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World: r3wp

[!REBOL3 Schemes] Implementors guide

Graham
10-Jan-2010
[874]
so with a write port ... the buffer is filled with my write data, 
it gets sent, and then cleared by the tcp device
Steeve
10-Jan-2010
[875x4]
no
write port data, can use any buffer
if you use the same buffer (ie port/data) for read and write, you 
may encounter some problems
i will not use the same buffer for read and write
Graham
10-Jan-2010
[879]
I'm sure I read that write port uses the port/data as its buffer
Steeve
10-Jan-2010
[880x3]
no, the write function uses any buffer you want as parameter
because it's a parameted
*parameter
Graham
10-Jan-2010
[883x3]
hm... I think we are not talking the same thing
http://www.rebol.net/wiki/TCP_Port_Details

says that the port/data is used by write
The details of the port actor for WRITE are:


   1. Set port/data to WRITE content (binary string) value. (Mainly 
   to keep it GC safe.)

   2. Obtain binary string as specified. The buffer is not copied. This 
   is a low level mechanism.
   3. Determine start position from index.

   4. Determine length from tail-index or from /part if specified.

   5. Set IO-request length and data. Zero the actual field (the length 
   actually transferred).
   6. Call the TCP device with the IO-request
   7. Check for errors

   8. Check for immediate completion. If done, set port/data to NONE.
So, this means that the port/data buffer is recreated on each read 
after a write
Steeve
10-Jan-2010
[886]
strange, you may be right
Graham
10-Jan-2010
[887x2]
sometimes I am known to be right ....
not often ...
Steeve
10-Jan-2010
[889x3]
but it's sayed futher that the buffer is not recreated each time 
a read occurs
Check IO-Request connection flag. This is not a socket check, it 
is a request state flag check.
Check the port/data for an existing buffer.

If no buffer found, allocate one that is of the default size (32,000). 
Note: not 32K.
Compute buffer space available.

If available space is less than half the default size, extend the 
buffer.
Recompute buffer space available.

Setup the IO-request data and length fields. Data is the buffer tail 
position. Length is the buffer space available from above. Clear 
the actual field.
Call the TCP device with READ command.
Check result for error. If error, throw it.
so i think i got it.
Graham
10-Jan-2010
[892x4]
it is saying it is recreated itf it does not exist
eg. after a tcp write
if there is sequential tcp read .. it does not recreate
seems a lot of gc must be happening at the tcp port
Steeve
10-Jan-2010
[896]
i wonder if the doc is up to date
Graham
10-Jan-2010
[897x2]
I guess Carl has his reasons on doing it this way instead of having 
separate buffers for read and write
Have you fixed my ftp scheme so that it works properly yet?
Steeve
10-Jan-2010
[899]
who me ? I never say that
Graham
10-Jan-2010
[900x2]
LOL ...
needs a lot of work ... :(
Pekr
10-Jan-2010
[902]
read/write buffers are shared?
Graham
10-Jan-2010
[903x2]
yes
seems to be according to the docs you linked to
Steeve
10-Jan-2010
[905]
i should make a try, i have some doubts
Pekr
10-Jan-2010
[906]
what is it good for? That way you have to read-out all data from 
buffer first, before you do "reverse" (read/write) operation, or 
you mess the data, no?
Graham
10-Jan-2010
[907x2]
yes, copy all your data first before doing a write
store it in port/locals somewhere
Pekr
10-Jan-2010
[909]
it sounds to me as an unnecessary complication. I don't like it. 
But maybe Carl tried to create push on programmers, pushing them 
to do sequency of read/write correctly?
Graham
10-Jan-2010
[910]
seems like a lot of overhead too ...
Steeve
10-Jan-2010
[911]
i tested. Alternating read/write causes the buffer cleared each times
Graham
10-Jan-2010
[912]
so the docs are correct
Steeve
10-Jan-2010
[913]
But the buffer is cleared only after a write action occured .

If you receive several read events the data are added to the buffer 
(buffer not cleared)
Graham
10-Jan-2010
[914]
Yep, I think that's what I said above
Steeve
10-Jan-2010
[915x2]
ok, i just confirmed it with tests
i encountered the famous stack overflow bug.

Never never use a [wait] when you treat an event in the awake handler
Graham
10-Jan-2010
[917]
I see in Gabriele's prot-http he has an http-awake handler that creates 
events which he passes on to another awake handler
Steeve
10-Jan-2010
[918x2]
yes but it"s fake events passed from tcp port thru the fake http 
port.

Actually, it's just calling the event handler function of the fake 
port
it's not asynchronous
Andreas
10-Jan-2010
[920x4]
it's a pity that we have to "fake" these events, currently
I'd love to be able to pass "real" events on, WAKE-UP would already 
be there, but other stuff seems to be missing
i tried sending with WAKE-UP from the tcp port to the scheme port, 
and the scheme port's AWAKE handler even got called
but a WAIT on the scheme port never returns, even though the scheme's 
AWAKE returns true