profile-generator.h

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// Copyright 2011 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_PROFILE_GENERATOR_H_
#define V8_PROFILE_GENERATOR_H_

#include "allocation.h"
#include "hashmap.h"
#include "../include/v8-profiler.h"

namespace v8 {
namespace internal {

class TokenEnumerator {
 public:
  TokenEnumerator();
  ~TokenEnumerator();
  int GetTokenId(Object* token);

  static const int kNoSecurityToken = -1;
  static const int kInheritsSecurityToken = -2;

 private:
  static void TokenRemovedCallback(v8::Persistent<v8::Value> handle,
                                   void* parameter);
  void TokenRemoved(Object** token_location);

  List<Object**> token_locations_;
  List<bool> token_removed_;

  friend class TokenEnumeratorTester;

  DISALLOW_COPY_AND_ASSIGN(TokenEnumerator);
};


// Provides a storage of strings allocated in C++ heap, to hold them
// forever, even if they disappear from JS heap or external storage.
class StringsStorage {
 public:
  StringsStorage();
  ~StringsStorage();

  const char* GetCopy(const char* src);
  const char* GetFormatted(const char* format, ...);
  const char* GetVFormatted(const char* format, va_list args);
  const char* GetName(String* name);
  const char* GetName(int index);
  inline const char* GetFunctionName(String* name);
  inline const char* GetFunctionName(const char* name);
  size_t GetUsedMemorySize() const;

 private:
  static const int kMaxNameSize = 1024;

  INLINE(static bool StringsMatch(void* key1, void* key2)) {
    return strcmp(reinterpret_cast<char*>(key1),
                  reinterpret_cast<char*>(key2)) == 0;
  }
  const char* AddOrDisposeString(char* str, uint32_t hash);

  // Mapping of strings by String::Hash to const char* strings.
  HashMap names_;

  DISALLOW_COPY_AND_ASSIGN(StringsStorage);
};


class CodeEntry {
 public:
  // CodeEntry doesn't own name strings, just references them.
  INLINE(CodeEntry(Logger::LogEventsAndTags tag,
                   const char* name_prefix,
                   const char* name,
                   const char* resource_name,
                   int line_number,
                   int security_token_id));

  INLINE(bool is_js_function() const) { return is_js_function_tag(tag_); }
  INLINE(const char* name_prefix() const) { return name_prefix_; }
  INLINE(bool has_name_prefix() const) { return name_prefix_[0] != '\0'; }
  INLINE(const char* name() const) { return name_; }
  INLINE(const char* resource_name() const) { return resource_name_; }
  INLINE(int line_number() const) { return line_number_; }
  INLINE(int shared_id() const) { return shared_id_; }
  INLINE(void set_shared_id(int shared_id)) { shared_id_ = shared_id; }
  INLINE(int security_token_id() const) { return security_token_id_; }

  INLINE(static bool is_js_function_tag(Logger::LogEventsAndTags tag));

  void CopyData(const CodeEntry& source);
  uint32_t GetCallUid() const;
  bool IsSameAs(CodeEntry* entry) const;

  static const char* const kEmptyNamePrefix;

 private:
  Logger::LogEventsAndTags tag_;
  const char* name_prefix_;
  const char* name_;
  const char* resource_name_;
  int line_number_;
  int shared_id_;
  int security_token_id_;

  DISALLOW_COPY_AND_ASSIGN(CodeEntry);
};


class ProfileTree;

class ProfileNode {
 public:
  INLINE(ProfileNode(ProfileTree* tree, CodeEntry* entry));

  ProfileNode* FindChild(CodeEntry* entry);
  ProfileNode* FindOrAddChild(CodeEntry* entry);
  INLINE(void IncrementSelfTicks()) { ++self_ticks_; }
  INLINE(void IncreaseSelfTicks(unsigned amount)) { self_ticks_ += amount; }
  INLINE(void IncreaseTotalTicks(unsigned amount)) { total_ticks_ += amount; }

  INLINE(CodeEntry* entry() const) { return entry_; }
  INLINE(unsigned self_ticks() const) { return self_ticks_; }
  INLINE(unsigned total_ticks() const) { return total_ticks_; }
  INLINE(const List<ProfileNode*>* children() const) { return &children_list_; }
  double GetSelfMillis() const;
  double GetTotalMillis() const;

  void Print(int indent);

 private:
  INLINE(static bool CodeEntriesMatch(void* entry1, void* entry2)) {
    return reinterpret_cast<CodeEntry*>(entry1)->IsSameAs(
        reinterpret_cast<CodeEntry*>(entry2));
  }

  INLINE(static uint32_t CodeEntryHash(CodeEntry* entry)) {
    return entry->GetCallUid();
  }

