Node.js code tracing
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Node.js has a modular architecture with the V8 engine providing JavaScript execution and libuv handling asynchronous operations. Core modules can be implemented in either C++ or JavaScript. When a module is required, Node.js checks its cache and compiles the source before returning the exports object. This allows seamless usage of both native and JavaScript modules.
![Why NativeModule.require()
• src/node.js is invoked by node::Load() in src/node.cc, and
responsible for loading lib/*.js and bootstrapping the nodejs
core.
NativeModule.wrap = function(script) {
return NativeModule.wrapper[0] + script + NativeModule.wrapper[1];
};
NativeModule.wrapper = [
'(function (exports, require, module, __filename, __dirname) { ',
'n});'
];
NativeModule.prototype.compile = function() {
var source = NativeModule.getSource(this.id);
source = NativeModule.wrap(source);
var fn = runInThisContext(source, this.filename, true);
fn(this.exports, NativeModule.require, this, this.filename);
this.loaded = true;
};](https://image.slidesharecdn.com/nodejs-140507132306-phpapp02/85/Node-js-code-tracing-14-320.jpg)
![How to use core modules(revisit)
• Loading C++ module
process.binding(“fs”) -> get_builtin_module(“fs”) ->
NODE_MODULE(node_fs, node::InitFs)
• Loading js module
Require(“path”) -> NativeModule.require(“path”) ->
process.binding("natives")["path"] ->
DefineJavaScript() -> natives[] -> node_natives.h](https://image.slidesharecdn.com/nodejs-140507132306-phpapp02/85/Node-js-code-tracing-15-320.jpg)
Node.js code tracing
- 2. Node.js - Architecture v8 libuv C++ binding modules Js native modulesjavascript C++
- 3. Outline • libuv • V8 • Node.js modules
- 4. libuv • libuv enforces an asynchronous, event-driven style of programming
- 5. Libuv – hollow world • Callback
- 6. V8 • V8 provides C++ API o Access Javascript object in C++ o Access C++ objects in Javascript
- 7. Terms • Handler: An object reference managed by the v8 garbage collector • HandlerScopes: A stack-allocated class that governs a number of local handles • Context: A sandboxed execution context with its own set of built-in objects and functions • Templaates: A template is a blueprint for JavaScript functions and objects in a context.
- 8. Samples • Samples/shell.c o Main() o CreateShellContext()
- 9. Core modules • C++ modules (src/node_extensions.cc) o fs o http_parser o os o Zlib o … • Js modules (lib/) o fs.js o http.js o net.js o os.js o modules.js o …
- 10. How to use core modules ? … var util = require('util'); var pathModule = require('path'); var binding = process.binding('fs'); var constants = process.binding('constants'); var fs = exports; … Lib/fs.js
- 11. How modules inited ? node::Start(argc, argv) // Use original argv, as we're just copying values out of it. Handle<Object> process_l = SetupProcessObject(argc, argv); v8_typed_array::AttachBindings(context->Global()); // 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);
- 12. C++ modules • What process.binding (a.k.a Node::Binding) do o Check binding_cache if module is in cache already o If not cached, call node_extensions::get_builtin_module to bind the c++ module and call the module’s register_func() • How C++ modules implemented o node_file.cc
- 13. Js modules • When when requiring a js module in native modules, NativeModule.require() in node.js is called o If require(“native_module”), return NativeModule o If cached return getCached().exports o else return new NativeModule(id).compile().exports • NativeModule(id).compile() reads source and compiles source into js object in js heap
- 14. Why NativeModule.require() • src/node.js is invoked by node::Load() in src/node.cc, and responsible for loading lib/*.js and bootstrapping the nodejs core. NativeModule.wrap = function(script) { return NativeModule.wrapper[0] + script + NativeModule.wrapper[1]; }; NativeModule.wrapper = [ '(function (exports, require, module, __filename, __dirname) { ', 'n});' ]; NativeModule.prototype.compile = function() { var source = NativeModule.getSource(this.id); source = NativeModule.wrap(source); var fn = runInThisContext(source, this.filename, true); fn(this.exports, NativeModule.require, this, this.filename); this.loaded = true; };
- 15. How to use core modules(revisit) • Loading C++ module process.binding(“fs”) -> get_builtin_module(“fs”) -> NODE_MODULE(node_fs, node::InitFs) • Loading js module Require(“path”) -> NativeModule.require(“path”) -> process.binding("natives")["path"] -> DefineJavaScript() -> natives[] -> node_natives.h
- 16. More !! • How to write a C++ module o http://nodejs.org/api/addons.html • How about user-defined js module o lib/modules.js o http://nodejs.org/api/modules.html
- 17. Ref • 深入浅出Node.js, http://vdisk.weibo.com/s/G- kaugh6Z1f6 • Node.js源码研究之模块组织加载, http://developer.51cto.com/art/201109/290287.htm • http://nikhilm.github.io/uvbook/basics.html • https://developers.google.com/v8/embed