nodejs源码分析

（只是简单的分析一下nodejs的代码，看看大概的东西）

node_main.cc：只是一个入口而已

int main(int argc, char *argv[]) {
  return node::Start(argc, argv);
}

node.cc：

int Start(int argc, char *argv[]) {
  // This needs to run *before* V8::Initialize()
  // Use copy here as to not modify the original argv:
  Init(argc, argv_copy);
  V8::Initialize();
  {
    // Create all the objects, load modules, do everything.
    // so your next reading stop should be node::Load()!
    Load(process_l); 

    // All our arguments are loaded. We've evaluated all of the scripts. We
    // might even have created TCP servers. Now we enter the main eventloop. If
    // there are no watchers on the loop (except for the ones that were
    // uv_unref'd) then this function exits. As long as there are active
    // watchers, it blocks.
    uv_run(uv_default_loop(), UV_RUN_DEFAULT);

    EmitExit(process_l);
    RunAtExit();
  }
  return 0;
}

Init：方法处理跟输入参数相关的东西，另外就是得到了一个初始时间。

Load：所有的脚本都是在这个时候加载的。

uv_run(uv_default_loop(), UV_RUN_DEFAULT)：这个应该是nodejs消息循环的东西，但是它直接用的libuv的东西。

void Load(Handle<Object> process_l) {
  // Compile, execute the src/node.js file. (Which was included as static C
  // string in node_natives.h. 'natve_node' is the string containing that
  // source code.)

  // The node.js file returns a function 'f'
  atexit(AtExit);

  Local<Value> f_value = ExecuteString(MainSource(),
                                       IMMUTABLE_STRING("node.js"));
  assert(f_value->IsFunction());
  Local<Function> f = Local<Function>::Cast(f_value);

  // Now we call 'f' with the 'process' variable that we've built up with
  // all our bindings. Inside node.js we'll take care of assigning things to
  // their places.

  // We start the process this way in order to be more modular. Developers
  // who do not like how 'src/node.js' setups the module system but do like
  // Node's I/O bindings may want to replace 'f' with their own function.

  // Add a reference to the global object
  Local<Object> global = v8::Context::GetCurrent()->Global();
  Local<Value> args[1] = { Local<Value>::New(process_l) };

  f->Call(global, 1, args);

}

从这里可以看出，代码转到node.js里面，这也难怪此开源项目的名字要叫node.js了，C部分的代码实际就起到加载和运行的作用。而真正的内容在js部分，而node.js就是js部分的根。

总结：本质上来讲node.js相当于只是把libev和v8组合在一起，然后打造了一个js的服务器环境，它自身只是提供了有限的功能。例如，v8对buffer的支持不够好，然后它自己对这块进行加强了一下。

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