// Copyright (c) 2015, 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 <cstdlib>

#include "vm/atomic.h"
#include "vm/isolate.h"
#include "vm/json_stream.h"
#include "vm/lockers.h"
#include "vm/log.h"
#include "vm/object.h"
#include "vm/thread.h"
#include "vm/timeline.h"

namespace dart {

DEFINE_FLAG(bool, complete_timeline, false, "Record the complete timeline");
DEFINE_FLAG(bool, trace_timeline, false,
            "Trace timeline backend");
DEFINE_FLAG(bool, trace_timeline_analysis, false,
            "Trace timeline analysis backend");
DEFINE_FLAG(bool, timing, false,
            "Dump isolate timing information from timeline.");
DEFINE_FLAG(charp, timeline_dir, NULL,
            "Enable all timeline trace streams and output VM global trace "
            "into specified directory.");

// Implementation notes:
//
// Writing events:
// |TimelineEvent|s are written into |TimelineEventBlock|s. Each |Thread| caches
// a |TimelineEventBlock| object so that it can write events without
// synchronizing with other threads in the system. Even though the |Thread| owns
// the |TimelineEventBlock| the block may need to be reclaimed by the reporting
// system. To support that, a |Thread| must hold its |timeline_block_lock_|
// when operating on the |TimelineEventBlock|. This lock will only ever be
// busy if blocks are being reclaimed by the reporting system.
//
// Reporting:
// When requested, the timeline is serialized in the trace-event format
// (https://goo.gl/hDZw5M). The request can be for a VM-wide timeline or an
// isolate specific timeline. In both cases it may be that a thread has
// a |TimelineEventBlock| cached in TLS partially filled with events. In order
// to report a complete timeline the cached |TimelineEventBlock|s need to be
// reclaimed.
//
// Reclaiming open |TimelineEventBlock|s from threads:
//
// Each |Thread| can have one |TimelineEventBlock| cached in it.
//
// To reclaim blocks, we iterate over all threads and remove the cached
// |TimelineEventBlock| from each thread. This is safe because we hold the
// |Thread|'s |timeline_block_lock_| meaning the block can't be being modified.
//
// Locking notes:
// The following locks are used by the timeline system:
// - |TimelineEventRecorder::lock_| This lock is held whenever a
// |TimelineEventBlock| is being requested or reclaimed.
// - |Thread::timeline_block_lock_| This lock is held whenever a |Thread|'s
// cached block is being operated on.
// - |Thread::thread_list_lock_| This lock is held when iterating over
// |Thread|s.
//
// Locks must always be taken in the following order:
//   |Thread::thread_list_lock_|
//     |Thread::timeline_block_lock_|
//       |TimelineEventRecorder::lock_|
//

void Timeline::InitOnce() {
  ASSERT(recorder_ == NULL);
  // Default to ring recorder being enabled.
  const bool use_ring_recorder = true;
  // Some flags require that we use the endless recorder.
  const bool use_endless_recorder =
      (FLAG_timeline_dir != NULL) || FLAG_timing || FLAG_complete_timeline;
  if (use_endless_recorder) {
    recorder_ = new TimelineEventEndlessRecorder();
  } else if (use_ring_recorder) {
    recorder_ = new TimelineEventRingRecorder();
  }
  vm_stream_.Init("VM", EnableStreamByDefault("VM"), NULL);
  vm_api_stream_.Init("API",
                      EnableStreamByDefault("API"),
                      &stream_API_enabled_);
  // Global overrides.
#define ISOLATE_TIMELINE_STREAM_FLAG_DEFAULT(name, not_used)                   \
  stream_##name##_enabled_ = EnableStreamByDefault(#name);
  ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_FLAG_DEFAULT)
#undef ISOLATE_TIMELINE_STREAM_FLAG_DEFAULT
}


void Timeline::Shutdown() {
  ASSERT(recorder_ != NULL);
  if (FLAG_timeline_dir != NULL) {
    recorder_->WriteTo(FLAG_timeline_dir);
  }
  // Disable global streams.
  vm_stream_.set_enabled(false);
  vm_api_stream_.set_enabled(false);
#define ISOLATE_TIMELINE_STREAM_DISABLE(name, not_used)                   \
  stream_##name##_enabled_ = false;
  ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_DISABLE)
#undef ISOLATE_TIMELINE_STREAM_DISABLE
  delete recorder_;
  recorder_ = NULL;
}


TimelineEventRecorder* Timeline::recorder() {
  return recorder_;
}


bool Timeline::EnableStreamByDefault(const char* stream_name) {
  // TODO(johnmccutchan): Allow for command line control over streams.
  return (FLAG_timeline_dir != NULL) || FLAG_timing || FLAG_complete_timeline;
}


TimelineStream* Timeline::GetVMStream() {
  return &vm_stream_;
}


TimelineStream* Timeline::GetVMApiStream() {
  return &vm_api_stream_;
}


void Timeline::ReclaimCachedBlocksFromThreads() {
  TimelineEventRecorder* recorder = Timeline::recorder();
  if (recorder == NULL) {
    return;
  }

