// 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/container/internal/raw_hash_set.h"

#include <atomic>

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <cstring>

#include "absl/base/attributes.h"

#include "absl/base/config.h"

#include "absl/base/dynamic_annotations.h"

#include "absl/container/internal/container_memory.h"

#include "absl/hash/hash.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace container_internal {

// We have space for `growth_left` before a single block of control bytes. A

// single block of empty control bytes for tables without any slots allocated.

// This enables removing a branch in the hot path of find(). In order to ensure

// that the control bytes are aligned to 16, we have 16 bytes before the control

// bytes even though growth_left only needs 8.

constexpr ctrl_t ZeroCtrlT() { return static_cast<ctrl_t>(0); }

alignas(16) ABSL_CONST_INIT ABSL_DLL const ctrl_t kEmptyGroup[32] = {

    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),

    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),

    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),

    ZeroCtrlT(),       ZeroCtrlT(),    ZeroCtrlT(),    ZeroCtrlT(),

    ctrl_t::kSentinel, ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,

    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,

    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty,

    ctrl_t::kEmpty,    ctrl_t::kEmpty, ctrl_t::kEmpty, ctrl_t::kEmpty};

#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL

constexpr size_t Group::kWidth;

#endif

namespace {

// Returns "random" seed.

inline size_t RandomSeed() {

#ifdef ABSL_HAVE_THREAD_LOCAL

  static thread_local size_t counter = 0;

  // On Linux kernels >= 5.4 the MSAN runtime has a false-positive when

  // accessing thread local storage data from loaded libraries

  // (https://github.com/google/sanitizers/issues/1265), for this reason counter

  // needs to be annotated as initialized.

  ABSL_ANNOTATE_MEMORY_IS_INITIALIZED(&counter, sizeof(size_t));

  size_t value = ++counter;

#else   // ABSL_HAVE_THREAD_LOCAL

  static std::atomic<size_t> counter(0);

  size_t value = counter.fetch_add(1, std::memory_order_relaxed);

#endif  // ABSL_HAVE_THREAD_LOCAL

  return value ^ static_cast<size_t>(reinterpret_cast<uintptr_t>(&counter));

}

bool ShouldRehashForBugDetection(const ctrl_t* ctrl, size_t capacity) {

  // Note: we can't use the abseil-random library because abseil-random

  // depends on swisstable. We want to return true with probability

  // `min(1, RehashProbabilityConstant() / capacity())`. In order to do this,

  // we probe based on a random hash and see if the offset is less than

  // RehashProbabilityConstant().

  return probe(ctrl, capacity, absl::HashOf(RandomSeed())).offset() <

         RehashProbabilityConstant();

}

}  // namespace

GenerationType* EmptyGeneration() {

  if (SwisstableGenerationsEnabled()) {

    constexpr size_t kNumEmptyGenerations = 1024;

    static constexpr GenerationType kEmptyGenerations[kNumEmptyGenerations]{};

    return const_cast<GenerationType*>(

        &kEmptyGenerations[RandomSeed() % kNumEmptyGenerations]);

  }

  return nullptr;

}

bool CommonFieldsGenerationInfoEnabled::

    should_rehash_for_bug_detection_on_insert(const ctrl_t* ctrl,

                                              size_t capacity) const {

  if (reserved_growth_ == kReservedGrowthJustRanOut) return true;

  if (reserved_growth_ > 0) return false;

  return ShouldRehashForBugDetection(ctrl, capacity);

}

bool CommonFieldsGenerationInfoEnabled::should_rehash_for_bug_detection_on_move(

    const ctrl_t* ctrl, size_t capacity) const {

  return ShouldRehashForBugDetection(ctrl, capacity);

}

bool ShouldInsertBackwards(size_t hash, const ctrl_t* ctrl) {

  // To avoid problems with weak hashes and single bit tests, we use % 13.

