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 "background.h"
  48 #include "wtools.h"
  49 #include "layout.h"     /* repaint_screen() */
  50 #include "fileopctx.h"  /* FileOpContext */
  51 #include "lib/tty/key.h"        /* add_select_channel(), delete_select_channel() */
  52
  53 enum ReturnType {
  54     Return_String,
  55     Return_Integer
  56 };
  57
  58 /* If true, this is a background process */
  59 int we_are_background = 0;
  60
  61 /* File descriptor for talking to our parent */
  62 static int parent_fd;
  63
  64 /* File descriptor for messages from our parent */
  65 static int from_parent_fd;
  66
  67 #define MAXCALLARGS 4           /* Number of arguments supported */
  68
  69 struct TaskList *task_list = NULL;
  70
  71 static int background_attention (int fd, void *closure);
  72
  73 static void
  74 register_task_running (FileOpContext *ctx, pid_t pid, int fd, int to_child,
  75                                            char *info)
  76 {
  77     TaskList *new;
  78
  79     new = g_new (TaskList, 1);
  80     new->pid   = pid;
  81     new->info  = info;
  82     new->state = Task_Running;
  83     new->next  = task_list;
  84     new->fd    = fd;
  85     new->to_child_fd = to_child;
  86     task_list  = new;
  87
  88     add_select_channel (fd, background_attention, ctx);
  89 }
  90
  91 static int
  92 destroy_task_and_return_fd (pid_t pid)
  93 {
  94     TaskList *p = task_list;
  95     TaskList *prev = 0;
  96
  97     while (p){
  98         if (p->pid == pid){
  99             if (prev)
 100                 prev->next = p->next;
 101             else
 102                 task_list = p->next;
 103             g_free (p->info);
 104             g_free (p);
 105             return p->fd;
 106         }
 107         prev = p;
 108         p = p->next;
 109     }
 110
 111     /* pid not found */
 112     return -1;
 113 }
 114
 115 void
 116 unregister_task_running (pid_t pid, int fd)
 117 {
 118     destroy_task_and_return_fd(pid);
 119     delete_select_channel (fd);
 120 }
 121
 122 void
 123 unregister_task_with_pid (pid_t pid)
 124 {
 125     int fd = destroy_task_and_return_fd(pid);
 126     if (fd != -1)
 127         delete_select_channel (fd);
 128 }
 129
 130 /*
 131  * Try to make the Midnight Commander a background job
 132  *
 133  * Returns:
 134  *  1 for parent
 135  *  0 for child
 136  * -1 on failure
 137  */
 138 int
 139 do_background (struct FileOpContext *ctx, char *info)
 140 {
 141     int comm[2];                /* control connection stream */
 142     int back_comm[2];   /* back connection */
 143     pid_t pid;
 144
 145     if (pipe (comm) == -1)
 146         return -1;
 147
 148     if (pipe (back_comm) == -1)
 149         return -1;
 150
 151     if ((pid = fork ()) == -1) {
 152         int saved_errno = errno;
 153         (void) close (comm[0]);
 154         (void) close (comm[1]);
 155         (void) close (back_comm[0]);
 156         (void) close (back_comm[1]);
 157         errno = saved_errno;
 158         return -1;
 159     }
 160
 161     if (pid == 0) {
 162         int nullfd;
 163
 164         parent_fd = comm[1];
 165         from_parent_fd = back_comm[0];
 166
 167         we_are_background = 1;
 168         current_dlg = NULL;
 169
 170         /* Make stdin/stdout/stderr point somewhere */
 171         close (0);
 172         close (1);
 173         close (2);
 174
 175         if ((nullfd = open ("/dev/null", O_RDWR)) != -1) {
 176             while (dup2 (nullfd, 0) == -1 && errno == EINTR);
 177             while (dup2 (nullfd, 1) == -1 && errno == EINTR);
 178             while (dup2 (nullfd, 2) == -1 && errno == EINTR);
 179         }
 180
 181         return 0;
 182     } else {
 183         ctx->pid = pid;
 184         register_task_running (ctx, pid, comm[0], back_comm[1], info);
 185         return 1;
 186     }
 187 }
 188
 189 /* {{{ Parent handlers */
 190
 191 /* Parent/child protocol
 192  *
 193  * the child (the background) process send the following:
 194  * void *routine -- routine to be invoked in the parent
 195  * int  nargc    -- number of arguments
 196  * int  type     -- Return argument type.
 197  *
 198  * If the routine is zero, then it is a way to tell the parent
 199  * that the process is dying.
 200  *
 201  * nargc arguments in the following format:
 202  * int size of the coming block
 203  * size bytes with the block
 204  *
 205  * Now, the parent loads all those and then invokes
 206  * the routine with pointers to the information passed
 207  * (we just support pointers).