  ProfileTree* tree_;
  CodeEntry* entry_;
  unsigned total_ticks_;
  unsigned self_ticks_;
  // Mapping from CodeEntry* to ProfileNode*
  HashMap children_;
  List<ProfileNode*> children_list_;

  DISALLOW_COPY_AND_ASSIGN(ProfileNode);
};


class ProfileTree {
 public:
  ProfileTree();
  ~ProfileTree();

  void AddPathFromEnd(const Vector<CodeEntry*>& path);
  void AddPathFromStart(const Vector<CodeEntry*>& path);
  void CalculateTotalTicks();
  void FilteredClone(ProfileTree* src, int security_token_id);

  double TicksToMillis(unsigned ticks) const {
    return ticks * ms_to_ticks_scale_;
  }
  ProfileNode* root() const { return root_; }
  void SetTickRatePerMs(double ticks_per_ms);

  void ShortPrint();
  void Print() {
    root_->Print(0);
  }

 private:
  template <typename Callback>
  void TraverseDepthFirst(Callback* callback);

  CodeEntry root_entry_;
  ProfileNode* root_;
  double ms_to_ticks_scale_;

  DISALLOW_COPY_AND_ASSIGN(ProfileTree);
};


class CpuProfile {
 public:
  CpuProfile(const char* title, unsigned uid)
      : title_(title), uid_(uid) { }

  // Add pc -> ... -> main() call path to the profile.
  void AddPath(const Vector<CodeEntry*>& path);
  void CalculateTotalTicks();
  void SetActualSamplingRate(double actual_sampling_rate);
  CpuProfile* FilteredClone(int security_token_id);

  INLINE(const char* title() const) { return title_; }
  INLINE(unsigned uid() const) { return uid_; }
  INLINE(const ProfileTree* top_down() const) { return &top_down_; }
  INLINE(const ProfileTree* bottom_up() const) { return &bottom_up_; }

  void UpdateTicksScale();

  void ShortPrint();
  void Print();

 private:
  const char* title_;
  unsigned uid_;
  ProfileTree top_down_;
  ProfileTree bottom_up_;

  DISALLOW_COPY_AND_ASSIGN(CpuProfile);
};


class CodeMap {
 public:
  CodeMap() : next_shared_id_(1) { }
  void AddCode(Address addr, CodeEntry* entry, unsigned size);
  void MoveCode(Address from, Address to);
  CodeEntry* FindEntry(Address addr);
  int GetSharedId(Address addr);

  void Print();

 private:
  struct CodeEntryInfo {
    CodeEntryInfo(CodeEntry* an_entry, unsigned a_size)
        : entry(an_entry), size(a_size) { }
    CodeEntry* entry;
    unsigned size;
  };

  struct CodeTreeConfig {
    typedef Address Key;
    typedef CodeEntryInfo Value;
    static const Key kNoKey;
    static const Value NoValue() { return CodeEntryInfo(NULL, 0); }
    static int Compare(const Key& a, const Key& b) {
      return a < b ? -1 : (a > b ? 1 : 0);
    }
  };
  typedef SplayTree<CodeTreeConfig> CodeTree;

  class CodeTreePrinter {
   public:
    void Call(const Address& key, const CodeEntryInfo& value);
  };

  void DeleteAllCoveredCode(Address start, Address end);

  // Fake CodeEntry pointer to distinguish shared function entries.
  static CodeEntry* const kSharedFunctionCodeEntry;

  CodeTree tree_;
  int next_shared_id_;

  DISALLOW_COPY_AND_ASSIGN(CodeMap);
};


class CpuProfilesCollection {
 public:
  CpuProfilesCollection();
  ~CpuProfilesCollection();

  bool StartProfiling(const char* title, unsigned uid);
  bool StartProfiling(String* title, unsigned uid);
  CpuProfile* StopProfiling(int security_token_id,
                            const char* title,
                            double actual_sampling_rate);
  List<CpuProfile*>* Profiles(int security_token_id);
  const char* GetName(String* name) {
    return function_and_resource_names_.GetName(name);
  }
  const char* GetName(int args_count) {
    return function_and_resource_names_.GetName(args_count);
  }
  CpuProfile* GetProfile(int security_token_id, unsigned uid);
  bool IsLastProfile(const char* title);
  void RemoveProfile(CpuProfile* profile);
  bool HasDetachedProfiles() { return detached_profiles_.length() > 0; }

  CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                          String* name, String* resource_name, int line_number);
  CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag, const char* name);
  CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                          const char* name_prefix, String* name);
  CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag, int args_count);
  CodeEntry* NewCodeEntry(int security_token_id);

