File Dowload: Restart

Blitz3D Forums/Blitz3D Beginners Area/File Dowload: Restart

Gauge
 #1
How can you restart a downloading file, say you've read 5,000 bytes, and want to start at the 5001 byte, what do you need to send? Thanks.

Sledge
 #2
Use a download manager (Fresh is free and seems to do the job) or hope that IE resumes automatically when you retry (which it sometimes does).

Gauge
 #3
i have fresh actually, but i'm trying to do it with blitz, any help??

Sledge
 #4
Sorry, there's been so much OT posting lately I assumed you were making a general enquiry. Never explored this stuff with Blitz so I can't help you I'm afraid.

Erroneouss
 #5
Here's a Downloading code snippet from the Code Arcs...
; -----------------------------------------------------------------------------
; BlitzGet Deluxe -- based on Mark Sibly's HTTPGet code...
; -----------------------------------------------------------------------------
; WARNING: WILL OVERWRITE EXISTING FILES OF THE SAME NAME!
; -----------------------------------------------------------------------------

; -----------------------------------------------------------------------------
; To do:
; -----------------------------------------------------------------------------
; 
; NEED TO CHECK FOR CUTOFFS and... gulp... RESUME? Currently keeps d/l'ing
; nothing if the download is aborted by the server, until the full byte-count
; has been "downloaded"... maybe I'll just say "d/l bombed out" for now...! :)
;
; Parse headers for:
;	404
;
; More to come...
;
; -----------------------------------------------------------------------------

; -----------------------------------------------------------------------------
; Quick demo... downloads to your Windows "Temp" folder
; -----------------------------------------------------------------------------


AppTitle "BlitzGet Deluxe"
Graphics 640, 480, 0, 2
SetBuffer BackBuffer ()

; SMALL TEST (8K):
	;download$	 = "http://www.google.com/images/title_homepage4.gif"			; Google homepage logo
	download$    = "http://www.blitzbasic.com/img/brllogo-thin.png"
;	download$	 = "http://www.blitzbasic.co.nz/zbrowse/blitzfaq/blitzfaq.html" ; Blitz FAQ

; BIG TEST (360K):
;	download$	 = "http://www.hi-toro.com/mp3/diffusion.mp3"					; Pretty music... :P

; SAVE LOCATION: Windows Temp folder:
	downloadDir$ = SystemProperty ("TempDir")          ; "G:\My Documents\Downloads"

If BlitzGet (download$, downloadDir$, "")
	result$ = "Download Complete!" + Chr (10) + "Saved in " + downloadDir$
Else
	result$ = "Download error!  Version Not Released."
EndIf

RuntimeError result$

; Temporary, for quick results...

Global header$
Global bytesToRead
Global date$
Global server$
Global contentType$
Global initialReply$

; -----------------------------------------------------------------------------
; File download function
; -----------------------------------------------------------------------------
; webFile$  -- file to download
; saveDir$  -- directory to download into
; saveFile$ -- filename to save as (use "" to use name of downloaded file automatically)
; -----------------------------------------------------------------------------
; Note that if you just provide a web server address, the document downloaded will
; be named "Unknown file.txt"
; -----------------------------------------------------------------------------

Function BlitzGet (webFile$, saveDir$, saveFile$)

	; -------------------------------------------------------------------------
	; Strip "http://" if provided
	; -------------------------------------------------------------------------
	If Left (webFile$, 7) = "http://" Then webFile$ = Right (webFile$, Len (webFile$) - 7)

	; -------------------------------------------------------------------------
	; Split into hostname and path/filename to download
	; -------------------------------------------------------------------------
	slash = Instr (webFile$, "/")
	If slash
		webHost$ = Left (webFile$, slash - 1)
		webFile$ = Right (webFile$, Len (webFile$) - slash + 1)
	Else
		webHost$ = webFile$
		webFile$ = "/"
	EndIf
		
	; -------------------------------------------------------------------------
	; Add trailing slash to download dir if not given
	; -------------------------------------------------------------------------
	If Right (saveDir$, 1) <> "" Then saveDir$ = saveDir$ + ""

	; -------------------------------------------------------------------------
	; Save filename -- get from webFile$ if not provided
	; -------------------------------------------------------------------------
	If saveFile$ = ""
		If webFile = "/"
			saveFile$ = "Unknown file.txt"
		Else
			For findSlash = Len (webFile$) To 1 Step - 1
				testForSlash$ = Mid (webFile$, findSlash, 1)
				If testForSlash$ = "/"
					saveFile$ = Right (webFile$, Len (webFile$) - findSlash)
					Exit
				EndIf
			Next
			If saveFile$ = "" Then saveFile$ = "Unknown file.txt"
		EndIf
	EndIf

