使用libcurl POST数据和上传文件

为了具有通用性，将文件的内容读到了fc变量中，fclen是fc的长度。fc也可以是任何其它内容。curl 是 libcurl句柄。演示省略了很多显而易见的步骤。

1. 普通的post请求，这里用curl_easy_escape对fc做了编码

std::string data("req=plain");

data.append("&file=");

char *efc = curl_easy_escape(curl, fc, fclen);

data.append(efc)

curl_free(encoded);

curl_easy_setopt(curl, CURLOPT_URL, PURGE_URL);

curl_easy_setopt(curl, CURLOPT_POST, 1L);

curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str());

curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, data.size());

2. multipart/formdata请求

struct curl_httppost *formpost = 0;

struct curl_httppost *lastptr  = 0;

curl_formadd(&formpost, &lastptr, CURLFORM_PTRNAME, "reqformat", CURLFORM_PTRCONTENTS, "plain", CURLFORM_END);

curl_formadd(&formpost, &lastptr, CURLFORM_PTRNAME, "file", CURLFORM_PTRCONTENTS, fc, CURLFORM_CONTENTSLENGTH, fclen, CURLFORM_END);

curl_easy_setopt(curl, CURLOPT_URL, URL);

curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);

curl_easy_perform(curl);

curl_formfree(formpost);

3. multipart/formdata请求，不把文件读入fc，其它步骤相同

curl_formadd(&formpost, &lastptr, CURLFORM_PTRNAME, "file", CURLFORM_FILE, "/path/filename", CURLFORM_END);

4. 通过put上传文件

curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

curl_easy_setopt(curl, CURLOPT_PUT, 1L);

curl_easy_setopt(curl, CURLOPT_READDATA, fp);   // FILE *fp = fopen("/path/filename");

curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, fsize);  // fsize = sizeof /path/filename

5. 发送自己的Header

struct curl_slist *slist = 0;

slist = curl_slist_append(slist, "Blog-X-User: username");

slist = curl_slist_append(slist, "Blog-X-Signature: signature");

curl_easy_setopt(curl, CURLOPT_HTTPHEADER, slist);

curl_slist_free_all(slist);