src/background.c

   1 /* {{{ Copyright */
   2
   3 /* Background support.
   4    Copyright (C) 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007
   5    Free Software Foundation, Inc.
   6
   7    Written by: 1996 Miguel de Icaza
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  22
  23 /* }}} */
  24
  25 /** \file background.c
  26  *  \brief Source: Background support
  27  */
  28
  29 #include <config.h>
  30
  31 #ifdef WITH_BACKGROUND
  32
  33 #include <stdlib.h>
  34 #include <errno.h>
  35 #include <signal.h>
  36 #include <stdarg.h>
  37 #include <stdio.h>
  38 #include <string.h>
  39
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42 #include <sys/wait.h>           /* waitpid() */
  43 #include <unistd.h>
  44 #include <fcntl.h>
  45
  46 #include "lib/global.h"
  47 #include "lib/tty/key.h"        /* add_select_channel(), delete_select_channel() */
  48 #include "lib/widget.h"         /* message() */
  49
  50 #include "filemanager/layout.h" /* repaint_screen() */
  51 #include "filemanager/fileopctx.h"      /* FileOpContext */
  52
  53 #include "background.h"
  54
  55 /*** global variables ****************************************************************************/
  56
  57 #define MAXCALLARGS 4           /* Number of arguments supported */
  58
  59 /* If true, this is a background process */
  60 int we_are_background = 0;
  61
  62 /*** file scope macro definitions ****************************************************************/
  63
  64 /*** file scope type declarations ****************************************************************/
  65
  66 enum ReturnType
  67 {
  68     Return_String,
  69     Return_Integer
  70 };
  71
  72 /*** file scope variables ************************************************************************/
  73
  74 /* File descriptor for talking to our parent */
  75 static int parent_fd;
  76
  77 /* File descriptor for messages from our parent */
  78 static int from_parent_fd;
  79
  80 struct TaskList *task_list = NULL;
  81
  82 static int background_attention (int fd, void *closure);
  83
  84 /*** file scope functions ************************************************************************/
  85 /* --------------------------------------------------------------------------------------------- */
  86
  87 static void
  88 register_task_running (FileOpContext * ctx, pid_t pid, int fd, int to_child, char *info)
  89 {
  90     TaskList *new;
  91
  92     new = g_new (TaskList, 1);
  93     new->pid = pid;
  94     new->info = info;
  95     new->state = Task_Running;
  96     new->next = task_list;
  97     new->fd = fd;
  98     new->to_child_fd = to_child;
  99     task_list = new;
 100
 101     add_select_channel (fd, background_attention, ctx);
 102 }
 103
 104 /* --------------------------------------------------------------------------------------------- */
 105
 106 static int
 107 destroy_task_and_return_fd (pid_t pid)
 108 {
 109     TaskList *p = task_list;
 110     TaskList *prev = 0;
 111
 112     while (p)
 113     {
 114         if (p->pid == pid)
 115         {
 116             if (prev)
 117                 prev->next = p->next;
 118             else
 119                 task_list = p->next;
 120             g_free (p->info);
 121             g_free (p);
 122             return p->fd;
 123         }
 124         prev = p;
 125         p = p->next;
 126     }
 127
 128     /* pid not found */
 129     return -1;
 130 }
 131
 132 /* --------------------------------------------------------------------------------------------- */
 133 /* {{{ Parent handlers */
 134
 135 /* Parent/child protocol
 136  *
 137  * the child (the background) process send the following:
 138  * void *routine -- routine to be invoked in the parent
 139  * int  nargc    -- number of arguments
 140  * int  type     -- Return argument type.
 141  *
 142  * If the routine is zero, then it is a way to tell the parent
 143  * that the process is dying.
 144  *
 145  * nargc arguments in the following format:
 146  * int size of the coming block
 147  * size bytes with the block
 148  *
 149  * Now, the parent loads all those and then invokes
 150  * the routine with pointers to the information passed
 151  * (we just support pointers).
 152  *
 153  * If the return type is integer:
 154  *
 155  *     the parent then writes an int to the child with
 156  *     the return value from the routine and the values
 157  *     of any global variable that is modified in the parent
 158  *     currently: do_append and recursive_result.
 159  *
 160  * If the return type is a string:
 161  *
 162  *     the parent writes the resulting string length
 163  *     if the result string was NULL or the empty string,
 164  *     then the length is zero.
