v8-heap-profiler-agent-impl.cc

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// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#include "src/inspector/v8-heap-profiler-agent-impl.h"
 
#include "include/v8-context.h"
#include "include/v8-inspector.h"
#include "include/v8-platform.h"
#include "include/v8-profiler.h"
#include "src/base/platform/mutex.h"
#include "src/base/platform/time.h"
#include "src/inspector/injected-script.h"
#include "src/inspector/inspected-context.h"
#include "src/inspector/protocol/Protocol.h"
#include "src/inspector/string-util.h"
#include "src/inspector/v8-debugger.h"
#include "src/inspector/v8-inspector-impl.h"
#include "src/inspector/v8-inspector-session-impl.h"
 
namespace v8_inspector {
 
namespace {
 
namespace HeapProfilerAgentState {
static const char heapProfilerEnabled[] = "heapProfilerEnabled";
static const char heapObjectsTrackingEnabled[] = "heapObjectsTrackingEnabled";
static const char allocationTrackingEnabled[] = "allocationTrackingEnabled";
static const char samplingHeapProfilerEnabled[] = "samplingHeapProfilerEnabled";
static const char samplingHeapProfilerInterval[] =
    "samplingHeapProfilerInterval";
static const char samplingHeapProfilerFlags[] = "samplingHeapProfilerFlags";
}  // namespace HeapProfilerAgentState
 
class HeapSnapshotProgress final : public v8::ActivityControl {
 public:
  explicit HeapSnapshotProgress(protocol::HeapProfiler::Frontend* frontend)
      : m_frontend(frontend) {}
  ControlOption ReportProgressValue(uint32_t done, uint32_t total) override {
    m_frontend->reportHeapSnapshotProgress(done, total, std::nullopt);
    if (done >= total) {
      m_frontend->reportHeapSnapshotProgress(total, total, true);
    }
    m_frontend->flush();
    return kContinue;
  }
 
 private:
  protocol::HeapProfiler::Frontend* m_frontend;
};
 
class GlobalObjectNameResolver final
    : public v8::HeapProfiler::ObjectNameResolver {
 public:
  explicit GlobalObjectNameResolver(V8InspectorSessionImpl* session)
      : m_offset(0), m_strings(10000), m_session(session) {}
 
  const char* GetName(v8::Local<v8::Object> object) override {
    v8::Local<v8::Context> creationContext;
    if (!object->GetCreationContext(m_session->inspector()->isolate())
             .ToLocal(&creationContext)) {
      return "";
    }
    InspectedContext* context = m_session->inspector()->getContext(
        m_session->contextGroupId(),
        InspectedContext::contextId(creationContext));
    if (!context) return "";
    String16 name = context->origin();
    size_t length = name.length();
    if (m_offset + length + 1 >= m_strings.size()) return "";
    for (size_t i = 0; i < length; ++i) {
      UChar ch = name[i];
      m_strings[m_offset + i] = ch > 0xFF ? '?' : static_cast<char>(ch);
    }
    m_strings[m_offset + length] = '\0';
    char* result = &*m_strings.begin() + m_offset;
    m_offset += length + 1;
    return result;
  }
 
 private:
  size_t m_offset;
  std::vector<char> m_strings;
  V8InspectorSessionImpl* m_session;
};
 
class HeapSnapshotOutputStream final : public v8::OutputStream {
 public:
  explicit HeapSnapshotOutputStream(protocol::HeapProfiler::Frontend* frontend)
      : m_frontend(frontend) {}
  void EndOfStream() override {}
  int GetChunkSize() override { return 1 * v8::internal::MB; }
  WriteResult WriteAsciiChunk(char* data, int size) override {
    m_frontend->addHeapSnapshotChunk(String16(data, size));
    m_frontend->flush();
    return kContinue;
  }
 
 private:
  protocol::HeapProfiler::Frontend* m_frontend;
};
 
v8::Local<v8::Object> objectByHeapObjectId(v8::Isolate* isolate, int id) {
  v8::HeapProfiler* profiler = isolate->GetHeapProfiler();
  v8::Local<v8::Value> value = profiler->FindObjectById(id);
  if (value.IsEmpty() || !value->IsObject()) return v8::Local<v8::Object>();
  return value.As<v8::Object>();
}
 
