异步构建V8字符串数组

Question

我正在构建一个与libapt交互的节点模块，因此我可以列出并控制已安装的软件包。通过实现一个函数来获取每个已安装包的名称，我开始很简单。我已经撞墙了。

我目前有这段代码：

#include <apt-pkg/init.h>
#include <apt-pkg/cachefile.h>
#include <apt-pkg/pkgcache.h>
#include <node.h>
#include <v8.h>

using namespace v8;

typedef struct AsyncData {
  Persistent<Function> callback; // callback function
  Handle<Array> packageList;         // array of package names
} AsyncData;


void AsyncWork(uv_work_t *req) {
  AsyncData *asyncData = (AsyncData *)req->data;

  asyncData->packageList = Array::New();

  size_t i = 0;
  for (pkgCache::PkgIterator package = cache->PkgBegin(); !package.end(); package++) {
    if(package->CurrentVer == 0) continue;
    asyncData->packageList->Set(i++, String::New(package.Name()));
  }
}

void AsyncAfter(uv_work_t *req) {
  HandleScope scope;

  AsyncData *asyncData = (AsyncData *)req->data;

  Handle<Value> argv[] = {
    Null(),
    asyncData->packageList
  };

  TryCatch try_catch;
  asyncData->callback->Call(Context::GetCurrent()->Global(), 2, argv);
  if (try_catch.HasCaught())
    node::FatalException(try_catch);

  asyncData->callback.Dispose();

  delete asyncData;
  delete req;
}

Handle<Value> InstalledPackages(const Arguments& args) {
  HandleScope scope;

  uv_work_t *req = new uv_work_t;
  AsyncData *asyncData = new AsyncData;
  req->data = asyncData;

  asyncData->callback = Persistent<Function>::New(Local<Function>::Cast(args[1]));

  uv_queue_work(
    uv_default_loop(),
    req,                          // work token
    AsyncWork,                    // work function
    (uv_after_work_cb)AsyncAfter  // function to run when complete
  );

  return scope.Close(Undefined());
}

void Initialize(Handle<Object> exports) {
    pkgInitConfig(*_config);
  pkgInitSystem(*_config, _system);
    // function hello();
    exports->Set(String::NewSymbol("getInstalledPackages"), FunctionTemplate::New(InstalledPackages)->GetFunction());
}

NODE_MODULE(apt, Initialize)

这个问题的主要问题是你不能在主事件循环以外的线程中使用任何V8对象。这意味着我在上面的代码中得到了一个段错误。所以我将我的代码修改为以下内容：

#include <apt-pkg/init.h>
#include <apt-pkg/cachefile.h>
#include <apt-pkg/pkgcache.h>
#include <node.h>
#include <v8.h>

using namespace std;
using namespace v8;

typedef struct AsyncData {
  Persistent<Function> callback; // callback function
  vector<string> packageList; // array of package names
} AsyncData;


void AsyncWork(uv_work_t *req) {
  AsyncData *asyncData = (AsyncData *)req->data;

  pkgCacheFile cache_file;
  pkgCache* cache = cache_file.GetPkgCache();

  for (pkgCache::PkgIterator package = cache->PkgBegin(); !package.end(); package++) {
    // If the current package has Version of 0, its no installed
    if(package->CurrentVer == 0)
        continue;

    asyncData->packageList.push_back(package.Name());
  }
}

void AsyncAfter(uv_work_t *req) {
  HandleScope scope;

  AsyncData *asyncData = (AsyncData *)req->data;

  Handle<Array> packageArray = Array::New(asyncData->packageList.size());

  for(size_t i = 0; i < asyncData->packageList.size(); i++) {
    packageArray->Set(i, String::New(asyncData->packageList[i].c_str()));
  }

  Handle<Value> argv[] = {
    Null(),
    packageArray
  };

  TryCatch try_catch;
  asyncData->callback->Call(Context::GetCurrent()->Global(), 2, argv);
  if (try_catch.HasCaught())
    node::FatalException(try_catch);

  asyncData->callback.Dispose();

  delete asyncData;
  delete req;
}

Handle<Value> InstalledPackages(const Arguments& args) {
  HandleScope scope;

  uv_work_t *req = new uv_work_t;
  AsyncData *asyncData = new AsyncData;
  req->data = asyncData;

  asyncData->callback = Persistent<Function>::New(Local<Function>::Cast(args[0]));

  uv_queue_work(
    uv_default_loop(),
    req,                          // work token
    AsyncWork,                    // work function
    (uv_after_work_cb)AsyncAfter  // function to run when complete
  );

  return scope.Close(Undefined());
}

void Initialize(Handle<Object> exports) {
  pkgInitConfig(*_config);
  pkgInitSystem(*_config, _system);
  // function hello();
  exports->Set(String::NewSymbol("getInstalledPackages"), FunctionTemplate::New(InstalledPackages)->GetFunction());
}

NODE_MODULE(apt, Initialize)

此代码现在可以正常工作，但我现在循环遍历字符串列表并在主事件循环中使用新的V8字符串。我不妨同步完成所有这一切。由于包列表可能长达30,000个字符串，我不想在javascript事件循环中执行此操作。如何异步创建大型字符串数组？