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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:
-------

    #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_) */

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

    /* 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);

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

    #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;
    }

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

    #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;
    }

Makefile:
---------

    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

Building
--------

Do

    make stubs

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

    make all

Testing
-------

Start the data-server translator using:

    settrans -ac /tmp/trans data-server

You can check if it is running using

    ps -x | grep data-server

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

You can remove the translator using:

    settrans -fg /tmp/trans

To remove the built files use:

    make clean

Happy Hacking!