class InspectableHeapObject final : public V8InspectorSession::Inspectable {
 public:
  explicit InspectableHeapObject(int heapObjectId)
      : m_heapObjectId(heapObjectId) {}
  v8::Local<v8::Value> get(v8::Local<v8::Context> context) override {
    return objectByHeapObjectId(context->GetIsolate(), m_heapObjectId);
  }
 
 private:
  int m_heapObjectId;
};
 
class HeapStatsStream final : public v8::OutputStream {
 public:
  explicit HeapStatsStream(protocol::HeapProfiler::Frontend* frontend)
      : m_frontend(frontend) {}
 
  void EndOfStream() override {}
 
  WriteResult WriteAsciiChunk(char* data, int size) override {
    DCHECK(false);
    return kAbort;
  }
 
  WriteResult WriteHeapStatsChunk(v8::HeapStatsUpdate* updateData,
                                  int count) override {
    DCHECK_GT(count, 0);
    auto statsDiff = std::make_unique<protocol::Array<int>>();
    for (int i = 0; i < count; ++i) {
      statsDiff->emplace_back(updateData[i].index);
      statsDiff->emplace_back(updateData[i].count);
      statsDiff->emplace_back(updateData[i].size);
    }
    m_frontend->heapStatsUpdate(std::move(statsDiff));
    return kContinue;
  }
 
 private:
  protocol::HeapProfiler::Frontend* m_frontend;
};
 
}  // namespace
 
struct V8HeapProfilerAgentImpl::AsyncCallbacks {
  v8::base::Mutex m_mutex;
  bool m_canceled = false;
  std::vector<std::unique_ptr<CollectGarbageCallback>> m_gcCallbacks;
  std::vector<V8HeapProfilerAgentImpl::HeapSnapshotTask*> m_heapSnapshotTasks;
};
 
class V8HeapProfilerAgentImpl::GCTask : public v8::Task {
 public:
  GCTask(v8::Isolate* isolate, std::shared_ptr<AsyncCallbacks> asyncCallbacks)
      : m_isolate(isolate), m_asyncCallbacks(asyncCallbacks) {}
 
  void Run() override {
    std::shared_ptr<AsyncCallbacks> asyncCallbacks = m_asyncCallbacks.lock();
    if (!asyncCallbacks) return;
    v8::base::MutexGuard lock(&asyncCallbacks->m_mutex);
    if (asyncCallbacks->m_canceled) return;
    v8::debug::ForceGarbageCollection(m_isolate,
                                      v8::StackState::kNoHeapPointers);
    for (auto& callback : asyncCallbacks->m_gcCallbacks) {
      callback->sendSuccess();
    }
    asyncCallbacks->m_gcCallbacks.clear();
  }
 
 private:
  v8::Isolate* m_isolate;
  std::weak_ptr<AsyncCallbacks> m_asyncCallbacks;
};
 
struct V8HeapProfilerAgentImpl::HeapSnapshotProtocolOptions {
  HeapSnapshotProtocolOptions(std::optional<bool> reportProgress,
                              std::optional<bool> treatGlobalObjectsAsRoots,
                              std::optional<bool> captureNumericValue,
                              std::optional<bool> exposeInternals)
      : m_reportProgress(reportProgress.value_or(false)),
        m_treatGlobalObjectsAsRoots(treatGlobalObjectsAsRoots.value_or(true)),
        m_captureNumericValue(captureNumericValue.value_or(false)),
        m_exposeInternals(exposeInternals.value_or(false)) {}
  bool m_reportProgress;
  bool m_treatGlobalObjectsAsRoots;
  bool m_captureNumericValue;
  bool m_exposeInternals;
};
 
class V8HeapProfilerAgentImpl::HeapSnapshotTask : public v8::Task {
 public:
  HeapSnapshotTask(V8HeapProfilerAgentImpl* agent,
                   std::shared_ptr<AsyncCallbacks> asyncCallbacks,
                   HeapSnapshotProtocolOptions protocolOptions,
                   std::unique_ptr<TakeHeapSnapshotCallback> callback)
      : m_agent(agent),
        m_asyncCallbacks(asyncCallbacks),
        m_protocolOptions(protocolOptions),
        m_callback(std::move(callback)) {}
 
