使用HTTP协下载文件

通过发送HTTP请求，下载文件

头文件：

 #ifndef __HTTP__
 #define __HTTP__

 #include <stdio.h>
 #include <stdlib.h>
 #include <string>
 #include <winsock.h>

 using namespace std;

 /**
  * URL相关数据
  */
 typedef struct _URLData {
     string url;     // 完整的url地址
     string path;    // 文件路径
     string host;    // 主机名
     string ip;      // 点分隔的ip
     int    port;    // 端口
     string resName; // 资源名字
 } URLData;

 /**
  * 解析url
  */
 void parseURL(string url, URLData* data);

 /**
  * 链接http服务器
  */
 bool connectHttpServer(int socketId, string ip, int port);

 /**
  * 生成请求文本
  */
 void generateRequestTxt(URLData* data, string* requestTxt);

 /**
  * 发送http请求
  */
 bool sendHttpRequest(int socketId, string* requestTxt);

 /**
  * 接受响应数据
  */
 void recvHttpResponse(int socketId, string* responseTxt);

 /**
  * 保存http数据
  */
 bool saveHttpData(string* responseTxt, string filePath = "", string fileName = "");

 /**
  * 获取http资源
  */
 bool getHttpResource(string url, string filePath = "", string fileName = "");

 #endif

代码文件：

 #include "http.h"
 #include "DNS/DNS.h"
 #include "time.h"

 /**
  * 解析url
  */
 void parseURL(string url, URLData* data)
 {
     int startPos = ;
     string begin = url.substr(, );
     if (begin == "http") {
         startPos = ;
     }

     int i = startPos;
     int lastSplitPos = ;
     for (int len = url.length(); i<len; i++) {
         unsigned char ch = url.at(i);

         if (ch == ) {
             if (data->host.length() == ) {
                 data->host = url.substr(startPos, i - startPos);
                 data->path = url.substr(i, url.length() - i);

                 break;
             }

             lastSplitPos = i;
         }
     }
     // data->path = url.substr(iPath, url.length() - iPath);
     data->url = url;
     data->port = ;

     int resNameLastPos = url.length()-;
     int resNameFirstPos = ;
     for (int i = url.length()-; i>=; i--) {
         unsigned char ch = url.at(i);

         if (ch == '.')
             resNameLastPos = i;
         else if (ch == '/') {
             resNameFirstPos = i + ;
             break;
         }
     }
     data->resName = url.substr(resNameFirstPos, resNameLastPos - resNameFirstPos);
 }

 /**
  * 链接HTTP服务器
  */
 bool connectHttpServer(int socketId, string ip, int port)
 {
     // 初始套接字化地址
     struct sockaddr_in serverAddr;
     memset(&serverAddr, , sizeof(serverAddr));
     serverAddr.sin_family = AF_INET;
     serverAddr.sin_addr.S_un.S_addr = inet_addr(ip.c_str());
     serverAddr.sin_port = htons(port);

     if (connect(socketId, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) {
         return false;
     }
     return true;
 }

 /**
  * 生成请求文本
  */
 void generateRequestTxt(URLData* data, string* requestTxt)
 {
     requestTxt->append("GET "); requestTxt->append(data->path); requestTxt->append(" HTTP/1.1\r\n");
     requestTxt->append("Host: "); requestTxt->append(data->host); requestTxt->append("\r\n");
     requestTxt->append("Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n");
     requestTxt->append("Accept-Language: zh-CN,zh;q=0.8\r\n");
     requestTxt->append("User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36\r\n");
     requestTxt->append("Accept-Encoding: deflate,sdch\r\n");
     requestTxt->append("Connection: close\r\n\r\n");
 }

 /**
  * 发送http请求
  */
 bool sendHttpRequest(int socketId, string* requestTxt)
 {
     int sendBytes = send(socketId, requestTxt->c_str(), requestTxt->length(), );
     return sendBytes > ;
 }

 /**
  * 接受响应数据
  */
 void recvHttpResponse(int socketId, string* responseTxt)
 {
     char buff[];

     int recvBytes = ;
     while ((recvBytes = recv(socketId, buff, , )) > ) {
         responseTxt->append(buff, recvBytes);
     }
 }

 /**
  * 保存http数据
  */
 bool saveHttpData(string* responseTxt, string filePath, string fileName)
 {
     if (fileName == "") {
         char _fileName[];
         sprintf(_fileName, "%lld", time());
         fileName = _fileName;
     }

     string fileExt = ".";

     int i = , len = ;
     for (i = , len = responseTxt->length(); i<len; i++) {
         unsigned char ch = responseTxt->at(i);

         if (ch == 'C') {
             unsigned char metaKey[], typeMetaKey[] = "Content-Type";
             memset(metaKey, , );
             memcpy(metaKey, responseTxt->c_str() + i, );

             string metaValue;
             if ( strcmp((char*)metaKey, (char*)typeMetaKey) ==  ) {
                 for (int j = i+;;j++) {
                     unsigned char ch = responseTxt->at(j);

                     metaValue.push_back(ch);
                     if (ch == '\r') {
                         for (int k = , len = metaValue.length(); k<len; k++) {
                             if (metaValue.at(k) == '/') {
                                 fileExt.append( metaValue.substr(k+, metaValue.length() - k - ) );
                                 fileName.append(fileExt);

                                 break;
                             }
                         }

                         break;
                     }
                 }
             }
         }

         if (ch == '\r' &&
             responseTxt->at(i+) == '\n' &&
             responseTxt->at(i+) == '\r' &&
             responseTxt->at(i+) == '\n') {
             i += ;
             break;
         }
     }

     FILE* fp = fopen((filePath + fileName).c_str(), "wb+");
     if (fp) {
         fwrite(responseTxt->c_str() + i, , responseTxt->length() - i, fp);
         fclose(fp);

         return true;
     }
     return false;
 }

 /**
  * 获取http资源
  */
 bool getHttpResource(string url, string filePath, string fileName)
 {
     printf("-------------------------------------\n");

     int socketId = socket(AF_INET, SOCK_STREAM, );
     if (socketId == INVALID_SOCKET) {
         printf("Create sokcet failed\n");

         return false;
     }

     // 解析url数据
     URLData data;
     parseURL(url, &data);

     // 获取DNS信息
     if (!getIPAddrByDNS(data.host, &data.ip)) {
         printf("Get ip(%s) from DNS server failed\n", data.host.c_str());

         return false;
     }

     // 生成请求文本
     string requestTxt;
     generateRequestTxt(&data, &requestTxt);

     // 链接服务器
     if (!connectHttpServer(socketId, data.ip, data.port)) {
         printf("Connect http server failed, ip:%s\n", data.ip.c_str());

         return false;
     }

     printf("Send http request:\n%s\n", requestTxt.c_str());

     // 发送请求
     if (!sendHttpRequest(socketId, &requestTxt)) {
         printf("Send http request failed\n");

         return false;
     }

     // 接受响应
     string responseTxt;
     recvHttpResponse(socketId, &responseTxt);

     printf("Recive http response:\n%s\n", responseTxt.c_str());

     // 保存数据
     if (!saveHttpData(&responseTxt, filePath, (fileName.length() == ) ? data.resName : fileName)) {
         printf("Save response data failed\n");
         return false;
     }

     closesocket(socketId);

     printf("-------------------------------------\n");

     return true;
 }

使用方法：

 string url = "http://static.youku.com/index/img/master.png";
 getHttpResource(url);