vports from c questions

[William Morgan <wmorgan@masanjin.net>]

Dear Guile gurus,

I am now at the point in my application where I would like Guile to be
able to read from and write to a vport under my control. There is no
scm_c_make_soft_port, so what I'm doing is the following (for an
output-only port):

SCM vec = scm_c_make_vector(5, SCM_BOOL_F);
scm_vector_set_x(vec, scm_int2num(0), scm_c_make_gsubr("write a char",
		 1, 0, 0, (SCM (*)())handle_write_char);
scm_vector_set_x(vec, scm_int2num(1), scm_c_make_gsubr("write a string",
		 1, 0, 0, (SCM (*)())handle_write_string);
 
However, in the case of multiple vports, each of which references
my handle_write_char and handle_write_string functions, these two
functions have no way of telling which port is calling them, and thus
where in my application to send the output.

Questions:

1) Is there a nice way of specifying some kind of closure, from the C
   side, such that I can provide additional arguments to my
   handle_write_* functions? (I can think of two ways, one involving a
   scm_eval_string("(lambda (char) (...") in the above code, and one one
   involving a table of function pointers---but neither of these seems
   pretty.)

2) If not #1, do people see this as an API issue?

3) If #2, any suggestions on what you'd like the API to be if I were to
   submit a patch?

Thank you,

-- 
William <wmorgan@masanjin.net>


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