  void Run() override { Run(cppgc::EmbedderStackState::kNoHeapPointers); }
 
  void Run(cppgc::EmbedderStackState stackState) {
    Response response = Response::Success();
    {
      // If the async callbacks object still exists and is not canceled, then
      // the V8HeapProfilerAgentImpl still exists, so we can safely take a
      // snapshot.
      std::shared_ptr<AsyncCallbacks> asyncCallbacks = m_asyncCallbacks.lock();
      if (!asyncCallbacks) return;
      v8::base::MutexGuard lock(&asyncCallbacks->m_mutex);
      if (asyncCallbacks->m_canceled) return;
 
      auto& heapSnapshotTasks = asyncCallbacks->m_heapSnapshotTasks;
      auto it =
          std::find(heapSnapshotTasks.begin(), heapSnapshotTasks.end(), this);
      if (it == heapSnapshotTasks.end()) {
        // This task must have already been run. This can happen because the
        // task was queued with PostNonNestableTask but then got run early by
        // takePendingHeapSnapshots.
        return;
      }
      heapSnapshotTasks.erase(it);
 
      response = m_agent->takeHeapSnapshotNow(m_protocolOptions, stackState);
    }
 
    // The rest of this function runs without the mutex, because Node expects to
    // be able to dispose the profiler agent during the callback, which would
    // deadlock if this function still held the mutex. It's safe to call the
    // callback without the mutex; the internal implementation of the callback
    // uses weak pointers to avoid doing anything dangerous if other components
    // have been disposed (see DomainDispatcher::Callback::sendIfActive).
    if (response.IsSuccess()) {
      m_callback->sendSuccess();
    } else {
      m_callback->sendFailure(std::move(response));
    }
  }
 
 private:
  V8HeapProfilerAgentImpl* m_agent;
  std::weak_ptr<AsyncCallbacks> m_asyncCallbacks;
  HeapSnapshotProtocolOptions m_protocolOptions;
  std::unique_ptr<TakeHeapSnapshotCallback> m_callback;
};
 
V8HeapProfilerAgentImpl::V8HeapProfilerAgentImpl(
    V8InspectorSessionImpl* session, protocol::FrontendChannel* frontendChannel,
    protocol::DictionaryValue* state)
    : m_session(session),
      m_isolate(session->inspector()->isolate()),
      m_frontend(frontendChannel),
      m_state(state),
      m_hasTimer(false),
      m_asyncCallbacks(std::make_shared<AsyncCallbacks>()) {}
 
V8HeapProfilerAgentImpl::~V8HeapProfilerAgentImpl() {
  v8::base::MutexGuard lock(&m_asyncCallbacks->m_mutex);
  m_asyncCallbacks->m_canceled = true;
  m_asyncCallbacks->m_gcCallbacks.clear();
  m_asyncCallbacks->m_heapSnapshotTasks.clear();
}
 
void V8HeapProfilerAgentImpl::restore() {
  if (m_state->booleanProperty(HeapProfilerAgentState::heapProfilerEnabled,
                               false))
    m_frontend.resetProfiles();
  if (m_state->booleanProperty(
          HeapProfilerAgentState::heapObjectsTrackingEnabled, false))
    startTrackingHeapObjectsInternal(m_state->booleanProperty(
        HeapProfilerAgentState::allocationTrackingEnabled, false));
  if (m_state->booleanProperty(
          HeapProfilerAgentState::samplingHeapProfilerEnabled, false)) {
    double samplingInterval = m_state->doubleProperty(
        HeapProfilerAgentState::samplingHeapProfilerInterval, -1);
    DCHECK_GE(samplingInterval, 0);
    int flags = m_state->integerProperty(
        HeapProfilerAgentState::samplingHeapProfilerFlags, 0);
    startSampling(
        samplingInterval,
        flags & v8::HeapProfiler::kSamplingIncludeObjectsCollectedByMajorGC,
        flags & v8::HeapProfiler::kSamplingIncludeObjectsCollectedByMinorGC);
  }
}
 
void V8HeapProfilerAgentImpl::collectGarbage(
    std::unique_ptr<CollectGarbageCallback> callback) {
  v8::base::MutexGuard lock(&m_asyncCallbacks->m_mutex);
  m_asyncCallbacks->m_gcCallbacks.push_back(std::move(callback));
  v8::debug::GetCurrentPlatform()
      ->GetForegroundTaskRunner(m_isolate)
      ->PostNonNestableTask(
          std::make_unique<GCTask>(m_isolate, m_asyncCallbacks));
}
 
