Libcurl笔记五_easy模式运行原理

1，



curl_easy_init内部调用Curl_open创建一个结构体SessionHandle（里面包含了所以curl使用的数据和指针）并初始化一些数据，然后返回将其作为给外侧使用的句柄CURL*。

2，
curl_easy_setopt调用Curl_setopt,其内部一个switch,case所有支持的参数来设置上面init的SessionHandle中相应数据。

3，curl_easy_perform内部会创建一个multi结构并让其与相互指向
multi = data->multi_easy;
data->multi = multi;

static
CURLcode easy_perform(struct
SessionHandle *data, bool
events)
{

CURLM *multi;

CURLMcode mcode;

if(data->multi) {

failf(data, "easy handle already used in multi handle");

return CURLE_FAILED_INIT;

}

if(data->multi_easy)
multi = data->multi_easy;

else {

/* this multi handle will only ever have a single easy handled attached
to it, so make it use minimal hashes */
multi = Curl_multi_handle(1, 3);

if(!multi)

return CURLE_OUT_OF_MEMORY;

data->multi_easy = multi;
}

mcode = curl_multi_add_handle(multi, data);

data->multi = multi;

/* run the transfer */
result = events ? easy_events(multi) : easy_transfer(multi);
(void)curl_multi_remove_handle(multi, data);

return result;
}

4，curl_multi_perform内部由multi_runsingle执行真正的一些列http操作。
multi_runsingle由一个while循环内不断的switch-case 20种 CURLMstate状态执行相应操作并指定下一个状态传递操作直到结束。
static
CURLMcode multi_runsingle(struct
Curl_multi *multi,

struct
timeval
now,

struct
SessionHandle *data)

{

do {

switch(data->mstate) {

case CURLM_STATE_INIT:
result=Curl_pretransfer(data);

multistate(data, CURLM_STATE_CONNECT);

break;

case CURLM_STATE_CONNECT:
result = Curl_connect(data, &data->easy_conn,
&async, &protocol_connect);

multistate(data, CURLM_STATE_CONNECT_PEND);

break;
case CURLM_STATE_WAITCONNECT:
result = Curl_is_connected(data->easy_conn, FIRSTSOCKET, &connected);

multistate(data, data->easy_conn->bits.tunnel_proxy?
CURLM_STATE_WAITPROXYCONNECT:
CURLM_STATE_SENDPROTOCONNECT);

break;

case CURLM_STATE_PERFORM:
result = Curl_readwrite(data->easy_conn, data, &done);

multistate(data, CURLM_STATE_DONE);

break;
}while((rc == CURLM_CALL_MULTI_PERFORM) || multi_ischanged(multi, FALSE))
}

5，
case CURLM_STATE_INIT:
创建连接数据并初始化之



case CURLM_STATE_CONNECT:
为上面创建的连接结构绑定socket



case CURLM_STATE_WAITCONNECT:
使用select模型开始socket操作



case CURLM_STATE_PERFORM:
收到数据了，使用之前easy_setopt设置在SessionHandle结构中的回调函数写数据。



6，curl_easy_cleanup清空SessionHandle结构，
当然会先调用curl_multi_cleanup清空关联的multi结构。