Libcurl筆記一-創(chuàng)新互聯(lián)

一：
1，全局初始化及釋放：
CURLcode curl_global_init(long flags)

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flags: CURL_GLOBAL_ALL //初始化所有的可能的調(diào)用。

CURL_GLOBAL_SSL //初始化支持安全套接字層。

CURL_GLOBAL_WIN32 //初始化win32套接字庫。

CURL_GLOBAL_NOTHING //沒有額外的初始化。

這個函數(shù)只能用一次。(其實在調(diào)用curl_global_cleanup 函數(shù)后仍然可再用)

如果這個函數(shù)在curl_easy_init函數(shù)調(diào)用時還沒調(diào)用，它講由libcurl庫自動調(diào)用，所以多線程下最好主動調(diào)用該函數(shù)以防止在線程中curl_easy_init時多次調(diào)用。

注意：雖然libcurl是線程安全的，但curl_global_init是不能保證線程安全的，所以不要在每個線程中都調(diào)用curl_global_init，應(yīng)該將該函數(shù)的調(diào)用放在主線程中。

void curl_global_cleanup(void)

二：兩種模式
1，
The easy interface is a synchronous, efficient, quickly used and... yes, easy interface for file transfers. Numerous applications have been built using this.
The multi interface is the asynchronous brother in the family and it also offers multiple transfers using a single thread and more. Get a grip of how to work with it in the multi interface overview.

easy interface 同步的快速的，多用于文件傳輸。
multi interface 異步的，支持一個或多個線程里面的多個文件傳輸。

https://curl.haxx.se/libcurl/c/libcurl-easy.html
https://curl.haxx.se/libcurl/c/libcurl-multi.html

三：easy interface
1，初始化下載handle及釋放

CURL *easy_handle = curl_easy_init();

curl_easy_cleanup(easy_handle);

2，CURL_EXTERN CURLcode curl_easy_setopt(CURL *curl, CURLoption option, ...);

CURLoption枚舉了curl能做的所有操作。
設(shè)置回調(diào)函數(shù)，訪問URL，超時時間，斷點續(xù)傳等。

3，CURLcode curl_easy_perform(CURL * easy_handle );
前面初始化init,屬性steopt設(shè)置好后就調(diào)perform開始執(zhí)行起來。

4，easy interface常用的函數(shù)
curl_easy_init()
curl_easy_cleanup()
curl_easy_setopt()
curl_easy_perform()
curl_easy_getinfo()

While the above functions are the main functions to use in the easy interface, there is a series of other helpful functions too including:

curl_version()	returns a pointer to the libcurl version string
curl_getdate()	converts a date string to time_t
curl_formadd()	build multipart form-data posts
curl_formfree()	free a previously built form POST
curl_slist_append()	builds a linked list
curl_slist_free_all()	frees a whole curl_slist as made with curl_slist_append()
curl_easy_escape()	URL encodes a string
curl_easy_unescape()	URL decodes a string

5，
問題：
1>MCurl.obj : error LNK2019: unresolved external symbol __imp__curl_easy_cleanup referenced in function _main

1>MCurl.obj : error LNK2019: unresolved external symbol __imp__curl_easy_perform referenced in function _main

解決：
1，C/C++->Preprocessor->Definitions 增加:
BUILDING_LIBCURL HTTP_ONLY或 CURL_STATICLIB CURL_DISABLE_LDAP

2，附加ws2_32.lib和wldap32.lib