  // Iterate over threads.
  OSThreadIterator it;
  while (it.HasNext()) {
    OSThread* thread = it.Next();
    MutexLocker ml(thread->timeline_block_lock());
    // Grab block and clear it.
    TimelineEventBlock* block = thread->timeline_block();
    thread->set_timeline_block(NULL);
    // TODO(johnmccutchan): Consider dropping the timeline_block_lock here
    // if we can do it everywhere. This would simplify the lock ordering
    // requirements.
    recorder->FinishBlock(block);
  }
}


void Timeline::Clear() {
  TimelineEventRecorder* recorder = Timeline::recorder();
  if (recorder == NULL) {
    return;
  }
  ReclaimCachedBlocksFromThreads();
  recorder->Clear();
}


TimelineEventRecorder* Timeline::recorder_ = NULL;
TimelineStream Timeline::vm_stream_;
TimelineStream Timeline::vm_api_stream_;

#define ISOLATE_TIMELINE_STREAM_DEFINE_FLAG(name, enabled_by_default)          \
  bool Timeline::stream_##name##_enabled_ = enabled_by_default;
  ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_DEFINE_FLAG)
#undef ISOLATE_TIMELINE_STREAM_DEFINE_FLAG

TimelineEvent::TimelineEvent()
    : timestamp0_(0),
      timestamp1_(0),
      arguments_(NULL),
      arguments_length_(0),
      state_(0),
      label_(NULL),
      category_(""),
      thread_(OSThread::kInvalidThreadId),
      isolate_id_(ILLEGAL_PORT) {
}


TimelineEvent::~TimelineEvent() {
  Reset();
}


void TimelineEvent::Reset() {
  state_ = 0;
  thread_ = OSThread::kInvalidThreadId;
  isolate_id_ = ILLEGAL_PORT;
  category_ = "";
  label_ = NULL;
  FreeArguments();
  set_pre_serialized_json(false);
  set_event_type(kNone);
}


void TimelineEvent::AsyncBegin(const char* label,
                               int64_t async_id,
                               int64_t micros) {
  Init(kAsyncBegin, label);
  set_timestamp0(micros);
  // Overload timestamp1_ with the async_id.
  set_timestamp1(async_id);
}


void TimelineEvent::AsyncInstant(const char* label,
                                 int64_t async_id,
                                 int64_t micros) {
  Init(kAsyncInstant, label);
  set_timestamp0(micros);
  // Overload timestamp1_ with the async_id.
  set_timestamp1(async_id);
}


void TimelineEvent::AsyncEnd(const char* label,
                             int64_t async_id,
                             int64_t micros) {
  Init(kAsyncEnd, label);
  set_timestamp0(micros);
  // Overload timestamp1_ with the async_id.
  set_timestamp1(async_id);
}


void TimelineEvent::DurationBegin(const char* label,
                                  int64_t micros) {
  Init(kDuration, label);
  set_timestamp0(micros);
}


void TimelineEvent::DurationEnd(int64_t micros) {
  ASSERT(timestamp1_ == 0);
  set_timestamp1(micros);
}


void TimelineEvent::Instant(const char* label,
                            int64_t micros) {
  Init(kInstant, label);
  set_timestamp0(micros);
}


void TimelineEvent::Duration(const char* label,
                             int64_t start_micros,
                             int64_t end_micros) {
  Init(kDuration, label);
  set_timestamp0(start_micros);
  set_timestamp1(end_micros);
}


void TimelineEvent::Begin(const char* label,
                          int64_t micros) {
  Init(kBegin, label);
  set_timestamp0(micros);
}


void TimelineEvent::End(const char* label,
                        int64_t micros) {
  Init(kEnd, label);
  set_timestamp0(micros);
}


void TimelineEvent::CompleteWithPreSerializedJSON(const char* json) {
  set_pre_serialized_json(true);
  SetNumArguments(1);
  CopyArgument(0, "Dart", json);
  Complete();
}


void TimelineEvent::SetNumArguments(intptr_t length) {
  // Cannot call this twice.
  ASSERT(arguments_ == NULL);
  ASSERT(arguments_length_ == 0);
  if (length == 0) {
    return;
  }
  arguments_length_ = length;
  arguments_ = reinterpret_cast<TimelineEventArgument*>(
      calloc(sizeof(TimelineEventArgument), length));
}


void TimelineEvent::SetArgument(intptr_t i, const char* name, char* argument) {
  ASSERT(i >= 0);
  ASSERT(i < arguments_length_);
  arguments_[i].name = name;
  arguments_[i].value = argument;
}


void TimelineEvent::FormatArgument(intptr_t i, const char* name,
                                   const char* fmt, ...) {
  ASSERT(i >= 0);
  ASSERT(i < arguments_length_);
  va_list args;
  va_start(args, fmt);
  intptr_t len = OS::VSNPrint(NULL, 0, fmt, args);
  va_end(args);

  char* buffer = reinterpret_cast<char*>(malloc(len + 1));
  va_list args2;
  va_start(args2, fmt);
  OS::VSNPrint(buffer, (len + 1), fmt, args2);
  va_end(args2);

