6.3 Intersci

The directory SCIDIR/examples/intersci-examples-so contains several examples for using intersci which is a tool for producing gateway routines from a descriptor file. Let us describe a simple example, ex01. We want to build an interface for the following C function :
int ext1c(n, a, b, c)
     int *n;
     double *a, *b, *c;
  int k;
  for (k = 0; k < *n; ++k) 
      c[k] = a[k] + b[k];
This function just adds the two real vectors a and b with n entries and returns the result in c. We want to have in Scilab a function c=ext1c(a,b) which performs this operation by calling ext1c. For that, we provide a .desc file, ex01fi.desc :
ext1c	a b 
a 	vector	m
b 	vector	m
c	vector  m 

ext1c   m a b c 
m	integer 
a	double 
b	double 
c	double 

out	sequence	c
This file in divided into three parts separated by a blank line. The upper part (four first lines) describes the Scilab function c=ext1c(a,b). Then (next five lines) the C function is described. The last line of ex01fi.desc gives the name of output variables. To run intersci with this file as input we enter the command :
SCIDIR/bin/intersci-n ex01fi
Two files are created : ex01fi.c and ex01fi_builder.sce. The file ex01fi.c is the C gateway function needed for interfacing ext1c with Scilab. It is a gateway file built as explained above (see 6.2.2) :

#include "stack-c.h"

int intsext1c(fname)
   char *fname;
 int m1,n1,l1,mn1,m2,n2,l2,mn2,un=1,mn3,l3;
 /*  checking variable a */
 /*  checking variable b */
 /* cross variable size checking */
 CheckDimProp(1,2,m1*n1 != m2*n2);
 CreateVar(3,"d",(un=1,&un),(mn3=mn1,&mn3),&l3);/* named: c */
 LhsVar(1)= 3;
 return 0;

The file ex01fi_builder.sce is the following :

// generated with intersci 
ilib_name = 'libex01fi'		// interface library name

table =["ext1c","intsext1c"];

This builder file is to be executed by Scilab after the variables files and libs have been set :

-->files = ['ex01fi.o' , 'ex01c.o'];
-->libs  = [] ;
-->exec ex01fi_builder.sce

A dynamic library is then created as well as a file loader.sce. Executing loader.sce loads the library into Scilab and executes the addinter command to link the library and associate the name of the function ext1c to it. We can then call the new function ;

-->exec loader.sce
-->a=[1,2,3];b=[4,5,6]; c=ext1c(a,b);

To use intersci one has to construct a .desc file. The keywords which describe the Scilab function and the function to be called can be found in the examples given.