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// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/allocation.h"
#include "vm/object.h"
namespace dart {
class Isolate;
// Utility to traverse the object graph in an ordered fashion.
// Example uses:
// - find a retaining path from the isolate roots to a particular object, or
// - determine how much memory is retained by some particular object(s).
class ObjectGraph : public StackResource {
class Stack;
// Allows climbing the search tree all the way to the root.
class StackIterator {
// The object this iterator currently points to.
RawObject* Get() const;
// Returns false if there is no parent.
bool MoveToParent();
// Offset into parent for the pointer to current object. -1 if no parent.
intptr_t OffsetFromParentInWords() const;
StackIterator(const Stack* stack, intptr_t index)
: stack_(stack), index_(index) { }
const Stack* stack_;
intptr_t index_;
friend class ObjectGraph::Stack;
class Visitor {
// Directs how the search should continue after visiting an object.
enum Direction {
kProceed, // Recurse on this object's pointers.
kBacktrack, // Ignore this object's pointers.
kAbort, // Terminate the entire search immediately.
virtual ~Visitor() { }
// Visits the object pointed to by *it. The iterator is only valid
// during this call. This method must not allocate from the heap or
// trigger GC in any way.
virtual Direction VisitObject(StackIterator* it) = 0;
explicit ObjectGraph(Isolate* isolate);
// Visits all strongly reachable objects in the isolate's heap, in a
// pre-order, depth first traversal.
void IterateObjects(Visitor* visitor);
// Like 'IterateObjects', but restricted to objects reachable from 'root'
// (including 'root' itself).
void IterateObjectsFrom(const Object& root, Visitor* visitor);
// The number of bytes retained by 'obj'.
intptr_t SizeRetainedByInstance(const Object& obj);
// The number of bytes retained by the set of all objects of the given class.
intptr_t SizeRetainedByClass(intptr_t class_id);
// Finds some retaining path from the isolate roots to 'obj'. Populates the
// provided array with pairs of (object, offset from parent in words),
// starting with 'obj' itself, as far as there is room. Returns the number
// of objects on the full path. A null input array behaves like a zero-length
// input array. The 'offset' of a root is -1.
// To break the trivial path, the handle 'obj' is temporarily cleared during
// the search, but restored before returning. If no path is found (i.e., the
// provided handle was the only way to reach the object), zero is returned.
intptr_t RetainingPath(Object* obj, const Array& path);
// Find the objects that reference 'obj'. Populates the provided array with
// pairs of (object pointing to 'obj', offset of pointer in words), as far as
// there is room. Returns the number of objects found.
// An object for which this function answers no inbound references might still
// be live due to references from the stack or embedder handles.
intptr_t InboundReferences(Object* obj, const Array& references);
// Write the isolate's object graph to 'stream'. Smis and nulls are omitted.
// Returns the number of nodes in the stream, including the root.
// TODO(koda): Document format; support streaming/chunking.
intptr_t Serialize(WriteStream* stream);
} // namespace dart
#endif // VM_OBJECT_GRAPH_H_