heap.h.svn-base

Google浏览器V8内核代码

  void VisitPointers(Object** start, Object** end) {
    for (Object** current = start; current < end; current++) {
      if ((*current)->IsHeapObject()) {
        HeapObject* object = HeapObject::cast(*current);
        ASSERT(Heap::Contains(object));
        ASSERT(object->map()->IsMap());
      }
    }
  }
};


// Visitor class to verify interior pointers that have remembered set bits.
// As VerifyPointersVisitor but also checks that remembered set bits are
// always set for pointers into new space.
class VerifyPointersAndRSetVisitor: public ObjectVisitor {
 public:
  void VisitPointers(Object** start, Object** end) {
    for (Object** current = start; current < end; current++) {
      if ((*current)->IsHeapObject()) {
        HeapObject* object = HeapObject::cast(*current);
        ASSERT(Heap::Contains(object));
        ASSERT(object->map()->IsMap());
        if (Heap::InNewSpace(object)) {
          ASSERT(Page::IsRSetSet(reinterpret_cast<Address>(current), 0));
        }
      }
    }
  }
};
#endif


// Space iterator for iterating over all spaces of the heap.
// Returns each space in turn, and null when it is done.
class AllSpaces BASE_EMBEDDED {
 public:
  Space* next();
  AllSpaces() { counter_ = FIRST_SPACE; }
 private:
  int counter_;
};


// Space iterator for iterating over all old spaces of the heap: Old pointer
// space, old data space and code space.
// Returns each space in turn, and null when it is done.
class OldSpaces BASE_EMBEDDED {
 public:
  OldSpace* next();
  OldSpaces() { counter_ = OLD_POINTER_SPACE; }
 private:
  int counter_;
};


// Space iterator for iterating over all the paged spaces of the heap:
// Map space, old pointer space, old data space and code space.
// Returns each space in turn, and null when it is done.
class PagedSpaces BASE_EMBEDDED {
 public:
  PagedSpace* next();
  PagedSpaces() { counter_ = OLD_POINTER_SPACE; }
 private:
  int counter_;
};


// Space iterator for iterating over all spaces of the heap.
// For each space an object iterator is provided. The deallocation of the
// returned object iterators is handled by the space iterator.
class SpaceIterator : public Malloced {
 public:
  SpaceIterator();
  virtual ~SpaceIterator();

  bool has_next();
  ObjectIterator* next();

 private:
  ObjectIterator* CreateIterator();

  int current_space_;  // from enum AllocationSpace.
  ObjectIterator* iterator_;  // object iterator for the current space.
};


// A HeapIterator provides iteration over the whole heap It aggregates a the
// specific iterators for the different spaces as these can only iterate over
// one space only.

class HeapIterator BASE_EMBEDDED {
 public:
  explicit HeapIterator();
  virtual ~HeapIterator();

  bool has_next();
  HeapObject* next();
  void reset();

 private:
  // Perform the initialization.
  void Init();

  // Perform all necessary shutdown (destruction) work.
  void Shutdown();

  // Space iterator for iterating all the spaces.
  SpaceIterator* space_iterator_;
  // Object iterator for the space currently being iterated.
  ObjectIterator* object_iterator_;
};


// ----------------------------------------------------------------------------
// Marking stack for tracing live objects.

class MarkingStack {
 public:
  void Initialize(Address low, Address high) {
    top_ = low_ = reinterpret_cast<HeapObject**>(low);
    high_ = reinterpret_cast<HeapObject**>(high);
    overflowed_ = false;
  }

  bool is_full() { return top_ >= high_; }

  bool is_empty() { return top_ <= low_; }

  bool overflowed() { return overflowed_; }

  void clear_overflowed() { overflowed_ = false; }

  // Push the (marked) object on the marking stack if there is room,
  // otherwise mark the object as overflowed and wait for a rescan of the
  // heap.
  void Push(HeapObject* object) {
    CHECK(object->IsHeapObject());
    if (is_full()) {
      object->SetOverflow();
      overflowed_ = true;
    } else {
      *(top_++) = object;
    }
  }

