shared/heapsnapshot/HeapSnapshot.h

/* -*-  Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
/* 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/. */

#ifndef mozilla_devtools_HeapSnapshot__
#define mozilla_devtools_HeapSnapshot__

#include "js/HashTable.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/devtools/DeserializedNode.h"
#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/Nullable.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/Maybe.h"
#include "mozilla/RefCounted.h"
#include "mozilla/RefPtr.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/UniquePtr.h"

#include "CoreDump.pb.h"
#include "nsCOMPtr.h"
#include "nsCRTGlue.h"
#include "nsCycleCollectionParticipant.h"
#include "nsISupports.h"
#include "nsWrapperCache.h"
#include "nsXPCOM.h"

namespace mozilla {
namespace devtools {

class DominatorTree;

struct NSFreePolicy {
  void operator()(void* ptr) {
    NS_Free(ptr);
  }
};

using UniqueTwoByteString = UniquePtr<char16_t[], NSFreePolicy>;
using UniqueOneByteString = UniquePtr<char[], NSFreePolicy>;

class HeapSnapshot final : public nsISupports
                         , public nsWrapperCache
{
  friend struct DeserializedNode;
  friend struct DeserializedEdge;
  friend struct DeserializedStackFrame;
  friend class JS::ubi::Concrete<JS::ubi::DeserializedNode>;

  explicit HeapSnapshot(JSContext* cx, nsISupports* aParent)
    : timestamp(Nothing())
    , rootId(0)
    , nodes(cx)
    , frames(cx)
    , mParent(aParent)
  {
    MOZ_ASSERT(aParent);
  };

  // Initialize this HeapSnapshot from the given buffer that contains a
  // serialized core dump. Do NOT take ownership of the buffer, only borrow it
  // for the duration of the call. Return false on failure.
  bool init(JSContext* cx, const uint8_t* buffer, uint32_t size);

  using NodeIdSet = js::HashSet<NodeId>;

  // Save the given `protobuf::Node` message in this `HeapSnapshot` as a
  // `DeserializedNode`.
  bool saveNode(const protobuf::Node& node, NodeIdSet& edgeReferents);

  // Save the given `protobuf::StackFrame` message in this `HeapSnapshot` as a
  // `DeserializedStackFrame`. The saved stack frame's id is returned via the
  // out parameter.
  bool saveStackFrame(const protobuf::StackFrame& frame,
                      StackFrameId& outFrameId);

public:
  // The maximum number of stack frames that we will serialize into a core
  // dump. This helps prevent over-recursion in the protobuf library when
  // deserializing stacks.
  static const size_t MAX_STACK_DEPTH = 60;

private:
  // If present, a timestamp in the same units that `PR_Now` gives.
  Maybe<uint64_t> timestamp;

  // The id of the root node for this deserialized heap graph.
  NodeId rootId;

  // The set of nodes in this deserialized heap graph, keyed by id.
  using NodeSet = js::HashSet<DeserializedNode, DeserializedNode::HashPolicy>;
  NodeSet nodes;

  // The set of stack frames in this deserialized heap graph, keyed by id.
  using FrameSet = js::HashSet<DeserializedStackFrame,
                               DeserializedStackFrame::HashPolicy>;
  FrameSet frames;

  Vector<UniqueTwoByteString> internedTwoByteStrings;
  Vector<UniqueOneByteString> internedOneByteStrings;

  using StringOrRef = Variant<const std::string*, uint64_t>;

  template<typename CharT,
           typename InternedStringSet>
  const CharT* getOrInternString(InternedStringSet& internedStrings,
                                 Maybe<StringOrRef>& maybeStrOrRef);

protected:
  nsCOMPtr<nsISupports> mParent;

  virtual ~HeapSnapshot() { }

public:
  // Create a `HeapSnapshot` from the given buffer that contains a serialized
  // core dump. Do NOT take ownership of the buffer, only borrow it for the
  // duration of the call.
  static already_AddRefed<HeapSnapshot> Create(JSContext* cx,
                                               dom::GlobalObject& global,
                                               const uint8_t* buffer,
                                               uint32_t size,
                                               ErrorResult& rv);

  // Creates the `$TEMP_DIR/XXXXXX-XXX.fxsnapshot` core dump file that heap
  // snapshots are serialized into.
  static already_AddRefed<nsIFile> CreateUniqueCoreDumpFile(ErrorResult& rv,
                                                            const TimeStamp& now,
                                                            nsAString& outFilePath);

