Hi,
I'm doing some work with WebDAV representations in Zope 2, among other
things, and I'm trying to see if we should use zope.filerepresentation
as the central abstraction for file read/write operations.
However, I find myself lacking a couple of things:
1) A way for an IReadFile to return the file's MIME (content) type
(for the Content-Type, for example) and an optional filename (for the
Conent-Disposition header, for example)
2) A way for an IWriteFile to be told about the MIME type and encoding
of the data it is consuming. I know that IFileFactory() contains this,
but data is not always going to be written to a new file, so setting
this from the factory won't work.
3) I see this comment:
# TODO: We will add ILargeReadFile and ILargeWriteFile to efficiently
# handle large data.
But it seems this was never implemented. I need a way for the
IWriteFile.write() to be passed a file-like object (in fact, there's not
really any clear notion of what the 'data' parameter is, but I assume
it's meant to be a str object), and for IReadFile.read() to return a
file stream iterator of some kind instead of the full raw data.
I see two options here:
- add a new plone.filerepresentation that extends these interfaces
- commit some changes to zope.filerepresentation and make a new
release of this
Since zope.filerepresentation is really *just* interfaces, #2 seems
best. Any objections?
Here's an initial take on the interfaces:
class IReadFile(Interface):
"""Provide read access to file data
"""
def read():
"""Return the file data as a str
"""
def size():
"""Return the data length
"""
class ILargeReadFile(IReadFile):
"""Provide efficient read access to file data
"""
def getContentType():
"""Get the content/MIME type of the file as a string in the form
'major/minor'. Return None if this is not known.
"""
def getFilename():
"""Get the intended file name for this file. Return None if this
is not known.
"""
def getIterator():
"""Return an iterable of the file data
"""
class IWriteFile(Interface):
def write(data):
"""Update the file data
"""
class ILargeWriteFile(IWriteFile):
def writeFile(data, contentType=None, encoding=None):
"""Update the file data.
data is a file-like object containing input data
contentType is the content/MIME type of the data as a string in
the form 'major/minor'. It may be None if unknown.
encoding is the encoding of the string. It may be None
if unknown.
"""
This should be 100% backwards compatible. The downside is that people
will need to implement both write() and writeFile() / read() and
getIterator() to support both str based and stream based reading and
writing, but that's easily addressed with a StringIO.
And of course, nothing in the ZTK will actually use these new
interfaces, but that could come later. ;)
Martin
--
Author of `Professional Plone Development`, a book for developers who
want to work with Plone. See http://martinaspeli.net/plone-book
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