  SetArgument(i, name, buffer);
}


void TimelineEvent::CopyArgument(intptr_t i,
                                 const char* name,
                                 const char* argument) {
  SetArgument(i, name, strdup(argument));
}


void TimelineEvent::StealArguments(intptr_t arguments_length,
                                   TimelineEventArgument* arguments) {
  arguments_length_ = arguments_length;
  arguments_ = arguments;
}


void TimelineEvent::Complete() {
  TimelineEventRecorder* recorder = Timeline::recorder();
  if (recorder != NULL) {
    recorder->CompleteEvent(this);
  }
}


void TimelineEvent::FreeArguments() {
  if (arguments_ == NULL) {
    return;
  }
  for (intptr_t i = 0; i < arguments_length_; i++) {
    free(arguments_[i].value);
  }
  free(arguments_);
  arguments_ = NULL;
  arguments_length_ = 0;
}


void TimelineEvent::StreamInit(TimelineStream* stream) {
  if (stream != NULL) {
    category_ = stream->name();
  } else {
    category_ = "";
  }
}


void TimelineEvent::Init(EventType event_type,
                         const char* label) {
  ASSERT(label != NULL);
  state_ = 0;
  timestamp0_ = 0;
  timestamp1_ = 0;
  OSThread* os_thread = OSThread::Current();
  ASSERT(os_thread != NULL);
  thread_ = os_thread->trace_id();
  Isolate* isolate = Isolate::Current();
  if (isolate != NULL) {
    isolate_id_ = isolate->main_port();
  } else {
    isolate_id_ = ILLEGAL_PORT;
  }
  label_ = label;
  FreeArguments();
  set_pre_serialized_json(false);
  set_event_type(event_type);
}


bool TimelineEvent::Within(int64_t time_origin_micros,
                           int64_t time_extent_micros) {
  if ((time_origin_micros == -1) ||
      (time_extent_micros == -1)) {
    // No time range specified.
    return true;
  }
  if (IsFinishedDuration()) {
    // Event is from e_t0 to e_t1.
    int64_t e_t0 = TimeOrigin();
    int64_t e_t1 = TimeEnd();
    ASSERT(e_t0 <= e_t1);
    // Range is from r_t0 to r_t1.
    int64_t r_t0 = time_origin_micros;
    int64_t r_t1 = time_origin_micros + time_extent_micros;
    ASSERT(r_t0 <= r_t1);
    return !((r_t1 < e_t0) || (e_t1 < r_t0));
  }
  int64_t delta = TimeOrigin() - time_origin_micros;
  return (delta >= 0) && (delta <= time_extent_micros);
}


const char* TimelineEvent::GetSerializedJSON() const {
  ASSERT(pre_serialized_json());
  ASSERT(arguments_length_ == 1);
  ASSERT(arguments_ != NULL);
  return arguments_[0].value;
}


void TimelineEvent::PrintJSON(JSONStream* stream) const {
  if (pre_serialized_json()) {
    // Event has already been serialized into JSON- just append the
    // raw data.
    stream->AppendSerializedObject(GetSerializedJSON());
    return;
  }
  JSONObject obj(stream);
  int64_t pid = OS::ProcessId();
  int64_t tid = OSThread::ThreadIdToIntPtr(thread_);
  obj.AddProperty("name", label_);
  obj.AddProperty("cat", category_);
  obj.AddProperty64("tid", tid);
  obj.AddProperty64("pid", pid);
  obj.AddPropertyTimeMicros("ts", TimeOrigin());

  switch (event_type()) {
    case kBegin: {
      obj.AddProperty("ph", "B");
    }
    break;
    case kEnd: {
      obj.AddProperty("ph", "E");
    }
    break;
    case kDuration: {
      obj.AddProperty("ph", "X");
      obj.AddPropertyTimeMicros("dur", TimeDuration());
    }
    break;
    case kInstant: {
      obj.AddProperty("ph", "i");
      obj.AddProperty("s", "p");
    }
    break;
    case kAsyncBegin: {
      obj.AddProperty("ph", "b");
      obj.AddPropertyF("id", "%" Px64 "", AsyncId());
    }
    break;
    case kAsyncInstant: {
      obj.AddProperty("ph", "n");
      obj.AddPropertyF("id", "%" Px64 "", AsyncId());
    }
    break;
    case kAsyncEnd: {
      obj.AddProperty("ph", "e");
      obj.AddPropertyF("id", "%" Px64 "", AsyncId());
    }
    break;
    default:
      UNIMPLEMENTED();
  }
  {
    JSONObject args(&obj, "args");
    for (intptr_t i = 0; i < arguments_length_; i++) {
      const TimelineEventArgument& arg = arguments_[i];
      args.AddProperty(arg.name, arg.value);
    }
    if (isolate_id_ != ILLEGAL_PORT) {
      // If we have one, append the isolate id.
      args.AddPropertyF("isolateNumber", "%" Pd64 "",
                        static_cast<int64_t>(isolate_id_));
    }
  }
}


