// Copyright 2018 The Abseil Authors.

//

// 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

//

//      https://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.

#include "absl/hash/internal/hash.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <type_traits>

#include "absl/base/attributes.h"

#include "absl/base/config.h"

#include "absl/base/internal/unaligned_access.h"

#include "absl/base/optimization.h"

#include "absl/base/prefetch.h"

#include "absl/hash/internal/city.h"

#ifdef ABSL_AES_INTERNAL_HAVE_X86_SIMD

#error ABSL_AES_INTERNAL_HAVE_X86_SIMD cannot be directly set

#elif defined(__SSE4_2__) && defined(__AES__)

#define ABSL_AES_INTERNAL_HAVE_X86_SIMD

#endif

#ifdef ABSL_AES_INTERNAL_HAVE_X86_SIMD

#include <smmintrin.h>

#include <wmmintrin.h>

#include <xmmintrin.h>

#endif  // ABSL_AES_INTERNAL_HAVE_X86_SIMD

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace hash_internal {

namespace {

void PrefetchFutureDataToLocalCache(const uint8_t* ptr) {

  PrefetchToLocalCache(ptr + 5 * ABSL_CACHELINE_SIZE);

}

#ifdef ABSL_AES_INTERNAL_HAVE_X86_SIMD

uint64_t Mix4x16Vectors(__m128i a, __m128i b, __m128i c, __m128i d) {

  // res128 = encrypt(a + c, d) + decrypt(b - d, a)

  auto res128 = _mm_add_epi64(_mm_aesenc_si128(_mm_add_epi64(a, c), d),

                              _mm_aesdec_si128(_mm_sub_epi64(b, d), a));

  auto x64 = static_cast<uint64_t>(_mm_cvtsi128_si64(res128));

  auto y64 = static_cast<uint64_t>(_mm_extract_epi64(res128, 1));

  return x64 ^ y64;

}

uint64_t LowLevelHash33To64(uint64_t seed, const uint8_t* ptr, size_t len) {

  assert(len > 32);

  assert(len <= 64);

  __m128i state =

      _mm_set_epi64x(static_cast<int64_t>(seed), static_cast<int64_t>(len));

  auto a = _mm_loadu_si128(reinterpret_cast<const __m128i*>(ptr));

  auto b = _mm_loadu_si128(reinterpret_cast<const __m128i*>(ptr + 16));

  auto* last32_ptr = ptr + len - 32;

  auto c = _mm_loadu_si128(reinterpret_cast<const __m128i*>(last32_ptr));

  auto d = _mm_loadu_si128(reinterpret_cast<const __m128i*>(last32_ptr + 16));

  // Bits of the second argument to _mm_aesdec_si128/_mm_aesenc_si128 are

  // XORed with the state argument after encryption.

  // We use each value as the first argument to shuffle all the bits around.

  // We do not add any salt to the state or loaded data, instead we vary

  // instructions used to mix bits _mm_aesdec_si128/_mm_aesenc_si128 and

  // _mm_add_epi64/_mm_sub_epi64.

  // _mm_add_epi64/_mm_sub_epi64 are combined to one instruction with data

  // loading like `vpaddq  xmm1, xmm0, xmmword ptr [rdi]`.

  auto na = _mm_aesdec_si128(_mm_add_epi64(state, a), state);

  auto nb = _mm_aesdec_si128(_mm_sub_epi64(state, b), state);

  auto nc = _mm_aesenc_si128(_mm_add_epi64(state, c), state);

  auto nd = _mm_aesenc_si128(_mm_sub_epi64(state, d), state);

  // We perform another round of encryption to mix bits between two halves of

  // the input.

  return Mix4x16Vectors(na, nb, nc, nd);

}

[[maybe_unused]] ABSL_ATTRIBUTE_NOINLINE uint64_t

LowLevelHashLenGt64(uint64_t seed, const void* data, size_t len) {

  assert(len > 64);

  const uint8_t* ptr = static_cast<const uint8_t*>(data);

  const uint8_t* last_32_ptr = ptr + len - 32;

  // If we have more than 64 bytes, we're going to handle chunks of 64

  // bytes at a time. We're going to build up four separate hash states

  // which we will then hash together. This avoids short dependency chains.

  __m128i state0 =

      _mm_set_epi64x(static_cast<int64_t>(seed), static_cast<int64_t>(len));

  __m128i state1 = state0;

  __m128i state2 = state1;

  __m128i state3 = state2;

  // Mixing two 128-bit vectors at a time with corresponding states.

  // All variables are mixed slightly differently to avoid hash collision

  // due to trivial byte rotation.

