使用libcurl访问ltp之一--示例代码

#ifndef LTP_REQUEST_H
#define LTP_REQUEST_H
#include <string>
#include <map>

namespace ns_ltp{

//TODO:优化内存使用
class LtpRequest{
    private:
        char *buffer;
        size_t currentLength;

    public:
        LtpRequest();
        ~LtpRequest();

        void Reset();

        bool RequestAll(std::string &text, std::string &response, std::string &errorString);

        bool Request(std::string &text, std::string &ltpPattern, std::string &response, char *errorBuffer, size_t bufferLength);

        size_t ConsumeData(char *dataBuffer, size_t size, size_t nmemb);
};

extern LtpRequest ltpRequest;

};
#endif

#include <stdio.h>
#include <string>
#include <vector>
#include "LtpRequest.h"
#include <curl/curl.h>

using namespace std;
using namespace ns_ltp;

LtpRequest ns_ltp::ltpRequest;

size_t maxBufferLength = 1024 * 1024;

static size_t write_data(void *buffer, size_t size, size_t nmemb, void *tmp);

LtpRequest::LtpRequest()
{
    buffer = (char *)malloc(maxBufferLength);
    memset(buffer, 0, maxBufferLength);

    currentLength = 0;
}

LtpRequest::~LtpRequest()
{
    if (buffer)
    {
        free(buffer);
    }
}

void LtpRequest::Reset()
{
    currentLength = 0;
    memset(buffer, 0, maxBufferLength);
}

bool LtpRequest::RequestAll(std::string &text, std::string &response, std::string &errorString)
{
    //static string ltpPattern("all");
    //return Request(text, ltpPattern, response, errorString);
    return false;
}

bool LtpRequest::Request(std::string &text, std::string &ltpPattern, std::string &response, char *errorBuffer, size_t bufferLength)
{
    if ((!errorBuffer) || (!bufferLength))
        return false;
    if (text.empty())
    {
        snprintf(errorBuffer, bufferLength, "text missed");
        return false;
    }

    string newText;
    char *s = curl_easy_escape(NULL, text.c_str(), text.size());
    if (s)
    {
        newText = string(s);
        curl_free(s);
    }
    else
    {
        snprintf(errorBuffer, bufferLength, "failed to call CurlTranformText\n");
        return false;
    }

    //printf("new text: %s\n", newText.c_str());


    static string url = "";


    string myKey;
    string fields = "api_key=" + myKey;
    fields += "&text=" + newText;
    fields += "&pattern=" + ltpPattern;
    fields += "&format=json";

    //printf("%s\n", url.c_str());
    //printf("%s\n", fields.c_str());


    //bool result = false;
    //result = GetUrl(url.c_str(), response, errorString);

    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if (!curl)
    {
        snprintf(errorBuffer, bufferLength, "failed to init curl");
        return false;
    }

    curl_easy_setopt(curl, CURLOPT_URL, url.c_str()); //url地址
    curl_easy_setopt(curl, CURLOPT_POST, 1); //设置问非0表示本次操作为post

    //如果是以上的初始化代码放在本类的初始化部分，下面的请求ltp的代码可以重复调用。
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, fields.c_str()); //post参数

    //对返回的数据进行操作的函数地址, 如果不设置，返回值打印到控制台
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, this); //这是write_data的第四个参数值

    //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1); //打印调试信息
    //curl_easy_setopt(curl, CURLOPT_HEADER, 1); //将响应头信息和相应体一起传给write_data
    //curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1); //设置为非0,响应头信息location
    //curl_easy_setopt(curl, CURLOPT_COOKIEFILE, "/Users/zhu/CProjects/curlposttest.cookie");

    res = curl_easy_perform(curl);

    if (res != CURLE_OK)
    {
        switch(res)
        {
            case CURLE_UNSUPPORTED_PROTOCOL:
                snprintf(errorBuffer, bufferLength, "不支持的协议,由URL的头部指定\n");
            case CURLE_COULDNT_CONNECT:
                snprintf(errorBuffer, bufferLength, "不能连接到remote主机或者代理\n");
            case CURLE_HTTP_RETURNED_ERROR:
                snprintf(errorBuffer, bufferLength, "http返回错误\n");
            case CURLE_READ_ERROR:
                snprintf(errorBuffer, bufferLength, "读本地文件错误\n");
            default:
                snprintf(errorBuffer, bufferLength ,"返回值:%d\n", res);
        }
        curl_easy_cleanup(curl);
        return false;
    }

    if (currentLength == 0)
    {
        curl_easy_cleanup(curl);
        return false;
    }

    response = string(buffer);
    curl_easy_cleanup(curl);
    return true;
}

size_t LtpRequest::ConsumeData(char *dataBuffer, size_t size, size_t nmemb)
{
    size_t totalCount = size * nmemb;
    if (!totalCount)
    {
        //printf("failed ,total count is zero\n");
        return 0;
    }

    if (currentLength + totalCount >= maxBufferLength)
    {
        printf("ltp request memory not enough\n");
        abort();
    }

    memcpy(buffer + currentLength, dataBuffer, totalCount);
    currentLength += totalCount;

    //printf("results are: %s\n", buffer);

    return totalCount;
}

size_t write_data(void *buffer, size_t size, size_t nmemb, void *tmp)
{
    LtpRequest *request = (LtpRequest *)tmp;
    return request->ConsumeData((char *)buffer, size, nmemb);
}