int64_t TimelineEvent::TimeOrigin() const {
  return timestamp0_;
}


int64_t TimelineEvent::AsyncId() const {
  return timestamp1_;
}


int64_t TimelineEvent::TimeDuration() const {
  if (timestamp1_ == 0) {
    // This duration is still open, use current time as end.
    return OS::GetCurrentMonotonicMicros() - timestamp0_;
  }
  return timestamp1_ - timestamp0_;
}


TimelineStream::TimelineStream()
    : name_(NULL),
      enabled_(false),
      globally_enabled_(NULL) {
}


void TimelineStream::Init(const char* name,
                          bool enabled,
                          const bool* globally_enabled) {
  name_ = name;
  enabled_ = enabled;
  globally_enabled_ = globally_enabled;
}


TimelineEvent* TimelineStream::StartEvent() {
  TimelineEventRecorder* recorder = Timeline::recorder();
  if (!Enabled() || (recorder == NULL)) {
    return NULL;
  }
  ASSERT(name_ != NULL);
  TimelineEvent* event = recorder->StartEvent();
  if (event != NULL) {
    event->StreamInit(this);
  }
  return event;
}


TimelineEventScope::TimelineEventScope(TimelineStream* stream,
                                       const char* label)
    : StackResource(reinterpret_cast<Thread*>(NULL)),
      stream_(stream),
      label_(label),
      arguments_(NULL),
      arguments_length_(0),
      enabled_(false) {
  Init();
}


TimelineEventScope::TimelineEventScope(Thread* thread,
                                       TimelineStream* stream,
                                       const char* label)
    : StackResource(thread),
      stream_(stream),
      label_(label),
      arguments_(NULL),
      arguments_length_(0),
      enabled_(false) {
  Init();
}


TimelineEventScope::~TimelineEventScope() {
  FreeArguments();
}


void TimelineEventScope::Init() {
  ASSERT(enabled_ == false);
  ASSERT(label_ != NULL);
  ASSERT(stream_ != NULL);
  if (!stream_->Enabled()) {
    // Stream is not enabled, do nothing.
    return;
  }
  enabled_ = true;
}


void TimelineEventScope::SetNumArguments(intptr_t length) {
  if (!enabled()) {
    return;
  }
  ASSERT(arguments_ == NULL);
  ASSERT(arguments_length_ == 0);
  arguments_length_ = length;
  if (arguments_length_ == 0) {
    return;
  }
  arguments_ = reinterpret_cast<TimelineEventArgument*>(
      calloc(sizeof(TimelineEventArgument), length));
}


// |name| must be a compile time constant. Takes ownership of |argumentp|.
void TimelineEventScope::SetArgument(intptr_t i,
                                     const char* name,
                                     char* argument) {
  if (!enabled()) {
    return;
  }
  ASSERT(i >= 0);
  ASSERT(i < arguments_length_);
  arguments_[i].name = name;
  arguments_[i].value = argument;
}


// |name| must be a compile time constant. Copies |argument|.
void TimelineEventScope::CopyArgument(intptr_t i,
                                      const char* name,
                                      const char* argument) {
  if (!enabled()) {
    return;
  }
  SetArgument(i, name, strdup(argument));
}


void TimelineEventScope::FormatArgument(intptr_t i,
                                        const char* name,
                                        const char* fmt, ...) {
  if (!enabled()) {
    return;
  }
  va_list args;
  va_start(args, fmt);
  intptr_t len = OS::VSNPrint(NULL, 0, fmt, args);
  va_end(args);

  char* buffer = reinterpret_cast<char*>(malloc(len + 1));
  va_list args2;
  va_start(args2, fmt);
  OS::VSNPrint(buffer, (len + 1), fmt, args2);
  va_end(args2);

  SetArgument(i, name, buffer);
}


void TimelineEventScope::FreeArguments() {
  if (arguments_ == NULL) {
    return;
  }
  for (intptr_t i = 0; i < arguments_length_; i++) {
    free(arguments_[i].value);
  }
  free(arguments_);
  arguments_ = NULL;
  arguments_length_ = 0;
}


void TimelineEventScope::StealArguments(TimelineEvent* event) {
  if (event == NULL) {
    return;
  }
  event->StealArguments(arguments_length_, arguments_);
  arguments_length_ = 0;
  arguments_ = NULL;
}


TimelineDurationScope::TimelineDurationScope(TimelineStream* stream,
                                             const char* label)
    : TimelineEventScope(stream, label) {
  timestamp_ = OS::GetCurrentMonotonicMicros();
}