	; DEBUG

	www = OpenTCPStream (webHost$, 80)

	If www
	
		WriteLine www, "GET " + webFile$ + " HTTP/1.1" ; GET / gets default page...
		WriteLine www, "Host: " + webHost$
		WriteLine www, "User-Agent: BlitzGet Deluxe"
		WriteLine www, "Accept: */*"
		WriteLine www, ""
		
		; ---------------------------------------------------------------------
		; Find blank line after header data, where the action begins...
		; ---------------------------------------------------------------------
				
		Repeat

			Cls
			
			header$ = ReadLine (www)

			reply$ = ""
			pos = Instr (header$, ": ")
			If pos
				reply$ = Left (header$, pos + 1)
			EndIf

			Select Lower (reply$)
				Case "content-length: "
					bytesToRead = ReplyContent (header$, reply$)
				Case "date: "
					date$ = ReplyContent (header$, reply$)
				Case "server: "
					server$ = ReplyContent (header$, reply$)
				Case "content-type: "
					contentType$ = ReplyContent (header$, reply$)
				Default
					If gotReply = 0 Then initialReply$ = header$: gotReply = 1
			End Select

			DisplayResponse ()

			Flip
			
		Until header$ = "" Or (Eof (www))
				
		If bytesToRead = 0 Then Goto skipDownLoad
		
		; ---------------------------------------------------------------------
		; Create new file to write downloaded bytes into
		; ---------------------------------------------------------------------
		save = WriteFile (saveDir$ + saveFile$)
		If Not save Then Goto skipDownload

		; ---------------------------------------------------------------------
		; Incredibly complex download-to-file routine...
		; ---------------------------------------------------------------------

		For readWebFile = 1 To bytesToRead
		
			If Not Eof (www) Then WriteByte save, ReadByte (www)
			
			; Call BytesReceived with position and size every 100 bytes (slows down a LOT with smaller updates)
			
			tReadWebFile = readWebFile
			If tReadWebFile Mod 100 = 0 Then BytesReceived (readWebFile, bytesToRead)

		Next

		CloseFile save
		
		; Fully downloaded?
		If (readWebFile - 1) = bytesToRead
			success = 1
		EndIf
		
		; Final update (so it's not rounded to nearest 100 bytes!)
		BytesReceived (bytesToRead, bytesToRead)
		
		.skipDownload
		CloseTCPStream www
		
	Else
	
		RuntimeError "Failed to connect"
		
	EndIf
	
	Return success
	
End Function

; -----------------------------------------------------------------------------
; User-defined update function, called every 100 bytes of download -- alter to suit!
; -----------------------------------------------------------------------------
; TIP: Pass a user-defined type instead, with all data (this stuff plus URL, local filename, etc)
; -----------------------------------------------------------------------------
Function BytesReceived (posByte, totalBytes)
	; Example update code...
	Cls
	Text 0, 10, "Downloading file -- please wait..."
	Text 0, 30, "Received: " + posByte + "/" + totalBytes + " bytes (" + Percent (posByte, totalBytes) + "%)"
	DisplayResponse ()
	Flip
End Function

; -----------------------------------------------------------------------------
; Handy percentage function
; -----------------------------------------------------------------------------
Function Percent (part#, total#)
	Return Int (100 * (part / total))
End Function

Function ReplyContent$ (header$, reply$)
	Return Right (header$, Len (header$) - Len (reply$))
End Function

; Temporary, for quick results...

Function DisplayResponse ()
	Text 0, 80, "Header: " + initialReply$
	Text 0, 100, "Date: " + date$
	Text 0, 120, "Server: " + server$
	Text 0, 140, "Content-Type: " + contentType$
	Text 0, 160, "Content-Length: " + bytesToRead
End Function


Craig Kiesau
 #6
Look here for official information on resuming partial downloads: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35

Essentially add a header to the get part with "Range: <ByteToStartAt>-<ByteToStopAt>"

You should be able to omit the ByteToStopAt part if you don't know the Content-Length at the start.

Gauge
 #7
thanks all, I think i might have figured it out. I'll let ya know

Gauge
 #8
Okay i figured it out, all you have to do is add range: bytes downloaded- like this:

WriteLine www, "GET " + webFile$ + " HTTP/1.1"
Writeline www, "Range: bytes=500-"
WriteLine www, "Host: " + webHost$
WriteLine www, "User-Agent: BlitzGet"
WriteLine www, "Accept: */*"
WriteLine www, ""