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 <errno.h>
  34 #include <signal.h>
  35 #include <stdarg.h>
  36 #include <stdio.h>
  37 #include <string.h>
  38
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include <unistd.h>
  42
  43 #include "global.h"
  44 #include "background.h"
  45 #include "tty.h"        /* doupdate() */
  46 #include "dialog.h"     /* do_refresh() */
  47 #include "wtools.h"
  48 #include "fileopctx.h"  /* FileOpContext */
  49 #include "key.h"        /* add_select_channel(), delete_select_channel() */
  50
  51 enum ReturnType {
  52     Return_String,
  53     Return_Integer
  54 };
  55
  56 /* If true, this is a background process */
  57 int we_are_background = 0;
  58
  59 /* File descriptor for talking to our parent */
  60 static int parent_fd;
  61
  62 #define MAXCALLARGS 4           /* Number of arguments supported */
  63
  64 struct TaskList *task_list = NULL;
  65
  66 static int background_attention (int fd, void *closure);
  67
  68 static void
  69 register_task_running (FileOpContext *ctx, pid_t pid, int fd, char *info)
  70 {
  71     TaskList *new;
  72
  73     new = g_new (TaskList, 1);
  74     new->pid   = pid;
  75     new->info  = info;
  76     new->state = Task_Running;
  77     new->next  = task_list;
  78     new->fd    = fd;
  79     task_list  = new;
  80
  81     add_select_channel (fd, background_attention, ctx);
  82 }
  83
  84 void
  85 unregister_task_running (pid_t pid, int fd)
  86 {
  87     TaskList *p = task_list;
  88     TaskList *prev = 0;
  89
  90     while (p){
  91         if (p->pid == pid){
  92             if (prev)
  93                 prev->next = p->next;
  94             else
  95                 task_list = p->next;
  96             g_free (p->info);
  97             g_free (p);
  98             break;
  99         }
 100         prev = p;
 101         p = p->next;
 102     }
 103     delete_select_channel (fd);
 104 }
 105
 106 /*
 107  * Try to make the Midnight Commander a background job
 108  *
 109  * Returns:
 110  *  1 for parent
 111  *  0 for child
 112  * -1 on failure
 113  */
 114 int
 115 do_background (struct FileOpContext *ctx, char *info)
 116 {
 117     int comm[2];                /* control connection stream */
 118     pid_t pid;
 119
 120     if (pipe (comm) == -1)
 121         return -1;
 122
 123     if ((pid = fork ()) == -1) {
 124         int saved_errno = errno;
 125         (void) close (comm[0]);
 126         (void) close (comm[1]);
 127         errno = saved_errno;
 128         return -1;
 129     }
 130
 131     if (pid == 0) {
 132         int nullfd;
 133
 134         close (comm[0]);
 135         parent_fd = comm[1];
 136         we_are_background = 1;
 137         current_dlg = NULL;
 138
 139         /* Make stdin/stdout/stderr point somewhere */
 140         close (0);
 141         close (1);
 142         close (2);
 143
 144         if ((nullfd = open ("/dev/null", O_RDWR)) != -1) {
 145             while (dup2 (nullfd, 0) == -1 && errno == EINTR);
 146             while (dup2 (nullfd, 1) == -1 && errno == EINTR);
 147             while (dup2 (nullfd, 2) == -1 && errno == EINTR);
 148         }
 149
 150         return 0;
 151     } else {
 152         close (comm[1]);
 153         ctx->pid = pid;
 154         register_task_running (ctx, pid, comm[0], info);
 155         return 1;
 156     }
 157 }
 158
 159 /* {{{ Parent handlers */
 160
 161 /* Parent/child protocol
 162  *
 163  * the child (the background) process send the following:
 164  * void *routine -- routine to be invoked in the parent
 165  * int  nargc    -- number of arguments
 166  * int  type     -- Return argument type.
 167  *
 168  * If the routine is zero, then it is a way to tell the parent
 169  * that the process is dying.
 170  *
 171  * nargc arguments in the following format:
 172  * int size of the coming block
 173  * size bytes with the block
 174  *
 175  * Now, the parent loads all those and then invokes
 176  * the routine with pointers to the information passed
 177  * (we just support pointers).
