【nginx源码学习与运用 二】ngx_bufs_t 与 ngx_chain_t相关操作

【nginx源码学习与运用】系列博客中的示例代码在csdn的代码托管服务器CODE上，地址https://code.csdn.net/u012819339/nginx_study ，你可以将其自由的下载到本地，或者通过git来实时获取更新

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本篇博客是在上一篇的基础上又学习了nginx中ngx_buf_t 与ngx_chain_t相关知识与部分操作方法，并给出了例程，项目代码见csdn的

相关结构

ngx_buf_s结构：

struct ngx_buf_s {
    u_char          *pos;//当前处理位置，意义可以由使用者决定
    u_char          *last; //有效内容到此为止
    off_t            file_pos; //略
    off_t            file_last;

    u_char          *start;  //buffer起始位置   
    u_char          *end;   //buffer结束位置    
    ngx_buf_tag_t    tag;
    ngx_file_t      *file;
    ngx_buf_t       *shadow;


    /* the buf's content could be changed */
    unsigned         temporary:1;  //临时内存标志位，为1时表示数据在内存中且这段内存可以修改

    /*
     * the buf's content is in a memory cache or in a read only memory
     * and must not be changed
     */
    unsigned         memory:1;

    /* the buf's content is mmap()ed and must not be changed */
    unsigned         mmap:1;

    unsigned         recycled:1;
    unsigned         in_file:1;
    unsigned         flush:1;
    unsigned         sync:1;
    unsigned         last_buf:1;
    unsigned         last_in_chain:1;

    unsigned         last_shadow:1;
    unsigned         temp_file:1;

    /* STUB */ int   num;
};

ngx_chain_s以及ngx_bufs_t

struct ngx_chain_s {
    ngx_buf_t    *buf; //指向当前ngx_buf_t缓冲区
    ngx_chain_t  *next; //指向下一个ngx_chain_t结构
};


typedef struct {
    ngx_int_t    num; //缓冲区个数
    size_t       size; //缓冲区大小
} ngx_bufs_t;

结构图：

ngx_chain_t结构图：

操作方法：

函数	解释
ngx_create_temp_buf	从内存池中申请一块临时用的内存
ngx_create_chain_of_bufs	创建chain链
ngx_chain_add_copy	将in链 链接到chain链末尾

其它方法暂且略过，没有演示

使用方法与注意事项

见代码

示例代码

arvik将nginx中的部分基础结构代码提出来了，好作为新手学习练习使用。见 https://code.csdn.net/u012819339/nginx_study
main.c

/*
blog:   http://blog.csdn.net/u012819339
email:  1216601195@qq.com
author: arvik
*/

#include <stdio.h>
#include <string.h>
#include "ak_core.h"
#include "pt.h"

char h_buf[200] = "HTTP/1.1 200 OK\r\nAuthor: arvik\r\nDate: 20161205\r\nUpgrage: Websocket\r\nConnection: close\r\n";


int main()
{
    ngx_pool_t *p;
    ngx_uint_t i = 0;
    ngx_bufs_t my_bufs = {.num = 3, .size = 64*sizeof(char)};
    char *pb = NULL, *pb1 = NULL;
    int len;

    p = ngx_create_pool(1000);  //并不负责清零内存
    if(p == NULL)
        return -1;

    ngx_buf_t *buf1 = ngx_create_temp_buf(p, 64);  //申请一个临时缓冲区
    if(buf1 == NULL)
        return -1;

    strcpy(buf1->start, "hello world!");
    buf1->pos += strlen("hello world");

    PT_Info("buf1 : %.*s\n", buf1->pos - buf1->start, buf1->start);

    ngx_chain_t *ct = ngx_create_chain_of_bufs(p, &my_bufs);
    if(ct == NULL)
        return -1;

    ngx_chain_t *t = NULL;
    ngx_chain_t *t1 = NULL; 
    for(t = ct, pb= h_buf; t; t = t->next, i++)  //每个buf都是定长的chain
    {
        pb1 = strchr(pb, '\n');
        len = pb1 + 1 - pb;
        memcpy(t->buf->start, pb, len);
        t->buf->pos += len;

        pb = pb1+1;
    }

    PT_Info("now, add one buf to chain!\n");

    //以上chain中的buf都是定长，较为浪费内存，以下方式则根据字符串的长度分配一个长度恰好合适的buf并添加到chain链中
    pb1 = strchr(pb, '\n');
    len = pb1 + 1 - pb;
    my_bufs.num = 1;
    my_bufs.size = len; 

    ngx_chain_t *in = ngx_create_chain_of_bufs(p, &my_bufs); 
    memcpy(in->buf->start, pb, len);
    in->buf->pos += len;

    ngx_chain_add_copy(p, &ct, in);//将in链加入ct链尾部

    for(i = 0, t1 = ct; t1; t1 = t1->next, i++)  //答应chain中的每个buf内容
    {
        PT_Info("the buf %d of chains, len:%d, text: %.*s\n", i, t1->buf->pos - t1->buf->start, t1->buf->pos - t1->buf->start, t1->buf->start);
    }   

    PT_Info("complete!\n");
    ngx_destroy_pool(p);
}

运行结果

截图如下：