  // TODO(kfm,sbenza): revisit after we do unconditional mixing

  return (H1(hash, ctrl) ^ RandomSeed()) % 13 > 6;

}

void ConvertDeletedToEmptyAndFullToDeleted(ctrl_t* ctrl, size_t capacity) {

  assert(ctrl[capacity] == ctrl_t::kSentinel);

  assert(IsValidCapacity(capacity));

  for (ctrl_t* pos = ctrl; pos < ctrl + capacity; pos += Group::kWidth) {

    Group{pos}.ConvertSpecialToEmptyAndFullToDeleted(pos);

  }

  // Copy the cloned ctrl bytes.

  std::memcpy(ctrl + capacity + 1, ctrl, NumClonedBytes());

  ctrl[capacity] = ctrl_t::kSentinel;

}

// Extern template instantiation for inline function.

template FindInfo find_first_non_full(const CommonFields&, size_t);

FindInfo find_first_non_full_outofline(const CommonFields& common,

                                       size_t hash) {

  return find_first_non_full(common, hash);

}

// Returns the address of the slot just after slot assuming each slot has the

// specified size.

static inline void* NextSlot(void* slot, size_t slot_size) {

  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) + slot_size);

}

// Returns the address of the slot just before slot assuming each slot has the

// specified size.

static inline void* PrevSlot(void* slot, size_t slot_size) {

  return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(slot) - slot_size);

}

void DropDeletesWithoutResize(CommonFields& common,

                              const PolicyFunctions& policy, void* tmp_space) {

  void* set = &common;

  void* slot_array = common.slot_array();

  const size_t capacity = common.capacity();

  assert(IsValidCapacity(capacity));

  assert(!is_small(capacity));

  // Algorithm:

  // - mark all DELETED slots as EMPTY

  // - mark all FULL slots as DELETED

  // - for each slot marked as DELETED

  //     hash = Hash(element)

  //     target = find_first_non_full(hash)

  //     if target is in the same group

  //       mark slot as FULL

  //     else if target is EMPTY

  //       transfer element to target

  //       mark slot as EMPTY

  //       mark target as FULL

  //     else if target is DELETED

  //       swap current element with target element

  //       mark target as FULL

  //       repeat procedure for current slot with moved from element (target)

  ctrl_t* ctrl = common.control();

  ConvertDeletedToEmptyAndFullToDeleted(ctrl, capacity);

  auto hasher = policy.hash_slot;

  auto transfer = policy.transfer;

  const size_t slot_size = policy.slot_size;

  size_t total_probe_length = 0;

  void* slot_ptr = SlotAddress(slot_array, 0, slot_size);

  for (size_t i = 0; i != capacity;

       ++i, slot_ptr = NextSlot(slot_ptr, slot_size)) {

    assert(slot_ptr == SlotAddress(slot_array, i, slot_size));

    if (!IsDeleted(ctrl[i])) continue;

    const size_t hash = (*hasher)(set, slot_ptr);

    const FindInfo target = find_first_non_full(common, hash);

    const size_t new_i = target.offset;

    total_probe_length += target.probe_length;

    // Verify if the old and new i fall within the same group wrt the hash.

    // If they do, we don't need to move the object as it falls already in the

    // best probe we can.

    const size_t probe_offset = probe(common, hash).offset();

    const auto probe_index = [probe_offset, capacity](size_t pos) {

      return ((pos - probe_offset) & capacity) / Group::kWidth;

    };

    // Element doesn't move.

    if (ABSL_PREDICT_TRUE(probe_index(new_i) == probe_index(i))) {

      SetCtrl(common, i, H2(hash), slot_size);

      continue;

    }

    void* new_slot_ptr = SlotAddress(slot_array, new_i, slot_size);

    if (IsEmpty(ctrl[new_i])) {

      // Transfer element to the empty spot.

      // SetCtrl poisons/unpoisons the slots so we have to call it at the

      // right time.

