/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * Marking and sweeping APIs for use by implementations of different GC cell
 * kinds.
 */

#ifndef gc_Marking_h
#define gc_Marking_h

#include "gc/Barrier.h"
#include "gc/Tracer.h"
#include "js/TypeDecls.h"

class JSTracer;
struct JSClass;

namespace js {
class GCMarker;
class Shape;
class WeakMapBase;

namespace gc {

class Cell;

/*** Liveness ***/

// The IsMarkedInternal and IsAboutToBeFinalizedInternal function templates are
// used to implement the IsMarked and IsAboutToBeFinalized set of functions.
// These internal functions are instantiated for the base GC types and should
// not be called directly.
//
// Note that there are two function templates declared for each, not one
// template and a specialization. This is necessary so that pointer arguments
// (e.g. JSObject**) and tagged value arguments (e.g. JS::Value*) are routed to
// separate implementations.

template <typename T>
bool IsMarkedInternal(JSRuntime* rt, T* thing);

template <typename T>
bool IsAboutToBeFinalizedInternal(T* thing);
template <typename T>
bool IsAboutToBeFinalizedInternal(const T& thing);

// Report whether a GC thing has been marked with any color. Things which are in
// zones that are not currently being collected or are owned by another runtime
// are always reported as being marked.
template <typename T>
inline bool IsMarked(JSRuntime* rt, const BarrieredBase<T>& thing) {
  return IsMarkedInternal(rt, *ConvertToBase(thing.unbarrieredAddress()));
}
template <typename T>
inline bool IsMarkedUnbarriered(JSRuntime* rt, T thing) {
  return IsMarkedInternal(rt, *ConvertToBase(&thing));
}

// Report whether a GC thing is dead and will be finalized in the current sweep
// group. This is mainly used in read barriers for incremental sweeping.
//
// This no longer updates pointers moved by the GC (tracing should be used for
// this instead).
template <typename T>
inline bool IsAboutToBeFinalized(const BarrieredBase<T>& thing) {
  return IsAboutToBeFinalizedInternal(
      *ConvertToBase(thing.unbarrieredAddress()));
}
template <typename T>
inline bool IsAboutToBeFinalizedUnbarriered(T* thing) {
  return IsAboutToBeFinalizedInternal(*ConvertToBase(&thing));
}
template <typename T>
inline bool IsAboutToBeFinalizedUnbarriered(const T& thing) {
  return IsAboutToBeFinalizedInternal(thing);
}

inline Cell* ToMarkable(const Value& v) {
  if (v.isGCThing()) {
    return (Cell*)v.toGCThing();
  }
  return nullptr;
}

inline Cell* ToMarkable(Cell* cell) { return cell; }

bool UnmarkGrayGCThingUnchecked(GCMarker* marker, JS::GCCellPtr thing);

} /* namespace gc */

namespace gc {

// Functions for checking and updating GC thing pointers that might have been
// moved by compacting GC. Overloads are also provided that work with Values.
//
// IsForwarded    - check whether a pointer refers to an GC thing that has been
//                  moved.
//
// Forwarded      - return a pointer to the new location of a GC thing given a
//                  pointer to old location.
//
// MaybeForwarded - used before dereferencing a pointer that may refer to a
//                  moved GC thing without updating it. For JSObjects this will
//                  also update the object's shape pointer if it has been moved
//                  to allow slots to be accessed.

template <typename T>
inline bool IsForwarded(const T* t);
inline bool IsForwarded(const JS::Value& value);

template <typename T>
inline T* Forwarded(const T* t);
inline Value Forwarded(const JS::Value& value);

template <typename T>
inline T MaybeForwarded(const T& t);

// Helper functions for use in situations where the object's Shape or BaseShape
// might be forwarded, for example while marking.

inline const JSClass* MaybeForwardedObjectClass(const JSObject* obj);

template <typename T>
inline bool MaybeForwardedObjectIs(const JSObject* obj);

template <typename T>
inline T& MaybeForwardedObjectAs(JSObject* obj);

#ifdef JSGC_HASH_TABLE_CHECKS

template <typename T>
inline bool IsGCThingValidAfterMovingGC(T* t);

template <typename T>
inline void CheckGCThingAfterMovingGC(T* t);

template <typename T>
inline void CheckGCThingAfterMovingGC(const WeakHeapPtr<T*>& t);

#endif  // JSGC_HASH_TABLE_CHECKS

} /* namespace gc */

} /* namespace js */

#endif /* gc_Marking_h */