inotify-kernel.c

this is a glib for c language

/*
   Copyright (C) 2005 John McCutchan

   The Gnome Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The Gnome Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the Gnome Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.

   Authors:.
		John McCutchan <[e-mail]>
*/

#include "config.h"

#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <glib.h>
#include "inotify-kernel.h"
#include <sys/inotify.h>

/* Timings for pairing MOVED_TO / MOVED_FROM events */
#define PROCESS_EVENTS_TIME 1000 /* milliseconds (1 hz) */
#define DEFAULT_HOLD_UNTIL_TIME 0 /* 0 millisecond */
#define MOVE_HOLD_UNTIL_TIME 0 /* 0 milliseconds */

static int inotify_instance_fd = -1;
static GQueue *events_to_process = NULL;
static GQueue *event_queue = NULL;
static GHashTable * cookie_hash = NULL;
static GIOChannel *inotify_read_ioc;
static GPollFD ik_poll_fd;
static gboolean ik_poll_fd_enabled = TRUE;
static void (*user_cb)(ik_event_t *event);

static gboolean ik_read_callback (gpointer user_data);
static gboolean ik_process_eq_callback (gpointer user_data);

static guint32 ik_move_matches = 0;
static guint32 ik_move_misses = 0;

static gboolean process_eq_running = FALSE;

/* We use the lock from inotify-helper.c
 *
 * There are two places that we take this lock
 *
 * 1) In ik_read_callback
 *
 * 2) ik_process_eq_callback.
 *
 *
 * The rest of locking is taken care of in inotify-helper.c
 */
G_LOCK_EXTERN (inotify_lock);

typedef struct ik_event_internal {
  ik_event_t *event;
  gboolean seen;
  gboolean sent;
  GTimeVal hold_until;
  struct ik_event_internal *pair;
} ik_event_internal_t;

/* In order to perform non-sleeping inotify event chunking we need
 * a custom GSource
 */
static gboolean
ik_source_prepare (GSource *source,
		   gint    *timeout)
{
  return FALSE;
}

static gboolean
ik_source_timeout (gpointer data)
{
  GSource *source = (GSource *)data;
  
  /* Re-active the PollFD */
  g_source_add_poll (source, &ik_poll_fd);
  g_source_unref (source);
  ik_poll_fd_enabled = TRUE;
  
  return FALSE;
}

#define MAX_PENDING_COUNT 2
#define PENDING_THRESHOLD(qsize) ((qsize) >> 1)
#define PENDING_MARGINAL_COST(p) ((unsigned int)(1 << (p)))
#define MAX_QUEUED_EVENTS 2048
#define AVERAGE_EVENT_SIZE sizeof (struct inotify_event) + 16
#define TIMEOUT_MILLISECONDS 10

static gboolean
ik_source_check (GSource *source)
{
  static int prev_pending = 0, pending_count = 0;
  
  /* We already disabled the PollFD or
   * nothing to be read from inotify */
  if (!ik_poll_fd_enabled || !(ik_poll_fd.revents & G_IO_IN))
    return FALSE;

  if (pending_count < MAX_PENDING_COUNT)
    {
      unsigned int pending;
      
      if (ioctl (inotify_instance_fd, FIONREAD, &pending) == -1)
	goto do_read;
      
      pending /= AVERAGE_EVENT_SIZE;
      
      /* Don't wait if the number of pending events is too close
       * to the maximum queue size.
       */
      if (pending > PENDING_THRESHOLD (MAX_QUEUED_EVENTS))
	goto do_read;
      
      /* With each successive iteration, the minimum rate for
       * further sleep doubles. 
       */
      if (pending-prev_pending < PENDING_MARGINAL_COST (pending_count))
	goto do_read;
      
      prev_pending = pending;
      pending_count++;
      