TimelineDurationScope::TimelineDurationScope(Thread* thread,
                                             TimelineStream* stream,
                                             const char* label)
    : TimelineEventScope(thread, stream, label) {
  timestamp_ = OS::GetCurrentMonotonicMicros();
}


TimelineDurationScope::~TimelineDurationScope() {
  if (!ShouldEmitEvent()) {
    return;
  }
  TimelineEvent* event = stream()->StartEvent();
  if (event == NULL) {
    // Stream is now disabled.
    return;
  }
  ASSERT(event != NULL);
  // Emit a duration event.
  event->Duration(label(), timestamp_, OS::GetCurrentMonotonicMicros());
  StealArguments(event);
  event->Complete();
}


TimelineBeginEndScope::TimelineBeginEndScope(TimelineStream* stream,
                                             const char* label)
    : TimelineEventScope(stream, label) {
  EmitBegin();
}


TimelineBeginEndScope::TimelineBeginEndScope(Thread* thread,
                                             TimelineStream* stream,
                                             const char* label)
    : TimelineEventScope(thread, stream, label) {
  EmitBegin();
}


TimelineBeginEndScope::~TimelineBeginEndScope() {
  EmitEnd();
}


void TimelineBeginEndScope::EmitBegin() {
  if (!ShouldEmitEvent()) {
    return;
  }
  TimelineEvent* event = stream()->StartEvent();
  if (event == NULL) {
    // Stream is now disabled.
    set_enabled(false);
    return;
  }
  ASSERT(event != NULL);
  // Emit a begin event.
  event->Begin(label());
  event->Complete();
}


void TimelineBeginEndScope::EmitEnd() {
  if (!ShouldEmitEvent()) {
    return;
  }
  TimelineEvent* event = stream()->StartEvent();
  if (event == NULL) {
    // Stream is now disabled.
    set_enabled(false);
    return;
  }
  ASSERT(event != NULL);
  // Emit an end event.
  event->End(label());
  StealArguments(event);
  event->Complete();
}


TimelineEventFilter::TimelineEventFilter(int64_t time_origin_micros,
                                         int64_t time_extent_micros)
    : time_origin_micros_(time_origin_micros),
      time_extent_micros_(time_extent_micros) {
  ASSERT(time_origin_micros_ >= -1);
  ASSERT(time_extent_micros_ >= -1);
}


TimelineEventFilter::~TimelineEventFilter() {
}


IsolateTimelineEventFilter::IsolateTimelineEventFilter(
    Dart_Port isolate_id,
    int64_t time_origin_micros,
    int64_t time_extent_micros)
    : TimelineEventFilter(time_origin_micros,
                          time_extent_micros),
      isolate_id_(isolate_id) {
}


TimelineEventRecorder::TimelineEventRecorder()
    : async_id_(0) {
}


void TimelineEventRecorder::PrintJSONMeta(JSONArray* events) const {
  OSThreadIterator it;
  while (it.HasNext()) {
    OSThread* thread = it.Next();
    const char* thread_name = thread->name();
    if (thread_name == NULL) {
      // Only emit a thread name if one was set.
      continue;
    }
    JSONObject obj(events);
    int64_t pid = OS::ProcessId();
    int64_t tid = OSThread::ThreadIdToIntPtr(thread->trace_id());
    obj.AddProperty("name", "thread_name");
    obj.AddProperty("ph", "M");
    obj.AddProperty64("pid", pid);
    obj.AddProperty64("tid", tid);
    {
      JSONObject args(&obj, "args");
      args.AddPropertyF("name", "%s (%" Pd64 ")", thread_name, tid);
    }
  }
}


TimelineEvent* TimelineEventRecorder::ThreadBlockStartEvent() {
  // Grab the current thread.
  OSThread* thread = OSThread::Current();
  ASSERT(thread != NULL);
  Mutex* thread_block_lock = thread->timeline_block_lock();
  ASSERT(thread_block_lock != NULL);
  // We are accessing the thread's timeline block- so take the lock here.
  // This lock will be held until the call to |CompleteEvent| is made.
  thread_block_lock->Lock();
#if defined(DEBUG)
  Thread* T = Thread::Current();
  if (T != NULL) {
    T->IncrementNoSafepointScopeDepth();
  }
#endif  // defined(DEBUG)

