利用MFC的Wininet以http方式下载小文件

直接上函数代码：

#include <afxwin.h>         // MFC 核心组件和标准组件
#include <Wininet.h>
#include <iostream>
#include <string>
using namespace std;
//walker 2013.05
//hostname主机名，例如www.baidu.com
//suburl，例如asp/test.asp?num=3
//port，端口号
string GetHttpFile(const char hostname[], const char suburl[], unsigned short port)
{
    HINTERNET   hInternet = NULL,
        hConnect = NULL,
        hRequest = NULL;
    BOOL bRtn;
    string strResponse;
    hInternet = InternetOpen("User-Agent",INTERNET_OPEN_TYPE_PRECONFIG,NULL,NULL, 0 );
    if (NULL == hInternet)
    {
        cout << "InternetOpen Failed!" << endl;
        goto exception_over;
    }
    hConnect = InternetConnect(hInternet, hostname, port, NULL, " HTTP/1.1 " ,INTERNET_SERVICE_HTTP, 0 , 0 );
    if (NULL == hConnect)
    {
        cout << "InternetConnect Failed!" << endl;
        goto exception_over;
    }
    hRequest  =  HttpOpenRequest(hConnect, "GET", suburl, " HTTP/1.1 " ,NULL,NULL,INTERNET_FLAG_RELOAD, 0 );
    if (NULL == hRequest)
    {
        cout << "HttpOpenRequest Failed!" << endl;
        goto exception_over;
    }
    //三种超时值
    DWORD TimeOuts[] = {5*1000, 5*1000, 10*1000};
    InternetSetOption(hRequest,INTERNET_OPTION_CONNECT_TIMEOUT , &(TimeOuts[0]), sizeof(DWORD));
    InternetSetOption(hRequest,INTERNET_OPTION_SEND_TIMEOUT , &(TimeOuts[1]), sizeof(DWORD));
    InternetSetOption(hRequest,INTERNET_OPTION_RECEIVE_TIMEOUT, &(TimeOuts[2]), sizeof(DWORD));
    bRtn  =  HttpSendRequest(hRequest,NULL, 0 , NULL, 0);
    if (!bRtn)
    {
        cout << "HttpSendRequest Failed!" << endl;
        goto exception_over;
    }
    char buf[1000] = {0};
    DWORD dwLengthBufQuery = sizeof(buf);
    bRtn = HttpQueryInfo(hRequest,  HTTP_QUERY_CONTENT_LENGTH, buf, &dwLengthBufQuery, NULL);
    if (!bRtn)
    {
        cout << "HttpQueryInfo Failed!" << endl;
        goto exception_over;
    }
    int file_len = atoi(buf);
    cout << "filelen: " << file_len << "bytes" << endl;
    int i = 1;
    const int BUF_LEN = 256;
    char cReadBuffer[BUF_LEN] = {0};
    unsigned long sum_recv = 0;
    unsigned long read_len;
    while (TRUE)
    {
        memset(cReadBuffer, 0 , BUF_LEN);
        unsigned long  lNumberOfBytesRead;
        read_len = (file_len - sum_recv) > (BUF_LEN - 1) ? (BUF_LEN - 1) : (file_len - sum_recv);
        bRtn  =  InternetReadFile(hRequest, cReadBuffer, read_len , &lNumberOfBytesRead);
        //注意：这里认为文件中不会有'\0'
        strResponse  =  strResponse +  cReadBuffer;
        cout << "第" << i << "次: " << lNumberOfBytesRead << "bytes" << endl;
        if ( !bRtn  || strResponse.size() >= (unsigned int)file_len)
        {
            break ;
        }
        ++i;
    }
exception_over:
    if (NULL != hRequest)
    {
        InternetCloseHandle(hRequest);
    }
    if (NULL != hConnect)
    {
        InternetCloseHandle(hConnect);
    }
    if (NULL != hInternet)
    {
        InternetCloseHandle(hInternet);
    }
    return strResponse;
}

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