FEX-Emu--FEX/FEXCore/Source/Utils/BucketList.h

// SPDX-License-Identifier: MIT
#pragma once

#include <cstddef>
#include <FEXCore/Utils/LogManager.h>
#include <FEXCore/fextl/memory.h>

namespace FEXCore {

// BucketList is an optimized container, it includes an inline array of Size
// and can overflow to a linked list of further buckets
//
// To optimize for best performance, Size should be big enough to allocate one or two
// buckets for the typical case
// Picking a Size so sizeof(Bucket<...>) is a power of two is also a small win
template<size_t _Size, typename T = uint32_t>
struct BucketList {
  static constexpr size_t Size = _Size;

  T Items[Size];
  fextl::unique_ptr<BucketList<Size, T>> Next;

  void Clear() {
    Items[0] = T {};
#if defined(ASSERTIONS_ENABLED) && ASSERTIONS_ENABLED
    for (size_t i = 1; i < Size; i++) {
      Items[i] = T {0xDEADBEEF};
    }
#endif
    Next.reset();
  }

  BucketList() {
    Clear();
  }

  template<typename EnumeratorFn>
  void Iterate(EnumeratorFn Enumerator) const {
    size_t i = 0;
    auto Bucket = this;

    while (true) {
      auto Item = Bucket->Items[i];
      if (Item == T {}) {
        break;
      }

      Enumerator(Item);

      if (++i == Size) {
        LOGMAN_THROW_A_FMT(Bucket->Next != nullptr, "Interference bug");
        Bucket = Bucket->Next.get();
        i = 0;
      }
    }
  }

  template<typename EnumeratorFn>
  bool Find(EnumeratorFn Enumerator) const {
    size_t i = 0;
    auto Bucket = this;

    while (true) {
      auto Item = Bucket->Items[i];
      if (Item == T {}) {
        break;
      }

      if (Enumerator(Item)) {
        return true;
      }

      if (++i == Size) {
        LOGMAN_THROW_A_FMT(Bucket->Next != nullptr, "Bucket in bad state");
        Bucket = Bucket->Next.get();
        i = 0;
      }
    }

    return false;
  }

  void Append(T Val) {
    auto that = this;

    while (that->Next) {
      that = that->Next.get();
    }

    size_t i;
    for (i = 0; i < Size; i++) {
      if (that->Items[i] == T {}) {
        that->Items[i] = Val;
        break;
      }
    }

    if (i < (Size - 1)) {
      that->Items[i + 1] = T {};
    } else {
      that->Next = fextl::make_unique<BucketList<Size, T>>();
    }
  }
  void Erase(T Val) {
    size_t i = 0;
    auto that = this;
    auto foundThat = this;
    size_t foundI = 0;

    while (true) {
      if (that->Items[i] == Val) {
        foundThat = that;
        foundI = i;
        break;
      } else if (++i == Size) {
        i = 0;
        LOGMAN_THROW_A_FMT(that->Next != nullptr, "Bucket::Erase but element not contained");
        that = that->Next.get();
      }
    }

    while (true) {
      if (that->Items[i] == T {}) {
        foundThat->Items[foundI] = that->Items[i - 1];
        that->Items[i - 1] = T {};
        break;
      } else if (++i == Size) {
        if (that->Next->Items[0] == T {}) {
          that->Next.reset();
          foundThat->Items[foundI] = that->Items[Size - 1];
          that->Items[Size - 1] = T {};
          break;
        }
        i = 0;
        that = that->Next.get();
      }
    }
  }
};

} // namespace FEXCore