Node.js Manual & Documentation

Addons 扩展插件

Addons 扩展插件

Addons are dynamically linked shared objects. They can provide glue to C and C++ libraries. The API (at the moment) is rather complex, involving knowledge of several libraries:

扩展插件（Addons）是动态链接的共享对象，这些对象提供了使用C/C++类库的能力。由于涉及了多个类库导致了这类API目前比较繁杂，主要包括下述几个主要类库：

V8 JavaScript, a C++ library. Used for interfacing with JavaScript: creating objects, calling functions, etc. Documented mostly in the v8.h header file (deps/v8/include/v8.h in the Node source tree).
V8 JavaScript，C++类库，作为JavaScript的接口类，主要用于创建对象、调用方法等功能。大部分功能在头文件v8.h （在node文件夹下的路径为deps/v8/include/v8.h）中有详细文档。
libev, C event loop library. Anytime one needs to wait for a file descriptor to become readable, wait for a timer, or wait for a signal to received one will need to interface with libev. That is, if you perform any I/O, libev will need to be used. Node uses the EV_DEFAULT event loop. Documentation can be found here.
libev，基于C的事件循环库。当需要等待文件描述（file descriptor）为可读时，等待定时器时，或者等待接受信号时，会需要调用libev库。也可以说，任何IO操作都需要调用libev库。Node使用EV_DEFAULT事件循环机制。在这里可以查阅相关文档。
libeio, C thread pool library. Used to execute blocking POSIX system calls asynchronously. Mostly wrappers already exist for such calls, in src/file.cc so you will probably not need to use it. If you do need it, look at the header file deps/libeio/eio.h.
libeio，基于C的线程池库，用于以异步方式执行阻塞式POSIX系统调用。因为大部分这类调用都在src/file.cc中被封装了，你一般不需要直接使用libeio。如果必须使用该类库时，可查看其头文件deps/libeio/eio.h。
Internal Node libraries. Most importantly is the node::ObjectWrap class which you will likely want to derive from.
内部Node库。在该库中，最重要的类是我们可能用于进行派生的node::ObjectWrap基类。
Others. Look in deps/ for what else is available.
其他的一些类库同样可以在deps/ 中找到。

Node statically compiles all its dependencies into the executable. When compiling your module, you don't need to worry about linking to any of these libraries.

Node已将所有依赖关系静态地编译成可执行文件，因此我们在编译自己的组件时不需要担心和这些类库的链接问题。

To get started let's make a small Addon which does the following except in C++:

让我们着手编写一个Addon的小例子，来达到如下模块同样的效果：

exports.hello = 'world';

To get started we create a file hello.cc:

首先我们需要创建一个hello.cc文件：

#include <v8.h>

using namespace v8;

extern "C" void
init (Handle<Object> target)
{
  HandleScope scope;
  target->Set(String::New("hello"), String::New("world"));
}

This source code needs to be built into hello.node, the binary Addon. To do this we create a file called wscript which is python code and looks like this:

这些源码会编译成一个二进制的Addon文件hello.node。为此我们用python编写如下的名为wscript的文件：

srcdir = '.'
blddir = 'build'
VERSION = '0.0.1'

def set_options(opt):
  opt.tool_options('compiler_cxx')

def configure(conf):
  conf.check_tool('compiler_cxx')
  conf.check_tool('node_addon')

def build(bld):
  obj = bld.new_task_gen('cxx', 'shlib', 'node_addon')
  obj.target = 'hello'
  obj.source = 'hello.cc'

Running node-waf configure build will create a file build/default/hello.node which is our Addon.

运行node-waf configure build，我们就创建了一个Addon实例build/default/hello.node。

node-waf is just WAF, the python-based build system. node-waf is provided for the ease of users.

node-waf就是WAF,，一种基于python的编译系统，而node-waf更加易于使用。

All Node addons must export a function called init with this signature:

另外，在Node中任何的Addon必须使用输出一个如下声明的init函数：

extern 'C' void init (Handle<Object> target)

For the moment, that is all the documentation on addons. Please see http://github.com/ry/node_postgres for a real example.

目前关于addon的所有文档就是这些。另外，在http://github.com/ry/node_postgres中还提供了一个Addon的实例。

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Addons 扩展插件