Here's an idea for you. I use some of the code below in my FileBase
product to receive uploads, although, I've added some "code" I think might
help you for grabbing just the header.

Although I'm not sure if the file descriptor that infile claims from the
form has already been loaded into either a StringIO or some other
"buffer" (i.e. already received in full from client), it's possible that
this is reading directly from the http stream coming from the client.

    infilename = REQUEST.form['attached_file'].filename  # Get filename
    infile = REQUEST.form['attached_file']     # Get the file descriptor
    myheader =    # Read up to 500 bytes
    infile.close()                 # Close the stream

This should be in an external method or product.

I haven't tested whether or not this will only let the client upload the
first 500 bytes, it's very possible zope takes in the entire file, and
puts it into a buffer that is like a file descriptor (hence StringIO).


On Wed, 11 Oct 2000, Paul Winkler wrote:

> Another way to look at it:
> I want to start uploading the file, but stop the upload
> almost immediately - after I've got enough to read the file
> header, but long before the upload would normally finish.
> Chris McDonough wrote:
> > 
> > Paul,
> > 
> > I'm sorry if I'm dropping context here, but I'm not sure what you mean when
> > you say "headers of files".
> > 
> > Do you just want to check the size of files before you put them in the ZODB?
> That would be useful, but I need more information than that.
> I need to read some of the file's description of itself
> that's commonly kept in a header at the beginning of a file.
> For example, take a .gif or .jpeg file and throw away all
> but the first (let's say) 1 kb of the file.
> If you try to open this truncated file with an image editor
> (gimp, photoshop, whatever) you'll have problems. But useful
> information is still stored in that first part of the file,
> as we can see using python and PIL.
> Example, on linux:
> head --bytes 1000 foo.gif > foo_truncated.gif
> python
> ...
> >>> import Image
> >>> test ='foo_truncated.gif', 'r')
> >>> test.size
> (210, 210)
> So in this case, we can find out that foo.gif is 210 x 210
> pixels even if we only have access to the first 1 kb of the
> 12 kb file.
> If the file in question is 1 MB or so, this trick becomes
> really useful.
> Suppose your web application needs an image about 1000 x
> 1000 pixels. You could warn the user if their image is too
> small to look good, or so big it's a waste of their time.
> So basically what I want to do is start uploading the file,
> but stop quickly.
> Now then, does anyone know how to do it?
> Thanks again,
> Paul
> -- 
> .................    paul winkler    ..................
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