  // Called from profile generator thread.
  void AddPathToCurrentProfiles(const Vector<CodeEntry*>& path);

  // Limits the number of profiles that can be simultaneously collected.
  static const int kMaxSimultaneousProfiles = 100;

 private:
  const char* GetFunctionName(String* name) {
    return function_and_resource_names_.GetFunctionName(name);
  }
  const char* GetFunctionName(const char* name) {
    return function_and_resource_names_.GetFunctionName(name);
  }
  int GetProfileIndex(unsigned uid);
  List<CpuProfile*>* GetProfilesList(int security_token_id);
  int TokenToIndex(int security_token_id);

  INLINE(static bool UidsMatch(void* key1, void* key2)) {
    return key1 == key2;
  }

  StringsStorage function_and_resource_names_;
  List<CodeEntry*> code_entries_;
  List<List<CpuProfile*>* > profiles_by_token_;
  // Mapping from profiles' uids to indexes in the second nested list
  // of profiles_by_token_.
  HashMap profiles_uids_;
  List<CpuProfile*> detached_profiles_;

  // Accessed by VM thread and profile generator thread.
  List<CpuProfile*> current_profiles_;
  Semaphore* current_profiles_semaphore_;

  DISALLOW_COPY_AND_ASSIGN(CpuProfilesCollection);
};


class SampleRateCalculator {
 public:
  SampleRateCalculator()
      : result_(Logger::kSamplingIntervalMs * kResultScale),
        ticks_per_ms_(Logger::kSamplingIntervalMs),
        measurements_count_(0),
        wall_time_query_countdown_(1) {
  }

  double ticks_per_ms() {
    return result_ / static_cast<double>(kResultScale);
  }
  void Tick();
  void UpdateMeasurements(double current_time);

  // Instead of querying current wall time each tick,
  // we use this constant to control query intervals.
  static const unsigned kWallTimeQueryIntervalMs = 100;

 private:
  // As the result needs to be accessed from a different thread, we
  // use type that guarantees atomic writes to memory.  There should
  // be <= 1000 ticks per second, thus storing a value of a 10 ** 5
  // order should provide enough precision while keeping away from a
  // potential overflow.
  static const int kResultScale = 100000;

  AtomicWord result_;
  // All other fields are accessed only from the sampler thread.
  double ticks_per_ms_;
  unsigned measurements_count_;
  unsigned wall_time_query_countdown_;
  double last_wall_time_;

  DISALLOW_COPY_AND_ASSIGN(SampleRateCalculator);
};


class ProfileGenerator {
 public:
  explicit ProfileGenerator(CpuProfilesCollection* profiles);

  INLINE(CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                                 String* name,
                                 String* resource_name,
                                 int line_number)) {
    return profiles_->NewCodeEntry(tag, name, resource_name, line_number);
  }

  INLINE(CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                                 const char* name)) {
    return profiles_->NewCodeEntry(tag, name);
  }

  INLINE(CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                                 const char* name_prefix,
                                 String* name)) {
    return profiles_->NewCodeEntry(tag, name_prefix, name);
  }

  INLINE(CodeEntry* NewCodeEntry(Logger::LogEventsAndTags tag,
                                 int args_count)) {
    return profiles_->NewCodeEntry(tag, args_count);
  }

  INLINE(CodeEntry* NewCodeEntry(int security_token_id)) {
    return profiles_->NewCodeEntry(security_token_id);
  }

  void RecordTickSample(const TickSample& sample);

  INLINE(CodeMap* code_map()) { return &code_map_; }

  INLINE(void Tick()) { sample_rate_calc_.Tick(); }
  INLINE(double actual_sampling_rate()) {
    return sample_rate_calc_.ticks_per_ms();
  }

  static const char* const kAnonymousFunctionName;
  static const char* const kProgramEntryName;
  static const char* const kGarbageCollectorEntryName;

 private:
  INLINE(CodeEntry* EntryForVMState(StateTag tag));

  CpuProfilesCollection* profiles_;
  CodeMap code_map_;
  CodeEntry* program_entry_;
  CodeEntry* gc_entry_;
  SampleRateCalculator sample_rate_calc_;

  DISALLOW_COPY_AND_ASSIGN(ProfileGenerator);
};


class HeapEntry;
class HeapSnapshot;

class HeapGraphEdge BASE_EMBEDDED {
 public:
  enum Type {
    kContextVariable = v8::HeapGraphEdge::kContextVariable,
    kElement = v8::HeapGraphEdge::kElement,
    kProperty = v8::HeapGraphEdge::kProperty,
    kInternal = v8::HeapGraphEdge::kInternal,
    kHidden = v8::HeapGraphEdge::kHidden,
    kShortcut = v8::HeapGraphEdge::kShortcut,
    kWeak = v8::HeapGraphEdge::kWeak
  };

