libdpf/include/dpf/prg_dummy.hpp

/// @file dpf/prg_dummy.hpp
/// @brief Identity PRG. `eval` returns the seed and ignores the lane.
/// @details Used where a PRG-shaped type is required and the block must stay
///          equal to the seed. The batched entry points write that seed into
///          every output lane.
/// @author Ryan Henry <ryan.henry@ucalgary.ca>
/// @copyright Copyright (c) 2019-2024 Ryan Henry and [others](@ref authors)
/// @license Released under a GNU General Public v2.0 (GPLv2) license;
///          see [LICENSE.md](@ref license) for details.

#ifndef LIBDPF_INCLUDE_DPF_PRG_DUMMY_HPP__
#define LIBDPF_INCLUDE_DPF_PRG_DUMMY_HPP__

#include <array>
#include <algorithm>
#include <cstddef>

#include "hedley/hedley.h"
#include "portable-snippets/exact-int/exact-int.h"

#include "dpf/utils.hpp"

namespace dpf
{

namespace prg
{

struct dummy final
{
    using block_type = simde__m128i;

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    HEDLEY_CONST
    static block_type eval(block_type seed, psnip_uint32_t) noexcept
    {
        return seed;
    }

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    HEDLEY_CONST
    static auto eval01(block_type seed) noexcept
    {
HEDLEY_PRAGMA(GCC diagnostic push)
HEDLEY_PRAGMA(GCC diagnostic ignored "-Wignored-attributes")
        return std::array<block_type, 2>{seed, seed};
HEDLEY_PRAGMA(GCC diagnostic pop)
    }

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    static void eval(block_type seed, block_type * HEDLEY_RESTRICT output,
        psnip_uint32_t count_, psnip_uint32_t = 0) noexcept
    {
        std::fill_n(output, count_, seed);
    }

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    HEDLEY_NON_NULL(1, 2, 3)
    static void eval01_x4(const block_type * HEDLEY_RESTRICT seeds,
        block_type * HEDLEY_RESTRICT left,
        block_type * HEDLEY_RESTRICT right) noexcept
    {
        for (std::size_t i = 0; i < 4; ++i)
        {
            left[i] = right[i] = seeds[i];
        }
    }

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    HEDLEY_NON_NULL(1, 2)
    static void eval_x4(const block_type * HEDLEY_RESTRICT seeds,
        block_type * HEDLEY_RESTRICT output, psnip_uint32_t = 0) noexcept
    {
        std::copy_n(seeds, 4, output);
    }

    HEDLEY_NO_THROW
    HEDLEY_ALWAYS_INLINE
    HEDLEY_NON_NULL(1, 2)
    static void eval_x8(const block_type * HEDLEY_RESTRICT seeds,
        block_type * HEDLEY_RESTRICT output, psnip_uint32_t = 0) noexcept
    {
        std::copy_n(seeds, 8, output);
    }

    /// @brief Raw-bit subtractive share of `T` for party `Party` (see `prg.hpp`).
    /// @tparam T value type
    /// @tparam Party party index, `0` or `1`
    /// @param seed the PRG seed
    /// @param pos the 0-based index
    /// @return Raw-bit subtractive share of `T` for party `Party` (see `prg.hpp`)
    /// @see `prg.hpp`
    template <typename T, std::size_t Party>
    HEDLEY_NO_THROW
    static auto expand(block_type seed, psnip_uint32_t pos = 0) noexcept;
};  // struct dummy

}  // namespace prg

}  // namespace dpf

#endif  // LIBDPF_INCLUDE_DPF_PRG_DUMMY_HPP__