file size limit in Response.binarywrite

[S N]

I am using the following code to hide the download url of files on my website. The code uses Response.Binarywrite to send file to the client.
Kindly indicate the maximum size of the file that can be downloaded using this method.
I am hosting this site on a public server, so I will not be able to change anything on the webserver. Kindly indicate what can be done to ensure that the above method remains valid for any file size download.

call Response.AddHeader("Content-Disposition","attachment; filename=""" & strFileSave & """")
Response.ContentType = "bad/type"
Set Fsys = Server.CreateObject("Scripting.FileSystemObject")
Set TS = Fsys.GetFile(strFile).OpenAsTextStream(1, -1)
Do While Not (TS.AtEndOfStream)
Response.BinaryWrite(TS.Read(1))
Loop

 

[Old Pedant]

I am using the following code to hide the download url of files on my website. The code uses Response.Binarywrite to send file to the client.
Kindly indicate the maximum size of the file that can be downloaded using this method.
call Response.AddHeader("Content-Disposition","attachment; filename=""" & strFileSave & """")
Response.ContentType = "bad/type"
Set Fsys = Server.CreateObject("Scripting.FileSystemObject")
Set TS = Fsys.GetFile(strFile).OpenAsTextStream(1, -1)
Do While Not (TS.AtEndOfStream)
Response.BinaryWrite(TS.Read(1))
Loop

Ummm...that code isn't goint to work, anyway. See the method
OpenAsTEXTstream
???

You really can only use FileSystemObject reliably with text files; it wasn't
designed to work with binary files.

You need to use ADODB.Stream object, instead.
http://msdn.microsoft.com/en-us/library/ms675032(VS.85).aspx

And then you could easily control the amount you write in each chunk by just
limiting the amount you Read each time.

 

[S N]

Thanks for the advice. I was under the impression that ADODB can be used
only for databases. This is the first instance of using it on files.
Can you please provide a sample code to hide download url by using ADODB
stream, while there should be no limit on the size of files to be
downloaded.

..

 

[Old Pedant]

Can you please provide a sample code to hide download url by using ADODB
stream, while there should be no limit on the size of files to be
downloaded.

Good old Atrax has a couple of demos.

Note that his code is written in JScript for ASP, but conversion to VBScript
should be easy.

http://rtfm.atrax.co.uk/infinitemonkeys/articles/asp/934.asp
and
http://rtfm.atrax.co.uk/infinitemonkeys/articles/asp/935.asp

If you need more help, ask.

 

[S N]

I would be grateful if you can give me vbscript code as well.
I would also like to clarify that the code for jscript forces save as
dialog. What if we want to hide the download url but dont want to force the
save as dialog, instead just want to see the pdf file within the browser
window itself.
Kindly advise on this.

Thanks in anticipation.

 

[Anthony Jones]

I am using the following code to hide the download url of files on my
website. The code uses Response.Binarywrite to send file to the >client.
Kindly indicate the maximum size of the file that can be downloaded using
this method.
I am hosting this site on a public server, so I will not be able to change
anything on the webserver. Kindly indicate what can be done to >ensure that
the above method remains valid for any file size download.

call Response.AddHeader("Content-Disposition","attachment; filename=""" &
strFileSave & """")
Response.ContentType = "bad/type"
Set Fsys = Server.CreateObject("Scripting.FileSystemObject")
Set TS = Fsys.GetFile(strFile).OpenAsTextStream(1, -1)
Do While Not (TS.AtEndOfStream)
Response.BinaryWrite(TS.Read(1))
Loop

Use this code:-

Sub SendFileToResponse(FilePath, FileName)

Const clChunkSize = 1048576 ' 1MB

Dim oStream, i
Response.Buffer = False

Response.ContentType = "application/octet-stream"
Response.AddHeader "Content-Disposition", _
"attachment; Filename=" & FileName

Set oStream = Server.CreateObject("ADODB.Stream")
oStream.Type = 1 ' Binary
oStream.Open
oStream.LoadFromFile FilePath

For i = 1 To oStream.Size \ clChunkSize
Response.BinaryWrite oStream.Read(clChunkSize)
Next
If (oStream.Size Mod clChunkSize) <> 0 Then
Response.BinaryWrite oStream.Read(oStream.Size Mod clChunkSize)
End If
oStream.Close

End Sub

SendFileToResponse strFile, strFileSave

Note the Response.Buffer = false allows you to send a file of any size.

 

[S N]

What if we want to use sendfiletoresponse but dont want to force the save as
dialog, instead just want to see the pdf file within the browser window
itself.
is there any change required in the code to achieve this.

 

[Anthony Jones]

What if we want to use sendfiletoresponse but dont want to force the save
as dialog, instead just want to see the pdf file within the browser window
itself.
is there any change required in the code to achieve this.

If you know its a pdf then change content-type to application/pdf and remove
the attachment; keyword from content-disposition.

