Here's a function to create new connections. It returns and SEXP that
can be returned to R code, but before that, the user can set up all the
function pointer members via passing in the address of an Rconnection.
Here's how you'd call it:
SEXP newcon;
Rconnection conptr;
newcon = R_NewConnection("newcon","newdesc","w",&conptr);
conptr->vfprintf = apachecon_vfprintf;
conptr->write = apachecon_write;
...
conptr->private = apachecon_init(); /* or whathaveyou */
return newcon;
And if you wanted to know the index, all you have to do is get it from
asInteger(newcon). Here's the code for R_NewConnection;
SEXP R_NewConnection(char *class, char *description, char *mode,
Rconnection *con)
{
SEXP sclass, ans;
Rconnection new = NULL;
int ncon;
/* Get index before we allocate memory */
ncon = NextConnection();
new = (Rconnection) malloc(sizeof(struct Rconn));
if(!new) error(_("allocation of new connection failed"));
new->class = (char *) malloc(strlen(class) + 1);
if(!new->class) {
free(new);
error(_("allocation of terminal connection failed"));
}
strcpy(new->class, class);
new->description = (char *) malloc(strlen(description) + 1);
if(!new->description) {
free(new->class); free(new);
error(_("allocation of terminal connection failed"));
}
init_con(new, description, mode);
new->isopen = TRUE;
new->canread = (strcmp(mode, "r") == 0);
new->canwrite = (strcmp(mode, "w") == 0);
new->destroy = &null_close;
new->private = NULL;
/* Add to Connections, and also
* allow users to assign function
* pointer members
*/
*con = Connections[ncon] = new;
/* Create something to pass to R code */
PROTECT(ans = allocVector(INTSXP, 1));
INTEGER(ans)[0] = ncon;
PROTECT(sclass = allocVector(STRSXP, 2));
SET_STRING_ELT(sclass, 0, mkChar(class));
SET_STRING_ELT(sclass, 1, mkChar("connection"));
classgets(ans, sclass);
UNPROTECT(2);
return ans;
}
Jeff
--
http://biostat.mc.vanderbilt.edu/JeffreyHorner
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