 208  *
 209  * If the return type is integer:
 210  *
 211  *     the parent then writes an int to the child with
 212  *     the return value from the routine and the values
 213  *     of any global variable that is modified in the parent
 214  *     currently: do_append and recursive_result.
 215  *
 216  * If the return type is a string:
 217  *
 218  *     the parent writes the resulting string length
 219  *     if the result string was NULL or the empty string,
 220  *     then the length is zero.
 221  *     The parent then writes the string length and frees
 222  *     the result string.
 223  */
 224 /*
 225  * Receive requests from background process and invoke the
 226  * specified routine
 227  */
 228
 229 static int
 230 background_attention (int fd, void *closure)
 231 {
 232     FileOpContext *ctx;
 233     int have_ctx;
 234     union
 235     {
 236       int (*have_ctx0)(int);
 237       int (*have_ctx1)(int, char *);
 238       int (*have_ctx2)(int, char *, char *);
 239       int (*have_ctx3)(int, char *, char *, char *);
 240       int (*have_ctx4)(int, char *, char *, char *, char *);
 241
 242       int (*non_have_ctx0)(FileOpContext *, int);
 243       int (*non_have_ctx1)(FileOpContext *, int, char *);
 244       int (*non_have_ctx2)(FileOpContext *, int, char *, char *);
 245       int (*non_have_ctx3)(FileOpContext *, int, char *, char *, char *);
 246       int (*non_have_ctx4)(FileOpContext *, int, char *, char *, char *, char *);
 247
 248       char * (*ret_str0)();
 249       char * (*ret_str1)(char *);
 250       char * (*ret_str2)(char *, char *);
 251       char * (*ret_str3)(char *, char *, char *);
 252       char * (*ret_str4)(char *, char *, char *, char *);
 253
 254       void *pointer;
 255     } routine;
 256 /*    void *routine;*/
 257     int  argc, i, result, status;
 258     char *data [MAXCALLARGS];
 259     ssize_t bytes;
 260         struct TaskList *p;
 261         int to_child_fd = -1;
 262     enum ReturnType type;
 263
 264     ctx = closure;
 265
 266     bytes = read (fd, &routine.pointer, sizeof (routine));
 267     if (bytes == -1 || (size_t) bytes < (sizeof (routine))) {
 268         const char *background_process_error = _(" Background process error ");
 269
 270         unregister_task_running (ctx->pid, fd);
 271         if (!waitpid (ctx->pid, &status, WNOHANG)) {
 272             /* the process is still running, but it misbehaves - kill it */
 273             kill (ctx->pid, SIGTERM);
 274             message (D_ERROR, background_process_error, _(" Unknown error in child "));
 275             return 0;
 276         }
 277
 278         /* 0 means happy end */
 279         if (WIFEXITED (status) && (WEXITSTATUS (status) == 0))
 280             return 0;
 281
 282         message (D_ERROR, background_process_error, _(" Child died unexpectedly "));
 283
 284         return 0;
 285     }
 286
 287     read (fd, &argc, sizeof (argc));
 288     if (argc > MAXCALLARGS){
 289         message (D_ERROR, _(" Background protocol error "),
 290                  _(" Background process sent us a request for more arguments \n"
 291                  " than we can handle. \n"));
 292     }
 293     read (fd, &type, sizeof (type));
 294     read (fd, &have_ctx, sizeof (have_ctx));
 295     if (have_ctx)
 296             read (fd, ctx, sizeof (FileOpContext));
 297
 298     for (i = 0; i < argc; i++){
 299         int size;
 300
 301         read (fd, &size, sizeof (size));
 302         data [i] = g_malloc (size+1);
 303         read (fd, data [i], size);
 304
 305         data [i][size] = 0;     /* NULL terminate the blocks (they could be strings) */
 306     }
 307
 308         /* Find child task info by descriptor */
 309         /* Find before call, because process can destroy self after */
 310         for (p = task_list; p; p = p->next) {
 311                 if (p->fd == fd)
 312                         break;
 313         }
 314
 315         if (p) to_child_fd = p->to_child_fd;
 316
 317     if (to_child_fd == -1)
 318         message (D_ERROR, _(" Background process error "), _(" Unknown error in child "));
 319
 320     /* Handle the call */
 321     if (type == Return_Integer){
 322         if (!have_ctx)
 323             switch (argc){
 324             case 0:
 325                 result = routine.have_ctx0 (Background);
 326                 break;
 327             case 1:
 328                 result = routine.have_ctx1 (Background, data [0]);
 329                 break;
 330             case 2:
 331                 result = routine.have_ctx2 (Background, data [0], data [1]);
 332                 break;
 333             case 3:
 334                 result = routine.have_ctx3 (Background, data [0], data [1], data [2]);
 335                 break;
 336             case 4:
