a4306b9e56
In cases where the size is not a known constant when inlining, AlignUp<std::size_t> currently generates two 64-bit div instructions. This generates one div and a cmov which is significantly cheaper.
119 lines
3.2 KiB
C++
119 lines
3.2 KiB
C++
// This file is under the public domain.
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#pragma once
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#include <cstddef>
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#include <memory>
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#include <type_traits>
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namespace Common {
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template <typename T>
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constexpr T AlignUp(T value, std::size_t size) {
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static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
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auto mod{value % size};
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value -= mod;
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return static_cast<T>(mod == T{0} ? value : value + size);
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}
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template <typename T>
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constexpr T AlignDown(T value, std::size_t size) {
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static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
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return static_cast<T>(value - value % size);
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}
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template <typename T>
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constexpr T AlignBits(T value, std::size_t align) {
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static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
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return static_cast<T>((value + ((1ULL << align) - 1)) >> align << align);
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}
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template <typename T>
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constexpr bool Is4KBAligned(T value) {
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static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
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return (value & 0xFFF) == 0;
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}
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template <typename T>
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constexpr bool IsWordAligned(T value) {
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static_assert(std::is_unsigned_v<T>, "T must be an unsigned value.");
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return (value & 0b11) == 0;
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}
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template <typename T>
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constexpr bool IsAligned(T value, std::size_t alignment) {
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using U = typename std::make_unsigned<T>::type;
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const U mask = static_cast<U>(alignment - 1);
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return (value & mask) == 0;
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}
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template <typename T, std::size_t Align = 16>
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class AlignmentAllocator {
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public:
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using value_type = T;
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using size_type = std::size_t;
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using difference_type = std::ptrdiff_t;
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using propagate_on_container_copy_assignment = std::true_type;
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using propagate_on_container_move_assignment = std::true_type;
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using propagate_on_container_swap = std::true_type;
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using is_always_equal = std::true_type;
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public:
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constexpr AlignmentAllocator() noexcept = default;
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template <typename T2>
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constexpr AlignmentAllocator(const AlignmentAllocator<T2, Align>&) noexcept {}
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pointer address(reference r) noexcept {
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return std::addressof(r);
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}
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const_pointer address(const_reference r) const noexcept {
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return std::addressof(r);
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}
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pointer allocate(size_type n) {
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return static_cast<pointer>(::operator new (n, std::align_val_t{Align}));
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}
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void deallocate(pointer p, size_type) {
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::operator delete (p, std::align_val_t{Align});
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}
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void construct(pointer p, const value_type& wert) {
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new (p) value_type(wert);
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}
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void destroy(pointer p) {
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p->~value_type();
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}
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size_type max_size() const noexcept {
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return size_type(-1) / sizeof(value_type);
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}
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template <typename T2>
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struct rebind {
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using other = AlignmentAllocator<T2, Align>;
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};
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bool operator!=(const AlignmentAllocator<T, Align>& other) const noexcept {
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return !(*this == other);
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}
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// Returns true if and only if storage allocated from *this
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// can be deallocated from other, and vice versa.
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// Always returns true for stateless allocators.
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bool operator==(const AlignmentAllocator<T, Align>& other) const noexcept {
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return true;
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}
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};
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} // namespace Common
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