/*
 * Copyright 2017 - 2021 Justas Masiulis
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef JM_XORSTR_HPP
#define JM_XORSTR_HPP
#define JM_XORSTR_DISABLE_AVX_INTRINSICS

#if defined(_M_ARM64) || defined(__aarch64__) || defined(_M_ARM) ||            \
    defined(__arm__)
#include <arm_neon.h>
#elif defined(_M_X64) || defined(__amd64__) || defined(_M_IX86) ||             \
    defined(__i386__)
#include <immintrin.h>
#else
#error Unsupported platform
#endif

#include <cstddef>
#include <cstdint>
#include <type_traits>
#include <utility>


#define xorstr(str)                                                            \
  ::jm::xor_string(                                                            \
      []() { return str; },                                                    \
      std::integral_constant<std::size_t, sizeof(str) / sizeof(*str)>{},       \
      std::make_index_sequence<::jm::detail::_buffer_size<sizeof(str)>()>{})
#define xorstr2(str)                                                           \
  ::jm::xor_string(                                                            \
      []() { return str; },                                                    \
      std::integral_constant<std::size_t, (sizeof(str) / sizeof(*str)) + 1>{}, \
      std::make_index_sequence<                                                \
          ::jm::detail::_buffer_size<sizeof(str) + 1>()>{})
#define xorstr_(str) xorstr(str).crypt_get()
#define _xor_(str) xorstr(str).crypt_get()
#define _x(str) xorstr(str).crypt_get()

#ifdef _MSC_VER
#define XORSTR_FORCEINLINE __forceinline
#else
#define XORSTR_FORCEINLINE __attribute__((always_inline)) inline
#endif

#if defined(__clang__) || defined(__GNUC__)
#define JM_XORSTR_LOAD_FROM_REG(x) ::jm::detail::load_from_reg(x)
#else
#define JM_XORSTR_LOAD_FROM_REG
#endif

namespace jm {

namespace detail {

template <std::size_t Size>
XORSTR_FORCEINLINE constexpr std::size_t _buffer_size() {
  return ((Size / 16) + (Size % 16 != 0)) * 2;
}

template <std::uint32_t Seed>
XORSTR_FORCEINLINE constexpr std::uint32_t key4() noexcept {
  std::uint32_t value = Seed;
  for (char c : __TIME__)
    value = static_cast<std::uint32_t>((value ^ c) * 16777619ull);
  return value;
}

template <std::size_t S> XORSTR_FORCEINLINE constexpr std::uint64_t key8() {
  constexpr auto first_part = key4<2166136261 + S>();
  constexpr auto second_part = key4<first_part>();
  return (static_cast<std::uint64_t>(first_part) << 32) | second_part;
}

// loads up to 8 characters of string into uint64 and xors it with the key
template <std::size_t N, class CharT>
XORSTR_FORCEINLINE constexpr std::uint64_t
load_xored_str8(std::uint64_t key, std::size_t idx, const CharT *str) noexcept {
  using cast_type = typename std::make_unsigned<CharT>::type;
  constexpr auto value_size = sizeof(CharT);
  constexpr auto idx_offset = 8 / value_size;

  std::uint64_t value = key;
  for (std::size_t i = 0; i < idx_offset && i + idx * idx_offset < N; ++i)
    value ^= (std::uint64_t{static_cast<cast_type>(str[i + idx * idx_offset])}
              << ((i % idx_offset) * 8 * value_size));

  return value;
}

// forces compiler to use registers instead of stuffing constants in rdata
XORSTR_FORCEINLINE std::uint64_t load_from_reg(std::uint64_t value) noexcept {
#if defined(__clang__) || defined(__GNUC__)
  asm("" : "=r"(value) : "0"(value) :);
#endif
  return value;
}