 337                 result = routine.have_ctx4 (Background, data [0], data [1], data [2], data [3]);
 338                 break;
 339             }
 340         else
 341             switch (argc){
 342             case 0:
 343                 result = routine.non_have_ctx0 (ctx, Background);
 344                 break;
 345             case 1:
 346                 result = routine.non_have_ctx1 (ctx, Background, data [0]);
 347                 break;
 348             case 2:
 349                 result = routine.non_have_ctx2 (ctx, Background, data [0], data [1]);
 350                 break;
 351             case 3:
 352                 result = routine.non_have_ctx3 (ctx, Background, data [0], data [1], data [2]);
 353                 break;
 354             case 4:
 355                 result = routine.non_have_ctx4 (ctx, Background, data [0], data [1], data [2], data [3]);
 356                 break;
 357             }
 358
 359         /* Send the result code and the value for shared variables */
 360         write (to_child_fd, &result, sizeof (int));
 361         if (have_ctx && to_child_fd != -1)
 362             write (to_child_fd, ctx, sizeof (FileOpContext));
 363     } else if (type == Return_String) {
 364         int len;
 365         char *resstr = NULL;
 366
 367         /* FIXME: string routines should also use the Foreground/Background
 368          * parameter.  Currently, this is not used here
 369          */
 370         switch (argc){
 371         case 0:
 372             resstr = routine.ret_str0 ();
 373             break;
 374         case 1:
 375             resstr = routine.ret_str1 (data [0]);
 376             break;
 377         case 2:
 378             resstr = routine.ret_str2 (data [0], data [1]);
 379             break;
 380         case 3:
 381             resstr = routine.ret_str3 (data [0], data [1], data [2]);
 382             break;
 383         case 4:
 384             resstr = routine.ret_str4 (data [0], data [1], data [2], data [3]);
 385             break;
 386         default: g_assert_not_reached();
 387         }
 388         if (resstr){
 389             len = strlen (resstr);
 390             write (to_child_fd, &len, sizeof (len));
 391             if (len){
 392                 write (to_child_fd, resstr, len);
 393                 g_free (resstr);
 394             }
 395         } else {
 396             len = 0;
 397             write (to_child_fd, &len, sizeof (len));
 398         }
 399     }
 400     for (i = 0; i < argc; i++)
 401         g_free (data [i]);
 402
 403     repaint_screen ();
 404     return 0;
 405 }
 406
 407
 408 /* }}} */
 409
 410 /* {{{ client RPC routines */
 411
 412 /* Sends the header for a call to a routine in the parent process.  If the file
 413  * operation context is not NULL, then it requests that the first parameter of
 414  * the call be a file operation context.
 415  */
 416 static void
 417 parent_call_header (void *routine, int argc, enum ReturnType type, FileOpContext *ctx)
 418 {
 419     int have_ctx;
 420
 421     have_ctx = (ctx != NULL);
 422
 423     write (parent_fd, &routine, sizeof (routine));
 424     write (parent_fd, &argc, sizeof (int));
 425     write (parent_fd, &type, sizeof (type));
 426     write (parent_fd, &have_ctx, sizeof (have_ctx));
 427
 428     if (have_ctx)
 429         write (parent_fd, ctx, sizeof (FileOpContext));
 430 }
 431
 432 int
 433 parent_call (void *routine, struct FileOpContext *ctx, int argc, ...)
 434 {
 435     va_list ap;
 436     int i;
 437
 438     va_start (ap, argc);
 439     parent_call_header (routine, argc, Return_Integer, ctx);
 440     for (i = 0; i < argc; i++) {
 441         int  len;
 442         void *value;
 443
 444         len   = va_arg (ap, int);
 445         value = va_arg (ap, void *);
 446         write (parent_fd, &len, sizeof (int));
 447         write (parent_fd, value, len);
 448     }
 449
 450     read (from_parent_fd, &i, sizeof (int));
 451     if (ctx)
 452         read (from_parent_fd, ctx, sizeof (FileOpContext));
 453
 454     return i;
 455 }
 456
 457 char *
 458 parent_call_string (void *routine, int argc, ...)
 459 {
 460     va_list ap;
 461     char *str;
 462     int i;
 463
 464     va_start (ap, argc);
 465     parent_call_header (routine, argc, Return_String, NULL);
 466     for (i = 0; i < argc; i++){
 467         int  len;
 468         void *value;
 469
 470         len   = va_arg (ap, int);
 471         value = va_arg (ap, void *);
 472         write (parent_fd, &len, sizeof (int));
 473         write (parent_fd, value, len);
 474     }
 475     read (from_parent_fd, &i, sizeof (int));
 476     if (!i)
 477         return NULL;
 478     str = g_malloc (i + 1);
 479     read (from_parent_fd, str, i);
 480     str [i] = 0;
 481     return str;
 482 }
 483
 484 #endif                          /* WITH_BACKGROUND */