1 files changed, 332 insertions, 0 deletions
diff --git a/lib/vfs/gc.c b/lib/vfs/gc.c
new file mode 100644
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--- /dev/null
+++ b/lib/vfs/gc.c
@@ -0,0 +1,332 @@
+/*
+   Virtual File System garbage collection code
+
+   Copyright (C) 2003-2022
+   Free Software Foundation, Inc.
+
+   Written by:
+   Miguel de Icaza, 1995
+   Jakub Jelinek, 1995
+   Pavel Machek, 1998
+   Pavel Roskin, 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: Virtual File System: garbage collection code
+ * \author Miguel de Icaza
+ * \author Jakub Jelinek
+ * \author Pavel Machek
+ * \author Pavel Roskin
+ * \date 1995, 1998, 2003
+ */
+
+
+#include <config.h>
+
+#include <stdlib.h>
+
+#include "lib/global.h"
+#include "lib/event.h"
+#include "lib/util.h"           /* MC_PTR_FREE */
+
+#include "vfs.h"
+#include "utilvfs.h"
+
+#include "gc.h"
+
+/*
+ * The garbage collection mechanism is based on "stamps".
+ *
+ * A stamp is a record that says "I'm a filesystem which is no longer in
+ * use. Free me when you get a chance."
+ *
+ * This file contains a set of functions used for managing this stamp. You
+ * should use them when you write your own filesystem. Here are some rules
+ * of thumb:
+ *
+ * (1) When the last open file in your filesystem gets closed, conditionally
+ *     create a stamp. You do this with vfs_stamp_create(). (The meaning
+ *     of "conditionaly" is explained below.)
+ *
+ * (2) When a file in your filesystem is opened, delete the stamp. You do
+ *     this with vfs_rmstamp().
+ *
+ * (3) When a path inside your filesystem is invoked, call vfs_stamp() to
+ *     postpone the free'ing of your filesystem a bit. (This simply updates
+ *     a timestamp variable inside the stamp.)
+ *
+ * Additionally, when a user navigates to a new directory in a panel (or a
+ * programmer uses mc_chdir()), a stamp is conditionally created for the
+ * previous directory's filesystem. This ensures that that filesystem is
+ * free'ed. (see: _do_panel_cd() -> vfs_release_path(); mc_chdir()).
+ *
+ * We've spoken here of "conditionally creating" a stamp. What we mean is
+ * that vfs_stamp_create() is to be used: this function creates a stamp
+ * only if no directories are open (aka "active") in your filesystem. (If
+ * there _are_ directories open, it means that the filesystem is in use, in
+ * which case we don't want to free it.)
+ */
+
+/*** global variables ****************************************************************************/
+
+int vfs_timeout = 60;           /* VFS timeout in seconds */
+
+/*** file scope macro definitions ****************************************************************/
+
+#define VFS_STAMPING(a) ((struct vfs_stamping *)(a))
+
+/*** file scope type declarations ****************************************************************/
+
+struct vfs_stamping
+{
+    struct vfs_class *v;
+    vfsid id;
+    gint64 time;
+};
+
+/*** file scope variables ************************************************************************/
+
+static GSList *stamps = NULL;
+
+/* --------------------------------------------------------------------------------------------- */
+/*** file scope functions ************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+static gint
+vfs_stamp_compare (gconstpointer a, gconstpointer b)
+{
+    const struct vfs_stamping *vsa = (const struct vfs_stamping *) a;
+    const struct vfs_stamping *vsb = (const struct vfs_stamping *) b;
+
+    return (vsa == NULL || vsb == NULL || (vsa->v == vsb->v && vsa->id == vsb->id)) ? 0 : 1;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+static void
+vfs_addstamp (struct vfs_class *v, vfsid id)
+{
+    if ((v->flags & VFSF_LOCAL) == 0 && id != NULL && !vfs_stamp (v, id))
+    {
+        struct vfs_stamping *stamp;
+
+        stamp = g_new (struct vfs_stamping, 1);
+        stamp->v = v;
+        stamp->id = id;
+        stamp->time = g_get_monotonic_time ();
+
+        stamps = g_slist_append (stamps, stamp);
+    }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*** public functions ****************************************************************************/
+/* --------------------------------------------------------------------------------------------- */
+
+gboolean
+vfs_stamp (struct vfs_class *v, vfsid id)
+{
+    struct vfs_stamping what = {
+        .v = v,
+        .id = id
+    };
+    GSList *stamp;
+    gboolean ret = FALSE;
+
+    stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
+    if (stamp != NULL && stamp->data != NULL)
+    {
+        VFS_STAMPING (stamp->data)->time = g_get_monotonic_time ();
+        ret = TRUE;
+    }
+
+    return ret;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+vfs_rmstamp (struct vfs_class *v, vfsid id)
+{
+    struct vfs_stamping what = {
+        .v = v,
+        .id = id
+    };
+    GSList *stamp;
+
+    stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
+    if (stamp != NULL)
+    {
+        g_free (stamp->data);
+        stamps = g_slist_delete_link (stamps, stamp);
+    }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+vfs_stamp_path (const vfs_path_t * vpath)
+{
+    vfsid id;
+    const vfs_path_element_t *path_element;
+
+    path_element = vfs_path_get_by_index (vpath, -1);
+
+    id = vfs_getid (vpath);
+    vfs_addstamp (path_element->class, id);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/**
+ * Create a new timestamp item by VFS class and VFS id.
