HTTP APPEND [Was: Re: [ANN] bzr.webdav: a writable hhtp transport]

[Goffredo Baroncelli]

On Tuesday 22 August 2006 17:48, Vincent LADEUIL wrote:
Hello Vincent,

[...]
>     jam> Does WebDAV not have any sort of Append command?
> 
> Don't hold your  breath. I don't have the  reference handy, but a
> draft  exists   (dated  07/2006),  proposing   APPEND  and  PATCH
> additions to DAV.

On the basis of my search, in order to write a part of a file we have to use 
the PUT method + the "Content-Range:" header directive. A typical request 
should be:

PUT /path/to/file HTTP/1.1
Host: www.somehost.net
Content-Range: bytes 5-14/15
Content-Length: 10
[...]

The example above highlight how append 10 bytes of data to a file with a 
(initial) length of 5 bytes.

The enclosed patch implement an example of the append method. The patch was 
tested on a apache webdav implementation. I don't know if it work with other 
web servers ( IIS ?? ). If you want understand better the protocol you can 
watch on what curl does ( see the -C curl option ).

Open point:
1) the append phase is performed in two steps:
   a) get the length of the destination (via the HEAD method )
   b) append the content at the end of the file ( via PUT + Content-Range: )
  We have to prevent that another client update the file between "a" and "b"
2) test with other web server
3) it is not very clear the meaning of the third parameter of the 
Contenet-Range option ( the one after the '/' ): is it the length of the old 
or the new file ?

Comment are welcome
Goffredo


Reference:
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.16
http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.6 (see the part 
related to "Content-Range" )
http://www.hpl.hp.com/personal/ange/archives/archives-97/http-wg-archive/0079.html
http://www.hpl.hp.com/personal/ange/archives/archives-97/http-wg-archive/2530.html

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