<xstd/ints/memory/is_aligned.hpp>

xstd::is_aligned

// (1)
template<alignable T>
  constexpr auto is_aligned(T value, size_t alignment) noexcept(nothrow_alignable<T>) -> bool;

// (2)
template<class T>
  auto is_aligned(T* pointer, size_t alignment) noexcept -> bool;

Whether a value is a multiple of a power-of-two alignment.

1. For an alignable value.
2. For a pointer, through its address.

Parameters

Parameter	Meaning
value	the value to test
pointer	the pointer whose address is tested
alignment	a power of two

Constraints: (1) T models alignable.

Preconditions: (1) alignment is a power of two.

Return value

1. Returns: true exactly when value is a multiple of alignment, computed as T(value & m) == T(0UZ) for m = T(alignment - 1), as a bool whatever T is. It is a constant expression.
2. Returns: is_aligned(reinterpret_cast<uintptr_t>(pointer), alignment).

Exceptions

1. The exception specification is nothrow_alignable<T>: noexcept for size_t and uint8_t, and not for absl::uint128.
2. It is noexcept.

Remarks

(2) It is not constexpr.

Notes

(1) It holds of what align_up and align_down return, and of value exactly when align_down leaves it unchanged.

See also

Entity	Relation
align_up, align_down	what they return satisfies it
alignable	what (1) asks of T
boost::alignment::is_aligned	the Boost.Align function it agrees with