Response V8HeapProfilerAgentImpl::startTrackingHeapObjects(
    std::optional<bool> trackAllocations) {
  m_state->setBoolean(HeapProfilerAgentState::heapObjectsTrackingEnabled, true);
  bool allocationTrackingEnabled = trackAllocations.value_or(false);
  m_state->setBoolean(HeapProfilerAgentState::allocationTrackingEnabled,
                      allocationTrackingEnabled);
  startTrackingHeapObjectsInternal(allocationTrackingEnabled);
  return Response::Success();
}
 
Response V8HeapProfilerAgentImpl::stopTrackingHeapObjects(
    std::optional<bool> reportProgress,
    std::optional<bool> treatGlobalObjectsAsRoots,
    std::optional<bool> captureNumericValue,
    std::optional<bool> exposeInternals) {
  requestHeapStatsUpdate();
  takeHeapSnapshotNow(
      HeapSnapshotProtocolOptions(
          std::move(reportProgress), std::move(treatGlobalObjectsAsRoots),
          std::move(captureNumericValue), std::move(exposeInternals)),
      cppgc::EmbedderStackState::kMayContainHeapPointers);
  stopTrackingHeapObjectsInternal();
  return Response::Success();
}
 
Response V8HeapProfilerAgentImpl::enable() {
  m_state->setBoolean(HeapProfilerAgentState::heapProfilerEnabled, true);
  return Response::Success();
}
 
Response V8HeapProfilerAgentImpl::disable() {
  stopTrackingHeapObjectsInternal();
  v8::HeapProfiler* profiler = m_isolate->GetHeapProfiler();
  DCHECK(profiler);
  if (m_state->booleanProperty(
          HeapProfilerAgentState::samplingHeapProfilerEnabled, false)) {
    profiler->StopSamplingHeapProfiler();
  }
  profiler->ClearObjectIds();
  m_state->setBoolean(HeapProfilerAgentState::heapProfilerEnabled, false);
  return Response::Success();
}
 
void V8HeapProfilerAgentImpl::takeHeapSnapshot(
    std::optional<bool> reportProgress,
    std::optional<bool> treatGlobalObjectsAsRoots,
    std::optional<bool> captureNumericValue,
    std::optional<bool> exposeInternals,
    std::unique_ptr<TakeHeapSnapshotCallback> callback) {
  HeapSnapshotProtocolOptions protocolOptions(
      std::move(reportProgress), std::move(treatGlobalObjectsAsRoots),
      std::move(captureNumericValue), std::move(exposeInternals));
  std::shared_ptr<v8::TaskRunner> task_runner =
      v8::debug::GetCurrentPlatform()->GetForegroundTaskRunner(m_isolate);
 
  // Heap snapshots can be more accurate if we wait until the stack is empty and
  // run the garbage collector without conservative stack scanning, as done in
  // V8HeapProfilerAgentImpl::collectGarbage. However, heap snapshots can also
  // be requested while paused in the debugger, in which case the snapshot must
  // be taken immediately with conservative stack scanning enabled.
  if (m_session->inspector()->debugger()->isPaused() ||
      !task_runner->NonNestableTasksEnabled()) {
    Response response = takeHeapSnapshotNow(
        protocolOptions, cppgc::EmbedderStackState::kMayContainHeapPointers);
    if (response.IsSuccess()) {
      callback->sendSuccess();
    } else {
      callback->sendFailure(std::move(response));
    }
    return;
  }
 
  std::unique_ptr<HeapSnapshotTask> task = std::make_unique<HeapSnapshotTask>(
      this, m_asyncCallbacks, protocolOptions, std::move(callback));
  m_asyncCallbacks->m_heapSnapshotTasks.push_back(task.get());
  task_runner->PostNonNestableTask(std::move(task));
}
 