  TimelineEventBlock* thread_block = thread->timeline_block();

  if ((thread_block != NULL) && thread_block->IsFull()) {
    MutexLocker ml(&lock_);
    // Thread has a block and it is full:
    // 1) Mark it as finished.
    thread_block->Finish();
    // 2) Allocate a new block.
    thread_block = GetNewBlockLocked();
    thread->set_timeline_block(thread_block);
  } else if (thread_block == NULL) {
    MutexLocker ml(&lock_);
    // Thread has no block. Attempt to allocate one.
    thread_block = GetNewBlockLocked();
    thread->set_timeline_block(thread_block);
  }
  if (thread_block != NULL) {
    // NOTE: We are exiting this function with the thread's block lock held.
    ASSERT(!thread_block->IsFull());
    TimelineEvent* event = thread_block->StartEvent();
    return event;
  }
  // Drop lock here as no event is being handed out.
#if defined(DEBUG)
  if (T != NULL) {
    T->DecrementNoSafepointScopeDepth();
  }
#endif  // defined(DEBUG)
  thread_block_lock->Unlock();
  return NULL;
}


void TimelineEventRecorder::ThreadBlockCompleteEvent(TimelineEvent* event) {
  if (event == NULL) {
    return;
  }
  // Grab the current thread.
  OSThread* thread = OSThread::Current();
  ASSERT(thread != NULL);
  // Unlock the thread's block lock.
  Mutex* thread_block_lock = thread->timeline_block_lock();
  ASSERT(thread_block_lock != NULL);
#if defined(DEBUG)
  Thread* T = Thread::Current();
  if (T != NULL) {
    T->DecrementNoSafepointScopeDepth();
  }
#endif  // defined(DEBUG)
  thread_block_lock->Unlock();
}


void TimelineEventRecorder::WriteTo(const char* directory) {
  Dart_FileOpenCallback file_open = Isolate::file_open_callback();
  Dart_FileWriteCallback file_write = Isolate::file_write_callback();
  Dart_FileCloseCallback file_close = Isolate::file_close_callback();
  if ((file_open == NULL) || (file_write == NULL) || (file_close == NULL)) {
    return;
  }
  Thread* T = Thread::Current();
  StackZone zone(T);

  Timeline::ReclaimCachedBlocksFromThreads();

  intptr_t pid = OS::ProcessId();
  char* filename = OS::SCreate(NULL,
      "%s/dart-timeline-%" Pd ".json", directory, pid);
  void* file = (*file_open)(filename, true);
  if (file == NULL) {
    OS::Print("Failed to write timeline file: %s\n", filename);
    free(filename);
    return;
  }
  free(filename);

  JSONStream js;
  TimelineEventFilter filter;
  PrintTraceEvent(&js, &filter);
  // Steal output from JSONStream.
  char* output = NULL;
  intptr_t output_length = 0;
  js.Steal(const_cast<const char**>(&output), &output_length);
  (*file_write)(output, output_length, file);
  // Free the stolen output.
  free(output);
  (*file_close)(file);

  return;
}


int64_t TimelineEventRecorder::GetNextAsyncId() {
  // TODO(johnmccutchan): Gracefully handle wrap around.
  uint32_t next = static_cast<uint32_t>(
      AtomicOperations::FetchAndIncrement(&async_id_));
  return static_cast<int64_t>(next);
}


void TimelineEventRecorder::FinishBlock(TimelineEventBlock* block) {
  if (block == NULL) {
    return;
  }
  MutexLocker ml(&lock_);
  block->Finish();
}


TimelineEventBlock* TimelineEventRecorder::GetNewBlock() {
  MutexLocker ml(&lock_);
  return GetNewBlockLocked();
}


TimelineEventRingRecorder::TimelineEventRingRecorder(intptr_t capacity)
    : blocks_(NULL),
      capacity_(capacity),
      num_blocks_(0),
      block_cursor_(0) {
  // Capacity must be a multiple of TimelineEventBlock::kBlockSize
  ASSERT((capacity % TimelineEventBlock::kBlockSize) == 0);
  // Allocate blocks array.
  num_blocks_ = capacity / TimelineEventBlock::kBlockSize;
  blocks_ =
      reinterpret_cast<TimelineEventBlock**>(
          calloc(num_blocks_, sizeof(TimelineEventBlock*)));
  // Allocate each block.
  for (intptr_t i = 0; i < num_blocks_; i++) {
    blocks_[i] = new TimelineEventBlock(i);
  }
  // Chain blocks together.
  for (intptr_t i = 0; i < num_blocks_ - 1; i++) {
    blocks_[i]->set_next(blocks_[i + 1]);
  }
}


TimelineEventRingRecorder::~TimelineEventRingRecorder() {
  // Delete all blocks.
  for (intptr_t i = 0; i < num_blocks_; i++) {
    TimelineEventBlock* block = blocks_[i];
    delete block;
  }
  free(blocks_);
}


void TimelineEventRingRecorder::PrintJSONEvents(
    JSONArray* events,
    TimelineEventFilter* filter) {
  MutexLocker ml(&lock_);
  intptr_t block_offset = FindOldestBlockIndex();
  if (block_offset == -1) {
    // All blocks are empty.
    return;
  }
  for (intptr_t block_idx = 0; block_idx < num_blocks_; block_idx++) {
    TimelineEventBlock* block =
        blocks_[(block_idx + block_offset) % num_blocks_];
    if (!filter->IncludeBlock(block)) {
      continue;
    }
    for (intptr_t event_idx = 0; event_idx < block->length(); event_idx++) {
      TimelineEvent* event = block->At(event_idx);
      if (filter->IncludeEvent(event) &&
          event->Within(filter->time_origin_micros(),
                        filter->time_extent_micros())) {
        events->AddValue(event);
      }
    }
  }
}