  // We combine state and data with _mm_add_epi64/_mm_sub_epi64 before applying

  // AES encryption to make hash function dependent on the order of the blocks.

  // See comments in LowLevelHash33To64 for more considerations.

  auto mix_ab = [&state0,

                 &state1](const uint8_t* p) ABSL_ATTRIBUTE_ALWAYS_INLINE {

    // i128 a = *p;

    // i128 b = *(p + 16);

    // state0 = decrypt(state0 + a, state0);

    // state1 = decrypt(state1 - b, state1);

    auto a = _mm_loadu_si128(reinterpret_cast<const __m128i*>(p));

    auto b = _mm_loadu_si128(reinterpret_cast<const __m128i*>(p + 16));

    state0 = _mm_aesdec_si128(_mm_add_epi64(state0, a), state0);

    state1 = _mm_aesdec_si128(_mm_sub_epi64(state1, b), state1);

  };

  auto mix_cd = [&state2,

                 &state3](const uint8_t* p) ABSL_ATTRIBUTE_ALWAYS_INLINE {

    // i128 c = *p;

    // i128 d = *(p + 16);

    // state2 = encrypt(state2 + c, state2);

    // state3 = encrypt(state3 - d, state3);

    auto c = _mm_loadu_si128(reinterpret_cast<const __m128i*>(p));

    auto d = _mm_loadu_si128(reinterpret_cast<const __m128i*>(p + 16));

    state2 = _mm_aesenc_si128(_mm_add_epi64(state2, c), state2);

    state3 = _mm_aesenc_si128(_mm_sub_epi64(state3, d), state3);

  };

  do {

    PrefetchFutureDataToLocalCache(ptr);

    mix_ab(ptr);

    mix_cd(ptr + 32);

    ptr += 64;

    len -= 64;

  } while (len > 64);

  // We now have a data `ptr` with at most 64 bytes.

  if (len > 32) {

    mix_ab(ptr);

  }

  mix_cd(last_32_ptr);

  return Mix4x16Vectors(state0, state1, state2, state3);

}

#else

uint64_t Mix32Bytes(const uint8_t* ptr, uint64_t current_state) {

  uint64_t a = absl::base_internal::UnalignedLoad64(ptr);

  uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);

  uint64_t c = absl::base_internal::UnalignedLoad64(ptr + 16);

  uint64_t d = absl::base_internal::UnalignedLoad64(ptr + 24);

  uint64_t cs0 = Mix(a ^ kStaticRandomData[1], b ^ current_state);

  uint64_t cs1 = Mix(c ^ kStaticRandomData[2], d ^ current_state);

  return cs0 ^ cs1;

}

uint64_t LowLevelHash33To64(uint64_t seed, const uint8_t* ptr, size_t len) {

  assert(len > 32);

  assert(len <= 64);

  uint64_t current_state = seed ^ kStaticRandomData[0] ^ len;

  const uint8_t* last_32_ptr = ptr + len - 32;

  return Mix32Bytes(last_32_ptr, Mix32Bytes(ptr, current_state));

}

[[maybe_unused]] ABSL_ATTRIBUTE_NOINLINE uint64_t

LowLevelHashLenGt64(uint64_t seed, const void* data, size_t len) {

  assert(len > 64);

  const uint8_t* ptr = static_cast<const uint8_t*>(data);

  uint64_t current_state = seed ^ kStaticRandomData[0] ^ len;

  const uint8_t* last_32_ptr = ptr + len - 32;

  // If we have more than 64 bytes, we're going to handle chunks of 64

  // bytes at a time. We're going to build up four separate hash states

  // which we will then hash together. This avoids short dependency chains.

  uint64_t duplicated_state0 = current_state;

  uint64_t duplicated_state1 = current_state;

  uint64_t duplicated_state2 = current_state;

  do {

    PrefetchFutureDataToLocalCache(ptr);

    uint64_t a = absl::base_internal::UnalignedLoad64(ptr);

    uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);

    uint64_t c = absl::base_internal::UnalignedLoad64(ptr + 16);

    uint64_t d = absl::base_internal::UnalignedLoad64(ptr + 24);

    uint64_t e = absl::base_internal::UnalignedLoad64(ptr + 32);

    uint64_t f = absl::base_internal::UnalignedLoad64(ptr + 40);

    uint64_t g = absl::base_internal::UnalignedLoad64(ptr + 48);

    uint64_t h = absl::base_internal::UnalignedLoad64(ptr + 56);

    current_state = Mix(a ^ kStaticRandomData[1], b ^ current_state);

    duplicated_state0 = Mix(c ^ kStaticRandomData[2], d ^ duplicated_state0);

    duplicated_state1 = Mix(e ^ kStaticRandomData[3], f ^ duplicated_state1);

    duplicated_state2 = Mix(g ^ kStaticRandomData[4], h ^ duplicated_state2);

    ptr += 64;

    len -= 64;