} // namespace detail

template <class CharT, std::size_t Size, class Keys, class Indices>
class xor_string;

template <class CharT, std::size_t Size, std::uint64_t... Keys,
          std::size_t... Indices>
class xor_string<CharT, Size, std::integer_sequence<std::uint64_t, Keys...>,
                 std::index_sequence<Indices...>> {
#ifndef JM_XORSTR_DISABLE_AVX_INTRINSICS
  constexpr static inline std::uint64_t alignment = ((Size > 16) ? 32 : 16);
#else
  constexpr static inline std::uint64_t alignment = 16;
#endif

  alignas(alignment) std::uint64_t _storage[sizeof...(Keys)];

public:
  using value_type = CharT;
  using size_type = std::size_t;
  using pointer = CharT *;
  using const_pointer = const CharT *;

  template <class L>
  XORSTR_FORCEINLINE xor_string(L l, std::integral_constant<std::size_t, Size>,
                                std::index_sequence<Indices...>) noexcept
      : _storage{JM_XORSTR_LOAD_FROM_REG(
            (std::integral_constant<std::uint64_t,
                                    detail::load_xored_str8<Size>(
                                        Keys, Indices, l())>::value))...} {}

  XORSTR_FORCEINLINE constexpr size_type size() const noexcept {
    return Size - 1;
  }

  XORSTR_FORCEINLINE void crypt() noexcept {
    // everything is inlined by hand because a certain compiler with a certain
    // linker is _very_ slow
#if defined(__clang__)
    alignas(alignment) std::uint64_t arr[]{JM_XORSTR_LOAD_FROM_REG(Keys)...};
    std::uint64_t *keys =
        (std::uint64_t *)JM_XORSTR_LOAD_FROM_REG((std::uint64_t)arr);
#else
    alignas(alignment) std::uint64_t keys[]{JM_XORSTR_LOAD_FROM_REG(Keys)...};
#endif

#if defined(_M_ARM64) || defined(__aarch64__) || defined(_M_ARM) ||            \
    defined(__arm__)
#if defined(__clang__)
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : __builtin_neon_vst1q_v(
                reinterpret_cast<uint64_t *>(_storage) + Indices * 2,
                veorq_u64(
                    __builtin_neon_vld1q_v(
                        reinterpret_cast<const uint64_t *>(_storage) +
                            Indices * 2,
                        51),
                    __builtin_neon_vld1q_v(
                        reinterpret_cast<const uint64_t *>(keys) + Indices * 2,
                        51)),
                51)),
     ...);
#else // GCC, MSVC
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : vst1q_u64(
                reinterpret_cast<uint64_t *>(_storage) + Indices * 2,
                veorq_u64(
                    vld1q_u64(reinterpret_cast<const uint64_t *>(_storage) +
                              Indices * 2),
                    vld1q_u64(reinterpret_cast<const uint64_t *>(keys) +
                              Indices * 2)))),
     ...);
#endif
#elif !defined(JM_XORSTR_DISABLE_AVX_INTRINSICS)
    ((Indices >= sizeof(_storage) / 32
          ? static_cast<void>(0)
          : _mm256_store_si256(
                reinterpret_cast<__m256i *>(_storage) + Indices,
                _mm256_xor_si256(
                    _mm256_load_si256(
                        reinterpret_cast<const __m256i *>(_storage) + Indices),
                    _mm256_load_si256(reinterpret_cast<const __m256i *>(keys) +
                                      Indices)))),
     ...);

    if constexpr (sizeof(_storage) % 32 != 0)
      _mm_store_si128(
          reinterpret_cast<__m128i *>(_storage + sizeof...(Keys) - 2),
          _mm_xor_si128(_mm_load_si128(reinterpret_cast<const __m128i *>(
                            _storage + sizeof...(Keys) - 2)),
                        _mm_load_si128(reinterpret_cast<const __m128i *>(
                            keys + sizeof...(Keys) - 2))));
#else
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : _mm_store_si128(
                reinterpret_cast<__m128i *>(_storage) + Indices,
                _mm_xor_si128(
                    _mm_load_si128(reinterpret_cast<const __m128i *>(_storage) +
                                   Indices),
                    _mm_load_si128(reinterpret_cast<const __m128i *>(keys) +
                                   Indices)))),
     ...);
#endif
  }

