读Ruby for Rails的思考之Ruby的C扩展库

Ruby除了用Ruby写的扩展库以外，还有许多C写的扩展库，比如socket编程库/系统日志功能库/数据库驱动
这些库以.so或者.dll结尾，这也是我们require的时候不要使用.rb后缀的原因，比如

require 'gdbm'

Ruby开源项目、扩展库站点:
Ruby Application Archive(RAA)
RubyForge

怎样写Ruby的C扩展库呢？
我们来看看How to create a Ruby extension in C under 5 minutes
该程序的前提是需要在linux/unix环境下
MyTest/extconf.rb

# Loads mkmf which is used to make makefiles for Ruby extensions
require 'mkmf'

# Give it a name
extension_name = 'mytest'

# The destination
dir_config(extension_name)

# Do the work
create_makefile(extension_name)

MyTest/MyTest.c

// Include the Ruby headers and goodies
#include "ruby.h"

// Defining a space for information and references about the module to be stored internally
VALUE MyTest = Qnil;

// Prototype for the initialization method - Ruby calls this, not you
void Init_mytest();

// Prototype for our method 'test1' - methods are prefixed by 'method_' here
VALUE method_test1(VALUE self);

// The initialization method for this module
void Init_mytest() {
	MyTest = rb_define_module("MyTest");
	rb_define_method(MyTest, "test1", method_test1, 0);	
}

// Our 'test1' method.. it simply returns a value of '10' for now.
VALUE method_test1(VALUE self) {
	int x = 10;
	return INT2NUM(x);
}

就这么简单，我们进入MyTest目录，运行

ruby extconf.rb

这会为我们创建Makefile，然后我们运行

make

这样我们的C扩展库就compile和build好了，让我们运行mytest.rb测试一下:

# Load in the extension (on OS X this loads ./MyTest/mytest.bundle - unsure about Linux, possibly mytest.so)
require 'MyTest/mytest'

# MyTest is now a module, so we need to include it
include MyTest

# Call and print the result from the test1 method
puts test1

# => 10

该demo程序下载地址:extension-code.tar.gz