Workflow支持通过Http代理访问Http(s)服务啦

[kedixa]

PR: #378

Workflow支持通过Http代理访问Http(s)服务啦，使用方式与普通Http请求基本一致

std::string url = "https://www.sogou.com/";
std::string proxy = "http://user:[email protected]:port"; // proxy url here
WFHttpTask *task = WFTaskFactory::create_http_task(url, proxy, 3, 3, http_callback);
task->start();

如上述代码所示，仅需在创建Http任务时传入http proxy的url即可创建一个使用proxy的http任务

1. 若proxy无需使用密码，则忽略user:passwd@即可
2. 若需要进行重定向，则任务会自动处理且使用相同的proxy发起新的请求
3. 若Connect proxy时被proxy拒绝(例如密码认证失败)，用户会得到一个task->get_state() == WFT_STATE_TASK_ERROR && task->get_error() == WFT_ERR_HTTP_PROXY_CONNECT_FAILED的错误，此时proxy返回的内容被放在task->get_resp()中

一个较为完整的示例如下：

#include <iostream>
#include <string>
#include "workflow/HttpUtil.h"
#include "workflow/WFTaskFactory.h"
#include "workflow/WFFacilities.h"

using namespace std;
using namespace protocol;

WFFacilities::WaitGroup wait_group(1);

void http_callback(WFHttpTask *task) {
    int state = task->get_state();
    int error = task->get_error();
    const char *errstr = WFGlobal::get_error_string(state, error);
    HttpResponse *resp = task->get_resp();

    if (state == WFT_STATE_TASK_ERROR &&
        error == WFT_ERR_HTTP_PROXY_CONNECT_FAILED) {
        printf("Connect to proxy return non 200\n\n");
        printf("%s %s %s\n", resp->get_http_version(),
            resp->get_status_code(), resp->get_reason_phrase()
        );
    }
    else if (state != WFT_STATE_SUCCESS) {
        printf("error: %s\n", errstr);
    }
    else {
        const void *body;
        size_t size = 0;
        resp->get_parsed_body(&body, &size);
        printf("Get response from remote server\n\n");
        printf("%s %s %s\n", resp->get_http_version(),
            resp->get_status_code(), resp->get_reason_phrase()
        );

        string name, value;
        HttpHeaderCursor resp_cursor(resp);
        while (resp_cursor.next(name, value))
            printf("%s: %s\n", name.c_str(), value.c_str());
        printf("\n");
    }

    wait_group.done();
}

int main() {
    string url = "https://www.sogou.com/";
    // TODO use a real proxy here
    std::string proxy = "http://user:[email protected]:port";
    WFHttpTask *task;

    task = WFTaskFactory::create_http_task(url, proxy, 3, 3, http_callback);
    task->start();

    wait_group.wait();
    return 0;
}