准备写一个http下载，支持断点下载，多线程下载

实现这个功能，需要使用http中分块下载，先写个小程序试试http中使用Range:bytes功能

#include <iostream>#include <iosfwd>#include <fstream>#include <regex>#include <string>#include <winsock2.h>#include <pthread.h>#include <map>#include <queue>/***实现多线程http协议下载文件的功能，支持断点续传和多线程同时下载*http请求使用Range: bytes完成*为了保证文件的完整性，有两种方式*1,使用生产者/消费者模式，将读取的信息放入队列中，由队列写文件*2,同时写n个临时文件，最后执行完成拼接在一起***/using namespace std;SOCKET sock;//测试主机和端口const char *testHostName="ww3.sinaimg.cn";const short testPort=80;const string testPortChar="80";//文件地址const char *url="/mw690/60d02b59tw1ehspkw5ewfg20dm05wb1p.gif";//分块下载的块大小const int getSize=10000;int fileNameInt;//发送http请求包bool sendHttpQuery(string sendQueryStr){    int n=0;   //初始化socket    sock = socket(AF_INET, SOCK_STREAM, 0);    if (sock == INVALID_SOCKET)    {        cout << "建立socket失败！ 错误码： " << WSAGetLastError() << endl;        return false;    }    sockaddr_in sa = { AF_INET };    n = bind(sock, (sockaddr*)&sa, sizeof(sa));    if (n == SOCKET_ERROR)    {        cout << "bind函数失败！ 错误码： " << WSAGetLastError() << endl;        return false;    }    struct hostent *p = gethostbyname(testHostName);    if (p == NULL)    {        cout << "主机无法解析出ip! 错误吗： " << WSAGetLastError() << endl;        return false;    }    sa.sin_port = htons(testPort);    memcpy(&sa.sin_addr, p->h_addr, 4);//   with some problems ???    //sa.sin_addr.S_un.S_addr = inet_addr(*(p->h_addr_list));    //cout << *(p->h_addr_list) << endl;    //连接    n = connect(sock, (sockaddr*)&sa, sizeof(sa));    if (n == SOCKET_ERROR)    {        cout << "connect函数失败！ 错误码： " << WSAGetLastError() << endl;        return false;    }    //string  reqInfo = "GET / HTTP/1.1\r\n Host:www.baidu.com \r\n Connection:Keep-Alive\r\n\r\n ";    //string reqInfo ="GET http://c.csdnimg.cn/rabbit/notev2/js/notify.js HTTP/1.1 \r\n Host: c.csdnimg.cn \r\n Connection: keep-alive \r\n Accept: */* \r\n User-Agent: Mozilla/5.0 (Windows NT 10.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36 \r\n Referer: http://www.csdn.net/ \r\n Accept-Encoding: gzip, deflate, sdch \r\n Accept-Language: zh-CN,zh;q=0.8\r\n\r\n";    //string reqInfo = "GET /huajiao/huajiao.html HTTP/1.1 \r\n Host: se.360.cn \r\n Connection: close \r\n  Accept-Encoding: gzip, deflate, sdch \r\n Accept-Language: zh-CN,zh;q=0.8 \r\n Cookie: __huid=106HCYajdj5TzIlJ9HVN0evB27Lr1Z8JneHl8nAKepKUc%3D; __guid=132730903.2645167981534180400.1426119249932.2551; _ga=GA1.2.1411504458.1447744075; guid=54771369.514003739225082050.1466048704517.24 \r\n\r\n";    //string reqInfo = "GET /thread-551469-1.html HTTP/1.1\r\nHost:bbs.51cto.com:80\r\nConnection:Close\r\n\r\n";    //按照http送GET请求    cout<<"发送http请求:"+sendQueryStr<<endl;    if (SOCKET_ERROR == send(sock, sendQueryStr.c_str(), sendQueryStr.size(), 0))    {        cout << "send error! 