void TimelineEventRingRecorder::PrintJSON(JSONStream* js,
                                          TimelineEventFilter* filter) {
  JSONObject topLevel(js);
  topLevel.AddProperty("type", "_Timeline");
  {
    JSONArray events(&topLevel, "traceEvents");
    PrintJSONMeta(&events);
    PrintJSONEvents(&events, filter);
  }
}


void TimelineEventRingRecorder::PrintTraceEvent(JSONStream* js,
                                                TimelineEventFilter* filter) {
  JSONArray events(js);
  PrintJSONEvents(&events, filter);
}


TimelineEventBlock* TimelineEventRingRecorder::GetHeadBlockLocked() {
  return blocks_[0];
}


TimelineEventBlock* TimelineEventRingRecorder::GetNewBlockLocked() {
  // TODO(johnmccutchan): This function should only hand out blocks
  // which have been marked as finished.
  if (block_cursor_ == num_blocks_) {
    block_cursor_ = 0;
  }
  TimelineEventBlock* block = blocks_[block_cursor_++];
  block->Reset();
  block->Open();
  return block;
}


void TimelineEventRingRecorder::Clear() {
  MutexLocker ml(&lock_);
  for (intptr_t i = 0; i < num_blocks_; i++) {
    TimelineEventBlock* block = blocks_[i];
    block->Reset();
  }
}


intptr_t TimelineEventRingRecorder::FindOldestBlockIndex() const {
  int64_t earliest_time = kMaxInt64;
  intptr_t earliest_index = -1;
  for (intptr_t block_idx = 0; block_idx < num_blocks_; block_idx++) {
    TimelineEventBlock* block = blocks_[block_idx];
    if (block->IsEmpty()) {
      // Skip empty blocks.
      continue;
    }
    if (block->LowerTimeBound() < earliest_time) {
      earliest_time = block->LowerTimeBound();
      earliest_index = block_idx;
    }
  }
  return earliest_index;
}


TimelineEvent* TimelineEventRingRecorder::StartEvent() {
  return ThreadBlockStartEvent();
}


void TimelineEventRingRecorder::CompleteEvent(TimelineEvent* event) {
  if (event == NULL) {
    return;
  }
  ThreadBlockCompleteEvent(event);
}


TimelineEventStreamingRecorder::TimelineEventStreamingRecorder() {
}


TimelineEventStreamingRecorder::~TimelineEventStreamingRecorder() {
}


void TimelineEventStreamingRecorder::PrintJSON(JSONStream* js,
                                               TimelineEventFilter* filter) {
  JSONObject topLevel(js);
  topLevel.AddProperty("type", "_Timeline");
  {
    JSONArray events(&topLevel, "traceEvents");
    PrintJSONMeta(&events);
  }
}


void TimelineEventStreamingRecorder::PrintTraceEvent(
    JSONStream* js,
    TimelineEventFilter* filter) {
  JSONArray events(js);
}


TimelineEvent* TimelineEventStreamingRecorder::StartEvent() {
  TimelineEvent* event = new TimelineEvent();
  return event;
}


void TimelineEventStreamingRecorder::CompleteEvent(TimelineEvent* event) {
  StreamEvent(event);
  delete event;
}


TimelineEventEndlessRecorder::TimelineEventEndlessRecorder()
    : head_(NULL),
      block_index_(0) {
}


void TimelineEventEndlessRecorder::PrintJSON(JSONStream* js,
                                             TimelineEventFilter* filter) {
  JSONObject topLevel(js);
  topLevel.AddProperty("type", "_Timeline");
  {
    JSONArray events(&topLevel, "traceEvents");
    PrintJSONMeta(&events);
    PrintJSONEvents(&events, filter);
  }
}


void TimelineEventEndlessRecorder::PrintTraceEvent(
    JSONStream* js,
    TimelineEventFilter* filter) {
  JSONArray events(js);
  PrintJSONEvents(&events, filter);
}


TimelineEventBlock* TimelineEventEndlessRecorder::GetHeadBlockLocked() {
  return head_;
}


TimelineEvent* TimelineEventEndlessRecorder::StartEvent() {
  return ThreadBlockStartEvent();
}


void TimelineEventEndlessRecorder::CompleteEvent(TimelineEvent* event) {
  if (event == NULL) {
    return;
  }
  ThreadBlockCompleteEvent(event);
}


