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## Data User-Server Translator Example

The code examples were written by Anand Babu.

We have a data.h header file, a data.defs file, a data-user.c, data-server.c sources files and a Makefile.

data.h:
-------

<pre>
#ifndef	_data_user_
#define	_data_user_

/* Module data */

#include <mach/kern_return.h>
#include <mach/port.h>
#include <mach/message.h>

#include <mach/std_types.h>
#include <mach/mach_types.h>
#include <device/device_types.h>
#include <device/net_status.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <sys/resource.h>
#include <sys/utsname.h>
#include <hurd/hurd_types.h>

/* Routine data_set_value */
#ifdef	mig_external
mig_external
#else
extern
#endif
kern_return_t S_data_set_value
#if	defined(LINTLIBRARY)
    (data_port, value)
	mach_port_t data_port;
	int value;
{ return S_data_set_value(data_port, value); }
#else
(
	mach_port_t data_port,
	int value
);
#endif

/* Routine data_get_value */
#ifdef	mig_external
mig_external
#else
extern
#endif
kern_return_t S_data_get_value
#if	defined(LINTLIBRARY)
    (data_port, value)
	mach_port_t data_port;
	int *value;
{ return S_data_get_value(data_port, value); }
#else
(
	mach_port_t data_port,
	int *value
);
#endif

#endif	/* not defined(_data_user_) */
</pre>

data.defs:
----------

<pre>
/* Definitions for data interface

This file is part of the GNU Hurd.

The GNU Hurd is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

The GNU Hurd is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with the GNU Hurd; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

subsystem data 45000;

#include <hurd/hurd_types.defs>

#ifdef STACK_IMPORTS
STACK_IMPORTS
#endif

/* intr-rpc.defs defines the INTR_INTERFACE macro to make the generated RPC
stubs send-interruptible, and to prefix them with `hurd_intr_rpc_'. */
INTR_INTERFACE

/* set integer value to data */
routine data_set_value (
	data_port: mach_port_t;
	value: int);

/* get integer value from data */
routine data_get_value (
	data_port: mach_port_t;
	out value: int);
</pre>

data-user.c:
------------

<pre>
#include <stdio.h>
#include <hurd.h>
#include <hurd/hurd_types.h>
#include "data.h"

#ifndef _GNU_SOURCE
  #define _GNU_SOURCE
#endif

int
main(int argc, char *argv[])
{
  int value=0;
  mach_port_t data_server_port;

  data_server_port = file_name_lookup ("/tmp/trans", 0, 0);
  printf ("data_server_port [%u]\n", data_server_port);
  S_data_set_value (data_server_port, 99);
  S_data_get_value (data_server_port, &value);
  printf ("data->get_value: [%d]\n", value);
  
  return 0;
}
</pre>

data-server.c:
--------------

<pre>
#ifndef _GNU_SOURCE
  #define _GNU_SOURCE
#endif

#include <stdio.h>
#include <getopt.h>
#include <errno.h>
#include <sys/stat.h>
#include <error.h>

#include <hurd/ports.h>
#include <hurd/hurd_types.h>
#include <hurd/trivfs.h>

#include "data.h"

extern boolean_t S_data_server
(mach_msg_header_t *InHeadP, mach_msg_header_t *OutHeadP);

int trivfs_fstype = FSTYPE_MISC;
int trivfs_fsid = 0;
int trivfs_support_read = 0;
int trivfs_support_write = 0;
int trivfs_support_exec = 0;
int trivfs_allow_open = 0x00;
int trivfs_protid_nportclasses = 0;
int trivfs_cntl_nportclasses = 0;

int data_value;

int demuxer (mach_msg_header_t *inp, mach_msg_header_t *outp)
{
  return (S_data_server(inp,outp)||trivfs_demuxer(inp,outp));
}

void trivfs_modify_stat (struct trivfs_protid *cred, io_statbuf_t  *st)
{
}
error_t trivfs_goaway (struct trivfs_control *fsys, int flags)
{
  exit (0);
}

kern_return_t S_data_set_value (mach_port_t data_port, int value)
{
  data_value = value;
  return 0;
}

kern_return_t S_data_get_value (mach_port_t data_port, int *value)
{
  *value = data_value;
  return 0;
}

int
main(int argc, char *argv[])
{
  int err;
  mach_port_t bootstrap;
  struct trivfs_control *fsys;

  if (argc > 1)
    {
      fprintf(stderr, "Usage: settrans [opts] node %s\n", program_invocation_name); 
      exit (1);
    }

  task_get_bootstrap_port (mach_task_self (), &bootstrap);
  if (bootstrap == MACH_PORT_NULL)
    error(2, 0, "Must be started as a translator");

  /* Reply to our parent */
  err = trivfs_startup (bootstrap, 0, 0, 0, 0, 0,&fsys);
  mach_port_deallocate (mach_task_self (), bootstrap);
  if (err) {
    return (0);
  }

  ports_manage_port_operations_one_thread (fsys->pi.bucket, demuxer, 0);

  return 0;
}
</pre>

Makefile:
---------

<pre>
CC = gcc
MIG = mig
CFLAGS = -Wall -g  -D_GNU_SOURCE
LDFLAGS = -lthreads -lports -ltrivfs -lfshelp -lshouldbeinlibc
INCLUDES = -I.
LCHDRS = 
MIGCOMSFLAGS = -prefix S_
OBJS = $(SRCS:.c=.o)
TAGS = etags.emacs21

all: data-server data-user
tags:
	$(TAGS) $(SRCS) $(LCHDRS)

stubs: data.defs
	$(MIG) $(MIGCOMSFLAGS) -server dataServer.c -user dataUser.c $^
data-server: data-server.c dataServer.c 
	$(CC) $^ $(CFLAGS) $(INCLUDES) $(LDFLAGS) -o $@
data-user: data-user.c dataUser.c
	$(CC) $^ $(CFLAGS) $(INCLUDES) -o $@
clean:
	rm -f *.o data-server data-user

start: data-server data-user
	settrans -ac /tmp/trans data-server
	ps -x | grep data-server
end:
	settrans -fg /tmp/trans
</pre>

Building
--------

Do

<pre>  make stubs </pre>

to create the dataUser.c and dataServer.c files generated by mig. Create the executables using:

<pre>  make all </pre>

Testing
-------

Start the data-server translator using:

<pre>  settrans -ac /tmp/trans data-server  </pre>

You can check if it is running u sing

<pre>  ps -x | grep data-server </pre>

Run the data-user executable to get the resultant output.

You can remove the translator using:

<pre>  settrans -fg /tmp/trans </pre>

To remove the built files use:

<pre>  make clean </pre>.

Happy Hacking!

-- ShakthiKannan - 01 Dec 2006