwise_or(other.unsigned_value());
// See bitwise_and() for derivations.
if (!is_negative() && !other.is_negative())
return { unsigned_value().bitwise_or(other.unsigned_value()), false };
// The sign bit will have to be OR'd manually.
result.m_sign = is_negative() || other.is_negative();
size_t index = max(unsigned_value().one_based_index_of_highest_set_bit(), other.unsigned_value().one_based_index_of_highest_set_bit());
if (is_negative() && !other.is_negative())
return { unsigned_value().bitwise_not_fill_to_one_based_index(index).plus(1).bitwise_or(other.unsigned_value()).bitwise_not_fill_to_one_based_index(index).plus(1), true };
return result;
if (!is_negative() && other.is_negative())
return { unsigned_value().bitwise_or(other.unsigned_value().bitwise_not_fill_to_one_based_index(index).plus(1)).bitwise_not_fill_to_one_based_index(index).plus(1), true };
return { unsigned_value().minus(1).bitwise_and(other.unsigned_value().minus(1)).plus(1), true };
}
FLATTEN SignedBigInteger SignedBigInteger::bitwise_and(const SignedBigInteger& other) const
@ -200,12 +206,16 @@ FLATTEN SignedBigInteger SignedBigInteger::bitwise_and(const SignedBigInteger& o
// These two just use that -x == ~x + 1 (see below).
// -A & B == (~A + 1) & B.
if (is_negative() && !other.is_negative())
return { unsigned_value().bitwise_not_fill_to_size(other.trimmed_length()).plus(1).bitwise_and(other.unsigned_value()), false };
if (is_negative() && !other.is_negative()) {
size_t index = other.unsigned_value().one_based_index_of_highest_set_bit();
return { unsigned_value().bitwise_not_fill_to_one_based_index(index).plus(1).bitwise_and(other.unsigned_value()), false };
}
// A & -B == A & (~B + 1).
if (!is_negative() && other.is_negative())
return { unsigned_value().bitwise_and(other.unsigned_value().bitwise_not_fill_to_size(trimmed_length()).plus(1)), false };
if (!is_negative() && other.is_negative()) {
size_t index = unsigned_value().one_based_index_of_highest_set_bit();
return { unsigned_value().bitwise_and(other.unsigned_value().bitwise_not_fill_to_one_based_index(index).plus(1)), false };
}
// Both numbers are negative.
// x + ~x == 0xff...ff, up to however many bits x is wide.

16
Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.cpp
View file

@ -5,6 +5,7 @@
*/
#include "UnsignedBigInteger.h"
#include <AK/BuiltinWrappers.h>
#include <AK/CharacterTypes.h>
#include <AK/StringBuilder.h>
#include <AK/StringHash.h>
@ -173,6 +174,17 @@ void UnsignedBigInteger::resize_with_leading_zeros(size_t new_length)
}
}
size_t UnsignedBigInteger::one_based_index_of_highest_set_bit() const
{
size_t number_of_words = trimmed_length();
size_t index = 0;
if (number_of_words > 0) {
index += (number_of_words - 1) * BITS_IN_WORD;
index += BITS_IN_WORD - count_leading_zeroes(m_words[number_of_words - 1]);
}
return index;
}
FLATTEN UnsignedBigInteger UnsignedBigInteger::plus(const UnsignedBigInteger& other) const
{
UnsignedBigInteger result;
@ -218,11 +230,11 @@ FLATTEN UnsignedBigInteger UnsignedBigInteger::bitwise_xor(const UnsignedBigInte
return result;
}
FLATTEN UnsignedBigInteger UnsignedBigInteger::bitwise_not_fill_to_size(size_t size) const
FLATTEN UnsignedBigInteger UnsignedBigInteger::bitwise_not_fill_to_one_based_index(size_t size) const
{
UnsignedBigInteger result;
UnsignedBigIntegerAlgorithms::bitwise_not_fill_to_size_without_allocation(*this, size, result);
UnsignedBigIntegerAlgorithms::bitwise_not_fill_to_one_based_index_without_allocation(*this, size, result);
return result;
}

4
Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h
View file

@ -82,12 +82,14 @@ public:
void clamp_to_trimmed_length();
void resize_with_leading_zeros(size_t num_words);
size_t one_based_index_of_highest_set_bit() const;
UnsignedBigInteger plus(const UnsignedBigInteger& other) const;
UnsignedBigInteger minus(const UnsignedBigInteger& other) const;
UnsignedBigInteger bitwise_or(const UnsignedBigInteger& other) const;
UnsignedBigInteger bitwise_and(const UnsignedBigInteger& other) const;
UnsignedBigInteger bitwise_xor(const UnsignedBigInteger& other) const;
UnsignedBigInteger bitwise_not_fill_to_size(size_t) const;
UnsignedBigInteger bitwise_not_fill_to_one_based_index(size_t) const;
UnsignedBigInteger shift_left(size_t num_bits) const;
UnsignedBigInteger multiplied_by(const UnsignedBigInteger& other) const;
UnsignedDivisionResult divided_by(const UnsignedBigInteger& divisor) const;

2
Userland/Libraries/LibJS/Tests/builtins/BigInt/bigint-basic.js
View file

@ -40,8 +40,10 @@ describe("correct behavior", () => {
expect(3n & -2n).toBe(2n);
expect(-3n & -2n).toBe(-4n);
expect(-3n & 2n).toBe(0n);
expect(0xffff_ffffn & -1n).toBe(0xffff_ffffn);
expect(1n | 2n).toBe(3n);
expect(0n | -1n).toBe(-1n);
expect(5n ^ 3n).toBe(6n);

2
Userland/Utilities/test-crypto.cpp
View file

@ -2996,7 +2996,7 @@ static void bigint_signed_bitwise()
I_TEST((Signed BigInteger | Bitwise or handles sign));
auto num1 = "-1234567"_sbigint;
auto num2 = "1234567"_sbigint;
if (num1.bitwise_or(num2) == num1) {
if (num1.bitwise_or(num2) == "-1"_sbigint) {
PASS;
} else {
FAIL(Invalid value);