gstreamer/gst/gst.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gst.c: Initialization and non-pipeline operations
 *
 * This 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.
 *
 * This 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 this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/**
 * SECTION:gst
 * @short_description: Media library supporting arbitrary formats and filter
 *                     graphs.
 * @see_also: Check out both <ulink url="http://www.cse.ogi.edu/sysl/">OGI's
 *            pipeline</ulink> and Microsoft's DirectShow for some background.
 *
 * GStreamer is a framework for constructing graphs of various filters
 * (termed elements here) that will handle streaming media.  Any discreet
 * (packetizable) media type is supported, with provisions for automatically
 * determining source type.  Formatting/framing information is provided with
 * a powerful negotiation framework.  Plugins are heavily used to provide for
 * all elements, allowing one to construct plugins outside of the GST
 * library, even released binary-only if license require (please don't).
 *
 * GStreamer borrows heavily from both the <ulink
 * url="http://www.cse.ogi.edu/sysl/">OGI media pipeline</ulink> and
 * Microsoft's DirectShow, hopefully taking the best of both and leaving the
 * cruft behind. Its interface is slowly getting stable.
 *
 * The <application>GStreamer</application> library should be initialized with
 * gst_init() before it can be used. You should pass pointers to the main argc
 * and argv variables so that GStreamer can process its own command line
 * options, as shown in the following example.
 *
 * <example>
 * <title>Initializing the gstreamer library</title>
 * <programlisting language="c">
 * int
 * main (int argc, char *argv[])
 * {
 *   // initialize the GStreamer library
 *   gst_init (&amp;argc, &amp;argv);
 *   ...
 * }
 * </programlisting>
 * </example>
 *
 * It's allowed to pass two NULL pointers to gst_init() in case you don't want
 * to pass the command line args to GStreamer.
 *
 * You can also use GOption to initialize your own parameters as shown in
 * the next code fragment:
 * <example>
 * <title>Initializing own parameters when initializing gstreamer</title>
 * <programlisting>
 * static gboolean stats = FALSE;
 * ...
 * int
 * main (int argc, char *argv[])
 * {
 *  GOptionEntry options[] = {
 *   {"tags", 't', 0, G_OPTION_ARG_NONE, &amp;tags,
 *       N_("Output tags (also known as metadata)"), NULL},
 *   {NULL}
 *  };
 *  // must initialise the threading system before using any other GLib funtion
 *  if (!g_thread_supported ())
 *    g_thread_init (NULL);
 *  ctx = g_option_context_new ("[ADDITIONAL ARGUMENTS]");
 *  g_option_context_add_main_entries (ctx, options, GETTEXT_PACKAGE);
 *  g_option_context_add_group (ctx, gst_init_get_option_group ());
 *  if (!g_option_context_parse (ctx, &amp;argc, &amp;argv, &amp;err)) {
 *    g_print ("Error initializing: &percnt;s\n", GST_STR_NULL (err->message));
 *    exit (1);
 *  }
 *  g_option_context_free (ctx);
 * ...
 * }
 * </programlisting>
 * </example>
 *
 * Use gst_version() to query the library version at runtime or use the
 * GST_VERSION_* macros to find the version at compile time. Optionally
 * gst_version_string() returns a printable string.
 *
 * The gst_deinit() call is used to clean up all internal resources used
 * by <application>GStreamer</application>. It is mostly used in unit tests 
 * to check for leaks.
 *
 * Last reviewed on 2006-08-11 (0.10.10)
 */

#include "gst_private.h"
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#ifdef HAVE_FORK
#include <sys/wait.h>
#endif /* HAVE_FORK */
#ifdef HAVE_SYS_UTSNAME_H
#include <sys/utsname.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "gst-i18n-lib.h"
#include <locale.h>             /* for LC_ALL */

#include "gst.h"

#define GST_CAT_DEFAULT GST_CAT_GST_INIT

#define MAX_PATH_SPLIT  16
#define GST_PLUGIN_SEPARATOR ","

static gboolean gst_initialized = FALSE;

#ifndef GST_DISABLE_REGISTRY
static GList *plugin_paths = NULL;      /* for delayed processing in post_init */
#endif

extern gint _gst_trace_on;

/* defaults */
#ifdef HAVE_FORK
#define DEFAULT_FORK TRUE
#else
#define DEFAULT_FORK FALSE
#endif /* HAVE_FORK */

/* set to TRUE when segfaults need to be left as is, FIXME, this variable is
 * global. */
gboolean _gst_disable_segtrap = FALSE;

