// Copyright 2020 the V8 project authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

#ifndef INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_

#define INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_

#include <cstdint>

#include <type_traits>

#include "cppgc/internal/member-storage.h"

#include "cppgc/internal/write-barrier.h"

#include "cppgc/sentinel-pointer.h"

#include "cppgc/source-location.h"

#include "cppgc/type-traits.h"

#include "v8config.h"  // NOLINT(build/include_directory)

namespace cppgc {

namespace internal {

class HeapBase;

class PersistentRegion;

class CrossThreadPersistentRegion;

// Tags to distinguish between strong and weak member types.

class StrongMemberTag;

class WeakMemberTag;

class UntracedMemberTag;

struct DijkstraWriteBarrierPolicy {

  V8_INLINE static void InitializingBarrier(const void*, const void*) {

    // Since in initializing writes the source object is always white, having no

    // barrier doesn't break the tri-color invariant.

  }

  template <WriteBarrierSlotType SlotType>

  V8_INLINE static void AssigningBarrier(const void* slot, const void* value) {

#ifdef CPPGC_SLIM_WRITE_BARRIER

    if (V8_UNLIKELY(WriteBarrier::IsEnabled()))

      WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);

#else   // !CPPGC_SLIM_WRITE_BARRIER

    WriteBarrier::Params params;

    const WriteBarrier::Type type =

        WriteBarrier::GetWriteBarrierType(slot, value, params);

    WriteBarrier(type, params, slot, value);

#endif  // !CPPGC_SLIM_WRITE_BARRIER

  }

  template <WriteBarrierSlotType SlotType>

  V8_INLINE static void AssigningBarrier(const void* slot, RawPointer storage) {

    static_assert(

        SlotType == WriteBarrierSlotType::kUncompressed,

        "Assigning storages of Member and UncompressedMember is not supported");

#ifdef CPPGC_SLIM_WRITE_BARRIER

    if (V8_UNLIKELY(WriteBarrier::IsEnabled()))

      WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);

#else   // !CPPGC_SLIM_WRITE_BARRIER

    WriteBarrier::Params params;

    const WriteBarrier::Type type =

        WriteBarrier::GetWriteBarrierType(slot, storage, params);

    WriteBarrier(type, params, slot, storage.Load());

#endif  // !CPPGC_SLIM_WRITE_BARRIER

  }

#if defined(CPPGC_POINTER_COMPRESSION)

  template <WriteBarrierSlotType SlotType>

  V8_INLINE static void AssigningBarrier(const void* slot,

                                         CompressedPointer storage) {

    static_assert(

        SlotType == WriteBarrierSlotType::kCompressed,

        "Assigning storages of Member and UncompressedMember is not supported");

#ifdef CPPGC_SLIM_WRITE_BARRIER

    if (V8_UNLIKELY(WriteBarrier::IsEnabled()))

      WriteBarrier::CombinedWriteBarrierSlow<SlotType>(slot);

#else   // !CPPGC_SLIM_WRITE_BARRIER

    WriteBarrier::Params params;

    const WriteBarrier::Type type =

        WriteBarrier::GetWriteBarrierType(slot, storage, params);

    WriteBarrier(type, params, slot, storage.Load());

#endif  // !CPPGC_SLIM_WRITE_BARRIER

  }

#endif  // defined(CPPGC_POINTER_COMPRESSION)

 private:

  V8_INLINE static void WriteBarrier(WriteBarrier::Type type,

                                     const WriteBarrier::Params& params,

                                     const void* slot, const void* value) {

    switch (type) {

      case WriteBarrier::Type::kGenerational:

        WriteBarrier::GenerationalBarrier<

            WriteBarrier::GenerationalBarrierType::kPreciseSlot>(params, slot);

        break;

      case WriteBarrier::Type::kMarking:

        WriteBarrier::DijkstraMarkingBarrier(params, value);

        break;

      case WriteBarrier::Type::kNone:

        break;

    }

  }

};

struct NoWriteBarrierPolicy {

  V8_INLINE static void InitializingBarrier(const void*, const void*) {}

  template <WriteBarrierSlotType>

  V8_INLINE static void AssigningBarrier(const void*, const void*) {}

  template <WriteBarrierSlotType, typename MemberStorage>

  V8_INLINE static void AssigningBarrier(const void*, MemberStorage) {}

};

class V8_EXPORT SameThreadEnabledCheckingPolicyBase {

 protected:

  void CheckPointerImpl(const void* ptr, bool points_to_payload,

                        bool check_off_heap_assignments);

  const HeapBase* heap_ = nullptr;