错误码： " << WSAGetLastError() << endl;        closesocket(sock);        return false;    }    return true;}//从http的返回头信息中解析出文件长度char * getResponseLeng(const char receiveBuf[1024]){    //找到Content-Range: bytes 0-1/之后的字符串lengStartChar    char *lengStartChar = strstr(receiveBuf, "Content-Range: bytes 0-1/");    int tmpSize=sizeof("Content-Range: bytes 0-1/");//注意sizeof长度将结束符计算进去，后面需要减掉1    //char *tmpSizeChar;    //sprintf(tmpSizeChar,"%d",tmpSize);    //cout<<(string)tmpSizeChar<<endl;    //char *lengEndchar=strstr(buf, "\r\n");    int i=0;    bool isEnd=false;    //在lengStartChar找到\r\n之前的位置    while(!isEnd){        if(lengStartChar[i+1]!='\r')i++;        else{            if(lengStartChar[i+2]=='\n')isEnd=true;            else i++;        }    }    //将lengStartChar中关于长度的一段赋值给长度字符串，注意减去结束符    char *leng=new char(10);    memset(leng,0x00,10);    memcpy(leng,lengStartChar+tmpSize-1,i-tmpSize+2);    //cout<<"111  "+(string)leng+"  111"<<endl;    return leng;}int main(){    int n;    char buf[1024];    memset(buf, 0, sizeof(buf));    fstream file;    WORD version(0);    WSADATA wsadata;    int socket_return(0);    version = MAKEWORD(2,0);    socket_return = WSAStartup(version,&wsadata);    if (socket_return != 0)    {        return 0;    }    file.open("D:\\testmap\\test.gif" ,ios::out|ios::binary);    cout << " 文档打开 D:\\testmap\\test.gif"  << endl;    if(!file.is_open()){       cout << " 文档打开失败！ D:\\testmap\\test.gif" << endl;    }    //for()    string strFirst="GET "+(string)url+" HTTP/1.1\r\nHost:"+(string)testHostName+":"+testPortChar+"\r\nRange:bytes=0-1\r\nConnection:Close\r\n\r\n";    //发送http请求    if(!sendHttpQuery(strFirst)){        cout<<" http 请求发送失败！ "<<endl;        return 0;    }    //思路：将Content-Range: bytes 0-1/后面的值作为长度解析出来    //再根据文件长度决定循环几次请求（后续实现分配几个线程下载）    n = recv(sock, buf, sizeof(buf)-1, 0);    cout<<buf<<endl;    char *lengChar=getResponseLeng(buf);    cout<<"长度为 :"+(string)lengChar<<endl;    int lengInt=atoi(lengChar);    //得到每次取1000长度总共需要循环的次数    int getTimeInt=lengInt/getSize;    int i=0;    while(i<=getTimeInt){        char tmpBuf[1024];        memset(tmpBuf, 0, sizeof(tmpBuf));        char *startMark=new char(10);        char *endMark=new char(10);//设置开始地址，结束地址，注意        memset(startMark,0,10);        memset(endMark,0,10);        //string startMark;        //string endMark;       // startMark=itoa();        sprintf(startMark,"%d",(i*getSize+0));        sprintf(endMark,"%d",(i*getSize+(getSize-1)));        //startMark[5]='\0';        //endMark[5]='\0';        string strFirst="GET "+(string)url+" HTTP/1.1\r\nHost:"+(string)testHostName+":"+testPortChar+"\r\nRange:bytes="+(string)startMark+"-"+(string)endMark+"\r\nConnection:Close\r\n\r\n";        //发送http请求        if(!sendHttpQuery(strFirst)){            cout<<" http 请求发送失败！ "<<endl;            return 0;        }        n = recv(sock, tmpBuf, sizeof(tmpBuf)-1, 0);        char *cpos = strstr(tmpBuf, "\r\n\r\n");        //显示响应头        //char *requestHeader=new char(200);        //memset(requestHeader,0,200);        //memcpy(requestHeader,tmpBuf,cpos - tmpBuf+1);        file.write(cpos + strlen("\r\n\r\n"), n - (cpos - tmpBuf) - strlen("\r\n\r\n"));       // cout<<cpos + strlen("\r\n\r\n") <<endl;      //cout<<requestHeader<<endl;        while ((n = recv(sock, tmpBuf, sizeof(tmpBuf)-1, 0)) > 0)        {            file.write(tmpBuf, n);        }        i++;    }    file.close();    return 0;}