1 files changed, 318 insertions, 0 deletions
diff --git a/lib/lock.c b/lib/lock.c
new file mode 100644
index 0000000..2d14d22
--- /dev/null
+++ b/lib/lock.c
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+/*
+   File locking
+
+   Copyright (C) 2003-2022
+   Free Software Foundation, Inc.
+
+   Written by:
+   Adam Byrtek, 2003
+
+   This file is part of the Midnight Commander.
+
+   The Midnight Commander is free software: you can redistribute it
+   and/or modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of the License,
+   or (at your option) any later version.
+
+   The Midnight Commander 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** \file
+ *  \brief Source: file locking
+ *  \author Adam Byrtek
+ *  \date 2003
+ *
+ *  Locking scheme is based on a documentation found
+ *  in JED editor sources. Abstract from lock.c file (by John E. Davis):
+ *
+ *  The basic idea here is quite simple.  Whenever a buffer is attached to
+ *  a file, and that buffer is modified, then attempt to lock the
+ *  file. Moreover, before writing to a file for any reason, lock the
+ *  file. The lock is really a protocol respected and not a real lock.
+ *  The protocol is this: If in the directory of the file is a
+ *  symbolic link with name ".#FILE", the FILE is considered to be locked
+ *  by the process specified by the link.
+ */
+
+#include <config.h>
+
+#include <signal.h>             /* kill() */
+#include <stdio.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <string.h>
+#include <ctype.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <pwd.h>
+#include <stdlib.h>
+
+#include "lib/global.h"
+#include "lib/vfs/vfs.h"
+#include "lib/util.h"           /* tilde_expand() */
+#include "lib/lock.h"
+#include "lib/widget.h"         /* query_dialog() */
+
+/*** global variables ****************************************************************************/
+
+/*** file scope macro definitions ****************************************************************/
+
+#define BUF_SIZE 255
+#define PID_BUF_SIZE 10
+
+/*** file scope type declarations ****************************************************************/
+
+typedef struct
+{
+    char *who;
+    pid_t pid;
+} lock_s;
+
+/*** file scope variables ************************************************************************/
+
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+/** \fn static char * lock_build_name (void)
+ *  \brief builds user@host.domain.pid string (need to be freed)
+ *  \return a pointer to lock filename
+ */
+
+static char *
+lock_build_name (void)
+{
+    char host[BUF_SIZE];
+    const char *user = NULL;
+    struct passwd *pw;
+
+    pw = getpwuid (getuid ());
+    if (pw)
+        user = pw->pw_name;
+    if (!user)
+        user = getenv ("USER");
+    if (!user)
+        user = getenv ("USERNAME");
+    if (!user)
+        user = getenv ("LOGNAME");
+    if (!user)
+        user = "";
+
+    /** \todo Use FQDN, no clean interface, so requires lot of code */
+    if (gethostname (host, BUF_SIZE - 1) == -1)
+        *host = '\0';
+
+    return g_strdup_printf ("%s@%s.%d", user, host, (int) getpid ());
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static char *
+lock_build_symlink_name (const vfs_path_t * fname_vpath)
+{
+    const char *elpath;
+    char *str_filename, *str_dirname, *symlink_name;
+
+    /* get first path piece */
+    elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
+
+    str_filename = g_path_get_basename (elpath);
+    str_dirname = g_path_get_dirname (elpath);
+    symlink_name = g_strconcat (str_dirname, PATH_SEP_STR ".#", str_filename, (char *) NULL);
+    g_free (str_dirname);
+    g_free (str_filename);
+
+    return symlink_name;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/**
+ * Extract pid from user@host.domain.pid string
+ */
+
+static lock_s *
+lock_extract_info (const char *str)
+{
+    size_t i, len;
+    const char *p, *s;
+    static char pid[PID_BUF_SIZE], who[BUF_SIZE];
+    static lock_s lock;
+
+    len = strlen (str);
+
+    for (p = str + len - 1; p >= str; p--)
+        if (*p == '.')
