[gambit-list] Is there a way to derive file descriptor values from Gambit-internal TCP socket ports, and use them in non-Gambit-internal I/O routines in C?

Christian Jaeger christian at pflanze.mine.nu
Fri Sep 5 09:08:14 EDT 2008


Mikael More wrote:
> Now that we have found a way to make a Gambit-internal port of OS file
> descriptors, how about the other way around, i.e.,
>
> a) How get file descriptor values of active Gambit-internal TCP socket
> connection ports?
>   

I don't have an answer, but Gambit is handling the lowlevel stuff in C 
code (lib/os_io.c), and it seems the filehandle (either a stdio stream 
or an fd) in C structs, as can also be seen when inspecting the port 
structure. For inspecting random Scheme objects, I've written a helper 
library here which turns objects to a sexpr based representation so that 
you can see it more easily. It also detects cycles (it will output a 
<seen> sexpr in that case).

http://scheme.mine.nu/gambit/experimental/object-to-sexpr/
git clone http://scheme.mine.nu/gambit/experimental/object-to-sexpr/.git

Using this you'll for example see (for an output-only port in this case):

...
 (rdevice-condvar #f)
 (wdevice-condvar
  (<structure>
   (value: #<condition-variable #51 #<foreign #52 0x6a0ea0>>)
   (type-chain: (#<type #53 condition-variable>))
   (btq-deq-next (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-deq-prev (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-color (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-parent (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-left (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-leftmost (<seen> #<condition-variable #51 #<foreign #52 0x6a0ea0>>))
   (btq-owner 2)
   (name #<foreign #52 0x6a0ea0>)
   (specific #!void)))


and it seems Gambit accesses the filehandle from that foreign object. I 
haven't looked at the code yet how it gets to it (and won't have time 
today).

Christian.



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