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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <cstddef>
#include <limits>
namespace vespalib::datastore {
inline constexpr size_t dynamic_alignment = std::numeric_limits<size_t>::max();
/*
* Class used to align offsets to specified alignment.
*
* Alignment template parameter must be a power of 2 or the
* dynamic_alignment value (which triggers specialization below).
*/
template <size_t alignment_v = dynamic_alignment>
class Aligner {
public:
explicit constexpr Aligner() = default;
explicit constexpr Aligner(size_t); // Never used but must be declared
static constexpr size_t align(size_t unaligned) noexcept { return (unaligned + alignment_v - 1) & (- alignment_v); }
static constexpr size_t pad(size_t unaligned) noexcept { return (- unaligned & (alignment_v - 1)); }
static constexpr size_t alignment() noexcept { return alignment_v; }
};
/*
* Specialization when alignment template argument is dynamic_alignment.
* The constructor argument must be a power of 2.
*/
template <>
class Aligner<dynamic_alignment> {
size_t _alignment;
public:
explicit constexpr Aligner(size_t alignment_)
: _alignment(alignment_)
{
}
constexpr size_t align(size_t unaligned) const noexcept { return (unaligned + _alignment - 1) & (- _alignment); }
constexpr size_t pad(size_t unaligned) const noexcept { return (- unaligned & (_alignment - 1)); }
constexpr size_t alignment() const noexcept { return _alignment; }
};
}
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