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From: Dale Stanbrough <dale@goanna.cs.rmit.edu.au>
Newsgroups: comp.lang.ada
Subject: Re: Interfaces.C
Date: 1 Nov 1994 22:45:34 GMT
Organization: RMIT, Melbourne, Australia
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Date: 1994-11-01T22:45:34+00:00
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Subject: Interfaces.C
From: Ken Thomas, kst@ecs.soton.ac.uk
Date: 1 Nov 1994 15:50:18 -0000
In article <395o3q$2j1@wynkyn.ecs.soton.ac.uk> Ken Thomas, kst@ecs.soton.ac.uk
writes:
>I am attempting to write an Ada9X interface for a C function
>with specification
>
>void foo(int *a, int l)
>
>the aim being to pass an integer array to the C-function. What is the
>correct usage of the package Interfaces.C and its children?
>
>Ken Thomas
>University of Southampton
>U.K.
>kst@uk.ac.soton.ecs

-- presuming l is the length of the array...

type list is array(integer range <>) of interfaces.C.int;

procedure foo(a:in out list) is
	procedure C_foo(a:in system'address; l:interfaces.c.int);
	pragma import(C, C_foo, "foo");
begin
	C_foo(a(a'first)'address, interfaces.c.int(a'length));
end;

or...
-- has the advantage of isolating the nasty C bits.

type list is array(integer range <>) of some_integer_type;

procedure foo(a:in out list) is

	procedure C_foo(a:in system'address; l:interfaces.c.int);
	pragma import(C, C_foo, "foo");
	temp	:array(a'range) of interfaces.c.int;

begin
	for i in a'range loop
		temp(i) := interfaces.c.int(a(i));
	end loop;

	C_foo(temp(temp'first)'address, interfaces.c.int(temp'length));

	for i in temp'range loop
		a(i) := some_integer_type(temp(i));
	end loop;
end;


Dale
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Dale Stanbrough, RMIT, Melbourne, Australia, dale@rmit.edu.au
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