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download an image using inet1.execute instead of .open

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  download an image using inet1.execute instead of .open David <rataxes@post.com> - 2012-07-18 15:13 -0700
    Re: download an image using inet1.execute instead of .open Deanna Earley <dee.earley@icode.co.uk> - 2012-07-19 10:22 +0100
      Re: download an image using inet1.execute instead of .open "Theo Tress" <rbk@online.de> - 2012-07-25 18:44 +0200
        Re: download an image using inet1.execute instead of .open Deanna Earley <dee.earley@icode.co.uk> - 2012-07-26 10:21 +0100

#1378 — download an image using inet1.execute instead of .open

Hello VB ppl,

I'm writing a custom scraper tool that will fetch web data from a specific site.  Normally I would use the open method with internet transfer control but this specific site rejects http requests from the user agent associated with open.  If I use the execute method and custom user agent string I can get in.  The tool works fine for the text of the page, but now I want to tweak it to fetch images as well.  I'm having trouble figuring out how to populate my binary data variable to take in the stream produced by the control.  I've searched this group and other resources but I'm just more confused now.  Maybe someone can help me out.

The basic fetch code:

sub getImage()
  Inet1.Protocol = icHTTP
  Inet1.Execute URL, "GET", , "User-Agent: testing" & vbCrLf
  While Inet1.StillExecuting
    DoEvents
  Wend
end sub

Now if this was still text data I wanted I would use this:

Sub Inet1_StateChanged(ByVal state As Integer)
Dim data$, finalData$
    Select Case state
      Case 12 'icResponseCompleted
        data = Inet1.getChunk(4096)
        While data <> ""
          finalData = finalData & data
          data = Inet1.getChunk(4096)
        Wend
        'file write routine using finalData
...
end sub

But with binary data I'm getting type mismatch errors and such.  For one thing I don't know how to test whether the stream is done or not (as done above by testing if data="").  Nor do I know how to concatenate two binary variables or what the equivalent process would be if concatenate is the wrong concept.

Sub Inet1_StateChanged(ByVal state As Integer)
Dim data() As Byte, finalData() As Byte
  Select Case state
    Case 12 'icResponseCompleted
      data = Inet1.getChunk(1024, icByteArray)
      While data > 0
        finalData = finalData & data
        data = Inet1.getChunk(1024, icByteArray)
      Wend
      'file write routine using data().
...
  End Select
End Sub


Any ideas or suggestions?  I think once I get the data into the variable properly I can figure out how to write it out as a file.  Thanks for any assistance.

--David

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#1384

On 18/07/2012 23:13, David wrote:
> Hello VB ppl,
>
> I'm writing a custom scraper tool that will fetch web data from a
> specific site.  Normally I would use the open method with internet
> transfer control but this specific site rejects http requests from
> the user agent associated with open.  If I use the execute method and
> custom user agent string I can get in.  The tool works fine for the
> text of the page, but now I want to tweak it to fetch images as well.
> I'm having trouble figuring out how to populate my binary data
> variable to take in the stream produced by the control.  I've
> searched this group and other resources but I'm just more confused
> now.  Maybe someone can help me out.
>
> The basic fetch code:
>
> sub getImage()
>    Inet1.Protocol = icHTTP
>    Inet1.Execute URL, "GET", , "User-Agent: testing" & vbCrLf
>    While Inet1.StillExecuting
>      DoEvents
>    Wend
> end sub
>
> Now if this was still text data I wanted I would use this:
>
<SNIP>
>
> But with binary data I'm getting type mismatch errors and such.  For
> one thing I don't know how to test whether the stream is done or not
> (as done above by testing if data="").  Nor do I know how to
> concatenate two binary variables or what the equivalent process would
> be if concatenate is the wrong concept.
>
<SNIP>
>
> Any ideas or suggestions?  I think once I get the data into the
> variable properly I can figure out how to write it out as a file.
> Thanks for any assistance.

VB6 doesn't allow you to just append to an array.

Your best bet is to create a large byte array (to fit the image you 
expect), and then CopyMemory() each chunk into that point of your final 
buffer.
You can check the size to see if the new buffer will fit first then 
extend it (Redim Preserve) by a reasonable amount if needed.
When it's finished, you know how much you've received and then truncate 
the array (Redim Preserve again).

-- 
Deanna Earley (dee.earley@icode.co.uk)
i-Catcher Development Team
http://www.icode.co.uk/icatcher/

iCode Systems

(Replies direct to my email address will be ignored. Please reply to the 
group.)

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#1446

> VB6 doesn't allow you to just append to an array.

But having an array A(100) you can do a ReDim Preserve A(300) to obtain a 
larger array and specify A(100) as base address in a subroutine call instead 
of A() which would implicitly specify A(0), and in that way you can import 
dara into an array beginning at position 100 in an easy way. 

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#1454

On 25/07/2012 17:44, Theo Tress wrote:
>> VB6 doesn't allow you to just append to an array.
>
> But having an array A(100) you can do a ReDim Preserve A(300) to obtain
> a larger array and specify A(100) as base address in a subroutine call

Correct.

> instead of A() which would implicitly specify A(0)

Incorrect.

A or A() passes the array itself.
A(0) passes the first item (whatever type it is)
A(100) Passes the 101th item (whatever type it is)

IF you're calling a Win32 API function (like CopyMemory) that expects a 
pointer, you can pass VarPtr(a(XX)) (or a(XX) by ref) and they can work 
out the rest from there, but anything that expects or returns "an array" 
needs the full array, unless it also accepts an offset as a separate 
parameter.

-- 
Deanna Earley (dee.earley@icode.co.uk)
i-Catcher Development Team
http://www.icode.co.uk/icatcher/

iCode Systems

(Replies direct to my email address will be ignored. Please reply to the 
group.)

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