  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(HeapSnapshot)
  MOZ_DECLARE_REFCOUNTED_TYPENAME(HeapSnapshot)

  nsISupports* GetParentObject() const { return mParent; }

  virtual JSObject* WrapObject(JSContext* aCx,
                               JS::Handle<JSObject*> aGivenProto) override;

  const char16_t* borrowUniqueString(const char16_t* duplicateString,
                                     size_t length);

  // Get the root node of this heap snapshot's graph.
  JS::ubi::Node getRoot() {
    MOZ_ASSERT(nodes.initialized());
    auto p = nodes.lookup(rootId);
    MOZ_ASSERT(p);
    const DeserializedNode& node = *p;
    return JS::ubi::Node(const_cast<DeserializedNode*>(&node));
  }

  Maybe<JS::ubi::Node> getNodeById(JS::ubi::Node::Id nodeId) {
    auto p = nodes.lookup(nodeId);
    if (!p)
      return Nothing();
    return Some(JS::ubi::Node(const_cast<DeserializedNode*>(&*p)));
  }

  void TakeCensus(JSContext* cx, JS::HandleObject options,
                  JS::MutableHandleValue rval, ErrorResult& rv);

  void DescribeNode(JSContext* cx, JS::HandleObject breakdown, uint64_t nodeId,
                    JS::MutableHandleValue rval, ErrorResult& rv);

  already_AddRefed<DominatorTree> ComputeDominatorTree(ErrorResult& rv);

  void ComputeShortestPaths(JSContext*cx, uint64_t start,
                            const dom::Sequence<uint64_t>& targets,
                            uint64_t maxNumPaths,
                            JS::MutableHandleObject results,
                            ErrorResult& rv);

  dom::Nullable<uint64_t> GetCreationTime() {
    static const uint64_t maxTime = uint64_t(1) << 53;
    if (timestamp.isSome() && timestamp.ref() <= maxTime) {
      return dom::Nullable<uint64_t>(timestamp.ref());
    }

    return dom::Nullable<uint64_t>();
  }
};

// A `CoreDumpWriter` is given the data we wish to save in a core dump and
// serializes it to disk, or memory, or a socket, etc.
class CoreDumpWriter
{
public:
  virtual ~CoreDumpWriter() { };

  // Write the given bits of metadata we would like to associate with this core
  // dump.
  virtual bool writeMetadata(uint64_t timestamp) = 0;

  enum EdgePolicy : bool {
    INCLUDE_EDGES = true,
    EXCLUDE_EDGES = false
  };

  // Write the given `JS::ubi::Node` to the core dump. The given `EdgePolicy`
  // dictates whether its outgoing edges should also be written to the core
  // dump, or excluded.
  virtual bool writeNode(const JS::ubi::Node& node,
                         EdgePolicy includeEdges) = 0;
};

// Serialize the heap graph as seen from `node` with the given `CoreDumpWriter`.
// If `wantNames` is true, capture edge names. If `zones` is non-null, only
// capture the sub-graph within the zone set, otherwise capture the whole heap
// graph. Returns false on failure.
bool
WriteHeapGraph(JSContext* cx,
               const JS::ubi::Node& node,
               CoreDumpWriter& writer,
               bool wantNames,
               JS::CompartmentSet* compartments,
               JS::AutoCheckCannotGC& noGC,
               uint32_t& outNodeCount,
               uint32_t& outEdgeCount);
inline bool
WriteHeapGraph(JSContext* cx,
               const JS::ubi::Node& node,
               CoreDumpWriter& writer,
               bool wantNames,
               JS::CompartmentSet* compartments,
               JS::AutoCheckCannotGC& noGC)
{
  uint32_t ignoreNodeCount;
  uint32_t ignoreEdgeCount;
  return WriteHeapGraph(cx, node, writer, wantNames, compartments, noGC,
                        ignoreNodeCount, ignoreEdgeCount);
}

// Get the mozilla::MallocSizeOf for the current thread's JSRuntime.
MallocSizeOf GetCurrentThreadDebuggerMallocSizeOf();

} // namespace devtools
} // namespace mozilla

#endif // mozilla_devtools_HeapSnapshot__