};

template <bool kCheckOffHeapAssignments>

class V8_EXPORT SameThreadEnabledCheckingPolicy

    : private SameThreadEnabledCheckingPolicyBase {

 protected:

  template <typename T>

  void CheckPointer(const T* ptr) {

    if (!ptr || (kSentinelPointer == ptr)) return;

    CheckPointersImplTrampoline<T>::Call(this, ptr);

  }

 private:

  template <typename T, bool = IsCompleteV<T>>

  struct CheckPointersImplTrampoline {

    static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) {

      policy->CheckPointerImpl(ptr, false, kCheckOffHeapAssignments);

    }

  };

  template <typename T>

  struct CheckPointersImplTrampoline<T, true> {

    static void Call(SameThreadEnabledCheckingPolicy* policy, const T* ptr) {

      policy->CheckPointerImpl(ptr, IsGarbageCollectedTypeV<T>,

                               kCheckOffHeapAssignments);

    }

  };

};

class DisabledCheckingPolicy {

 protected:

  V8_INLINE void CheckPointer(const void*) {}

};

#ifdef DEBUG

// Off heap members are not connected to object graph and thus cannot ressurect

// dead objects.

using DefaultMemberCheckingPolicy =

    SameThreadEnabledCheckingPolicy<false /* kCheckOffHeapAssignments*/>;

using DefaultPersistentCheckingPolicy =

    SameThreadEnabledCheckingPolicy<true /* kCheckOffHeapAssignments*/>;

#else   // !DEBUG

using DefaultMemberCheckingPolicy = DisabledCheckingPolicy;

using DefaultPersistentCheckingPolicy = DisabledCheckingPolicy;

#endif  // !DEBUG

// For CT(W)P neither marking information (for value), nor objectstart bitmap

// (for slot) are guaranteed to be present because there's no synchronization

// between heaps after marking.

using DefaultCrossThreadPersistentCheckingPolicy = DisabledCheckingPolicy;

class KeepLocationPolicy {

 public:

  constexpr const SourceLocation& Location() const { return location_; }

 protected:

  constexpr KeepLocationPolicy() = default;

  constexpr explicit KeepLocationPolicy(const SourceLocation& location)

      : location_(location) {}

  // KeepLocationPolicy must not copy underlying source locations.

  KeepLocationPolicy(const KeepLocationPolicy&) = delete;

  KeepLocationPolicy& operator=(const KeepLocationPolicy&) = delete;

  // Location of the original moved from object should be preserved.

  KeepLocationPolicy(KeepLocationPolicy&&) = default;

  KeepLocationPolicy& operator=(KeepLocationPolicy&&) = default;

 private:

  SourceLocation location_;

};

class IgnoreLocationPolicy {

 public:

  constexpr SourceLocation Location() const { return {}; }

 protected:

  constexpr IgnoreLocationPolicy() = default;

  constexpr explicit IgnoreLocationPolicy(const SourceLocation&) {}

};

#if CPPGC_SUPPORTS_OBJECT_NAMES

using DefaultLocationPolicy = KeepLocationPolicy;

#else

using DefaultLocationPolicy = IgnoreLocationPolicy;

#endif

struct StrongPersistentPolicy {

  using IsStrongPersistent = std::true_type;

  static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object);

};

struct WeakPersistentPolicy {

  using IsStrongPersistent = std::false_type;

  static V8_EXPORT PersistentRegion& GetPersistentRegion(const void* object);

};

struct StrongCrossThreadPersistentPolicy {

  using IsStrongPersistent = std::true_type;

  static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion(

      const void* object);

};

struct WeakCrossThreadPersistentPolicy {

  using IsStrongPersistent = std::false_type;

  static V8_EXPORT CrossThreadPersistentRegion& GetPersistentRegion(

      const void* object);

};

// Forward declarations setting up the default policies.

template <typename T, typename WeaknessPolicy,

          typename LocationPolicy = DefaultLocationPolicy,

          typename CheckingPolicy = DefaultCrossThreadPersistentCheckingPolicy>

class BasicCrossThreadPersistent;

template <typename T, typename WeaknessPolicy,

          typename LocationPolicy = DefaultLocationPolicy,

          typename CheckingPolicy = DefaultPersistentCheckingPolicy>

class BasicPersistent;

template <typename T, typename WeaknessTag, typename WriteBarrierPolicy,

          typename CheckingPolicy = DefaultMemberCheckingPolicy,

          typename StorageType = DefaultMemberStorage>

class BasicMember;

}  // namespace internal

}  // namespace cppgc

#endif  // INCLUDE_CPPGC_INTERNAL_POINTER_POLICIES_H_