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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,138 @@ | ||
| #pragma once | ||
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| #include <cinttypes> | ||
| #include <cstring> | ||
| #include <limits> | ||
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| #include "cista/bit_counting.h" | ||
| #include "cista/containers/array.h" | ||
| #include "cista/next_power_of_2.h" | ||
| #include "cista/verify.h" | ||
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| namespace cista { | ||
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| template <typename SizeType> | ||
| struct page { | ||
| bool valid() const { return capacity_ != 0U; } | ||
| SizeType size() const noexcept { return size_; } | ||
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| SizeType size_{0U}; | ||
| SizeType capacity_{0U}; | ||
| SizeType start_{0U}; | ||
| }; | ||
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| template <typename DataVec, typename SizeType = typename DataVec::size_type, | ||
| SizeType MinPageSize = next_power_of_two(3U * sizeof(SizeType)), | ||
| SizeType MaxPageSize = 65536U> | ||
| struct paged { | ||
| using value_type = typename DataVec::value_type; | ||
| using iterator = typename DataVec::iterator; | ||
| using const_iterator = typename DataVec::const_iterator; | ||
| using reference = typename DataVec::reference; | ||
| using const_reference = typename DataVec::const_reference; | ||
| using size_type = SizeType; | ||
| using page_t = page<SizeType>; | ||
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| static_assert(sizeof(value_type) * MinPageSize >= sizeof(page_t)); | ||
| static_assert(std::is_trivially_copyable_v<value_type>); | ||
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| static constexpr size_type free_list_index(size_type const capacity) { | ||
| return static_cast<size_type>(constexpr_trailing_zeros(capacity) - | ||
| constexpr_trailing_zeros(MinPageSize)); | ||
| } | ||
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| static constexpr size_type free_list_size = free_list_index(MaxPageSize) + 1U; | ||
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| page_t resize_page(page_t const& p, size_type const size) { | ||
| if (size <= p.capacity_) { | ||
| return {size, p.capacity_, p.start_}; | ||
| } else { | ||
| auto const new_page = create_page(size); | ||
| copy(new_page, p); | ||
| free_page(p); | ||
| return new_page; | ||
| } | ||
| } | ||
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| page_t create_page(size_type const size) { | ||
| auto const capacity = next_power_of_two(std::max(MinPageSize, size)); | ||
| auto const i = free_list_index(capacity); | ||
| verify(i < free_list_.size(), "paged::create_page: size > max capacity"); | ||
| if (!free_list_[i].empty()) { | ||
| auto start = free_list_[i].pop(*this); | ||
| return {size, capacity, start}; | ||
| } else { | ||
| auto const start = data_.size(); | ||
| data_.resize(data_.size() + capacity); | ||
| return {size, capacity, start}; | ||
| } | ||
| } | ||
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| void free_page(page_t const& p) { | ||
| if (!p.valid()) { | ||
| return; | ||
| } | ||
| auto const i = free_list_index(p.capacity_); | ||
| verify(i < free_list_.size(), "paged::free_page: size > max capacity"); | ||
| free_list_[i].push(*this, p.start_); | ||
| } | ||
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| template <typename T> | ||
| T read(size_type const offset) { | ||
| static_assert(std::is_trivially_copyable_v<T>); | ||
| auto x = T{}; | ||
| std::memcpy(&x, &data_[offset], sizeof(x)); | ||
| return x; | ||
| } | ||
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| template <typename T> | ||
| void write(size_type const offset, T const& x) { | ||
| static_assert(std::is_trivially_copyable_v<T>); | ||
| std::memcpy(&data_[offset], &x, sizeof(T)); | ||
| } | ||
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| value_type* data(page_t const& p) { return &data_[p.start_]; } | ||
| value_type const* data(page_t const& p) const { return &data_[p.start_]; } | ||
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| value_type* begin(page_t const& p) { return data(p); } | ||
| value_type const* begin(page_t const& p) const { return data(p); } | ||
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| value_type* end(page_t& p) const { return begin(p) + p.size(); } | ||
| value_type const* end(page_t const& p) const { return begin() + p.size; } | ||
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| void copy(page_t const& to, page_t const& from) { | ||
| std::memcpy(data(to), data(from), from.size() * sizeof(value_type)); | ||
| } | ||
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| template <typename ItA, typename ItB> | ||
| void copy(page_t const& to, ItA begin, ItB end) { | ||
| std::memcpy(data(to), &*begin, | ||
| static_cast<std::size_t>(std::distance(begin, end))); | ||
| } | ||
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| struct node { | ||
| bool empty() const { | ||
| return next_ == std::numeric_limits<size_type>::max(); | ||
| } | ||
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| void push(paged& m, size_type const start) { | ||
| m.write(start, next_); | ||
| next_ = start; | ||
| } | ||
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| size_type pop(paged& m) { | ||
| verify(!empty(), "paged: invalid read access to empty free list entry"); | ||
| auto const next_start = m.read<size_type>(next_); | ||
| auto start = next_; | ||
| next_ = next_start; | ||
| return start; | ||
| } | ||
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| size_type next_{std::numeric_limits<size_type>::max()}; | ||
| }; | ||
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| DataVec data_; | ||
| array<node, free_list_size> free_list_{}; | ||
| }; | ||
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| } // namespace cista |
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