使用Boost实现Http断点续传

不多说了, 自已也是一知半解的, 按虎画猫的..

慢慢学, 不要着急,
将它揉碎了, 嚼烂了, 变成自已的. .

上代码:

// testc.cpp : Defines the entry point for the console application.//#include "stdafx.h"#include <fstream>#include <boost/asio.hpp>#include <boost/asio/ip/tcp.hpp>#include <boost/algorithm/string.hpp>using boost::asio::ip::tcp;struct HttpResponse{public:explicit HttpResponse(){ clear();}std::string http_version;// 版本unsigned int status_code;// 状态码std::string status_message;// 状态std::string header;// HTTP包头std::string body;           // HTTP返回的内容std::string content_type;std::string modify_time;unsigned int content_length;unsigned int total_length;unsigned int offset;void clear(){http_version.clear();status_code = -1;status_message.clear();header.clear();content_type.clear();modify_time.clear();content_length = 0;total_length = 0;offset = 0;body.clear();}};struct DownloadInfo{DownloadInfo(){id = 0;url.clear();filename.clear();md5.clear();writesize = 0;continued = false;lasterr = 0;trycount = 0;}int id;std::string url;std::string filename;std::string md5;int writesize;bool continued;int lasterr;int trycount;};int  GetTempFileRange( const std::string& fn );bool GetHttpFile(const std::string& szHost, const std::string& szParam);bool AnalyseHeader(HttpResponse& result, std::string& packetString, int nEndHeader);bool WriteFile( const std::string& fn, int rangeStart, std::string& packetString, DownloadInfo* d_diCurrent );std::ofstream f_ofsSave;int _tmain(int argc, _TCHAR* argv[]){std::string szHost ("192.168.1.102");std::string szParam("/DoDo/aishen.mp4");GetHttpFile(szHost, szParam);return 0;}// 获取文件bool GetHttpFile(const std::string& szHost, const std::string& szParam){// 创建下载信息DownloadInfo* d_diCurrent = new DownloadInfo();d_diCurrent->filename = "DownLoadFile";d_diCurrent->continued = true;if(d_diCurrent->continued) {d_diCurrent->filename = d_diCurrent->filename+std::string(".td");}try{boost::asio::io_service io_serv;// Get a list of endpoints corresponding to the server name.std::string szService ("http");std::string szIp = szHost;int i = szHost.find(":") ;if (i != -1){szService = szHost.substr(i+1);szIp = szHost.substr(0, i);}tcp::resolver::query query(szIp, szService);tcp::resolver m_resolver(io_serv);// 创建SOCKETtcp::socket s_socket(io_serv); tcp::resolver::iterator endpoint_iterator = m_resolver.resolve(query), end_it;// Try each endpoint until we successfully establish a connection.tcp::resolver::iterator it = boost::asio::connect(s_socket, endpoint_iterator);if(it == end_it)return false;boost::asio::streambuf request;{// 封装请求HTTP GETstd::ostream request_stream(&request);request_stream << "GET " ;request_stream << szParam << " HTTP/1.1\r\n";request_stream << "Host: " << szHost << "\r\n";request_stream << "Accept: */*\r\n";request_stream << "Pragma: no-cache\r\n";request_stream << "Cache-Control: no-cache\r\n";request_stream << "Connection: close\r\n";// 1. 是否开启断点续传, 如是则读取临时文件长度int rangeStart = 0;if (d_diCurrent->continued) {rangeStart = GetTempFileRange(d_diCurrent->filename);if (rangeStart) {request_stream << "Range: bytes=" << rangeStart << "- \r\n";}request_stream << "\r\n";}boost::asio::write(s_socket, request);boost::asio::streambuf response;std::ostringstream packetStream;try{// Read until EOF, writing data to output as we go.bool hasReadHeader = false;boost::system::error_code error;HttpResponse result;result.body.clear();while (boost::asio::read(s_socket, response,boost::asio::transfer_at_least(1), error)){packetStream.str("");packetStream << &response;std::string packetString = packetStream.str(); // 2. 