+            break;
+
+    /* Everything before last '.' is user@host */
+    i = 0;
+    for (s = str; i < BUF_SIZE && s < p; s++)
+        who[i++] = *s;
+    if (i == BUF_SIZE)
+        i--;
+    who[i] = '\0';
+
+    /* Treat text between '.' and ':' or '\0' as pid */
+    i = 0;
+    for (p = p + 1; i < PID_BUF_SIZE && p < str + len && *p != ':'; p++)
+        pid[i++] = *p;
+    if (i == PID_BUF_SIZE)
+        i--;
+    pid[i] = '\0';
+
+    lock.pid = (pid_t) atol (pid);
+    lock.who = who;
+    return &lock;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/**
+ * Extract user@host.domain.pid from lock file (static string)
+ */
+
+static const char *
+lock_get_info (const char *lockfname)
+{
+    ssize_t cnt;
+    static char buf[BUF_SIZE];
+
+    cnt = readlink (lockfname, buf, BUF_SIZE - 1);
+    if (cnt == -1 || *buf == '\0')
+        return NULL;
+    buf[cnt] = '\0';
+    return buf;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+/* Tries to raise file lock
+   Returns 1 on success,  0 on failure, -1 if abort
+   Warning: Might do screen refresh and lose edit->force */
+
+int
+lock_file (const vfs_path_t * fname_vpath)
+{
+    char *lockfname = NULL, *newlock, *msg;
+    struct stat statbuf;
+    lock_s *lockinfo;
+    gboolean is_local;
+    gboolean symlink_ok = FALSE;
+    const char *elpath;
+
+    if (fname_vpath == NULL)
+        return 0;
+
+    elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
+    /* Just to be sure (and don't lock new file) */
+    if (*elpath == '\0')
+        return 0;
+
+    /* Locking on VFS is not supported */
+    is_local = vfs_file_is_local (fname_vpath);
+    if (is_local)
+    {
+        /* Check if already locked */
+        lockfname = lock_build_symlink_name (fname_vpath);
+    }
+
+    if (!is_local || lockfname == NULL)
+        return 0;
+
+    if (lstat (lockfname, &statbuf) == 0)
+    {
+        const char *lock;
+
+        lock = lock_get_info (lockfname);
+        if (lock == NULL)
+            goto ret;
+        lockinfo = lock_extract_info (lock);
+
+        /* Check if locking process alive, ask user if required */
+        if (lockinfo->pid == 0 || !(kill (lockinfo->pid, 0) == -1 && errno == ESRCH))
+        {
+            msg =
+                g_strdup_printf (_
+                                 ("File \"%s\" is already being edited.\n"
+                                  "User: %s\nProcess ID: %d"), x_basename (lockfname) + 2,
+                                 lockinfo->who, (int) lockinfo->pid);
+            /* TODO: Implement "Abort" - needs to rewind undo stack */
+            switch (query_dialog
+                    (_("File locked"), msg, D_NORMAL, 2, _("&Grab lock"), _("&Ignore lock")))
+            {
+            case 0:
+                break;
+            case 1:
+            case -1:
+            default:           /* Esc Esc */
+                g_free (msg);
+                goto ret;
+            }
+            g_free (msg);
+        }
+        unlink (lockfname);
+    }
+
+    /* Create lock symlink */
+    newlock = lock_build_name ();
+    symlink_ok = (symlink (newlock, lockfname) != -1);
+    g_free (newlock);
+
+  ret:
+    g_free (lockfname);
+    return symlink_ok ? 1 : 0;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/**
+ * Lowers file lock if possible
+ * @return  Always 0
+ */
+
+int
+unlock_file (const vfs_path_t * fname_vpath)
+{
+    char *lockfname;
+    struct stat statbuf;
+    const char *elpath, *lock;
+
+    if (fname_vpath == NULL)
+        return 0;
+
+    elpath = vfs_path_get_by_index (fname_vpath, 0)->path;
+    /* Just to be sure (and don't lock new file) */
+    if (*elpath == '\0')
+        return 0;
+
+    lockfname = lock_build_symlink_name (fname_vpath);
+
+    if (lockfname == NULL)
+        return 0;
+
+    /* Check if lock exists */
+    if (lstat (lockfname, &statbuf) == -1)
+        goto ret;
+
+    lock = lock_get_info (lockfname);
+    if (lock != NULL)
+    {
+        /* Don't touch if lock is not ours */
+        if (lock_extract_info (lock)->pid != getpid ())
+            goto ret;
+    }
+
+    /* Remove lock */
+    unlink (lockfname);
+
+  ret:
+    g_free (lockfname);
+    return 0;
+}
+
+/* --------------------------------------------------------------------------------------------- */