Libuv 1.34.2 源码详解 ---- 以uvCat为例讲解

末蓝、 2023-07-02 13:25 5阅读 0赞

这些天病毒肆虐，心里很难过。一直对libuv高并发处理的能力好奇，只好呆家里看了一下libuv的源码。

libuva其实代码量很小，很精悍。但理解起来并不容易。网络上有不少解析的文章，不过大多见树叶而不见森林，我前几天刚在网上找资料时，看了一天都还没摸着头脑。我想对于很多刚开始学习libuv的朋友，可能不少和我类似，最重要的应该是知道谁，起的作用是什么？整个框架大概是什么样子的？这样，当碰到具体的细节时，可以大大加速对源码的理解。

我用的版本是最新版v1.34.2，源码是网上找的uvCat，就是读取一个文件，再把文件内容显示出来，命令类似uvCat d:\\test.txt。

其实大家平常使用最多的UDP/TCP，其原理都类似的。全部源码如下，

#include <assert.h>
    #include <stdio.h>
    #include <fcntl.h>
    #include <io.h> //#include <unistd.h>
    
    #include "../libuv/include/uv.h"
    
    #pragma comment(lib, "ws2_32.lib")
    #pragma comment(lib, "Iphlpapi.lib")
    #pragma comment(lib, "Userenv.lib")
    #pragma comment(lib, "Psapi.lib")
    
    // gcc -Wall main.c -o uvcat -luv
    // ./uvcat ./1.txt
    
    void on_read(uv_fs_t* req);
    
    uv_fs_t open_req;
    uv_fs_t read_req;
    uv_fs_t write_req;
    
    static char buffer[1024];
    
    static uv_buf_t iov;
    
    void on_write(uv_fs_t* req) {
        if (req->result < 0) {
            fprintf(stderr, "Write error: %s\n", uv_strerror((int)req->result));
        }
        else {
            uv_fs_read(uv_default_loop(), &read_req, open_req.result, &iov, 1, -1, on_read);
        }
    }
    
    void on_read(uv_fs_t* req) {
        if (req->result < 0) {
            fprintf(stderr, "Read error: %s\n", uv_strerror(req->result));
        }
        else if (req->result == 0) {
            uv_fs_t close_req;
            // synchronous
            uv_fs_close(uv_default_loop(), &close_req, open_req.result, NULL);
            printf("******Read file done!!!");
        }
        else if (req->result > 0) {
            iov.len = req->result;  // 读取数据的长度(数据读写完毕才触发回调)
            // 因为cat功能，所以将读取的数据写入控制台
            uv_fs_write(uv_default_loop(), &write_req, 1, &iov, 1, -1, on_write);
        }
    }
    
    void on_open(uv_fs_t* req) {
        // The request passed to the callback is the same as the one the call setup
        // function was passed.
        assert(req == &open_req);
        if (req->result >= 0) {
            iov = uv_buf_init(buffer, sizeof(buffer));
            uv_fs_read(uv_default_loop(), &read_req, req->result,
                &iov, 1, -1, on_read);
        }
        else {
            fprintf(stderr, "error opening file: %s\n", uv_strerror((int)req->result));
        }
    }
    
    int main(int argc, char** argv) {
        uv_fs_open(uv_default_loop(), &open_req, argv[1], O_RDONLY, 0, on_open);
        uv_run(uv_default_loop(), UV_RUN_DEFAULT);
    
        uv_fs_req_cleanup(&open_req);
        uv_fs_req_cleanup(&read_req);
        uv_fs_req_cleanup(&write_req);
        return 0;
    }

整体上来说，刚开始看到这种不断callback(算是循环递交作业的一种程序架构吧)的风格，让人印象深刻，

![20200130223752854.png][]

我们的函数是从uv\_fs\_open开始的，我们先看一下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70][]

可见，该函数的主要作用是初始化主结构如uv\_loop\_s/ uv\_loop\_t等并递交作业。

了解下初始化过程，

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 1][]

作业是如何递交的

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 2][]

作业的执行是在线程启动后在线程中进行的，我们看一下，

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 4][]

当然，你可以在uv\_ran持续不断地递交作业，这里尽量简化，不涉及这个，所以uv\_run只是做了些善后的活，

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 6][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 7][]

图片文件我已经转成PDF，这里可以下载：[https://download.csdn.net/download/tanmx219/12125728][https_download.csdn.net_download_tanmx219_12125728]

细节上，我建议参考这个：

[https://my.oschina.net/fileoptions/blog/1036629][https_my.oschina.net_fileoptions_blog_1036629]

[20200130223752854.png]: https://img-blog.csdnimg.cn/20200130223752854.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200130142625182.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/202001301428235.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20200130143023627.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20200130143040245.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 5]: https://img-blog.csdnimg.cn/20200130143400215.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 6]: https://img-blog.csdnimg.cn/20200130143408944.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5_size_16_color_FFFFFF_t_70 7]: https://img-blog.csdnimg.cn/20200130145325633.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3Rhbm14MjE5,size_16,color_FFFFFF,t_70
[https_download.csdn.net_download_tanmx219_12125728]: https://download.csdn.net/download/tanmx219/12125728
[https_my.oschina.net_fileoptions_blog_1036629]: https://my.oschina.net/fileoptions/blog/1036629