  HeapGraphEdge() { }
  HeapGraphEdge(Type type, const char* name, int from, int to);
  HeapGraphEdge(Type type, int index, int from, int to);
  void ReplaceToIndexWithEntry(HeapSnapshot* snapshot);

  Type type() const { return static_cast<Type>(type_); }
  int index() const {
    ASSERT(type_ == kElement || type_ == kHidden || type_ == kWeak);
    return index_;
  }
  const char* name() const {
    ASSERT(type_ == kContextVariable
        || type_ == kProperty
        || type_ == kInternal
        || type_ == kShortcut);
    return name_;
  }
  INLINE(HeapEntry* from() const);
  HeapEntry* to() const { return to_entry_; }

 private:
  INLINE(HeapSnapshot* snapshot() const);

  unsigned type_ : 3;
  int from_index_ : 29;
  union {
    // During entries population |to_index_| is used for storing the index,
    // afterwards it is replaced with a pointer to the entry.
    int to_index_;
    HeapEntry* to_entry_;
  };
  union {
    int index_;
    const char* name_;
  };
};


// HeapEntry instances represent an entity from the heap (or a special
// virtual node, e.g. root).
class HeapEntry BASE_EMBEDDED {
 public:
  enum Type {
    kHidden = v8::HeapGraphNode::kHidden,
    kArray = v8::HeapGraphNode::kArray,
    kString = v8::HeapGraphNode::kString,
    kObject = v8::HeapGraphNode::kObject,
    kCode = v8::HeapGraphNode::kCode,
    kClosure = v8::HeapGraphNode::kClosure,
    kRegExp = v8::HeapGraphNode::kRegExp,
    kHeapNumber = v8::HeapGraphNode::kHeapNumber,
    kNative = v8::HeapGraphNode::kNative,
    kSynthetic = v8::HeapGraphNode::kSynthetic
  };
  static const int kNoEntry;

  HeapEntry() { }
  HeapEntry(HeapSnapshot* snapshot,
            Type type,
            const char* name,
            SnapshotObjectId id,
            int self_size);

  HeapSnapshot* snapshot() { return snapshot_; }
  Type type() { return static_cast<Type>(type_); }
  const char* name() { return name_; }
  void set_name(const char* name) { name_ = name; }
  inline SnapshotObjectId id() { return id_; }
  int self_size() { return self_size_; }
  INLINE(int index() const);
  int children_count() const { return children_count_; }
  INLINE(int set_children_index(int index));
  void add_child(HeapGraphEdge* edge) {
    children_arr()[children_count_++] = edge;
  }
  Vector<HeapGraphEdge*> children() {
    return Vector<HeapGraphEdge*>(children_arr(), children_count_); }

  void SetIndexedReference(
      HeapGraphEdge::Type type, int index, HeapEntry* entry);
  void SetNamedReference(
      HeapGraphEdge::Type type, const char* name, HeapEntry* entry);

  void Print(
      const char* prefix, const char* edge_name, int max_depth, int indent);

  Handle<HeapObject> GetHeapObject();

 private:
  INLINE(HeapGraphEdge** children_arr());
  const char* TypeAsString();

  unsigned type_: 4;
  int children_count_: 28;
  int children_index_;
  int self_size_;
  SnapshotObjectId id_;
  HeapSnapshot* snapshot_;
  const char* name_;
};


class HeapSnapshotsCollection;

// HeapSnapshot represents a single heap snapshot. It is stored in
// HeapSnapshotsCollection, which is also a factory for
// HeapSnapshots. All HeapSnapshots share strings copied from JS heap
// to be able to return them even if they were collected.
// HeapSnapshotGenerator fills in a HeapSnapshot.
class HeapSnapshot {
 public:
  enum Type {
    kFull = v8::HeapSnapshot::kFull
  };

  HeapSnapshot(HeapSnapshotsCollection* collection,
               Type type,
               const char* title,
               unsigned uid);
  void Delete();

  HeapSnapshotsCollection* collection() { return collection_; }
  Type type() { return type_; }
  const char* title() { return title_; }
  unsigned uid() { return uid_; }
  size_t RawSnapshotSize() const;
  HeapEntry* root() { return &entries_[root_index_]; }
  HeapEntry* gc_roots() { return &entries_[gc_roots_index_]; }
  HeapEntry* natives_root() { return &entries_[natives_root_index_]; }
  HeapEntry* gc_subroot(int index) {
    return &entries_[gc_subroot_indexes_[index]];
  }
  List<HeapEntry>& entries() { return entries_; }
  List<HeapGraphEdge>& edges() { return edges_; }
  List<HeapGraphEdge*>& children() { return children_; }
  void RememberLastJSObjectId();
  SnapshotObjectId max_snapshot_js_object_id() const {
    return max_snapshot_js_object_id_;
  }