Response V8HeapProfilerAgentImpl::takeHeapSnapshotNow(
    const HeapSnapshotProtocolOptions& protocolOptions,
    cppgc::EmbedderStackState stackState) {
  v8::HeapProfiler* profiler = m_isolate->GetHeapProfiler();
  DCHECK(profiler);
  std::unique_ptr<HeapSnapshotProgress> progress;
  if (protocolOptions.m_reportProgress)
    progress.reset(new HeapSnapshotProgress(&m_frontend));
 
  GlobalObjectNameResolver resolver(m_session);
  v8::HeapProfiler::HeapSnapshotOptions options;
  options.global_object_name_resolver = &resolver;
  options.control = progress.get();
  options.snapshot_mode =
      protocolOptions.m_exposeInternals ||
              // Not treating global objects as roots results into exposing
              // internals.
              !protocolOptions.m_treatGlobalObjectsAsRoots
          ? v8::HeapProfiler::HeapSnapshotMode::kExposeInternals
          : v8::HeapProfiler::HeapSnapshotMode::kRegular;
  options.numerics_mode =
      protocolOptions.m_captureNumericValue
          ? v8::HeapProfiler::NumericsMode::kExposeNumericValues
          : v8::HeapProfiler::NumericsMode::kHideNumericValues;
  options.stack_state = stackState;
  const v8::HeapSnapshot* snapshot = profiler->TakeHeapSnapshot(options);
  if (!snapshot) return Response::ServerError("Failed to take heap snapshot");
  HeapSnapshotOutputStream stream(&m_frontend);
  snapshot->Serialize(&stream);
  const_cast<v8::HeapSnapshot*>(snapshot)->Delete();
  return Response::Success();
}
 
Response V8HeapProfilerAgentImpl::getObjectByHeapObjectId(
    const String16& heapSnapshotObjectId, std::optional<String16> objectGroup,
    std::unique_ptr<protocol::Runtime::RemoteObject>* result) {
  bool ok;
  int id = heapSnapshotObjectId.toInteger(&ok);
  if (!ok) return Response::ServerError("Invalid heap snapshot object id");
 
  v8::HandleScope handles(m_isolate);
  v8::Local<v8::Object> heapObject = objectByHeapObjectId(m_isolate, id);
  if (heapObject.IsEmpty())
    return Response::ServerError("Object is not available");
 
  if (!m_session->inspector()->client()->isInspectableHeapObject(heapObject))
    return Response::ServerError("Object is not available");
 
  v8::Local<v8::Context> creationContext;
  if (!heapObject->GetCreationContext(m_isolate).ToLocal(&creationContext)) {
    return Response::ServerError("Object is not available");
  }
  *result = m_session->wrapObject(creationContext, heapObject,
                                  objectGroup.value_or(""), false);
  if (!*result) return Response::ServerError("Object is not available");
  return Response::Success();
}
 
void V8HeapProfilerAgentImpl::takePendingHeapSnapshots() {
  // Each task will remove itself from m_heapSnapshotTasks.
  while (!m_asyncCallbacks->m_heapSnapshotTasks.empty()) {
    m_asyncCallbacks->m_heapSnapshotTasks.front()->Run(
        cppgc::EmbedderStackState::kMayContainHeapPointers);
  }
}
 
Response V8HeapProfilerAgentImpl::addInspectedHeapObject(
    const String16& inspectedHeapObjectId) {
  bool ok;
  int id = inspectedHeapObjectId.toInteger(&ok);
  if (!ok) return Response::ServerError("Invalid heap snapshot object id");
 
  v8::HandleScope handles(m_isolate);
  v8::Local<v8::Object> heapObject = objectByHeapObjectId(m_isolate, id);
  if (heapObject.IsEmpty())
    return Response::ServerError("Object is not available");
 
  if (!m_session->inspector()->client()->isInspectableHeapObject(heapObject))
    return Response::ServerError("Object is not available");
  m_session->addInspectedObject(
      std::unique_ptr<InspectableHeapObject>(new InspectableHeapObject(id)));
  return Response::Success();
}
 
