Re: Do any java.io classes support inserting text into a file?
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On Wed, 20 Aug 2008, Eric Sosman wrote:
Tom Anderson wrote:
On Tue, 19 Aug 2008, Arne Vajh?j wrote:
Tom Anderson wrote:
[...]
But you could imagine a filesystem which did make efficient inserts
possible. The trick would be to allow partially-filled blocks inside a
file, so that if you want to insert or prepend less than a block's worth
(or some non-integer multiple of a block's worth) of data, you could
partially fill a block, then splice it into the middle of the file.
It could be done.
But I don't think anyone would.
Probably not!
You are wrong, with 100% probability. I was there.
What? Where were you? And who's wrong about what?
Because there are really not much usage for it.
Hmm. No, you're probably right. It might be useful if you were very limited
in RAM, but if you have a decent amount of memory, then cacheing makes the
rewrite-the-whole-file approach sufficiently efficient.
If the size of the file exceeds the size of the cache,
this is nonsense.
Yes. What i was trying to say was that these days, computers have enough
memory that for many situations, like text or word processor documents,
they have enough memory that the whole file can be cached. Certainly, if
the file is bigger than the cache, then you'll be doing a lot of
potentially unnecessary writing.
Even a big cache can do no more than stave off the delay of rewriting;
the rewriting and its consequent I/O must happen eventually in any case.
Also true. But you can amortize the cost of the write over lots of
mutations.
If there was an application which manipulated large files, needed to make
random, variable-sized insertions into them, and needed to run fast, then
such a filesystem would be useful. However, i suspect that such
applications don't exist, [...]
I repeat: I was there. You, obviously, were not there, so it
ill-becomes you to speak whereof you wottest not.
Quite, quite. But i'm still completely baffled as to where this place was
where you were but i wasn't. Doubtless, though, any such place is beyond
my ken.
tom
--
Also giving up smoking (cigarettes) today so apologies if it reads wierd
or I trail off into maddness at any point!! -- Agent D, 20051129
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