  HeapEntry* AddEntry(HeapEntry::Type type,
                      const char* name,
                      SnapshotObjectId id,
                      int size);
  HeapEntry* AddRootEntry();
  HeapEntry* AddGcRootsEntry();
  HeapEntry* AddGcSubrootEntry(int tag);
  HeapEntry* AddNativesRootEntry();
  HeapEntry* GetEntryById(SnapshotObjectId id);
  List<HeapEntry*>* GetSortedEntriesList();
  void FillChildren();

  void Print(int max_depth);
  void PrintEntriesSize();

 private:
  HeapSnapshotsCollection* collection_;
  Type type_;
  const char* title_;
  unsigned uid_;
  int root_index_;
  int gc_roots_index_;
  int natives_root_index_;
  int gc_subroot_indexes_[VisitorSynchronization::kNumberOfSyncTags];
  List<HeapEntry> entries_;
  List<HeapGraphEdge> edges_;
  List<HeapGraphEdge*> children_;
  List<HeapEntry*> sorted_entries_;
  SnapshotObjectId max_snapshot_js_object_id_;

  friend class HeapSnapshotTester;

  DISALLOW_COPY_AND_ASSIGN(HeapSnapshot);
};


class HeapObjectsMap {
 public:
  HeapObjectsMap();

  void SnapshotGenerationFinished();
  SnapshotObjectId FindEntry(Address addr);
  SnapshotObjectId FindOrAddEntry(Address addr, unsigned int size);
  void MoveObject(Address from, Address to);
  SnapshotObjectId last_assigned_id() const {
    return next_id_ - kObjectIdStep;
  }

  void StopHeapObjectsTracking();
  SnapshotObjectId PushHeapObjectsStats(OutputStream* stream);
  size_t GetUsedMemorySize() const;

  static SnapshotObjectId GenerateId(v8::RetainedObjectInfo* info);
  static inline SnapshotObjectId GetNthGcSubrootId(int delta);

  static const int kObjectIdStep = 2;
  static const SnapshotObjectId kInternalRootObjectId;
  static const SnapshotObjectId kGcRootsObjectId;
  static const SnapshotObjectId kNativesRootObjectId;
  static const SnapshotObjectId kGcRootsFirstSubrootId;
  static const SnapshotObjectId kFirstAvailableObjectId;

 private:
  struct EntryInfo {
  EntryInfo(SnapshotObjectId id, Address addr, unsigned int size)
      : id(id), addr(addr), size(size), accessed(true) { }
  EntryInfo(SnapshotObjectId id, Address addr, unsigned int size, bool accessed)
      : id(id), addr(addr), size(size), accessed(accessed) { }
    SnapshotObjectId id;
    Address addr;
    unsigned int size;
    bool accessed;
  };
  struct TimeInterval {
    explicit TimeInterval(SnapshotObjectId id) : id(id), size(0), count(0) { }
    SnapshotObjectId id;
    uint32_t size;
    uint32_t count;
  };

  void UpdateHeapObjectsMap();
  void RemoveDeadEntries();

  static bool AddressesMatch(void* key1, void* key2) {
    return key1 == key2;
  }

  static uint32_t AddressHash(Address addr) {
    return ComputeIntegerHash(
        static_cast<uint32_t>(reinterpret_cast<uintptr_t>(addr)),
        v8::internal::kZeroHashSeed);
  }

  SnapshotObjectId next_id_;
  HashMap entries_map_;
  List<EntryInfo> entries_;
  List<TimeInterval> time_intervals_;

  DISALLOW_COPY_AND_ASSIGN(HeapObjectsMap);
};


class HeapSnapshotsCollection {
 public:
  HeapSnapshotsCollection();
  ~HeapSnapshotsCollection();

  bool is_tracking_objects() { return is_tracking_objects_; }
  SnapshotObjectId PushHeapObjectsStats(OutputStream* stream) {
    return ids_.PushHeapObjectsStats(stream);
  }
  void StartHeapObjectsTracking() { is_tracking_objects_ = true; }
  void StopHeapObjectsTracking() { ids_.StopHeapObjectsTracking(); }

  HeapSnapshot* NewSnapshot(
      HeapSnapshot::Type type, const char* name, unsigned uid);
  void SnapshotGenerationFinished(HeapSnapshot* snapshot);
  List<HeapSnapshot*>* snapshots() { return &snapshots_; }
  HeapSnapshot* GetSnapshot(unsigned uid);
  void RemoveSnapshot(HeapSnapshot* snapshot);