Response V8HeapProfilerAgentImpl::getHeapObjectId(
    const String16& objectId, String16* heapSnapshotObjectId) {
  v8::HandleScope handles(m_isolate);
  v8::Local<v8::Value> value;
  v8::Local<v8::Context> context;
  Response response =
      m_session->unwrapObject(objectId, &value, &context, nullptr);
  if (!response.IsSuccess()) return response;
  if (value->IsUndefined()) return Response::InternalError();
 
  v8::SnapshotObjectId id = m_isolate->GetHeapProfiler()->GetObjectId(value);
  *heapSnapshotObjectId = String16::fromInteger(static_cast<size_t>(id));
  return Response::Success();
}
 
void V8HeapProfilerAgentImpl::requestHeapStatsUpdate() {
  HeapStatsStream stream(&m_frontend);
  v8::SnapshotObjectId lastSeenObjectId =
      m_isolate->GetHeapProfiler()->GetHeapStats(&stream);
  m_frontend.lastSeenObjectId(
      lastSeenObjectId, m_session->inspector()->client()->currentTimeMS());
}
 
// static
void V8HeapProfilerAgentImpl::onTimer(void* data) {
  reinterpret_cast<V8HeapProfilerAgentImpl*>(data)->onTimerImpl();
}
 
static constexpr v8::base::TimeDelta kDefaultTimerDelay =
    v8::base::TimeDelta::FromMilliseconds(50);
 
void V8HeapProfilerAgentImpl::onTimerImpl() {
  v8::base::TimeTicks start = v8::base::TimeTicks::Now();
  requestHeapStatsUpdate();
  v8::base::TimeDelta elapsed = v8::base::TimeTicks::Now() - start;
  if (m_hasTimer) {
    // requestHeapStatsUpdate can take a long time on large heaps. To ensure
    // that there is still some time for the thread to make progress on running
    // JavaScript or doing other useful work, we'll adjust the timer delay here.
    const v8::base::TimeDelta minAcceptableDelay =
        std::max(elapsed * 2, kDefaultTimerDelay);
    const v8::base::TimeDelta idealDelay =
        std::max(elapsed * 3, kDefaultTimerDelay);
    const v8::base::TimeDelta maxAcceptableDelay =
        std::max(elapsed * 4, kDefaultTimerDelay);
    if (m_timerDelayInSeconds < minAcceptableDelay.InSecondsF() ||
        m_timerDelayInSeconds > maxAcceptableDelay.InSecondsF()) {
      // The existing timer's speed is not very close to ideal, so cancel it and
      // start a new timer.
      m_session->inspector()->client()->cancelTimer(
          reinterpret_cast<void*>(this));
      m_timerDelayInSeconds = idealDelay.InSecondsF();
      m_session->inspector()->client()->startRepeatingTimer(
          m_timerDelayInSeconds, &V8HeapProfilerAgentImpl::onTimer,
          reinterpret_cast<void*>(this));
    }
  }
}
 
void V8HeapProfilerAgentImpl::startTrackingHeapObjectsInternal(
    bool trackAllocations) {
  m_isolate->GetHeapProfiler()->StartTrackingHeapObjects(trackAllocations);
  if (!m_hasTimer) {
    m_hasTimer = true;
    m_timerDelayInSeconds = kDefaultTimerDelay.InSecondsF();
    m_session->inspector()->client()->startRepeatingTimer(
        m_timerDelayInSeconds, &V8HeapProfilerAgentImpl::onTimer,
        reinterpret_cast<void*>(this));
  }
}
 
void V8HeapProfilerAgentImpl::stopTrackingHeapObjectsInternal() {
  if (m_hasTimer) {
    m_session->inspector()->client()->cancelTimer(
        reinterpret_cast<void*>(this));
    m_hasTimer = false;
  }
  m_isolate->GetHeapProfiler()->StopTrackingHeapObjects();
  m_state->setBoolean(HeapProfilerAgentState::heapObjectsTrackingEnabled,
                      false);
  m_state->setBoolean(HeapProfilerAgentState::allocationTrackingEnabled, false);
}
 
