Hi,
I'm a relatively new Python and brand new Flask user, so please bear with
me.
I'm developing a webapp that requires that I permit users to upload files
which are validated before I store them in their final location on the web
server's local filesystem. To satisfy this requirement, I have defined
helper methods that I use to create a temporary copy of a FileStorage
object that is processed to determine if it is valid. Once this check
passes, I then want to save the uploaded file in a permanent location.
Here's an example subset of my code:
def confirm():
amfile = request.files['zipfile']
if validate_file(amfile):
amfile.save(os.path.join("/www/docs",secure_filename(amfile.filename))
def validate_file(infile):
infile.save(os.path.join("/tmp",secure_filename(infile.filename))
# My validation code goes in here; I read the file in /tmp and return
true or false depending on the results
The problem I'm running into is that when I call the save() function on a
FileStorage object twice in a row, the second save() function creates an
empty copy of the file. In the code above, I have a valid copy of my file
stored in /tmp, but the file in /www/docs is zero file size. I don't think
that copying the file from /tmp to /www/docs is the right solution, because
the validation code could potentially destroy or overwrite the temp copy
(say if the file is a zip file as it is in my case)
Looking at the source of FileStorage.save(), it looks like the reason for
this behavior is that the shutil.copyfileobj function advances the
filepointer when it copies from the source, but it doesn't move it back to
the beginning of the file stream when it's finished (the copyfileobj docs
state as much).
As a simple test, I modified the FileStorage.save() function in my local
werkzeug install to add a file seek call before the copyfileobj call as
follows:
from shutil import copyfileobj
close_dst = False
if isinstance(dst, basestring):
dst = file(dst, 'wb')
close_dst = True
try:
# Reset file pointer before copying from object
self.stream.seek(0)
copyfileobj(self.stream, dst, buffer_size)
finally:
if close_dst:
dst.close()
With this change, I can use the FileStorage.save() multiple times to save
multiple copies of the FileStorage file.
Would it make sense to modify FileStorage.save() as I've done here, or is
there another, better way to achieve my goal?
Thanks,
Walter
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