  StringsStorage* names() { return &names_; }
  TokenEnumerator* token_enumerator() { return token_enumerator_; }

  SnapshotObjectId FindObjectId(Address object_addr) {
    return ids_.FindEntry(object_addr);
  }
  SnapshotObjectId GetObjectId(Address object_addr, int object_size) {
    return ids_.FindOrAddEntry(object_addr, object_size);
  }
  Handle<HeapObject> FindHeapObjectById(SnapshotObjectId id);
  void ObjectMoveEvent(Address from, Address to) { ids_.MoveObject(from, to); }
  SnapshotObjectId last_assigned_id() const {
    return ids_.last_assigned_id();
  }
  size_t GetUsedMemorySize() const;

 private:
  INLINE(static bool HeapSnapshotsMatch(void* key1, void* key2)) {
    return key1 == key2;
  }

  bool is_tracking_objects_;  // Whether tracking object moves is needed.
  List<HeapSnapshot*> snapshots_;
  // Mapping from snapshots' uids to HeapSnapshot* pointers.
  HashMap snapshots_uids_;
  StringsStorage names_;
  TokenEnumerator* token_enumerator_;
  // Mapping from HeapObject addresses to objects' uids.
  HeapObjectsMap ids_;

  DISALLOW_COPY_AND_ASSIGN(HeapSnapshotsCollection);
};


// A typedef for referencing anything that can be snapshotted living
// in any kind of heap memory.
typedef void* HeapThing;


// An interface that creates HeapEntries by HeapThings.
class HeapEntriesAllocator {
 public:
  virtual ~HeapEntriesAllocator() { }
  virtual HeapEntry* AllocateEntry(HeapThing ptr) = 0;
};


// The HeapEntriesMap instance is used to track a mapping between
// real heap objects and their representations in heap snapshots.
class HeapEntriesMap {
 public:
  HeapEntriesMap();

  int Map(HeapThing thing);
  void Pair(HeapThing thing, int entry);

 private:
  static uint32_t Hash(HeapThing thing) {
    return ComputeIntegerHash(
        static_cast<uint32_t>(reinterpret_cast<uintptr_t>(thing)),
        v8::internal::kZeroHashSeed);
  }
  static bool HeapThingsMatch(HeapThing key1, HeapThing key2) {
    return key1 == key2;
  }

  HashMap entries_;

  friend class HeapObjectsSet;

  DISALLOW_COPY_AND_ASSIGN(HeapEntriesMap);
};


class HeapObjectsSet {
 public:
  HeapObjectsSet();
  void Clear();
  bool Contains(Object* object);
  void Insert(Object* obj);
  const char* GetTag(Object* obj);
  void SetTag(Object* obj, const char* tag);
  bool is_empty() const { return entries_.occupancy() == 0; }

 private:
  HashMap entries_;

  DISALLOW_COPY_AND_ASSIGN(HeapObjectsSet);
};


// An interface used to populate a snapshot with nodes and edges.
class SnapshotFillerInterface {
 public:
  virtual ~SnapshotFillerInterface() { }
  virtual HeapEntry* AddEntry(HeapThing ptr,
                              HeapEntriesAllocator* allocator) = 0;
  virtual HeapEntry* FindEntry(HeapThing ptr) = 0;
  virtual HeapEntry* FindOrAddEntry(HeapThing ptr,
                                    HeapEntriesAllocator* allocator) = 0;
  virtual void SetIndexedReference(HeapGraphEdge::Type type,
                                   int parent_entry,
                                   int index,
                                   HeapEntry* child_entry) = 0;
  virtual void SetIndexedAutoIndexReference(HeapGraphEdge::Type type,
                                            int parent_entry,
                                            HeapEntry* child_entry) = 0;
  virtual void SetNamedReference(HeapGraphEdge::Type type,
                                 int parent_entry,
                                 const char* reference_name,
                                 HeapEntry* child_entry) = 0;
  virtual void SetNamedAutoIndexReference(HeapGraphEdge::Type type,
                                          int parent_entry,
                                          HeapEntry* child_entry) = 0;
};


class SnapshottingProgressReportingInterface {
 public:
  virtual ~SnapshottingProgressReportingInterface() { }
  virtual void ProgressStep() = 0;
  virtual bool ProgressReport(bool force) = 0;
};