是否已分析文件头if (!hasReadHeader){hasReadHeader = true;// 取出http headersize_t nEndHeader = packetString.find("\r\n\r\n");if(nEndHeader == std::string::npos)continue;if(!AnalyseHeader(result, packetString, nEndHeader)) {return false;}}// 3. 写入文件WriteFile(d_diCurrent->filename, rangeStart, packetString, d_diCurrent);}// 4. 关闭文件f_ofsSave.close();// 5. 文件改名std::string fn = "DownLoadFile.db";rename(d_diCurrent->filename.c_str(), fn.c_str());if (error != boost::asio::error::eof)throw boost::system::system_error(error);}catch (std::exception& e){std::cout << "Exception: " << e.what() << "\n";return false;}} }catch(std::exception& e) {std::cout << "Exception: " << e.what() << "\n";return false;}return true;}// *****************************************************// 分析文件头// *****************************************************bool AnalyseHeader(HttpResponse& result, std::string& packetString, int nEndHeader){result.header = packetString.substr(0, nEndHeader);// Check that response is OK.std::istringstream response_stream(result.header);response_stream >> result.http_version;response_stream >> result.status_code;std::string strLine;std::getline(response_stream, strLine);while (!strLine.empty()){if (strLine.find("Content-Type:") != std::string::npos){result.content_type = strLine.substr(strlen("Content-Type:"));result.content_type.erase(0, result.content_type.find_first_not_of(" "));}if (strLine.find("Content-Length:") != std::string::npos){result.content_length = atoi(strLine.substr(strlen("Content-Length:")).c_str());result.total_length = result.content_length;}if (strLine.find("Last-Modified:") != std::string::npos){result.modify_time = strLine.substr(strlen("Last-Modified:"));result.modify_time.erase(0, result.modify_time.find_first_not_of(" "));}if (strLine.find("Content-Range: bytes") != std::string::npos){std::string tmp = strLine.substr(strlen("Content-Range: bytes"));result.offset = atoi(tmp.substr(0, tmp.find('-')).c_str());int ipos = tmp.find('/');int ivalue = 0;if (ipos != std::string::npos){ivalue = atoi(tmp.substr(ipos+1).c_str());}if (ivalue) result.total_length = ivalue;}strLine.clear();std::getline(response_stream, strLine);}if ( result.http_version.substr(0, 5) != "HTTP/"){std::cout << "Invalid response\n";return false;}if (result.status_code != 200 && result.status_code != 206){std::cout << "Response returned with status code " << result.status_code << "\n";return false;}packetString.erase(0, nEndHeader + 4);return true;}// ************************************************************** // 获取临时文件大小// ************************************************************** int GetTempFileRange( const std::string& fn ){int rangeStart = 0;std::ifstream ifs;ifs.open(fn, std::ios_base::in | std::ios_base::binary );if (ifs.is_open()) {ifs.seekg(0, std::ios::end);rangeStart = ifs.tellg();}ifs.close();return rangeStart;}// **************************************************************// 写入文件// **************************************************************bool WriteFile( const std::string& fn, int rangeStart, std::string& packetString, DownloadInfo* d_diCurrent ){if (!f_ofsSave.is_open()){if (d_diCurrent->continued) {f_ofsSave.open(fn, std::ios_base::out | std::ios_base::binary | std::ios_base::app );if (f_ofsSave.is_open()) {f_ofsSave.seekp(rangeStart);d_diCurrent->writesize += rangeStart;//int range = f_ofsSave.tellp();}}else{f_ofsSave.open(fn, std::ios_base::out | std::ios_base::binary | std::ios_base::trunc );}if (!f_ofsSave.is_open()) {return false;}d_diCurrent->writesize = 0;}try {f_ofsSave.write(packetString.c_str(), packetString.length());d_diCurrent->writesize += packetString.length();}catch (std::exception &e){return false;}std::cout << " write size = "<<d_diCurrent->writesize<<"\n";return true;}