      SetCtrl(common, new_i, H2(hash), slot_size);

      (*transfer)(set, new_slot_ptr, slot_ptr);

      SetCtrl(common, i, ctrl_t::kEmpty, slot_size);

    } else {

      assert(IsDeleted(ctrl[new_i]));

      SetCtrl(common, new_i, H2(hash), slot_size);

      // Until we are done rehashing, DELETED marks previously FULL slots.

      // Swap i and new_i elements.

      (*transfer)(set, tmp_space, new_slot_ptr);

      (*transfer)(set, new_slot_ptr, slot_ptr);

      (*transfer)(set, slot_ptr, tmp_space);

      // repeat the processing of the ith slot

      --i;

      slot_ptr = PrevSlot(slot_ptr, slot_size);

    }

  }

  ResetGrowthLeft(common);

  common.infoz().RecordRehash(total_probe_length);

}

static bool WasNeverFull(CommonFields& c, size_t index) {

  if (is_single_group(c.capacity())) {

    return true;

  }

  const size_t index_before = (index - Group::kWidth) & c.capacity();

  const auto empty_after = Group(c.control() + index).MaskEmpty();

  const auto empty_before = Group(c.control() + index_before).MaskEmpty();

  // We count how many consecutive non empties we have to the right and to the

  // left of `it`. If the sum is >= kWidth then there is at least one probe

  // window that might have seen a full group.

  return empty_before && empty_after &&

         static_cast<size_t>(empty_after.TrailingZeros()) +

                 empty_before.LeadingZeros() <

             Group::kWidth;

}

void EraseMetaOnly(CommonFields& c, size_t index, size_t slot_size) {

  assert(IsFull(c.control()[index]) && "erasing a dangling iterator");

  c.decrement_size();

  c.infoz().RecordErase();

  if (WasNeverFull(c, index)) {

    SetCtrl(c, index, ctrl_t::kEmpty, slot_size);

    c.set_growth_left(c.growth_left() + 1);

    return;

  }

  SetCtrl(c, index, ctrl_t::kDeleted, slot_size);

}

void ClearBackingArray(CommonFields& c, const PolicyFunctions& policy,

                       bool reuse) {

  c.set_size(0);

  if (reuse) {

    ResetCtrl(c, policy.slot_size);

    ResetGrowthLeft(c);

    c.infoz().RecordStorageChanged(0, c.capacity());

  } else {

    // We need to record infoz before calling dealloc, which will unregister

    // infoz.

    c.infoz().RecordClearedReservation();

    c.infoz().RecordStorageChanged(0, 0);

    (*policy.dealloc)(c, policy);

    c.set_control(EmptyGroup());

    c.set_generation_ptr(EmptyGeneration());

    c.set_slots(nullptr);

    c.set_capacity(0);

  }

}

void HashSetResizeHelper::GrowIntoSingleGroupShuffleControlBytes(

    ctrl_t* new_ctrl, size_t new_capacity) const {

  assert(is_single_group(new_capacity));

  constexpr size_t kHalfWidth = Group::kWidth / 2;

  assert(old_capacity_ < kHalfWidth);

  const size_t half_old_capacity = old_capacity_ / 2;

  // NOTE: operations are done with compile time known size = kHalfWidth.

  // Compiler optimizes that into single ASM operation.

  // Copy second half of bytes to the beginning.

  // We potentially copy more bytes in order to have compile time known size.

  // Mirrored bytes from the old_ctrl_ will also be copied.

  // In case of old_capacity_ == 3, we will copy 1st element twice.

  // Examples:

  // old_ctrl = 0S0EEEEEEE...

  // new_ctrl = S0EEEEEEEE...

  //

  // old_ctrl = 01S01EEEEE...

  // new_ctrl = 1S01EEEEEE...

  //

  // old_ctrl = 0123456S0123456EE...