  XORSTR_FORCEINLINE const_pointer get() const noexcept {
    return reinterpret_cast<const_pointer>(_storage);
  }

  XORSTR_FORCEINLINE pointer get() noexcept {
    return reinterpret_cast<pointer>(_storage);
  }

  XORSTR_FORCEINLINE pointer crypt_get() noexcept {
    // crypt() is inlined by hand because a certain compiler with a certain
    // linker is _very_ slow
#if defined(__clang__)
    alignas(alignment) std::uint64_t arr[]{JM_XORSTR_LOAD_FROM_REG(Keys)...};
    std::uint64_t *keys =
        (std::uint64_t *)JM_XORSTR_LOAD_FROM_REG((std::uint64_t)arr);
#else
    alignas(alignment) std::uint64_t keys[]{JM_XORSTR_LOAD_FROM_REG(Keys)...};
#endif

#if defined(_M_ARM64) || defined(__aarch64__) || defined(_M_ARM) ||            \
    defined(__arm__)
#if defined(__clang__)
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : __builtin_neon_vst1q_v(
                reinterpret_cast<uint64_t *>(_storage) + Indices * 2,
                veorq_u64(
                    __builtin_neon_vld1q_v(
                        reinterpret_cast<const uint64_t *>(_storage) +
                            Indices * 2,
                        51),
                    __builtin_neon_vld1q_v(
                        reinterpret_cast<const uint64_t *>(keys) + Indices * 2,
                        51)),
                51)),
     ...);
#else // GCC, MSVC
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : vst1q_u64(
                reinterpret_cast<uint64_t *>(_storage) + Indices * 2,
                veorq_u64(
                    vld1q_u64(reinterpret_cast<const uint64_t *>(_storage) +
                              Indices * 2),
                    vld1q_u64(reinterpret_cast<const uint64_t *>(keys) +
                              Indices * 2)))),
     ...);
#endif
#elif !defined(JM_XORSTR_DISABLE_AVX_INTRINSICS)
    ((Indices >= sizeof(_storage) / 32
          ? static_cast<void>(0)
          : _mm256_store_si256(
                reinterpret_cast<__m256i *>(_storage) + Indices,
                _mm256_xor_si256(
                    _mm256_load_si256(
                        reinterpret_cast<const __m256i *>(_storage) + Indices),
                    _mm256_load_si256(reinterpret_cast<const __m256i *>(keys) +
                                      Indices)))),
     ...);

    if constexpr (sizeof(_storage) % 32 != 0)
      _mm_store_si128(
          reinterpret_cast<__m128i *>(_storage + sizeof...(Keys) - 2),
          _mm_xor_si128(_mm_load_si128(reinterpret_cast<const __m128i *>(
                            _storage + sizeof...(Keys) - 2)),
                        _mm_load_si128(reinterpret_cast<const __m128i *>(
                            keys + sizeof...(Keys) - 2))));
#else
    ((Indices >= sizeof(_storage) / 16
          ? static_cast<void>(0)
          : _mm_store_si128(
                reinterpret_cast<__m128i *>(_storage) + Indices,
                _mm_xor_si128(
                    _mm_load_si128(reinterpret_cast<const __m128i *>(_storage) +
                                   Indices),
                    _mm_load_si128(reinterpret_cast<const __m128i *>(keys) +
                                   Indices)))),
     ...);
#endif

    return (pointer)(_storage);
  }
};

template <class L, std::size_t Size, std::size_t... Indices>
xor_string(L l, std::integral_constant<std::size_t, Size>,
           std::index_sequence<Indices...>)
    -> xor_string<
        std::remove_const_t<std::remove_reference_t<decltype(l()[0])>>, Size,
        std::integer_sequence<std::uint64_t, detail::key8<Indices>()...>,
        std::index_sequence<Indices...>>;

} // namespace jm

#endif // include guard