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/*

 *  server.c  Set up and handle communications with a server process.

 *

 *  Server Handling copyright 1992-1999, 2001 The Free Software Foundation

 *

 *  Server Handling is free software.

 *  You may 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.

 *

 *  Server Handling 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 Server Handling.  See the file "COPYING".  If not,

 *  write to:  The Free Software Foundation, Inc.,

 *             51 Franklin Street, Fifth Floor,

 *             Boston,  MA  02110-1301, USA.

 *

 * As a special exception, The Free Software Foundation gives

 * permission for additional uses of the text contained in his release

 * of ServerHandler.

 *

 * The exception is that, if you link the ServerHandler library with other

 * files to produce an executable, this does not by itself cause the

 * resulting executable to be covered by the GNU General Public License.

 * Your use of that executable is in no way restricted on account of

 * linking the ServerHandler library code into it.

 *

 * This exception does not however invalidate any other reasons why

 * the executable file might be covered by the GNU General Public License.

 *

 * This exception applies only to the code released by The Free

 * Software Foundation under the name ServerHandler.  If you copy code

 * from other sources under the General Public License into a copy of

 * ServerHandler, as the General Public License permits, the exception

 * does not apply to the code that you add in this way.  To avoid

 * misleading anyone as to the status of such modified files, you must

 * delete this exception notice from them.

 *

 * If you write modifications of your own for ServerHandler, it is your

 * choice whether to permit this exception to apply to your modifications.

 * If you do not wish that, delete this exception notice.

 */

#include "fixlib.h"

#include "server.h"

STATIC volatile enum t_bool read_pipe_timeout;

STATIC pid_t server_master_pid = NOPROCESS;

tSCC* def_args[] =

{ (char *) NULL, (char *) NULL };

STATIC t_pf_pair server_pair =

{ (FILE *) NULL, (FILE *) NULL };

STATIC pid_t server_id = NULLPROCESS;

/*

 *  Arbitrary text that should not be found in the shell output.

 *  It must be a single line and appear verbatim at the start of

 *  the terminating output line.

 */

tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";

tSCC* p_cur_dir = (char *) NULL;

/*

 *  load_data

 *

 *  Read data from a file pointer (a pipe to a process in this context)

 *  until we either get EOF or we get a marker line back.

 *  The read data are stored in a malloc-ed string that is truncated

 *  to size at the end.  Input is assumed to be an ASCII string.

 */

static char *

load_data (FILE* fp)

{

  char *pz_text;

  size_t text_size;

  char *pz_scan;

  char z_line[1024];

  t_bool got_done = BOOL_FALSE;

  text_size = sizeof (z_line) * 2;

  pz_scan = pz_text = XNEWVEC (char, text_size);

  for (;;)

    {

      size_t used_ct;

      alarm (10);

      read_pipe_timeout = BOOL_FALSE;

      if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)

        break;

      if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)

        {

          got_done = BOOL_TRUE;

          break;

        }

      strcpy (pz_scan, z_line);

      pz_scan += strlen (z_line);

      used_ct = (size_t) (pz_scan - pz_text);

      if (text_size - used_ct < sizeof (z_line))

        {

          size_t off = (size_t) (pz_scan - pz_text);

          text_size += 4096;

          pz_text = XRESIZEVEC (char, pz_text, text_size);

          pz_scan = pz_text + off;

        }

    }

  alarm (0);

  if (read_pipe_timeout || ! got_done)

    {

      free ((void *) pz_text);

      return (char *) NULL;

    }

  while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))

    pz_scan--;

  *pz_scan = NUL;

  return XRESIZEVEC (char, pz_text, strlen (pz_text) + 1);

}

/*

 *  close_server

 *

 *  Make certain the server process is dead, close the

 *  pipes to it and from it, finally NULL out the file pointers

 */

void

close_server (void)

{

  if (  (server_id != NULLPROCESS)

     && (server_master_pid == getpid ()))

    {

      kill ((pid_t) server_id, SIGKILL);

      server_id = NULLPROCESS;

      server_master_pid = NOPROCESS;

      fclose (server_pair.pf_read);

      fclose (server_pair.pf_write);

      server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;

    }

}

/*

 *  sig_handler really only handles the timeout and pipe signals.

