mirror of
https://github.com/MidnightCommander/mc
synced 2024-12-22 20:36:50 +03:00
322 lines
9.0 KiB
C
322 lines
9.0 KiB
C
/*
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File locking
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Copyright (C) 2003-2023
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Free Software Foundation, Inc.
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Written by:
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Adam Byrtek, 2003
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This file is part of the Midnight Commander.
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The Midnight Commander is free software: you can redistribute it
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and/or modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation, either version 3 of the License,
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or (at your option) any later version.
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The Midnight Commander is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/** \file
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* \brief Source: file locking
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* \author Adam Byrtek
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* \date 2003
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*
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* Locking scheme is based on a documentation found
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* in JED editor sources. Abstract from lock.c file (by John E. Davis):
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*
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* The basic idea here is quite simple. Whenever a buffer is attached to
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* a file, and that buffer is modified, then attempt to lock the
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* file. Moreover, before writing to a file for any reason, lock the
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* file. The lock is really a protocol respected and not a real lock.
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* The protocol is this: If in the directory of the file is a
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* symbolic link with name ".#FILE", the FILE is considered to be locked
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* by the process specified by the link.
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*/
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#include <config.h>
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#include <signal.h> /* kill() */
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#include <stdio.h>
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#include <stdarg.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <string.h>
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#include <ctype.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <pwd.h>
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#include <stdlib.h>
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#include "lib/global.h"
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#include "lib/vfs/vfs.h"
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#include "lib/util.h" /* tilde_expand() */
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#include "lib/lock.h"
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#include "lib/widget.h" /* query_dialog() */
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/*** global variables ****************************************************************************/
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/*** file scope macro definitions ****************************************************************/
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#define BUF_SIZE 255
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#define PID_BUF_SIZE 10
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/*** file scope type declarations ****************************************************************/
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typedef struct
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{
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char *who;
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pid_t pid;
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} lock_s;
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/*** forward declarations (file scope functions) *************************************************/
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/*** file scope variables ************************************************************************/
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/* --------------------------------------------------------------------------------------------- */
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/*** file scope functions ************************************************************************/
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/* --------------------------------------------------------------------------------------------- */
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/** \fn static char * lock_build_name (void)
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* \brief builds user@host.domain.pid string (need to be freed)
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* \return a pointer to lock filename
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*/
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static char *
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lock_build_name (void)
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{
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char host[BUF_SIZE];
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const char *user = NULL;
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struct passwd *pw;
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pw = getpwuid (getuid ());
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if (pw != NULL)
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user = pw->pw_name;
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if (user == NULL)
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user = getenv ("USER");
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if (user == NULL)
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user = getenv ("USERNAME");
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if (user == NULL)
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user = getenv ("LOGNAME");
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if (user == NULL)
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user = "";
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/** \todo Use FQDN, no clean interface, so requires lot of code */
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if (gethostname (host, BUF_SIZE - 1) == -1)
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*host = '\0';
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return g_strdup_printf ("%s@%s.%d", user, host, (int) getpid ());
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}
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/* --------------------------------------------------------------------------------------------- */
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static char *
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lock_build_symlink_name (const vfs_path_t * fname_vpath)
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{
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const char *elpath;
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char *str_filename, *str_dirname, *symlink_name;
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/* get first path piece */
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elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
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str_filename = g_path_get_basename (elpath);
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str_dirname = g_path_get_dirname (elpath);
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symlink_name = g_strconcat (str_dirname, PATH_SEP_STR ".#", str_filename, (char *) NULL);
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g_free (str_dirname);
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g_free (str_filename);
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return symlink_name;
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}
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/* --------------------------------------------------------------------------------------------- */
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/**
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* Extract pid from user@host.domain.pid string
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*/
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static lock_s *
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lock_extract_info (const char *str)
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{
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size_t i, len;
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const char *p, *s;
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static char pid[PID_BUF_SIZE], who[BUF_SIZE];
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static lock_s lock;
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len = strlen (str);
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for (p = str + len - 1; p >= str; p--)
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if (*p == '.')