// An implementation of V8 heap graph extractor.
class V8HeapExplorer : public HeapEntriesAllocator {
 public:
  V8HeapExplorer(HeapSnapshot* snapshot,
                 SnapshottingProgressReportingInterface* progress);
  virtual ~V8HeapExplorer();
  virtual HeapEntry* AllocateEntry(HeapThing ptr);
  void AddRootEntries(SnapshotFillerInterface* filler);
  int EstimateObjectsCount(HeapIterator* iterator);
  bool IterateAndExtractReferences(SnapshotFillerInterface* filler);
  void TagGlobalObjects();

  static String* GetConstructorName(JSObject* object);

  static HeapObject* const kInternalRootObject;

 private:
  HeapEntry* AddEntry(HeapObject* object);
  HeapEntry* AddEntry(HeapObject* object,
                      HeapEntry::Type type,
                      const char* name);
  const char* GetSystemEntryName(HeapObject* object);

  void ExtractReferences(HeapObject* obj);
  void ExtractJSGlobalProxyReferences(JSGlobalProxy* proxy);
  void ExtractJSObjectReferences(int entry, JSObject* js_obj);
  void ExtractStringReferences(int entry, String* obj);
  void ExtractContextReferences(int entry, Context* context);
  void ExtractMapReferences(int entry, Map* map);
  void ExtractSharedFunctionInfoReferences(int entry,
                                           SharedFunctionInfo* shared);
  void ExtractScriptReferences(int entry, Script* script);
  void ExtractCodeCacheReferences(int entry, CodeCache* code_cache);
  void ExtractCodeReferences(int entry, Code* code);
  void ExtractJSGlobalPropertyCellReferences(int entry,
                                             JSGlobalPropertyCell* cell);
  void ExtractClosureReferences(JSObject* js_obj, int entry);
  void ExtractPropertyReferences(JSObject* js_obj, int entry);
  void ExtractElementReferences(JSObject* js_obj, int entry);
  void ExtractInternalReferences(JSObject* js_obj, int entry);
  bool IsEssentialObject(Object* object);
  void SetClosureReference(HeapObject* parent_obj,
                           int parent,
                           String* reference_name,
                           Object* child);
  void SetNativeBindReference(HeapObject* parent_obj,
                              int parent,
                              const char* reference_name,
                              Object* child);
  void SetElementReference(HeapObject* parent_obj,
                           int parent,
                           int index,
                           Object* child);
  void SetInternalReference(HeapObject* parent_obj,
                            int parent,
                            const char* reference_name,
                            Object* child,
                            int field_offset = -1);
  void SetInternalReference(HeapObject* parent_obj,
                            int parent,
                            int index,
                            Object* child,
                            int field_offset = -1);
  void SetHiddenReference(HeapObject* parent_obj,
                          int parent,
                          int index,
                          Object* child);
  void SetWeakReference(HeapObject* parent_obj,
                        int parent,
                        int index,
                        Object* child_obj,
                        int field_offset);
  void SetPropertyReference(HeapObject* parent_obj,
                            int parent,
                            String* reference_name,
                            Object* child,
                            const char* name_format_string = NULL,
                            int field_offset = -1);
  void SetUserGlobalReference(Object* user_global);
  void SetRootGcRootsReference();
  void SetGcRootsReference(VisitorSynchronization::SyncTag tag);
  void SetGcSubrootReference(
      VisitorSynchronization::SyncTag tag, bool is_weak, Object* child);
  const char* GetStrongGcSubrootName(Object* object);
  void TagObject(Object* obj, const char* tag);

  HeapEntry* GetEntry(Object* obj);

  static inline HeapObject* GetNthGcSubrootObject(int delta);
  static inline int GetGcSubrootOrder(HeapObject* subroot);

  Heap* heap_;
  HeapSnapshot* snapshot_;
  HeapSnapshotsCollection* collection_;
  SnapshottingProgressReportingInterface* progress_;
  SnapshotFillerInterface* filler_;
  HeapObjectsSet objects_tags_;
  HeapObjectsSet strong_gc_subroot_names_;

  static HeapObject* const kGcRootsObject;
  static HeapObject* const kFirstGcSubrootObject;
  static HeapObject* const kLastGcSubrootObject;

  friend class IndexedReferencesExtractor;
  friend class GcSubrootsEnumerator;
  friend class RootsReferencesExtractor;

  DISALLOW_COPY_AND_ASSIGN(V8HeapExplorer);
};


class NativeGroupRetainedObjectInfo;


