17-Jan-2014 18:52, Steven Schveighoffer пишет:
On Fri, 17 Jan 2014 09:12:56 -0500, Dmitry Olshansky
<[email protected]> wrote:
17-Jan-2014 18:03, Steven Schveighoffer пишет:
On Fri, 17 Jan 2014 05:01:35 -0500, Dmitry Olshansky
<[email protected]> wrote:
BTW I haven't thought of writing into the buffer, but it works exactly
the same. It could be even read/write -"discarded" data is written to
underlying stream, freshly loaded is read from stream. Now in case of
input stream only writes are nop, for output-only reads are nops.
With pinning it makes for cool multi-pass algorithms that actually
output stuff into the file.
In my experience, the code/process for a write buffer is significantly
different than the code for a read buffer. A read/write buffer is very
difficult to make, because you either need 2 file pointers, or need to
constantly seek the single file pointer to overwrite the existing data.
Agreed, read/write buffer is a bad idea. As for write-only buffer
implemented in the same style as read-only, well I need to try it first.
Keep in mind that a read/write buffered stream *should* exist. It's just
that you need to switch how you use the buffer.
I'm doubting that actually. Just use the freaking MM-file directly you'd
better off efficiency wise. And there would be no need to switch back
and forth. Modern OS use paging subsystem for files anyway (unless
opened with O_DIRECT or similar).
I think in my code, what I do is if someone wants to read, and is
currently writing (on a read/write stream), I flush the buffer, then
switch it to be in read mode, and then seek to the appropriate place, to
fill the buffer.
When switching from read to write, it's much easier, since the buffer
starts out empty.
So I think a buffer type that can be used for read *OR* write is good,
just not simultaneously.
See above. I don't think there is a need for these paces with flushing
stuff. And if it comes to pipes and sockets then just having 2 buffers
fits the bill better.
However, simultaneous read/write is probably something that could be
useful for a niche use case (e.g. some transformative process), as long
as you don't mind having 2 file descriptors open :)
--
Dmitry Olshansky
