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Big problem with lastModified and IfModifiedSince.

From: Alexandre Rafalovitch <alex@access.com.au>
Date: Fri, 21 Jun 1996 20:03:07 +1000
Message-Id: <v02140b00adf01fd86747@[]>
To: www-jigsaw@w3.org

I am trying to do something like DirectoryResource does and save some time
on requests by keeping htmlized version of my data in local variable and
reparsing it only when original data changes. This way if a client provides
If-Modified-Since header, I can reply with NOT_MODIFIED.

To achieve this, I have to jungle with three variables, listing_stamp for
my html version, lastModified as received from getLastModified() and ims
from request.getIfModifiedSince(). The problem is that some rounding
happens along the way and that breaks my checks of modified/non modified

I will give an example:
I have a resource with lastModified = 835349864096 which should be equal to
GMT string
'21 Jun 1996 09:37:44 GMT'. I parse the data and set my listing_stamp to
the same value.
When I send the reply, I set the header LastModified with that value too.
When I get the next request for the same place, I get IMS header with value
835349864000 which gives me GMT string
'21 Jun 1996 09:37:44 GMT'.

Surprise, surprise. It seams that by some reason some rounding happens
along the route. I assume it could happen because IMS is sent along in GMT
format and it gets truncated. Actually, if I turn 835349864096 into Date,
into GMT string, back parsed by Date to give long  I would get expected

That is all fine, but I have no idea, if that is the way it should work and
I would have to do triple conversion just so I could compare those dates.
Or is there any other reasons and I was just trying to reach my nose
through under my left leg?  :-}

I can provide sample code showing what I mean, if it was not clear. I am
actually suprised that it seems to work for DirectoryResource and
FileResource. Maybe I should try it under the same fire, I put my own
resources through...


--------| I feel as confused as a baby in a topless bar. |--------
Received on Friday, 21 June 1996 06:05:08 UTC

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