 178  *
 179  * If the return type is integer:
 180  *
 181  *     the parent then writes an int to the child with
 182  *     the return value from the routine and the values
 183  *     of any global variable that is modified in the parent
 184  *     currently: do_append and recursive_result.
 185  *
 186  * If the return type is a string:
 187  *
 188  *     the parent writes the resulting string length
 189  *     if the result string was NULL or the empty string,
 190  *     then the length is zero.
 191  *     The parent then writes the string length and frees
 192  *     the result string.
 193  */
 194 /*
 195  * Receive requests from background process and invoke the
 196  * specified routine
 197  */
 198
 199 static int
 200 background_attention (int fd, void *closure)
 201 {
 202     FileOpContext *ctx;
 203     int have_ctx;
 204     union
 205     {
 206       int (*have_ctx1)(int, char *);
 207       int (*have_ctx2)(int, char *, char *);
 208       int (*have_ctx3)(int, char *, char *, char *);
 209       int (*have_ctx4)(int, char *, char *, char *, char *);
 210
 211       int (*non_have_ctx1)(FileOpContext *, int, char *);
 212       int (*non_have_ctx2)(FileOpContext *, int, char *, char *);
 213       int (*non_have_ctx3)(FileOpContext *, int, char *, char *, char *);
 214       int (*non_have_ctx4)(FileOpContext *, int, char *, char *, char *, char *);
 215
 216       char * (*ret_str1)(char *);
 217       char * (*ret_str2)(char *, char *);
 218       char * (*ret_str3)(char *, char *, char *);
 219       char * (*ret_str4)(char *, char *, char *, char *);
 220
 221       void *pointer;
 222     } routine;
 223 /*    void *routine;*/
 224     int  argc, i, result, status;
 225     char *data [MAXCALLARGS];
 226     ssize_t bytes;
 227     enum ReturnType type;
 228
 229     ctx = closure;
 230
 231     bytes = read (fd, &routine.pointer, sizeof (routine));
 232     if (bytes == -1 || (size_t) bytes < (sizeof (routine))) {
 233         const char *background_process_error = _(" Background process error ");
 234
 235         unregister_task_running (ctx->pid, fd);
 236         if (!waitpid (ctx->pid, &status, WNOHANG)) {
 237             /* the process is still running, but it misbehaves - kill it */
 238             kill (ctx->pid, SIGTERM);
 239             message (D_ERROR, background_process_error, _(" Unknown error in child "));
 240             return 0;
 241         }
 242
 243         /* 0 means happy end */
 244         if (WIFEXITED (status) && (WEXITSTATUS (status) == 0))
 245             return 0;
 246
 247         message (D_ERROR, background_process_error, _(" Child died unexpectedly "));
 248
 249         return 0;
 250     }
 251
 252     read (fd, &argc, sizeof (argc));
 253     if (argc > MAXCALLARGS){
 254         message (D_ERROR, _(" Background protocol error "),
 255                  _(" Background process sent us a request for more arguments \n"
 256                  " than we can handle. \n"));
 257     }
 258     read (fd, &type, sizeof (type));
 259     read (fd, &have_ctx, sizeof (have_ctx));
 260     if (have_ctx)
 261             read (fd, ctx, sizeof (FileOpContext));
 262
 263     for (i = 0; i < argc; i++){
 264         int size;
 265
 266         read (fd, &size, sizeof (size));
 267         data [i] = g_malloc (size+1);
 268         read (fd, data [i], size);
 269
 270         data [i][size] = 0;     /* NULL terminate the blocks (they could be strings) */
 271     }
 272
 273     /* Handle the call */
 274     if (type == Return_Integer){
 275         if (!have_ctx)
 276             switch (argc){
 277             case 1:
 278                 result = routine.have_ctx1 (Background, data [0]);
 279                 break;
 280             case 2:
 281                 result = routine.have_ctx2 (Background, data [0], data [1]);
 282                 break;
 283             case 3:
 284                 result = routine.have_ctx3 (Background, data [0], data [1], data [2]);
 285                 break;
 286             case 4:
 287                 result = routine.have_ctx4 (Background, data [0], data [1], data [2], data [3]);
 288                 break;
 289             }
 290         else
 291             switch (argc){
 292             case 1:
 293                 result = routine.non_have_ctx1 (ctx, Background, data [0]);