 165  *     The parent then writes the string length and frees
 166  *     the result string.
 167  */
 168 /*
 169  * Receive requests from background process and invoke the
 170  * specified routine
 171  */
 172
 173 static int
 174 background_attention (int fd, void *closure)
 175 {
 176     FileOpContext *ctx;
 177     int have_ctx;
 178     union
 179     {
 180         int (*have_ctx0) (int);
 181         int (*have_ctx1) (int, char *);
 182         int (*have_ctx2) (int, char *, char *);
 183         int (*have_ctx3) (int, char *, char *, char *);
 184         int (*have_ctx4) (int, char *, char *, char *, char *);
 185
 186         int (*non_have_ctx0) (FileOpContext *, int);
 187         int (*non_have_ctx1) (FileOpContext *, int, char *);
 188         int (*non_have_ctx2) (FileOpContext *, int, char *, char *);
 189         int (*non_have_ctx3) (FileOpContext *, int, char *, char *, char *);
 190         int (*non_have_ctx4) (FileOpContext *, int, char *, char *, char *, char *);
 191
 192         char *(*ret_str0) ();
 193         char *(*ret_str1) (char *);
 194         char *(*ret_str2) (char *, char *);
 195         char *(*ret_str3) (char *, char *, char *);
 196         char *(*ret_str4) (char *, char *, char *, char *);
 197
 198         void *pointer;
 199     } routine;
 200     /*    void *routine; */
 201     int argc, i, result, status;
 202     char *data[MAXCALLARGS];
 203     ssize_t bytes, ret;
 204     struct TaskList *p;
 205     int to_child_fd = -1;
 206     enum ReturnType type;
 207
 208     ctx = closure;
 209
 210     bytes = read (fd, &routine.pointer, sizeof (routine));
 211     if (bytes == -1 || (size_t) bytes < (sizeof (routine)))
 212     {
 213         const char *background_process_error = _("Background process error");
 214
 215         unregister_task_running (ctx->pid, fd);
 216         if (!waitpid (ctx->pid, &status, WNOHANG))
 217         {
 218             /* the process is still running, but it misbehaves - kill it */
 219             kill (ctx->pid, SIGTERM);
 220             message (D_ERROR, background_process_error, _("Unknown error in child"));
 221             return 0;
 222         }
 223
 224         /* 0 means happy end */
 225         if (WIFEXITED (status) && (WEXITSTATUS (status) == 0))
 226             return 0;
 227
 228         message (D_ERROR, background_process_error, _("Child died unexpectedly"));
 229
 230         return 0;
 231     }
 232
 233     if ((read (fd, &argc, sizeof (argc)) != sizeof (argc)) ||
 234         (read (fd, &type, sizeof (type)) != sizeof (type)) ||
 235         (read (fd, &have_ctx, sizeof (have_ctx)) != sizeof (have_ctx)))
 236     {
 237         message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 238         return 0;
 239     }
 240
 241     if (argc > MAXCALLARGS)
 242     {
 243         message (D_ERROR, _("Background protocol error"),
 244                  _("Background process sent us a request for more arguments\n"
 245                    "than we can handle."));
 246     }
 247
 248     if (have_ctx)
 249     {
 250         if (read (fd, ctx, sizeof (FileOpContext)) != sizeof (FileOpContext))
 251         {
 252             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 253             return 0;
 254         }
 255     }
 256
 257     for (i = 0; i < argc; i++)
 258     {
 259         int size;
 260
 261         if (read (fd, &size, sizeof (size)) != sizeof (size))
 262         {
 263             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 264             return 0;
 265         }
 266         data[i] = g_malloc (size + 1);
 267         if (read (fd, data[i], size) != size)
 268         {
 269             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 270             return 0;
 271         }
 272         data[i][size] = 0;      /* NULL terminate the blocks (they could be strings) */
 273     }
 274
 275     /* Find child task info by descriptor */
 276     /* Find before call, because process can destroy self after */
 277     for (p = task_list; p; p = p->next)
 278     {
