src/api/hooks.cc

#include "env-inl.h"
#include "node_internals.h"
#include "node_process.h"
#include "async_wrap.h"

namespace node {

using v8::Context;
using v8::HandleScope;
using v8::Integer;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;
using v8::NewStringType;

void RunAtExit(Environment* env) {
  env->RunAtExitCallbacks();
}

void AtExit(void (*cb)(void* arg), void* arg) {
  auto env = Environment::GetThreadLocalEnv();
  AtExit(env, cb, arg);
}

void AtExit(Environment* env, void (*cb)(void* arg), void* arg) {
  CHECK_NOT_NULL(env);
  env->AtExit(cb, arg);
}

void EmitBeforeExit(Environment* env) {
  TraceEventScope trace_scope(TRACING_CATEGORY_NODE1(environment),
                              "BeforeExit", env);
  if (!env->destroy_async_id_list()->empty())
    AsyncWrap::DestroyAsyncIdsCallback(env);

  HandleScope handle_scope(env->isolate());
  Context::Scope context_scope(env->context());

  Local<Value> exit_code_v;
  if (!env->process_object()->Get(env->context(), env->exit_code_string())
      .ToLocal(&exit_code_v)) return;

  Local<Integer> exit_code;
  if (!exit_code_v->ToInteger(env->context()).ToLocal(&exit_code)) return;

  // TODO(addaleax): Provide variants of EmitExit() and EmitBeforeExit() that
  // actually forward empty MaybeLocal<>s (and check env->can_call_into_js()).
  USE(ProcessEmit(env, "beforeExit", exit_code));
}

int EmitExit(Environment* env) {
  // process.emit('exit')
  HandleScope handle_scope(env->isolate());
  Context::Scope context_scope(env->context());
  Local<Object> process_object = env->process_object();
  process_object
      ->Set(env->context(),
            FIXED_ONE_BYTE_STRING(env->isolate(), "_exiting"),
            True(env->isolate()))
      .Check();

  Local<String> exit_code = env->exit_code_string();
  int code = process_object->Get(env->context(), exit_code)
                 .ToLocalChecked()
                 ->Int32Value(env->context())
                 .ToChecked();
  ProcessEmit(env, "exit", Integer::New(env->isolate(), code));

  // Reload exit code, it may be changed by `emit('exit')`
  return process_object->Get(env->context(), exit_code)
      .ToLocalChecked()
      ->Int32Value(env->context())
      .ToChecked();
}

typedef void (*CleanupHook)(void* arg);
typedef void (*AsyncCleanupHook)(void* arg, void(*)(void*), void*);

struct AsyncCleanupHookInfo final {
  Environment* env;
  AsyncCleanupHook fun;
  void* arg;
  bool started = false;
  // Use a self-reference to make sure the storage is kept alive while the
  // cleanup hook is registered but not yet finished.
  std::shared_ptr<AsyncCleanupHookInfo> self;
};

// Opaque type that is basically an alias for `shared_ptr<AsyncCleanupHookInfo>`
// (but not publicly so for easier ABI/API changes). In particular,
// std::shared_ptr does not generally maintain a consistent ABI even on a
// specific platform.
struct ACHHandle final {
  std::shared_ptr<AsyncCleanupHookInfo> info;
};
// This is implemented as an operator on a struct because otherwise you can't
// default-initialize AsyncCleanupHookHandle, because in C++ for a
// std::unique_ptr to be default-initializable the deleter type also needs
// to be default-initializable; in particular, function types don't satisfy
// this.
void DeleteACHHandle::operator ()(ACHHandle* handle) const { delete handle; }

void AddEnvironmentCleanupHook(Isolate* isolate,
                               CleanupHook fun,
                               void* arg) {
  Environment* env = Environment::GetCurrent(isolate);
  CHECK_NOT_NULL(env);
  env->AddCleanupHook(fun, arg);
}

void RemoveEnvironmentCleanupHook(Isolate* isolate,
                                  CleanupHook fun,
                                  void* arg) {
  Environment* env = Environment::GetCurrent(isolate);
  CHECK_NOT_NULL(env);
  env->RemoveCleanupHook(fun, arg);
}

static void FinishAsyncCleanupHook(void* arg) {
  AsyncCleanupHookInfo* info = static_cast<AsyncCleanupHookInfo*>(arg);
  std::shared_ptr<AsyncCleanupHookInfo> keep_alive = info->self;

  info->env->DecreaseWaitingRequestCounter();
  info->self.reset();
}

static void RunAsyncCleanupHook(void* arg) {
  AsyncCleanupHookInfo* info = static_cast<AsyncCleanupHookInfo*>(arg);
  info->env->IncreaseWaitingRequestCounter();
  info->started = true;
  info->fun(info->arg, FinishAsyncCleanupHook, info);
}

AsyncCleanupHookHandle AddEnvironmentCleanupHook(
    Isolate* isolate,
    AsyncCleanupHook fun,
    void* arg) {
  Environment* env = Environment::GetCurrent(isolate);
  CHECK_NOT_NULL(env);
  auto info = std::make_shared<AsyncCleanupHookInfo>();
  info->env = env;
  info->fun = fun;
  info->arg = arg;
  info->self = info;
  env->AddCleanupHook(RunAsyncCleanupHook, info.get());
  return AsyncCleanupHookHandle(new ACHHandle { info });
}

void RemoveEnvironmentCleanupHook(
    AsyncCleanupHookHandle handle) {
  if (handle->info->started) return;
  handle->info->self.reset();
  handle->info->env->RemoveCleanupHook(RunAsyncCleanupHook, handle->info.get());
}

async_id AsyncHooksGetExecutionAsyncId(Isolate* isolate) {
  Environment* env = Environment::GetCurrent(isolate);
  if (env == nullptr) return -1;
  return env->execution_async_id();
}

async_id AsyncHooksGetTriggerAsyncId(Isolate* isolate) {
  Environment* env = Environment::GetCurrent(isolate);
  if (env == nullptr) return -1;
  return env->trigger_async_id();
}


async_context EmitAsyncInit(Isolate* isolate,
                            Local<Object> resource,
                            const char* name,
                            async_id trigger_async_id) {
  HandleScope handle_scope(isolate);
  Local<String> type =
      String::NewFromUtf8(isolate, name, NewStringType::kInternalized)
          .ToLocalChecked();
  return EmitAsyncInit(isolate, resource, type, trigger_async_id);
}

async_context EmitAsyncInit(Isolate* isolate,
                            Local<Object> resource,
                            Local<String> name,
                            async_id trigger_async_id) {
  DebugSealHandleScope handle_scope(isolate);
  Environment* env = Environment::GetCurrent(isolate);
  CHECK_NOT_NULL(env);

  // Initialize async context struct
  if (trigger_async_id == -1)
    trigger_async_id = env->get_default_trigger_async_id();

  async_context context = {
    env->new_async_id(),  // async_id_
    trigger_async_id  // trigger_async_id_
  };

  // Run init hooks
  AsyncWrap::EmitAsyncInit(env, resource, name, context.async_id,
                           context.trigger_async_id);

  return context;
}

void EmitAsyncDestroy(Isolate* isolate, async_context asyncContext) {
  EmitAsyncDestroy(Environment::GetCurrent(isolate), asyncContext);
}

void EmitAsyncDestroy(Environment* env, async_context asyncContext) {
  AsyncWrap::EmitDestroy(env, asyncContext.async_id);
}

}  // namespace node