Nginx阅读： typedef定义函数指针类型

/*function point definition*/
typedef u_char *(*ngx_log_handler_pt) (ngx_log_t *log, u_char *buf, size_t len);

struct ngx_log_s {
    ngx_uint_t           log_level;
    ngx_open_file_t     *file;

    ngx_atomic_uint_t    connection;

    ngx_log_handler_pt   handler;		//function ptr definition
    void                *data;

    /*
     * we declare "action" as "char *" because the actions are usually
     * the static strings and in the "u_char *" case we have to override
     * their types all the time
     */

    char                *action;

    ngx_log_t           *next;
};

此处ngx_log_handler_pt类型是对复杂函数指针的替代，使用起来更加方便，同时只要参数类型相同，ngx_log_handler_pt类型就可以指向并调用改函数，例如：

 此例子源自：http://www.cnblogs.com/csyisong/archive/2009/01/09/1372363.html， 关于typedef与#define的讲解，挺赞！

#include <iostream>
using namespace std;
typedef int (*A) (char, char);

int ss(char a, char b)
{
    cout<<"in func ss()"<<endl;
    cout<<a<<endl;
    cout<<b<<endl;

    return 0;
}

int bb(char a, char b)
{
    cout<<"in func bb()"<<endl;
    cout<<b<<endl;
    cout<<a<<endl;

    return 0;
}

int main()
{
    A a;
    a = ss;
    a('a','b');
    a = bb;
    a('a', 'b');
    return 0;
}