  HeapObject* Pop() {
    ASSERT(!is_empty());
    HeapObject* object = *(--top_);
    CHECK(object->IsHeapObject());
    return object;
  }

 private:
  HeapObject** low_;
  HeapObject** top_;
  HeapObject** high_;
  bool overflowed_;
};


// A helper class to document/test C++ scopes where we do not
// expect a GC. Usage:
//
// /* Allocation not allowed: we cannot handle a GC in this scope. */
// { AssertNoAllocation nogc;
//   ...
// }

#ifdef DEBUG

class DisallowAllocationFailure {
 public:
  DisallowAllocationFailure() {
    old_state_ = Heap::disallow_allocation_failure_;
    Heap::disallow_allocation_failure_ = true;
  }
  ~DisallowAllocationFailure() {
    Heap::disallow_allocation_failure_ = old_state_;
  }
 private:
  bool old_state_;
};

class AssertNoAllocation {
 public:
  AssertNoAllocation() {
    old_state_ = Heap::allow_allocation(false);
  }

  ~AssertNoAllocation() {
    Heap::allow_allocation(old_state_);
  }

 private:
  bool old_state_;
};

#else  // ndef DEBUG

class AssertNoAllocation {
 public:
  AssertNoAllocation() { }
  ~AssertNoAllocation() { }
};

#endif

#ifdef ENABLE_LOGGING_AND_PROFILING
// The HeapProfiler writes data to the log files, which can be postprocessed
// to generate .hp files for use by the GHC/Valgrind tool hp2ps.
class HeapProfiler {
 public:
  // Write a single heap sample to the log file.
  static void WriteSample();

 private:
  // Update the array info with stats from obj.
  static void CollectStats(HeapObject* obj, HistogramInfo* info);
};
#endif

// GCTracer collects and prints ONE line after each garbage collector
// invocation IFF --trace_gc is used.

class GCTracer BASE_EMBEDDED {
 public:
  GCTracer();

  ~GCTracer();

  // Sets the collector.
  void set_collector(GarbageCollector collector) { collector_ = collector; }

  // Sets the GC count.
  void set_gc_count(int count) { gc_count_ = count; }

  // Sets the full GC count.
  void set_full_gc_count(int count) { full_gc_count_ = count; }

  // Sets the flag that this is a compacting full GC.
  void set_is_compacting() { is_compacting_ = true; }

  // Increment and decrement the count of marked objects.
  void increment_marked_count() { ++marked_count_; }
  void decrement_marked_count() { --marked_count_; }

  int marked_count() { return marked_count_; }

 private:
  // Returns a string matching the collector.
  const char* CollectorString();

  // Returns size of object in heap (in MB).
  double SizeOfHeapObjects() {
    return (static_cast<double>(Heap::SizeOfObjects())) / MB;
  }

  double start_time_;  // Timestamp set in the constructor.
  double start_size_;  // Size of objects in heap set in constructor.
  GarbageCollector collector_;  // Type of collector.

  // A count (including this one, eg, the first collection is 1) of the
  // number of garbage collections.
  int gc_count_;

  // A count (including this one) of the number of full garbage collections.
  int full_gc_count_;

  // True if the current GC is a compacting full collection, false
  // otherwise.
  bool is_compacting_;

  // True if the *previous* full GC cwas a compacting collection (will be
  // false if there has not been a previous full GC).
  bool previous_has_compacted_;

  // On a full GC, a count of the number of marked objects.  Incremented
  // when an object is marked and decremented when an object's mark bit is
  // cleared.  Will be zero on a scavenge collection.
  int marked_count_;

  // The count from the end of the previous full GC.  Will be zero if there
  // was no previous full GC.
  int previous_marked_count_;
};

} }  // namespace v8::internal

#endif  // V8_HEAP_H_