/* port_driver.c */

#include <stdio.h>
#include "erl_driver.h"

typedef struct {
    ErlDrvPort port;
} example_data;

static ErlDrvData example_drv_start(ErlDrvPort port, char *buff)
{
    example_data* d = (example_data*)driver_alloc(sizeof(example_data));
    d->port = port;
    return (ErlDrvData)d;
}

static void example_drv_stop(ErlDrvData handle)
{
    driver_free((char*)handle);
}

static void example_drv_output(ErlDrvData handle, char *buff, 
			       ErlDrvSizeT bufflen)
{
    example_data* d = (example_data*)handle;
    char fn = buff[0], arg = buff[1], res;
    if (fn == 1) {
      res = foo(arg);
    } else if (fn == 2) {
      res = bar(arg);
    }
    driver_output(d->port, &res, 1);
}

ErlDrvEntry example_driver_entry = {
    NULL,			/* F_PTR init, called when driver is loaded */
    example_drv_start,		/* L_PTR start, called when port is opened */
    example_drv_stop,		/* F_PTR stop, called when port is closed */
    example_drv_output,		/* F_PTR output, called when erlang has sent */
    NULL,			/* F_PTR ready_input, called when input descriptor ready */
    NULL,			/* F_PTR ready_output, called when output descriptor ready */
    "example_drv",		/* char *driver_name, the argument to open_port */
    NULL,			/* F_PTR finish, called when unloaded */
    NULL,                       /* void *handle, Reserved by VM */
    NULL,			/* F_PTR control, port_command callback */
    NULL,			/* F_PTR timeout, reserved */
    NULL,			/* F_PTR outputv, reserved */
    NULL,                       /* F_PTR ready_async, only for async drivers */
    NULL,                       /* F_PTR flush, called when port is about 
				   to be closed, but there is data in driver 
				   queue */
    NULL,                       /* F_PTR call, much like control, sync call
				   to driver */
    NULL,                       /* F_PTR event, called when an event selected 
				   by driver_event() occurs. */
    ERL_DRV_EXTENDED_MARKER,    /* int extended marker, Should always be 
				   set to indicate driver versioning */
    ERL_DRV_EXTENDED_MAJOR_VERSION, /* int major_version, should always be 
				       set to this value */
    ERL_DRV_EXTENDED_MINOR_VERSION, /* int minor_version, should always be 
				       set to this value */
    0,                          /* int driver_flags, see documentation */
    NULL,                       /* void *handle2, reserved for VM use */
    NULL,                       /* F_PTR process_exit, called when a 
				   monitored process dies */
    NULL                        /* F_PTR stop_select, called to close an 
				   event object */
};

DRIVER_INIT(example_drv) /* must match name in driver_entry */
{
    return &example_driver_entry;
}