 

[S N]

Following error received:

Response object error 'ASP 0157 : 80004005'
Buffering On

/test/dl.asp, line 2

Buffering cannot be turned off once it is already turned on.


Please note that I am hosting the site on a public server so there is no way
to ask the web admin to configure the server specifically for me. In such a
situation is it possible to eliminate the error as indicated above. Further,
if I am not able to switch off the response.buffer, will there be any
limitation on the size of file that i can download using
response.binarywrite?

 

[S N]

Also advise the content type in case the file is an excel file, word
document, exe file, zip file etc.

Thanks in advance.

 

[Anthony Jones]

Following error received:

Response object error 'ASP 0157 : 80004005'
Buffering On

/test/dl.asp, line 2

Buffering cannot be turned off once it is already turned on.

You get this error if there is anything in your page or includes at the top
of the page which writes stuff to the response before your code has run.
Note any static content in the page will be sent.

Typical a page of this sort looks like:-

<!-- #include .... some common include -->
<%

' Code here that should note writing anything.
'My code I posted to you with your mods.
%>

Where the include is of a similar structure defininng constants and utility
functions.

Please note that I am hosting the site on a public server so there is no
way to ask the web admin to configure the server specifically for me.

Whilst an admin may have configured the buffer to be on (which is the
default) you can set it off as long as you do so before sending anything.

In such a situation is it possible to eliminate the error as indicated
above. Further, if I am not able to switch off the response.buffer, will
there be any limitation on the size of file that i can download using
response.binarywrite?

Without turning it off there will be a limitation. The is a buffer size
limit that a public server administrator will almost certainly have
configured (the default on IIS6 is 4MB).

 

[Anthony Jones]

Also advise the content type in case the file is an excel file, word
document, exe file, zip file etc.

Try Google: mime type xxx where xxx = doc, exe etc.

 

[S N]

Got it. But now a new problem.
When I place <%Response.Buffer=False%> as the first line of my asp file, no
file is downloaded and no message comes.
However, when I delete the <%Response.Buffer=False%> line then the file
downloads as expected.

Please advise.

 

[S N]

Also I am linking the download code from another file. When I run the
download code without referring to it from another file, it runs. But When I
refer it from another file and it has <%Response.Buffer=False%> line, then I
get the message
Response object error 'ASP 0156 : 80004005'

Header Error

/test/dl.asp, line 114

The HTTP headers are already written to the client browser. Any HTTP header
modifications must be made before writing page content.



Please help

 

[S N]

I got it finally. Thanks.
Just one clarification
You intended
For i = 1 To oStream.Size / clChunkSize

or

For i = 1 To oStream.Size \ clChunkSize

Please clarify.

Also I am linking the download code from another file. When I run the
download code without referring to it from another file, it runs. But When
I refer it from another file and it has <%Response.Buffer=False%> line,
then I get the message
Response object error 'ASP 0156 : 80004005'

Header Error

/test/dl.asp, line 114

The HTTP headers are already written to the client browser. Any HTTP
header modifications must be made before writing page content.



Please help

 

[Old Pedant]

Just one clarification
You intended
For i = 1 To oStream.Size / clChunkSize
or
For i = 1 To oStream.Size \ clChunkSize

He *intended* the latter.

The backslash operator means "integer division" in VBScript (and VB and
VB.NET) code.

That is,
a \ b
is equivalent to
INT( a / b )

********************

Also, you don't need to mess with Response.Buffer=False, at all.

Just follow each
Response.BinaryWrite
with
Response.Flush

Now the buffer will never get more full than one "chunkSize".

 

[Anthony Jones]

He *intended* the latter.

The backslash operator means "integer division" in VBScript (and VB and
VB.NET) code.

That is,
a \ b
is equivalent to
INT( a / b )

********************

Also, you don't need to mess with Response.Buffer=False, at all.

Just follow each
Response.BinaryWrite
with
Response.Flush

Now the buffer will never get more full than one "chunkSize".

Yes that would work. However it would mask unintended errors that turning
the buffer off right at the top of the code exposes.

 

[S N]

Yes that would work. However it would mask unintended errors that turning
the buffer off right at the top of the code exposes.

what kind of errors would be exposed by turning off the buffer. kindly
elaborate.

 

[Anthony Jones]

what kind of errors would be exposed by turning off the buffer. kindly
elaborate.

Well the sort of problems you've discovered where you may unintentionaly be
placing things in the output buffer that you didn't want present. Example:-

<!-- #include /virtual="/someinclude.asp" -->
<%
Response.ContentType = "application/octet-stream"
Do Until ....
Response.BinaryWrite SomeStuff
Response.Flush
Loop
%>

'someinclude.asp

<!-- Ooops some accidental static content here -->
<%

'utility code

%>

Placing a Response.Buffer at the top of your page would barf immediately on
that line alerting you to a problem.
It also saves you having to remember to Response.Flush if you have multiple
places where you write to the buffer.