TimelineEventBlock* TimelineEventEndlessRecorder::GetNewBlockLocked() {
  TimelineEventBlock* block = new TimelineEventBlock(block_index_++);
  block->set_next(head_);
  block->Open();
  head_ = block;
  if (FLAG_trace_timeline) {
    OS::Print("Created new block %p\n", block);
  }
  return head_;
}

static int TimelineEventBlockCompare(TimelineEventBlock* const* a,
                                     TimelineEventBlock* const* b) {
  return (*a)->LowerTimeBound() - (*b)->LowerTimeBound();
}


void TimelineEventEndlessRecorder::PrintJSONEvents(
    JSONArray* events,
    TimelineEventFilter* filter) {
  MutexLocker ml(&lock_);
  // Collect all interesting blocks.
  MallocGrowableArray<TimelineEventBlock*> blocks(8);
  TimelineEventBlock* current = head_;
  while (current != NULL) {
    if (filter->IncludeBlock(current)) {
      blocks.Add(current);
    }
    current = current->next();
  }
  // Bail early.
  if (blocks.length() == 0) {
    return;
  }
  // Sort the interesting blocks so that blocks with earlier events are
  // outputted first.
  blocks.Sort(TimelineEventBlockCompare);
  // Output blocks in sorted order.
  for (intptr_t block_idx = 0; block_idx < blocks.length(); block_idx++) {
    current = blocks[block_idx];
    intptr_t length = current->length();
    for (intptr_t i = 0; i < length; i++) {
      TimelineEvent* event = current->At(i);
      if (filter->IncludeEvent(event) &&
          event->Within(filter->time_origin_micros(),
                        filter->time_extent_micros())) {
        events->AddValue(event);
      }
    }
  }
}


void TimelineEventEndlessRecorder::Clear() {
  TimelineEventBlock* current = head_;
  while (current != NULL) {
    TimelineEventBlock* next = current->next();
    delete current;
    current = next;
  }
  head_ = NULL;
  block_index_ = 0;
  OSThread* thread = OSThread::Current();
  thread->set_timeline_block(NULL);
}


TimelineEventBlock::TimelineEventBlock(intptr_t block_index)
    : next_(NULL),
      length_(0),
      block_index_(block_index),
      thread_id_(OSThread::kInvalidThreadId),
      in_use_(false) {
}


TimelineEventBlock::~TimelineEventBlock() {
  Reset();
}


TimelineEvent* TimelineEventBlock::StartEvent() {
  ASSERT(!IsFull());
  if (FLAG_trace_timeline) {
    OSThread* os_thread = OSThread::Current();
    ASSERT(os_thread != NULL);
    intptr_t tid = OSThread::ThreadIdToIntPtr(os_thread->id());
    OS::Print("StartEvent in block %p for thread %" Px "\n", this, tid);
  }
  return &events_[length_++];
}


int64_t TimelineEventBlock::LowerTimeBound() const {
  if (length_ == 0) {
    return kMaxInt64;
  }
  ASSERT(length_ > 0);
  return events_[0].TimeOrigin();
}


bool TimelineEventBlock::CheckBlock() {
  if (length() == 0) {
    return true;
  }

  for (intptr_t i = 0; i < length(); i++) {
    if (At(i)->thread() != thread_id()) {
      return false;
    }
  }

  // - events have monotonically increasing timestamps.
  int64_t last_time = LowerTimeBound();
  for (intptr_t i = 0; i < length(); i++) {
    if (last_time > At(i)->TimeOrigin()) {
      return false;
    }
    last_time = At(i)->TimeOrigin();
  }

  return true;
}


void TimelineEventBlock::Reset() {
  for (intptr_t i = 0; i < kBlockSize; i++) {
    // Clear any extra data.
    events_[i].Reset();
  }
  length_ = 0;
  thread_id_ = OSThread::kInvalidThreadId;
  in_use_ = false;
}


void TimelineEventBlock::Open() {
  OSThread* os_thread = OSThread::Current();
  ASSERT(os_thread != NULL);
  thread_id_ = os_thread->trace_id();
  in_use_ = true;
}


void TimelineEventBlock::Finish() {
  if (FLAG_trace_timeline) {
    OS::Print("Finish block %p\n", this);
  }
  in_use_ = false;
}


TimelineEventBlockIterator::TimelineEventBlockIterator(
    TimelineEventRecorder* recorder)
    : current_(NULL),
      recorder_(NULL) {
  Reset(recorder);
}


TimelineEventBlockIterator::~TimelineEventBlockIterator() {
  Reset(NULL);
}


void TimelineEventBlockIterator::Reset(TimelineEventRecorder* recorder) {
  // Clear current.
  current_ = NULL;
  if (recorder_ != NULL) {
    // Unlock old recorder.
    recorder_->lock_.Unlock();
  }
  recorder_ = recorder;
  if (recorder_ == NULL) {
    return;
  }
  // Lock new recorder.
  recorder_->lock_.Lock();
  // Queue up first block.
  current_ = recorder_->GetHeadBlockLocked();
}


bool TimelineEventBlockIterator::HasNext() const {
  return current_ != NULL;
}


TimelineEventBlock* TimelineEventBlockIterator::Next() {
  ASSERT(current_ != NULL);
  TimelineEventBlock* r = current_;
  current_ = current_->next();
  return r;
}

}  // namespace dart