lisyarus
2c3565df61
* Use uint64_t instead of size_t as hash return value * Expect alignof(uint64_t) <= 8 instead of == 8
110 lines
2 KiB
C++
110 lines
2 KiB
C++
#include <psemek/util/big_int.hpp>
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#include <algorithm>
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namespace psemek::util
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{
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namespace
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{
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struct adder
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{
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std::uint32_t sum = 0;
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std::uint32_t carry = 0;
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void add(std::uint32_t x)
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{
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auto result = static_cast<std::uint64_t>(sum) + x;
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sum = result & std::uint32_t(-1);
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carry += result >> 32;
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}
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};
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}
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void big_int::canonicalize()
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{
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auto size = this->size();
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auto negative = this->negative();
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while (size > 0 && digits_[size - 1] == 0)
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--size;
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set_size(size);
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set_negative(size > 0 && negative);
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}
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void big_int::ensure_capacity(std::uint32_t new_capacity)
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{
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if (new_capacity == 0)
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{
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digits_ = nullptr;
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size_ = 0;
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capacity_ = 0;
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}
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else if (new_capacity > capacity_)
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{
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new_capacity = std::max({static_cast<std::uint32_t>(1.6 * size()), static_cast<std::uint32_t>(16), new_capacity});
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auto new_digits = std::make_unique<digit[]>(new_capacity);
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std::size_t i = 0;
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for (; i < size(); ++i)
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new_digits[i] = digits_[i];
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for (; i < new_capacity; ++i)
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new_digits[i] = 0;
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digits_ = std::move(new_digits);
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capacity_ = new_capacity;
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}
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}
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void big_int::add_positive(span<digit const> digits)
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{
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digit carry = 0;
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std::size_t i = 0;
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std::size_t min_size = std::min<std::size_t>(size(), digits.size());
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for (; i < min_size; ++i)
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{
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adder adder{digits_[i]};
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adder.add(digits[i]);
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adder.add(carry);
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std::tie(digits_[i], carry) = {adder.sum, adder.carry};
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}
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if (i < digits.size())
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{
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ensure_capacity(digits.size());
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for (; i < digits.size(); ++i)
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{
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adder adder{digits[i]};
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adder.add(carry);
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std::tie(digits_[i], carry) = {adder.sum, adder.carry};
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}
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set_size(digits.size());
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}
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if (i < size())
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{
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for (; i < size() && carry != 0; ++i)
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{
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adder adder{digits_[i]};
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adder.add(carry);
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std::tie(digits_[i], carry) = {adder.sum, adder.carry};
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}
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}
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if (carry != 0)
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{
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ensure_capacity(size() + 1);
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digits_[size()] = carry;
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set_size(size() + 1);
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}
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canonicalize();
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}
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}
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