Ftp的断点下载实现-白红宇

Ftp的断点下载实现

阅读量：6628 次

发布时间：2019-06-25

本文共 3051 字，大约阅读时间需要 10 分钟。

思路：首先获取本地临时文件的大小，在通过FTp的REST命令获取远程文件的偏移，然后再RETR命令在偏移处下载。while循环对比本地文件和远程文件的字节大小，如此

不断的反复以上过程，直到远程文件字节和本地文件字节一样，退出循环，下载完成。

1    long remote_file_size = m_ftp->getFileLength(remoteFileName.toStdString()); 2     long recvSize = 0; 3  4     if (remote_file_size == -1 ) 5     { 6         return false; 7     } 8  9     int conn_count = 10;10     11     while (conn_count != 0 && local_file_size != remote_file_size)12     {13         recvSize = m_ftp->Get2(remoteFileName.toStdString(), tmp_save_file_name.toStdString(), local_file_size);14         if (recvSize <= 0)15         {16             msleep(50);17             if (!reConnect())18             {19                 break;20             }21             conn_count--;22         }23        24         local_file_size = getLocalFileSize(tmp_save_file_name);25     }

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1 FTP_API CFTP::Get2(const std::string &strRemoteFile, const std::string &strLocalFile, const int pos)2 {3     return downLoad2(strRemoteFile, strLocalFile, pos);4 }

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1 FTP_API CFTP::downLoad2(const std::string &strRemoteFile, const std::string& strLocalFile, const int pos /*= 0*/, const unsigned int length /*= 0*/) 2 { 3     assert(length >= 0); 4  5     FILE *file = NULL; 6     unsigned long nDataLen = FTP_DEFAULT_BUFFER; 7     char strPos[MAX_PATH] = { 0 }; 8     int data_fd = socket(AF_INET, SOCK_STREAM, 0); 9 10     assert(data_fd != -1);11 12     if ((length != 0) && (length < nDataLen))13     {14         nDataLen = length;15     }16     char *dataBuf = new char[nDataLen];17     if (dataBuf == NULL)18     {19         return -1;20     }21     memset(dataBuf, 0, sizeof(dataBuf));22 23     //assert(dataBuf != NULL);24 25     sprintf(strPos, "%d", pos);26 27     if (createDataLink(data_fd) < 0)28     {29         trace("@@@@ Create Data Link error!!!\n");30         return -1;31     }32 33 34     std::string strCmdLine = parseCommand(FTP_COMMAND_DOWNLOAD_POS, strPos);//param 1 为REST命令35     if (Send(m_cmdSocket, strCmdLine) < 0)36     {37         return -1;38     }39     trace("@@@@Response: %s\n", serverResponse(m_cmdSocket).c_str());40 41 42     strCmdLine = parseCommand(FTP_COMMAND_DOWNLOAD_FILE, strRemoteFile);//param 1为RETR命令43 44     if (Send(m_cmdSocket, strCmdLine) < 0)45     {46         return -1;47     }48 49     std::string strResponse = serverResponse(m_cmdSocket);50     trace("@@@@Response: %s\n", strResponse.c_str());51 52     file = createLocalFile2(std::string(strLocalFile));53     assert(file != NULL);54 55     int len = 0;56     int nReceiveLen = 0;57     while ((len = getData(data_fd, dataBuf, nDataLen)) > 0)58     {59         nReceiveLen += len;60 61         int num = fwrite(dataBuf, 1, len, file);62         memset(dataBuf, 0, sizeof(dataBuf));63 64       65         trace("Num:%d, nReceiveLen:%d\n", num, nReceiveLen);66      67     }68 69     Close(data_fd);70     fclose(file);71     delete[]dataBuf;72 73     return nReceiveLen;74 75 }

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references:

http://blog.chinaunix.net/uid-7377299-id-112977.html

转载于:https://www.cnblogs.com/foohack/p/5640106.html

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