 279         if (p->fd == fd)
 280             break;
 281     }
 282
 283     if (p)
 284         to_child_fd = p->to_child_fd;
 285
 286     if (to_child_fd == -1)
 287         message (D_ERROR, _("Background process error"), _("Unknown error in child"));
 288
 289     /* Handle the call */
 290     if (type == Return_Integer)
 291     {
 292         if (!have_ctx)
 293             switch (argc)
 294             {
 295             case 0:
 296                 result = routine.have_ctx0 (Background);
 297                 break;
 298             case 1:
 299                 result = routine.have_ctx1 (Background, data[0]);
 300                 break;
 301             case 2:
 302                 result = routine.have_ctx2 (Background, data[0], data[1]);
 303                 break;
 304             case 3:
 305                 result = routine.have_ctx3 (Background, data[0], data[1], data[2]);
 306                 break;
 307             case 4:
 308                 result = routine.have_ctx4 (Background, data[0], data[1], data[2], data[3]);
 309                 break;
 310             }
 311         else
 312             switch (argc)
 313             {
 314             case 0:
 315                 result = routine.non_have_ctx0 (ctx, Background);
 316                 break;
 317             case 1:
 318                 result = routine.non_have_ctx1 (ctx, Background, data[0]);
 319                 break;
 320             case 2:
 321                 result = routine.non_have_ctx2 (ctx, Background, data[0], data[1]);
 322                 break;
 323             case 3:
 324                 result = routine.non_have_ctx3 (ctx, Background, data[0], data[1], data[2]);
 325                 break;
 326             case 4:
 327                 result =
 328                     routine.non_have_ctx4 (ctx, Background, data[0], data[1], data[2], data[3]);
 329                 break;
 330             }
 331
 332         /* Send the result code and the value for shared variables */
 333         ret = write (to_child_fd, &result, sizeof (int));
 334         if (have_ctx && to_child_fd != -1)
 335             ret = write (to_child_fd, ctx, sizeof (FileOpContext));
 336     }
 337     else if (type == Return_String)
 338     {
 339         int len;
 340         char *resstr = NULL;
 341
 342         /* FIXME: string routines should also use the Foreground/Background
 343          * parameter.  Currently, this is not used here
 344          */
 345         switch (argc)
 346         {
 347         case 0:
 348             resstr = routine.ret_str0 ();
 349             break;
 350         case 1:
 351             resstr = routine.ret_str1 (data[0]);
 352             break;
 353         case 2:
 354             resstr = routine.ret_str2 (data[0], data[1]);
 355             break;
 356         case 3:
 357             resstr = routine.ret_str3 (data[0], data[1], data[2]);
 358             break;
 359         case 4:
 360             resstr = routine.ret_str4 (data[0], data[1], data[2], data[3]);
 361             break;
 362         default:
 363             g_assert_not_reached ();
 364         }
 365         if (resstr)
 366         {
 367             len = strlen (resstr);
 368             ret = write (to_child_fd, &len, sizeof (len));
 369             if (len != 0)
 370                 ret = write (to_child_fd, resstr, len);
 371             g_free (resstr);
 372         }
 373         else
 374         {
 375             len = 0;
 376             ret = write (to_child_fd, &len, sizeof (len));
 377         }
 378     }
 379     for (i = 0; i < argc; i++)
 380         g_free (data[i]);
 381
 382     repaint_screen ();
 383     return 0;
 384 }
 385
 386
 387 /* --------------------------------------------------------------------------------------------- */
 388 /* }}} */
 389
 390 /* {{{ client RPC routines */
 391
 392 /* Sends the header for a call to a routine in the parent process.  If the file
 393  * operation context is not NULL, then it requests that the first parameter of
 394  * the call be a file operation context.