 294                 break;
 295             case 2:
 296                 result = routine.non_have_ctx2 (ctx, Background, data [0], data [1]);
 297                 break;
 298             case 3:
 299                 result = routine.non_have_ctx3 (ctx, Background, data [0], data [1], data [2]);
 300                 break;
 301             case 4:
 302                 result = routine.non_have_ctx4 (ctx, Background, data [0], data [1], data [2], data [3]);
 303                 break;
 304             }
 305
 306         /* Send the result code and the value for shared variables */
 307         write (fd, &result, sizeof (int));
 308         if (have_ctx)
 309             write (fd, ctx, sizeof (FileOpContext));
 310     } else if (type == Return_String) {
 311         int len;
 312         char *resstr = NULL;
 313
 314         /* FIXME: string routines should also use the Foreground/Background
 315          * parameter.  Currently, this is not used here
 316          */
 317         switch (argc){
 318         case 1:
 319             resstr = routine.ret_str1 (data [0]);
 320             break;
 321         case 2:
 322             resstr = routine.ret_str2 (data [0], data [1]);
 323             break;
 324         case 3:
 325             resstr = routine.ret_str3 (data [0], data [1], data [2]);
 326             break;
 327         case 4:
 328             resstr = routine.ret_str4 (data [0], data [1], data [2], data [3]);
 329             break;
 330         default: g_assert_not_reached();
 331         }
 332         if (resstr){
 333             len = strlen (resstr);
 334             write (fd, &len, sizeof (len));
 335             if (len){
 336                 write (fd, resstr, len);
 337                 g_free (resstr);
 338             }
 339         } else {
 340             len = 0;
 341             write (fd, &len, sizeof (len));
 342         }
 343     }
 344     for (i = 0; i < argc; i++)
 345         g_free (data [i]);
 346
 347     do_refresh ();
 348     mc_refresh ();
 349     doupdate ();
 350     return 0;
 351 }
 352
 353
 354 /* }}} */
 355
 356 /* {{{ client RPC routines */
 357
 358 /* Sends the header for a call to a routine in the parent process.  If the file
 359  * operation context is not NULL, then it requests that the first parameter of
 360  * the call be a file operation context.
 361  */
 362 static void
 363 parent_call_header (void *routine, int argc, enum ReturnType type, FileOpContext *ctx)
 364 {
 365     int have_ctx;
 366
 367     have_ctx = (ctx != NULL);
 368
 369     write (parent_fd, &routine, sizeof (routine));
 370     write (parent_fd, &argc, sizeof (int));
 371     write (parent_fd, &type, sizeof (type));
 372     write (parent_fd, &have_ctx, sizeof (have_ctx));
 373
 374     if (have_ctx)
 375         write (parent_fd, ctx, sizeof (FileOpContext));
 376 }
 377
 378 int
 379 parent_call (void *routine, struct FileOpContext *ctx, int argc, ...)
 380 {
 381     va_list ap;
 382     int i;
 383
 384     va_start (ap, argc);
 385     parent_call_header (routine, argc, Return_Integer, ctx);
 386     for (i = 0; i < argc; i++) {
 387         int  len;
 388         void *value;
 389
 390         len   = va_arg (ap, int);
 391         value = va_arg (ap, void *);
 392         write (parent_fd, &len, sizeof (int));
 393         write (parent_fd, value, len);
 394     }
 395     read (parent_fd, &i, sizeof (int));
 396     if (ctx)
 397         read (parent_fd, ctx, sizeof (FileOpContext));
 398
 399     return i;
 400 }
 401
 402 char *
 403 parent_call_string (void *routine, int argc, ...)
 404 {
 405     va_list ap;
 406     char *str;
 407     int i;
 408
 409     va_start (ap, argc);
 410     parent_call_header (routine, argc, Return_String, NULL);
 411     for (i = 0; i < argc; i++){
 412         int  len;
 413         void *value;
 414
 415         len   = va_arg (ap, int);
 416         value = va_arg (ap, void *);
 417         write (parent_fd, &len, sizeof (int));
 418         write (parent_fd, value, len);
 419     }
 420     read (parent_fd, &i, sizeof (int));
 421     if (!i)
 422         return NULL;
 423     str = g_malloc (i + 1);
 424     read (parent_fd, str, i);
 425     str [i] = 0;
 426     return str;
 427 }
 428
 429 #endif                          /* WITH_BACKGROUND */