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[[!meta copyright="Copyright © 2008, 2013 Free Software Foundation, Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
id="license" text="Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
is included in the section entitled [[GNU Free Documentation
License|/fdl]]."]]"""]]
`xmlfs` is a translator that provides access to XML documents through the
filesystem.
# How to Use xmlfs
xmlfs - a translator for accessing XML documents
This is only an alpha version. It works in read only. It supports
text nodes and attributes. It doesn't do anything fancy like size
computing, though. Here is an example of how to use it:
$ wget http://cvs.savannah.nongnu.org/viewvc/*checkout*/hurdextras/xmlfs/example.xml?content-type=text%2Fplain;
$ settrans -ca xml /hurd/xmlfs example.xml #the website says to use ./xmlfs
$ cd xml; ls
library0 library1
$ cd library0; ls -A
.text1 .text2 @name book0 book1 book2 sub-library0 sub-library1
$ cat .text2
CDATA, again !
$ cat book0
<book>
<author>Mark Twain</author>
<title>La case de l'oncle Tom</title>
<isbn>4242</isbn>
</book>
$ cat book0/author/.text
Mark Twain
As you can see, text nodes are named .textN, with N an integer
starting from 0. Sorting is supposed to be stable, so you get the same
N every time you access the same file. If there is only one text node
at this level, N is ommitted. Attributes are prefixed with @.
An example file, example.xml, is provided. Of course, it does not
contain anything useful. xmlfs has been tested on several-megabytes
XML documents, though.
Comments are welcome.
-- Manuel Menal <mmenal@hurdfr.org>
# TODO
- Handle memory usage in a clever way:
- do not dump the nodes at each read, try to guess if read()
is called in a sequence of read() operations (e.g. cat reads
8192 bytes by 8192 bytes) and if it is, cache the node
contents. That'd need a very small ftpfs-like GC.
- perhaps we shouldn't store the node informations from
first access to end and have a pool of them. That might come
with next entries though.
- Handle changes of the backing store (XML document) while running.
(Idea: we should probably attach to the XML node and handle
read()/write() operations ourselves, with libxml primitives.)
- Write support. Making things like echo >, sed and so on work is
quite obvious. Editing is not -that- simple, 'cause we could
want to save a not XML well-formed, and libxml will just return
an error. Perhaps we should use something like 'sync'.
- Handle error cases in a more clever way ; there are many error
conditions that will just cause xmlfs to crash or do strange
things. We should review them.
- Make sorting *really* stable.
# TODO WISHLIST
--------
- Kilobug suggested a --xslt option that would make xmlfs provide
a tree matching the XSLT-modified document.
(Problem: In this case we cannot attach easily to the .xml 'cause
the user would loose access to theirs original document. Perhaps
we should allow an optional "file.xml" argument and check if it
is not the same as the file we are attaching to when --xslt is
specified.)
- DTD support ; perhaps XML schema/RelaxNG when I'm sure I understand
them ;-)
# Source
<http://www.nongnu.org/hurdextras/#xmlfs>
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