      /* We are going to wait to read the events: */
      
      /* Remove the PollFD from the source */
      g_source_remove_poll (source, &ik_poll_fd);
      /* To avoid threading issues we need to flag that we've done that */
      ik_poll_fd_enabled = FALSE;
      /* Set a timeout to re-add the PollFD to the source */
      g_source_ref (source);
      g_timeout_add (TIMEOUT_MILLISECONDS, ik_source_timeout, source);
      
      return FALSE;
    }

do_read:
  /* We are ready to read events from inotify */

  prev_pending = 0;
  pending_count = 0;
  
  return TRUE;
}

static gboolean
ik_source_dispatch (GSource     *source,
		    GSourceFunc  callback,
		    gpointer     user_data)
{
  if (callback)
    return callback (user_data);
  return TRUE;
}

static GSourceFuncs ik_source_funcs =
{
  ik_source_prepare,
  ik_source_check,
  ik_source_dispatch,
  NULL
};

gboolean _ik_startup (void (*cb)(ik_event_t *event))
{
  static gboolean initialized = FALSE;
  GSource *source;
  
  user_cb = cb;
  /* Ignore multi-calls */
  if (initialized) 
    return inotify_instance_fd >= 0;
  
  initialized = TRUE;
  inotify_instance_fd = inotify_init ();
  
  if (inotify_instance_fd < 0)
    return FALSE;

  inotify_read_ioc = g_io_channel_unix_new (inotify_instance_fd);
  ik_poll_fd.fd = inotify_instance_fd;
  ik_poll_fd.events = G_IO_IN | G_IO_HUP | G_IO_ERR;
  g_io_channel_set_encoding (inotify_read_ioc, NULL, NULL);
  g_io_channel_set_flags (inotify_read_ioc, G_IO_FLAG_NONBLOCK, NULL);

  source = g_source_new (&ik_source_funcs, sizeof (GSource));
  g_source_add_poll (source, &ik_poll_fd);
  g_source_set_callback (source, ik_read_callback, NULL, NULL);
  g_source_attach (source, NULL);
  g_source_unref (source);

  cookie_hash = g_hash_table_new (g_direct_hash, g_direct_equal);
  event_queue = g_queue_new ();
  events_to_process = g_queue_new ();
  
  return TRUE;
}

static ik_event_internal_t *
ik_event_internal_new (ik_event_t *event)
{
  ik_event_internal_t *internal_event = g_new0 (ik_event_internal_t, 1);
  GTimeVal tv;
  
  g_assert (event);
  
  g_get_current_time (&tv);
  g_time_val_add (&tv, DEFAULT_HOLD_UNTIL_TIME);
  internal_event->event = event;
  internal_event->hold_until = tv;
  
  return internal_event;
}

static ik_event_t *
ik_event_new (char *buffer)
{
  struct inotify_event *kevent = (struct inotify_event *)buffer;
  ik_event_t *event = g_new0 (ik_event_t, 1);
  
  g_assert (buffer);
  
  event->wd = kevent->wd;
  event->mask = kevent->mask;
  event->cookie = kevent->cookie;
  event->len = kevent->len;
  if (event->len)
    event->name = g_strdup (kevent->name);
  else
    event->name = g_strdup ("");
  
  return event;
}

ik_event_t *
_ik_event_new_dummy (const char *name, 
                     gint32      wd, 
                     guint32     mask)
{
  ik_event_t *event = g_new0 (ik_event_t, 1);
  event->wd = wd;
  event->mask = mask;
  event->cookie = 0;
  if (name)
    event->name = g_strdup (name);
  else
    event->name = g_strdup("");
  
  event->len = strlen (event->name);
  
  return event;
}

void
_ik_event_free (ik_event_t *event)
{
  if (event->pair)
    _ik_event_free (event->pair);
  g_free (event->name);
  g_free (event);
}

gint32
_ik_watch (const char *path, 
           guint32     mask, 
           int        *err)
{
  gint32 wd = -1;
  
  g_assert (path != NULL);
  g_assert (inotify_instance_fd >= 0);
  
  wd = inotify_add_watch (inotify_instance_fd, path, mask);
  
  if (wd < 0)
    {
      int e = errno;
      /* FIXME: debug msg failed to add watch */
      if (err)
	*err = e;
      return wd;
    }
  
  g_assert (wd >= 0);
  return wd;
}

int
_ik_ignore (const char *path, 
            gint32      wd)
{
  g_assert (wd >= 0);
  g_assert (inotify_instance_fd >= 0);
  
  if (inotify_rm_watch (inotify_instance_fd, wd) < 0)
    {
      /* int e = errno; */
      /* failed to rm watch */
      return -1;
    }
  
  return 0;
}

void
_ik_move_stats (guint32 *matches, 
                guint32 *misses)
{
  if (matches)
    *matches = ik_move_matches;
  
  if (misses)
    *misses = ik_move_misses;
}

const char *
_ik_mask_to_string (guint32 mask)
{
  gboolean is_dir = mask & IN_ISDIR;
  mask &= ~IN_ISDIR;