// An implementation of retained native objects extractor.
class NativeObjectsExplorer {
 public:
  NativeObjectsExplorer(HeapSnapshot* snapshot,
                      SnapshottingProgressReportingInterface* progress);
  virtual ~NativeObjectsExplorer();
  void AddRootEntries(SnapshotFillerInterface* filler);
  int EstimateObjectsCount();
  bool IterateAndExtractReferences(SnapshotFillerInterface* filler);

 private:
  void FillRetainedObjects();
  void FillImplicitReferences();
  List<HeapObject*>* GetListMaybeDisposeInfo(v8::RetainedObjectInfo* info);
  void SetNativeRootReference(v8::RetainedObjectInfo* info);
  void SetRootNativeRootsReference();
  void SetWrapperNativeReferences(HeapObject* wrapper,
                                      v8::RetainedObjectInfo* info);
  void VisitSubtreeWrapper(Object** p, uint16_t class_id);

  static uint32_t InfoHash(v8::RetainedObjectInfo* info) {
    return ComputeIntegerHash(static_cast<uint32_t>(info->GetHash()),
                              v8::internal::kZeroHashSeed);
  }
  static bool RetainedInfosMatch(void* key1, void* key2) {
    return key1 == key2 ||
        (reinterpret_cast<v8::RetainedObjectInfo*>(key1))->IsEquivalent(
            reinterpret_cast<v8::RetainedObjectInfo*>(key2));
  }
  INLINE(static bool StringsMatch(void* key1, void* key2)) {
    return strcmp(reinterpret_cast<char*>(key1),
                  reinterpret_cast<char*>(key2)) == 0;
  }

  NativeGroupRetainedObjectInfo* FindOrAddGroupInfo(const char* label);

  HeapSnapshot* snapshot_;
  HeapSnapshotsCollection* collection_;
  SnapshottingProgressReportingInterface* progress_;
  bool embedder_queried_;
  HeapObjectsSet in_groups_;
  // RetainedObjectInfo* -> List<HeapObject*>*
  HashMap objects_by_info_;
  HashMap native_groups_;
  HeapEntriesAllocator* synthetic_entries_allocator_;
  HeapEntriesAllocator* native_entries_allocator_;
  // Used during references extraction.
  SnapshotFillerInterface* filler_;

  static HeapThing const kNativesRootObject;

  friend class GlobalHandlesExtractor;

  DISALLOW_COPY_AND_ASSIGN(NativeObjectsExplorer);
};


class HeapSnapshotGenerator : public SnapshottingProgressReportingInterface {
 public:
  HeapSnapshotGenerator(HeapSnapshot* snapshot,
                        v8::ActivityControl* control);
  bool GenerateSnapshot();

 private:
  bool FillReferences();
  void ProgressStep();
  bool ProgressReport(bool force = false);
  void SetProgressTotal(int iterations_count);

  HeapSnapshot* snapshot_;
  v8::ActivityControl* control_;
  V8HeapExplorer v8_heap_explorer_;
  NativeObjectsExplorer dom_explorer_;
  // Mapping from HeapThing pointers to HeapEntry* pointers.
  HeapEntriesMap entries_;
  // Used during snapshot generation.
  int progress_counter_;
  int progress_total_;

  DISALLOW_COPY_AND_ASSIGN(HeapSnapshotGenerator);
};

class OutputStreamWriter;

class HeapSnapshotJSONSerializer {
 public:
  explicit HeapSnapshotJSONSerializer(HeapSnapshot* snapshot)
      : snapshot_(snapshot),
        strings_(ObjectsMatch),
        next_node_id_(1),
        next_string_id_(1),
        writer_(NULL) {
  }
  void Serialize(v8::OutputStream* stream);

 private:
  INLINE(static bool ObjectsMatch(void* key1, void* key2)) {
    return key1 == key2;
  }

  INLINE(static uint32_t ObjectHash(const void* key)) {
    return ComputeIntegerHash(
        static_cast<uint32_t>(reinterpret_cast<uintptr_t>(key)),
        v8::internal::kZeroHashSeed);
  }

  HeapSnapshot* CreateFakeSnapshot();
  int GetStringId(const char* s);
  int entry_index(HeapEntry* e) { return e->index() * kNodeFieldsCount; }
  void SerializeEdge(HeapGraphEdge* edge, bool first_edge);
  void SerializeEdges();
  void SerializeImpl();
  void SerializeNode(HeapEntry* entry);
  void SerializeNodes();
  void SerializeSnapshot();
  void SerializeString(const unsigned char* s);
  void SerializeStrings();
  void SortHashMap(HashMap* map, List<HashMap::Entry*>* sorted_entries);

  static const int kEdgeFieldsCount;
  static const int kNodeFieldsCount;

  HeapSnapshot* snapshot_;
  HashMap strings_;
  int next_node_id_;
  int next_string_id_;
  OutputStreamWriter* writer_;

  friend class HeapSnapshotJSONSerializerEnumerator;
  friend class HeapSnapshotJSONSerializerIterator;

  DISALLOW_COPY_AND_ASSIGN(HeapSnapshotJSONSerializer);
};

} }  // namespace v8::internal

#endif  // V8_PROFILE_GENERATOR_H_