Response V8HeapProfilerAgentImpl::startSampling(
    std::optional<double> samplingInterval,
    std::optional<bool> includeObjectsCollectedByMajorGC,
    std::optional<bool> includeObjectsCollectedByMinorGC) {
  v8::HeapProfiler* profiler = m_isolate->GetHeapProfiler();
  DCHECK(profiler);
  const unsigned defaultSamplingInterval = 1 << 15;
  double samplingIntervalValue =
      samplingInterval.value_or(defaultSamplingInterval);
  if (samplingIntervalValue <= 0.0) {
    return Response::ServerError("Invalid sampling interval");
  }
  m_state->setDouble(HeapProfilerAgentState::samplingHeapProfilerInterval,
                     samplingIntervalValue);
  m_state->setBoolean(HeapProfilerAgentState::samplingHeapProfilerEnabled,
                      true);
  int flags = v8::HeapProfiler::kSamplingForceGC;
  if (includeObjectsCollectedByMajorGC.value_or(false)) {
    flags |= v8::HeapProfiler::kSamplingIncludeObjectsCollectedByMajorGC;
  }
  if (includeObjectsCollectedByMinorGC.value_or(false)) {
    flags |= v8::HeapProfiler::kSamplingIncludeObjectsCollectedByMinorGC;
  }
  m_state->setInteger(HeapProfilerAgentState::samplingHeapProfilerFlags, flags);
  profiler->StartSamplingHeapProfiler(
      static_cast<uint64_t>(samplingIntervalValue), 128,
      static_cast<v8::HeapProfiler::SamplingFlags>(flags));
  return Response::Success();
}
 
namespace {
std::unique_ptr<protocol::HeapProfiler::SamplingHeapProfileNode>
buildSampingHeapProfileNode(v8::Isolate* isolate,
                            const v8::AllocationProfile::Node* node) {
  auto children = std::make_unique<
      protocol::Array<protocol::HeapProfiler::SamplingHeapProfileNode>>();
  for (const auto* child : node->children)
    children->emplace_back(buildSampingHeapProfileNode(isolate, child));
  size_t selfSize = 0;
  for (const auto& allocation : node->allocations)
    selfSize += allocation.size * allocation.count;
  std::unique_ptr<protocol::Runtime::CallFrame> callFrame =
      protocol::Runtime::CallFrame::create()
          .setFunctionName(toProtocolString(isolate, node->name))
          .setScriptId(String16::fromInteger(node->script_id))
          .setUrl(toProtocolString(isolate, node->script_name))
          .setLineNumber(node->line_number - 1)
          .setColumnNumber(node->column_number - 1)
          .build();
  std::unique_ptr<protocol::HeapProfiler::SamplingHeapProfileNode> result =
      protocol::HeapProfiler::SamplingHeapProfileNode::create()
          .setCallFrame(std::move(callFrame))
          .setSelfSize(selfSize)
          .setChildren(std::move(children))
          .setId(node->node_id)
          .build();
  return result;
}
}  // namespace
 
Response V8HeapProfilerAgentImpl::stopSampling(
    std::unique_ptr<protocol::HeapProfiler::SamplingHeapProfile>* profile) {
  Response result = getSamplingProfile(profile);
  if (result.IsSuccess()) {
    m_isolate->GetHeapProfiler()->StopSamplingHeapProfiler();
    m_state->setBoolean(HeapProfilerAgentState::samplingHeapProfilerEnabled,
                        false);
  }
  return result;
}
 
Response V8HeapProfilerAgentImpl::getSamplingProfile(
    std::unique_ptr<protocol::HeapProfiler::SamplingHeapProfile>* profile) {
  v8::HeapProfiler* profiler = m_isolate->GetHeapProfiler();
  // Need a scope as v8::AllocationProfile contains Local handles.
  v8::HandleScope scope(m_isolate);
  std::unique_ptr<v8::AllocationProfile> v8Profile(
      profiler->GetAllocationProfile());
  if (!v8Profile)
    return Response::ServerError("V8 sampling heap profiler was not started.");
  v8::AllocationProfile::Node* root = v8Profile->GetRootNode();
  auto samples = std::make_unique<
      protocol::Array<protocol::HeapProfiler::SamplingHeapProfileSample>>();
  for (const auto& sample : v8Profile->GetSamples()) {
    samples->emplace_back(
        protocol::HeapProfiler::SamplingHeapProfileSample::create()
            .setSize(sample.size * sample.count)
            .setNodeId(sample.node_id)
            .setOrdinal(static_cast<double>(sample.sample_id))
            .build());
  }
  *profile = protocol::HeapProfiler::SamplingHeapProfile::create()
                 .setHead(buildSampingHeapProfileNode(m_isolate, root))
                 .setSamples(std::move(samples))
                 .build();
  return Response::Success();
}
 
}  // namespace v8_inspector