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A class to download files from the net

, 16 Apr 2002 CPOL
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A simple class to ease the task of downloading files from the net

Sample Image - WebGrab.gif

CWebGrab is a simple class that allows you to quickly and easily download files from the net. The class is merely a light wrapper for the MFC internet classes, and as such supports any protocol that the MFC classes support.

The class is extremely simple to use and has only one main function that you need to call: CWebGrab::GetFile. The syntax is:

BOOL GetFile(LPCTSTR szURL, CString& strBuffer, 
             LPCTSTR szAgentName = NULL, CWnd* pWnd = NULL);

Downloads a file from the given URL

  • szURL is the URL
  • strBuffer is a CString buffer that will hold the contents of the downloaded file
  • szAgentName is the agent name you want to send to the website (may be NULL)
  • pWnd is a status window. Status updates will be sent to this window using SetWindowText()
BOOL GetFileInfo(LPCTSTR  szURL, CString& strLastModified, DWORD& dwSize,
                 DWORD& dwServerError, LPCTSTR szAgentName = NULL, 
                 CWnd* pWnd = NULL);

(Added by Ravi Bhavnani) Retrieves the information about a file from the given URL

  • szURL is the URL
  • strLastModified is a CString buffer that will hold the last modified date of the file
  • dwServerError will return any error codes that were raised.
  • szAgentName is the agent name you want to send to the website (may be NULL)
  • pWnd is a status window. Status updates will be sent to this window using SetWindowText()

Bryce Burrows kindly updated the code to include the following functions:

void SetUseProxy(bool use);

Sets whether or not to use a proxy

void SetProxyServer(LPCSTR server);

Sets the proxy server

void SetProxyPort(UINT port);

Sets the proxy port

void SetProxy(LPCSTR proxy, WORD port, bool use=true);

Sets the proxy information in one call

void SetForceReload (bool bForceReload)

Sets whether or not to force a reload when downloading a document. If a force reload is set the the document will not be a cached version.

void GetForceReload()

Gets whether or not to force a reload when downloading a document.

void SetTimeOut(DWORD timeOut);

Sets the timeout for the operation

double GetRate();

Retrieves the download rate in Kb/sec

SHORT GetErrorCode();
CString GetErrorMessage();

Get the error code and message (if any)

Example of use

#include "webgrab.h"

void CWebGrabberDlg::OnDownload() 
{
    CString strBuffer;
    CWebGrab grab;
    if (grab.GetFile("http://www.mysite.com/index.htm", // the url
                     strBuffer,                         // buffer for data
                     _T("WebGrab demo"),                // agent name
                     GetDlgItem(IDC_STATUS)))           // Plain ol' CStatic window
    {
        TRACE0("everything went OK\n")
    }
}

History

26 Jan 2002 - Bryce Burrows kindly added the proxy code.

16 Feb 2002 - Bryce Burrows source code update.

2 Mar 2002 - Ravi Bhavnani added a "force reload" option to ensure that the downloaded data is not read from the cache, plus Get/SetForceReload() functions.

17 Apr 2002 - Ravi Bhavnani added a GetFileInfo

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Chris Maunder
Founder CodeProject
Canada Canada
Chris is the Co-founder, Administrator, Architect, Chief Editor and Shameless Hack who wrote and runs The Code Project. He's been programming since 1988 while pretending to be, in various guises, an astrophysicist, mathematician, physicist, hydrologist, geomorphologist, defence intelligence researcher and then, when all that got a bit rough on the nerves, a web developer. He is a Microsoft Visual C++ MVP both globally and for Canada locally.
 
His programming experience includes C/C++, C#, SQL, MFC, ASP, ASP.NET, and far, far too much FORTRAN. He has worked on PocketPCs, AIX mainframes, Sun workstations, and a CRAY YMP C90 behemoth but finds notebooks take up less desk space.
 
He dodges, he weaves, and he never gets enough sleep. He is kind to small animals.
 
Chris was born and bred in Australia but splits his time between Toronto and Melbourne, depending on the weather. For relaxation he is into road cycling, snowboarding, rock climbing, and storm chasing.
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Comments and Discussions

 
QuestionDownloaded file corrupt in VS2013 - UNICODE problem? Pinmemberrenninha18-Jun-14 3:51 
QuestionPOST instead of GET Pinmember.dan.g.5-Feb-12 17:27 
QuestionProblem with files Pinmembervantomas12-Aug-11 4:08 
Generalsame code in "pure c++" (non-MFC) Pinmembermimosa10-Jun-11 21:27 
QuestionHow to grab an html file generated with embebded javascript? Pinmembermimosa7-Aug-10 10:56 
GeneralWhere are downloaded files Pinmembernicolla100331-Jul-10 7:35 
Generaltype files Pinmemberbarhouming9-Jul-10 0:54 
QuestionHow can I write to the net? PinmemberDanYELL14-Feb-09 15:32 
GeneralQuestion about WebGrab... PinmemberLilMoke25-Nov-08 5:13 
GeneralWebGrab with SSL and Invalid Certificate PinmemberDoug Knudson15-Oct-07 3:15 
GeneralRe: WebGrab with SSL and Invalid Certificate PinmemberLery7817-Apr-08 11:59 
GeneralProblems [modified] PinmemberAtridas16-Feb-07 9:09 
GeneralRe: Problems Pinmembereffem22-Feb-07 0:57 
Questionproxy ? Pinmembereffem16-Feb-07 1:36 
AnswerRe: proxy ? PinmemberA duley31-Aug-07 7:02 
GeneralHTTP Authentication PinmemberPriyank Bolia3-Mar-06 2:47 
GeneralBUG: Unicode is not supported, wrong buffer size PinmemberAlex_Raider28-Feb-06 22:19 
GeneralRe: BUG: Unicode is not supported, wrong buffer size PinmemberSandro7819-Jun-08 4:01 
GeneralProxy Not working Pinmembersrivathsan.a9-Jan-06 20:45 
Generalhttps PinmemberOrxorand21-Nov-05 0:50 
GeneralAnother buggie Pinmemberdchris_med29-Oct-05 11:06 
GeneralConnect Timout Failed !!! Hung my machine ! Pinmembersonawane ajay23-Mar-05 0:36 
GeneralProblem with setting timeout PinmemberPetoG15-Dec-04 0:02 
Generaluse in pocketPC Pinmemberchupas228-Nov-04 23:32 
GeneralA Bug and and how to fix it! PinmemberEhsan-de-Burge28-Aug-04 20:50 

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