  // new_ctrl = 456S0123?????????...

  std::memcpy(new_ctrl, old_ctrl_ + half_old_capacity + 1, kHalfWidth);

  // Clean up copied kSentinel from old_ctrl.

  new_ctrl[half_old_capacity] = ctrl_t::kEmpty;

  // Clean up damaged or uninitialized bytes.

  // Clean bytes after the intended size of the copy.

  // Example:

  // new_ctrl = 1E01EEEEEEE????

  // *new_ctrl= 1E0EEEEEEEE????

  // position      /

  std::memset(new_ctrl + old_capacity_ + 1, static_cast<int8_t>(ctrl_t::kEmpty),

              kHalfWidth);

  // Clean non-mirrored bytes that are not initialized.

  // For small old_capacity that may be inside of mirrored bytes zone.

  // Examples:

  // new_ctrl = 1E0EEEEEEEE??????????....

  // *new_ctrl= 1E0EEEEEEEEEEEEE?????....

  // position           /

  //

  // new_ctrl = 456E0123???????????...

  // *new_ctrl= 456E0123EEEEEEEE???...

  // position           /

  std::memset(new_ctrl + kHalfWidth, static_cast<int8_t>(ctrl_t::kEmpty),

              kHalfWidth);

  // Clean last mirrored bytes that are not initialized

  // and will not be overwritten by mirroring.

  // Examples:

  // new_ctrl = 1E0EEEEEEEEEEEEE????????

  // *new_ctrl= 1E0EEEEEEEEEEEEEEEEEEEEE

  // position           S       /

  //

  // new_ctrl = 456E0123EEEEEEEE???????????????

  // *new_ctrl= 456E0123EEEEEEEE???????EEEEEEEE

  // position                  S       /

  std::memset(new_ctrl + new_capacity + kHalfWidth,

              static_cast<int8_t>(ctrl_t::kEmpty), kHalfWidth);

  // Create mirrored bytes. old_capacity_ < kHalfWidth

  // Example:

  // new_ctrl = 456E0123EEEEEEEE???????EEEEEEEE

  // *new_ctrl= 456E0123EEEEEEEE456E0123EEEEEEE

  // position                  S/

  ctrl_t g[kHalfWidth];

  std::memcpy(g, new_ctrl, kHalfWidth);

  std::memcpy(new_ctrl + new_capacity + 1, g, kHalfWidth);

  // Finally set sentinel to its place.

  new_ctrl[new_capacity] = ctrl_t::kSentinel;

}

void HashSetResizeHelper::GrowIntoSingleGroupShuffleTransferableSlots(

    void* old_slots, void* new_slots, size_t slot_size) const {

  assert(old_capacity_ > 0);

  const size_t half_old_capacity = old_capacity_ / 2;

  SanitizerUnpoisonMemoryRegion(old_slots, slot_size * old_capacity_);

  std::memcpy(new_slots,

              SlotAddress(old_slots, half_old_capacity + 1, slot_size),

              slot_size * half_old_capacity);

  std::memcpy(SlotAddress(new_slots, half_old_capacity + 1, slot_size),

              old_slots, slot_size * (half_old_capacity + 1));

}

void HashSetResizeHelper::GrowSizeIntoSingleGroupTransferable(

    CommonFields& c, void* old_slots, size_t slot_size) {

  assert(old_capacity_ < Group::kWidth / 2);

  assert(is_single_group(c.capacity()));

  assert(IsGrowingIntoSingleGroupApplicable(old_capacity_, c.capacity()));

  GrowIntoSingleGroupShuffleControlBytes(c.control(), c.capacity());

  GrowIntoSingleGroupShuffleTransferableSlots(old_slots, c.slot_array(),

                                              slot_size);

  // We poison since GrowIntoSingleGroupShuffleTransferableSlots

  // may leave empty slots unpoisoned.

  PoisonSingleGroupEmptySlots(c, slot_size);

}

}  // namespace container_internal

ABSL_NAMESPACE_END

}  // namespace absl