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break;
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/* Everything before last '.' is user@host */
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i = 0;
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for (s = str; i < BUF_SIZE && s < p; s++)
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who[i++] = *s;
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if (i == BUF_SIZE)
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i--;
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who[i] = '\0';
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/* Treat text between '.' and ':' or '\0' as pid */
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i = 0;
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for (p = p + 1; i < PID_BUF_SIZE && p < str + len && *p != ':'; p++)
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pid[i++] = *p;
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if (i == PID_BUF_SIZE)
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i--;
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pid[i] = '\0';
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lock.pid = (pid_t) atol (pid);
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lock.who = who;
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return &lock;
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}
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/* --------------------------------------------------------------------------------------------- */
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/**
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* Extract user@host.domain.pid from lock file (static string)
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*/
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static const char *
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lock_get_info (const char *lockfname)
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{
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ssize_t cnt;
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static char buf[BUF_SIZE];
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cnt = readlink (lockfname, buf, BUF_SIZE - 1);
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if (cnt == -1 || *buf == '\0')
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return NULL;
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buf[cnt] = '\0';
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return buf;
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}
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/* --------------------------------------------------------------------------------------------- */
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/*** public functions ****************************************************************************/
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/* --------------------------------------------------------------------------------------------- */
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/* Tries to raise file lock
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Returns 1 on success, 0 on failure, -1 if abort
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Warning: Might do screen refresh and lose edit->force */
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int
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lock_file (const vfs_path_t * fname_vpath)
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{
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char *lockfname = NULL, *newlock, *msg;
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struct stat statbuf;
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lock_s *lockinfo;
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gboolean is_local;
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gboolean symlink_ok = FALSE;
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const char *elpath;
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if (fname_vpath == NULL)
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return 0;
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elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
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/* Just to be sure (and don't lock new file) */
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if (*elpath == '\0')
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return 0;
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/* Locking on VFS is not supported */
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is_local = vfs_file_is_local (fname_vpath);
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if (is_local)
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{
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/* Check if already locked */
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lockfname = lock_build_symlink_name (fname_vpath);
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}
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if (!is_local || lockfname == NULL)
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return 0;
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if (lstat (lockfname, &statbuf) == 0)
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{
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const char *lock;
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lock = lock_get_info (lockfname);
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if (lock == NULL)
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goto ret;
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lockinfo = lock_extract_info (lock);
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/* Check if locking process alive, ask user if required */
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if (lockinfo->pid == 0 || !(kill (lockinfo->pid, 0) == -1 && errno == ESRCH))
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{
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msg =
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g_strdup_printf (_
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("File \"%s\" is already being edited.\n"
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"User: %s\nProcess ID: %d"), x_basename (lockfname) + 2,
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lockinfo->who, (int) lockinfo->pid);
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/* TODO: Implement "Abort" - needs to rewind undo stack */
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switch (query_dialog
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(_("File locked"), msg, D_NORMAL, 2, _("&Grab lock"), _("&Ignore lock")))
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{
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case 0:
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break;
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case 1:
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case -1:
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default: /* Esc Esc */
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g_free (msg);
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goto ret;
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}
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g_free (msg);
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}
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unlink (lockfname);
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}
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/* Create lock symlink */
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newlock = lock_build_name ();
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symlink_ok = (symlink (newlock, lockfname) != -1);
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g_free (newlock);
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ret:
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g_free (lockfname);
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return symlink_ok ? 1 : 0;
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}
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/* --------------------------------------------------------------------------------------------- */
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/**
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* Lowers file lock if possible
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* @return Always 0
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*/
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int
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unlock_file (const vfs_path_t * fname_vpath)
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{
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char *lockfname;
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struct stat statbuf;
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const char *elpath, *lock;
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if (fname_vpath == NULL)
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return 0;
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elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
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/* Just to be sure (and don't lock new file) */
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if (*elpath == '\0')
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return 0;
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lockfname = lock_build_symlink_name (fname_vpath);
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if (lockfname == NULL)
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return 0;
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/* Check if lock exists */
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if (lstat (lockfname, &statbuf) == -1)
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goto ret;
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lock = lock_get_info (lockfname);
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if (lock != NULL)
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{
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/* Don't touch if lock is not ours */
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if (lock_extract_info (lock)->pid != getpid ())
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goto ret;
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}
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/* Remove lock */
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unlink (lockfname);
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ret:
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g_free (lockfname);
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return 0;
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}
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/* --------------------------------------------------------------------------------------------- */
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