  } while (len > 64);

  current_state = (current_state ^ duplicated_state0) ^

                  (duplicated_state1 + duplicated_state2);

  // We now have a data `ptr` with at most 64 bytes and the current state

  // of the hashing state machine stored in current_state.

  if (len > 32) {

    current_state = Mix32Bytes(ptr, current_state);

  }

  // We now have a data `ptr` with at most 32 bytes and the current state

  // of the hashing state machine stored in current_state. But we can

  // safely read from `ptr + len - 32`.

  return Mix32Bytes(last_32_ptr, current_state);

}

#endif  // ABSL_AES_INTERNAL_HAVE_X86_SIMD

[[maybe_unused]] uint64_t LowLevelHashLenGt32(uint64_t seed, const void* data,

                                              size_t len) {

  assert(len > 32);

  if (ABSL_PREDICT_FALSE(len > 64)) {

    return LowLevelHashLenGt64(seed, data, len);

  }

  return LowLevelHash33To64(seed, static_cast<const uint8_t*>(data), len);

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t HashBlockOn32Bit(

    uint64_t state, const unsigned char* data, size_t len) {

  // TODO(b/417141985): expose and use CityHash32WithSeed.

  // Note: we can't use PrecombineLengthMix here because len can be up to 1024.

  return CombineRawImpl(

      state + len,

      hash_internal::CityHash32(reinterpret_cast<const char*>(data), len));

}

ABSL_ATTRIBUTE_NOINLINE uint64_t

SplitAndCombineOn32Bit(uint64_t state, const unsigned char* first, size_t len) {

  while (len >= PiecewiseChunkSize()) {

    state = HashBlockOn32Bit(state, first, PiecewiseChunkSize());

    len -= PiecewiseChunkSize();

    first += PiecewiseChunkSize();

  }

  // Do not call CombineContiguousImpl for empty range since it is modifying

  // state.

  if (len == 0) {

    return state;

  }

  // Handle the remainder.

  return CombineContiguousImpl(state, first, len,

                               std::integral_constant<int, 4>{});

}

ABSL_ATTRIBUTE_ALWAYS_INLINE inline uint64_t HashBlockOn64Bit(

    uint64_t state, const unsigned char* data, size_t len) {

#ifdef ABSL_HAVE_INTRINSIC_INT128

  return LowLevelHashLenGt32(state, data, len);

#else

  return hash_internal::CityHash64WithSeed(reinterpret_cast<const char*>(data),

                                           len, state);

#endif

}

ABSL_ATTRIBUTE_NOINLINE uint64_t

SplitAndCombineOn64Bit(uint64_t state, const unsigned char* first, size_t len) {

  while (len >= PiecewiseChunkSize()) {

    state = HashBlockOn64Bit(state, first, PiecewiseChunkSize());

    len -= PiecewiseChunkSize();

    first += PiecewiseChunkSize();

  }

  // Do not call CombineContiguousImpl for empty range since it is modifying

  // state.

  if (len == 0) {

    return state;

  }

  // Handle the remainder.

  return CombineContiguousImpl(state, first, len,

                               std::integral_constant<int, 8>{});

}

}  // namespace

uint64_t CombineLargeContiguousImplOn32BitLengthGt8(uint64_t state,

                                                    const unsigned char* first,

                                                    size_t len) {

  assert(len > 8);

  assert(sizeof(size_t) == 4);  // NOLINT(misc-static-assert)

  if (ABSL_PREDICT_TRUE(len <= PiecewiseChunkSize())) {

    return HashBlockOn32Bit(state, first, len);

  }

  return SplitAndCombineOn32Bit(state, first, len);

}

uint64_t CombineLargeContiguousImplOn64BitLengthGt32(uint64_t state,

                                                     const unsigned char* first,

                                                     size_t len) {

  assert(len > 32);

  assert(sizeof(size_t) == 8);  // NOLINT(misc-static-assert)

  if (ABSL_PREDICT_TRUE(len <= PiecewiseChunkSize())) {

    return HashBlockOn64Bit(state, first, len);

  }

  return SplitAndCombineOn64Bit(state, first, len);

}

ABSL_CONST_INIT const void* const MixingHashState::kSeed = &kSeed;

}  // namespace hash_internal

ABSL_NAMESPACE_END

}  // namespace absl