soagen::allocator struct

The default allocator used by soagen tables.

Customizing allocators for soagen

Custom allocators may implement two soagen-specific extensions relating to memory alignment to assist the compiler with generating performant code. These are detailed below.

Specifying a min_alignment

If you know that your allocator will never align allocations on a boundary smaller than a particular value (say, 64 bytes), you can make soagen aware of this by adding a constexpr constant called min_alignment. Example:

struct my_allocator
{
    inline constexpr std::size_t min_alignment = 64;
}

Soagen will then propagate this information to the tables where it may be of use to the compiler.

Providing an alignment-aware allocate()

If your environment has some aligned-allocation facility you wish to make soagen aware of, you can do so by providing an alignment-aware overload of allocate() taking a std::align_val_t for alignment:

struct my_allocator
{
    value_type* allocate(std::size_t size, std::align_val_t alignment)
    {
        return my_aligned_alloc_function(size, static_cast<std::size_t>(alignment));
    }
}

Soagen will choose this overload over any others if it is present.

Public types

using is_always_equal = std::true_type: Instances of this allocator are always equal.
using propagate_on_container_copy_assignment = std::false_type: Instances of this allocator don't propagate on copy-assignment.
using propagate_on_container_move_assignment = std::false_type: Instances of this allocator don't propagate on move-assignment.
using propagate_on_container_swap = std::false_type: Instances of this allocator don't propagate on swap.
using value_type = std::byte: The value type allocated by this allocator.

Public static variables

static size_type min_alignment constexpr: The minimum alignment of any allocations created by this allocator.

Public functions

auto allocate(size_type size, std::align_val_t alignment = std::align_val_t{ min_alignment }) → value_type*: Alignment-aware allocation.
void deallocate(value_type* ptr, ] size_type size) noexcept: Deallocation.

Friends

auto operator!=(const allocator&, const allocator&) → bool noexcept: Inequality operator.
auto operator==(const allocator&, const allocator&) → bool noexcept: Equality operator.

Function documentation

value_type* soagen::allocator::allocate(size_type size, std::align_val_t alignment = std::align_val_t{ min_alignment })

Alignment-aware allocation.

Parameters
size	The size of the allocation, in bytes.
alignment	The minimum alignment, in bytes. Must be a power-of-two.
Returns	A new allocation.
Exceptions
std::bad_alloc	If the system aligned-allocation function failed.

void soagen::allocator::deallocate(value_type* ptr, ] size_type size) noexcept

Deallocation.

Parameters
ptr	The pointer to the memory being deallocated. Must have been acquired via allocate().
size	The size of the allocation, in bytes. Must be the value used for previous call to allocate().