 395  */
 396
 397 static void
 398 parent_call_header (void *routine, int argc, enum ReturnType type, FileOpContext * ctx)
 399 {
 400     int have_ctx;
 401     ssize_t ret;
 402
 403     have_ctx = (ctx != NULL);
 404
 405     ret = write (parent_fd, &routine, sizeof (routine));
 406     ret = write (parent_fd, &argc, sizeof (int));
 407     ret = write (parent_fd, &type, sizeof (type));
 408     ret = write (parent_fd, &have_ctx, sizeof (have_ctx));
 409
 410     if (have_ctx)
 411         ret = write (parent_fd, ctx, sizeof (FileOpContext));
 412 }
 413
 414 /* --------------------------------------------------------------------------------------------- */
 415 /*** public functions ****************************************************************************/
 416 /* --------------------------------------------------------------------------------------------- */
 417
 418 void
 419 unregister_task_running (pid_t pid, int fd)
 420 {
 421     destroy_task_and_return_fd (pid);
 422     delete_select_channel (fd);
 423 }
 424
 425 /* --------------------------------------------------------------------------------------------- */
 426
 427 void
 428 unregister_task_with_pid (pid_t pid)
 429 {
 430     int fd = destroy_task_and_return_fd (pid);
 431     if (fd != -1)
 432         delete_select_channel (fd);
 433 }
 434
 435
 436 /* --------------------------------------------------------------------------------------------- */
 437 /**
 438  * Try to make the Midnight Commander a background job
 439  *
 440  * Returns:
 441  *  1 for parent
 442  *  0 for child
 443  * -1 on failure
 444  */
 445 int
 446 do_background (struct FileOpContext *ctx, char *info)
 447 {
 448     int comm[2];                /* control connection stream */
 449     int back_comm[2];           /* back connection */
 450     pid_t pid;
 451
 452     if (pipe (comm) == -1)
 453         return -1;
 454
 455     if (pipe (back_comm) == -1)
 456         return -1;
 457
 458     pid = fork ();
 459     if (pid == -1)
 460     {
 461         int saved_errno = errno;
 462
 463         (void) close (comm[0]);
 464         (void) close (comm[1]);
 465         (void) close (back_comm[0]);
 466         (void) close (back_comm[1]);
 467         errno = saved_errno;
 468         return -1;
 469     }
 470
 471     if (pid == 0)
 472     {
 473         int nullfd;
 474
 475         parent_fd = comm[1];
 476         from_parent_fd = back_comm[0];
 477
 478         we_are_background = 1;
 479         top_dlg = NULL;
 480
 481         /* Make stdin/stdout/stderr point somewhere */
 482         close (0);
 483         close (1);
 484         close (2);
 485
 486         nullfd = open ("/dev/null", O_RDWR);
 487         if (nullfd != -1)
 488         {
 489             while (dup2 (nullfd, 0) == -1 && errno == EINTR)
 490                 ;
 491             while (dup2 (nullfd, 1) == -1 && errno == EINTR)
 492                 ;
 493             while (dup2 (nullfd, 2) == -1 && errno == EINTR)
 494                 ;
 495         }
 496
 497         return 0;
 498     }
 499     else
 500     {
 501         ctx->pid = pid;
 502         register_task_running (ctx, pid, comm[0], back_comm[1], info);
 503         return 1;
 504     }
 505 }
 506
 507 /* --------------------------------------------------------------------------------------------- */
 508
 509 int
 510 parent_call (void *routine, struct FileOpContext *ctx, int argc, ...)
 511 {
 512     va_list ap;
 513     int i;
 514     ssize_t ret;
 515
 516     va_start (ap, argc);
 517     parent_call_header (routine, argc, Return_Integer, ctx);
 518     for (i = 0; i < argc; i++)
 519     {
 520         int len;
 521         void *value;
 522
 523         len = va_arg (ap, int);
 524         value = va_arg (ap, void *);
 525         ret = write (parent_fd, &len, sizeof (int));
 526         ret = write (parent_fd, value, len);
 527     }
 528
 529     ret = read (from_parent_fd, &i, sizeof (int));
 530     if (ctx)
 531         ret = read (from_parent_fd, ctx, sizeof (FileOpContext));
 532
 533     return i;
 534 }
 535
 536 /* --------------------------------------------------------------------------------------------- */
 537
 538 char *
 539 parent_call_string (void *routine, int argc, ...)
 540 {
 541     va_list ap;
 542     char *str;
 543     int i;
 544
 545     va_start (ap, argc);
 546     parent_call_header (routine, argc, Return_String, NULL);
 547     for (i = 0; i < argc; i++)
 548     {
 549         int len;
 550         void *value;
 551
 552         len = va_arg (ap, int);
 553         value = va_arg (ap, void *);
 554         if ((write (parent_fd, &len, sizeof (int)) != sizeof (int)) ||
 555             (write (parent_fd, value, len) != len))
 556             return NULL;
 557     }
 558     if (read (from_parent_fd, &i, sizeof (int)) != sizeof (int))
 559         return NULL;
 560     if (!i)
 561         return NULL;
 562     str = g_malloc (i + 1);
 563     if (read (from_parent_fd, str, i) != i)
 564     {
 565         g_free (str);
 566         return NULL;
 567     }
 568     str[i] = 0;
 569     return str;
 570 }
 571
 572 /* --------------------------------------------------------------------------------------------- */
 573
 574 #endif /* WITH_BACKGROUND */