 *  This ensures that we do not wait forever on a request

 *  to our server, and also that if the server dies, we do not

 *  die from a sigpipe problem.

 */

static void

sig_handler (int signo ATTRIBUTE_UNUSED)

{

#ifdef DEBUG

  /* FIXME: this is illegal to do in a signal handler.  */

  fprintf (stderr,

          "fixincl ERROR:  sig_handler: killed pid %ld due to %s\n",

          (long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");

#endif

  close_server ();

  read_pipe_timeout = BOOL_TRUE;

}

/*

 *  server_setup  Establish the signal handler for PIPE and ALARM.

 *  Also establishes the current directory to give to the

 *  server process at the start of every server command.

 */

static void

server_setup (void)

{

  static int atexit_done = 0;

  char buff [MAXPATHLEN + 1];

  if (atexit_done++ == 0)

    atexit (close_server);

  else

    fputs ("NOTE: server restarted\n", stderr);

  server_master_pid = getpid ();

  signal (SIGPIPE, sig_handler);

  signal (SIGALRM, sig_handler);

  fputs ("trap : 1\n", server_pair.pf_write);

  fflush (server_pair.pf_write);

  getcwd (buff, MAXPATHLEN + 1);

  p_cur_dir = xstrdup (buff);

}

/*

 *  find_shell

 *

 *  Locate a shell suitable for use.  For various reasons

 *  (like the use of "trap" in server_setup(), it must be a

 *  Bourne-like shell.

 *

 *  Most of the time, /bin/sh is preferred, but sometimes

 *  it's quite broken (like on Ultrix).  autoconf lets you

 *  override with $CONFIG_SHELL, so we do the same.

 */

static const char *

find_shell (void)

{

  char * shell = getenv ("CONFIG_SHELL");

  if (shell)

    return shell;

  return "/bin/sh";

}

/*

 *  run_shell

 *

 *  Run a shell command on the server.  The command string

 *  passed in is wrapped inside the sequence:

 *

 *     cd <original directory>

 *     <command string>

 *     echo

 *     echo <end-of-command-marker>

 *

 *  This ensures that all commands start at a known place in

 *  the directory structure, that any incomplete output lines

 *  are completed and that our special marker sequence appears on

 *  a line by itself.  We have chosen a marker that is

 *  excessively unlikely to be reproduced in normal output:

 *

 *     "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"

 */

char *

run_shell (const char* pz_cmd)

{

  tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";

  t_bool retry = BOOL_TRUE;

 do_retry:

  /*  IF the shell server process is not running yet,

      THEN try to start it.  */

  if (server_id == NULLPROCESS)

    {

      def_args[0] = find_shell ();

      server_id = proc2_fopen (&server_pair, def_args);

      if (server_id > 0)

        server_setup ();

    }

  /*  IF it is still not running, THEN return the nil string.  */

  if (server_id <= 0)

    {

      fprintf (stderr, zNoServer, pz_cmd);

      return XCNEW (char);

    }

  /*  Make sure the process will pay attention to us, send the

     supplied command, and then have it output a special marker that

     we can find.  */

  fprintf (server_pair.pf_write, "cd \"%s\"\n%s\n\necho\necho %s\n",

           p_cur_dir, pz_cmd, z_done);

  fflush (server_pair.pf_write);

  /*  IF the server died and we received a SIGPIPE,

      THEN return an empty string.  */

  if (server_id == NULLPROCESS)

    {

      fprintf (stderr, zNoServer, pz_cmd);

      return XCNEW (char);

    }

  /*  Now try to read back all the data.  If we fail due to either a

     sigpipe or sigalrm (timeout), we will return the nil string.  */

  {

    char *pz = load_data (server_pair.pf_read);

    if (pz == (char *) NULL)

      {

        close_server ();

        if (retry)

          {

            retry = BOOL_FALSE;

            goto do_retry;

          }

        fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",

                 pz_cmd);

        pz = XCNEW (char);

      }

#ifdef DEBUG

    fprintf( stderr, "run_shell command success:  %s\n", pz );

#endif

    return pz;

  }

}