+ */
+
+void
+vfs_stamp_create (struct vfs_class *vclass, vfsid id)
+{
+    vfsid nvfsid;
+
+    ev_vfs_stamp_create_t event_data = { vclass, id, FALSE };
+    const vfs_path_t *vpath;
+    const vfs_path_element_t *path_element;
+
+    /* There are three directories we have to take care of: current_dir,
+       current_panel->cwd and other_panel->cwd. Athough most of the time either
+       current_dir and current_panel->cwd or current_dir and other_panel->cwd are the
+       same, it's possible that all three are different -- Norbert */
+
+    if (!mc_event_present (MCEVENT_GROUP_CORE, "vfs_timestamp"))
+        return;
+
+    vpath = vfs_get_raw_current_dir ();
+    path_element = vfs_path_get_by_index (vpath, -1);
+
+    nvfsid = vfs_getid (vpath);
+    vfs_rmstamp (path_element->class, nvfsid);
+
+    if (!(id == NULL || (path_element->class == vclass && nvfsid == id)))
+    {
+        mc_event_raise (MCEVENT_GROUP_CORE, "vfs_timestamp", (gpointer) & event_data);
+
+        if (!event_data.ret && vclass != NULL && vclass->nothingisopen != NULL
+            && vclass->nothingisopen (id))
+            vfs_addstamp (vclass, id);
+    }
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/** This is called from timeout handler with now = FALSE,
+    or can be called with now = TRUE to force freeing all filesystems */
+
+void
+vfs_expire (gboolean now)
+{
+    static gboolean locked = FALSE;
+    gint64 curr_time, exp_time;
+    GSList *stamp;
+
+    /* Avoid recursive invocation, e.g. when one of the free functions
+       calls message */
+    if (locked)
+        return;
+    locked = TRUE;
+
+    curr_time = g_get_monotonic_time ();
+    exp_time = curr_time - vfs_timeout * G_USEC_PER_SEC;
+
+    if (now)
+    {
+        /* reverse list to free nested VFSes at first */
+        stamps = g_slist_reverse (stamps);
+    }
+
+    /* NULLize stamps that point to expired VFS */
+    for (stamp = stamps; stamp != NULL; stamp = g_slist_next (stamp))
+    {
+        struct vfs_stamping *stamping = VFS_STAMPING (stamp->data);
+
+        if (now)
+        {
+            /* free VFS forced */
+            if (stamping->v->free != NULL)
+                stamping->v->free (stamping->id);
+            MC_PTR_FREE (stamp->data);
+        }
+        else if (stamping->time <= exp_time)
+        {
+            /* update timestamp of VFS that is in use, or free unused VFS */
+            if (stamping->v->nothingisopen != NULL && !stamping->v->nothingisopen (stamping->id))
+                stamping->time = curr_time;
+            else
+            {
+                if (stamping->v->free != NULL)
+                    stamping->v->free (stamping->id);
+                MC_PTR_FREE (stamp->data);
+            }
+        }
+    }
+
+    /* then remove NULLized stamps */
+    stamps = g_slist_remove_all (stamps, NULL);
+
+    locked = FALSE;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/*
+ * Return the number of seconds remaining to the vfs timeout.
+ * FIXME: The code should be improved to actually return the number of
+ * seconds until the next item times out.
+ */
+
+int
+vfs_timeouts (void)
+{
+    return stamps != NULL ? 10 : 0;
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+vfs_timeout_handler (void)
+{
+    vfs_expire (FALSE);
+}
+
+/* --------------------------------------------------------------------------------------------- */
+
+void
+vfs_release_path (const vfs_path_t * vpath)
+{
+    const vfs_path_element_t *path_element;
+
+    path_element = vfs_path_get_by_index (vpath, -1);
+    vfs_stamp_create (path_element->class, vfs_getid (vpath));
+}
+
+/* --------------------------------------------------------------------------------------------- */
+/* Free all data */
+
+void
+vfs_gc_done (void)
+{
+    vfs_expire (TRUE);
+}
+
+/* --------------------------------------------------------------------------------------------- */