Creating a new port in C for use in guile

Creating a new port in C for use in guile

[Joshua Datko]

I want to make a new Port. I would like to write the port implementation
in C and use that port in scheme.

I'm a bit confused on how to proceed though. From reading the docs, it
seems I have to create a C function, in the form of an extension, that
calls scm_make_port_type.

However, the manual states [1] that the return value from
scm_make_port_type is a scm_ptob_descriptor. I'm confused on how I
instantiate this new port type to get a scm_port.

What am I missing?

Thanks,

Josh

[1] https://www.gnu.org/software/guile/manual/guile.html#Port-Implementation

Re: Creating a new port in C for use in guile

[Ludovic Courtès]

Joshua Datko <jbdatko@gmail.com> skribis:

> I want to make a new Port. I would like to write the port implementation
> in C and use that port in scheme.
>
> I'm a bit confused on how to proceed though. From reading the docs, it
> seems I have to create a C function, in the form of an extension, that
> calls scm_make_port_type.
>
> However, the manual states [1] that the return value from
> scm_make_port_type is a scm_ptob_descriptor. I'm confused on how I
> instantiate this new port type to get a scm_port.

‘scm_make_port_type’ returns a number of the ‘scm_t_bits’ type.  That
number identifies the port type internally.

Then, to instantiate a port of that type, use
‘scm_new_port_table_entry’:

--8<---------------cut here---------------start------------->8---
  scm_t_bits port_type;
  port_type = scm_make_port_type (...);

  [...]

  SCM port;
  port = scm_new_port_table_entry (port_type);
--8<---------------cut here---------------end--------------->8---

Here’s a couple of examples:

  http://git.savannah.gnu.org/cgit/guile.git/tree/libguile/r6rs-ports.c#n73
  https://gitorious.org/gnutls/gnutls/source/12e50aa449a8f6bb7b2c2fa3c177812e463ea4c7:guile/src/core.c#L923

Hope this helps!

Ludo’.