/* control the behaviour of registry rebuild */
static gboolean _gst_enable_registry_fork = DEFAULT_FORK;

static void load_plugin_func (gpointer data, gpointer user_data);
static gboolean init_pre (GOptionContext * context, GOptionGroup * group,
    gpointer data, GError ** error);
static gboolean init_post (GOptionContext * context, GOptionGroup * group,
    gpointer data, GError ** error);
static gboolean parse_goption_arg (const gchar * s_opt,
    const gchar * arg, gpointer data, GError ** err);

static GSList *preload_plugins = NULL;

const gchar g_log_domain_gstreamer[] = "GStreamer";

static void
debug_log_handler (const gchar * log_domain,
    GLogLevelFlags log_level, const gchar * message, gpointer user_data)
{
  g_log_default_handler (log_domain, log_level, message, user_data);
  /* FIXME: do we still need this ? fatal errors these days are all
   * other than core errors */
  /* g_on_error_query (NULL); */
}

enum
{
  ARG_VERSION = 1,
  ARG_FATAL_WARNINGS,
#ifndef GST_DISABLE_GST_DEBUG
  ARG_DEBUG_LEVEL,
  ARG_DEBUG,
  ARG_DEBUG_DISABLE,
  ARG_DEBUG_NO_COLOR,
  ARG_DEBUG_HELP,
#endif
  ARG_PLUGIN_SPEW,
  ARG_PLUGIN_PATH,
  ARG_PLUGIN_LOAD,
  ARG_SEGTRAP_DISABLE,
  ARG_REGISTRY_FORK_DISABLE
};

/* debug-spec ::= category-spec [, category-spec]*
 * category-spec ::= category:val | val
 * category ::= [^:]+
 * val ::= [0-5]
 */

#ifndef NUL
#define NUL '\0'
#endif

#ifndef GST_DISABLE_GST_DEBUG
static gboolean
parse_debug_category (gchar * str, const gchar ** category)
{
  if (!str)
    return FALSE;

  /* works in place */
  g_strstrip (str);

  if (str[0] != NUL) {
    *category = str;
    return TRUE;
  }

  return FALSE;
}

static gboolean
parse_debug_level (gchar * str, gint * level)
{
  if (!str)
    return FALSE;

  /* works in place */
  g_strstrip (str);

  if (str[0] != NUL && str[1] == NUL
      && str[0] >= '0' && str[0] < '0' + GST_LEVEL_COUNT) {
    *level = str[0] - '0';
    return TRUE;
  }

  return FALSE;
}

static void
parse_debug_list (const gchar * list)
{
  gchar **split;
  gchar **walk;

  g_return_if_fail (list != NULL);

  split = g_strsplit (list, ",", 0);

  for (walk = split; *walk; walk++) {
    if (strchr (*walk, ':')) {
      gchar **values = g_strsplit (*walk, ":", 2);

      if (values[0] && values[1]) {
        gint level;
        const gchar *category;

        if (parse_debug_category (values[0], &category)
            && parse_debug_level (values[1], &level))
          gst_debug_set_threshold_for_name (category, level);
      }

      g_strfreev (values);
    } else {
      gint level;

      if (parse_debug_level (*walk, &level))
        gst_debug_set_default_threshold (level);
    }
  }

  g_strfreev (split);
}
#endif

/**
 * gst_init_get_option_group:
 *
 * Returns a #GOptionGroup with GStreamer's argument specifications. The
 * group is set up to use standard GOption callbacks, so when using this
 * group in combination with GOption parsing methods, all argument parsing
 * and initialization is automated.
 *
 * This function is useful if you want to integrate GStreamer with other
 * libraries that use GOption (see g_option_context_add_group() ).
 *
 * If you use this function, you should make sure you initialise the GLib
 * threading system as one of the very first things in your program
 * (see the example at the beginning of this section).
 *
 * Returns: a pointer to GStreamer's option group.
 */

GOptionGroup *
gst_init_get_option_group (void)
{
  GOptionGroup *group;
  const static GOptionEntry gst_args[] = {
    {"gst-version", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
        (gpointer) parse_goption_arg, N_("Print the GStreamer version"), NULL},
    {"gst-fatal-warnings", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
        (gpointer) parse_goption_arg, N_("Make all warnings fatal"), NULL},
#ifndef GST_DISABLE_GST_DEBUG
    {"gst-debug-help", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Print available debug categories and exit"),
        NULL},
    {"gst-debug-level", 0, 0, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Default debug level from 1 (only error) to 5 (anything) or "
              "0 for no output"),
        N_("LEVEL")},
    {"gst-debug", 0, 0, G_OPTION_ARG_CALLBACK, (gpointer) parse_goption_arg,
          N_("Comma-separated list of category_name:level pairs to set "
              "specific levels for the individual categories. Example: "
              "GST_AUTOPLUG:5,GST_ELEMENT_*:3"),
        N_("LIST")},
    {"gst-debug-no-color", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg, N_("Disable colored debugging output"),
        NULL},
    {"gst-debug-disable", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
        (gpointer) parse_goption_arg, N_("Disable debugging"), NULL},
#endif
    {"gst-plugin-spew", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Enable verbose plugin loading diagnostics"),
        NULL},
    {"gst-plugin-path", 0, 0, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
        N_("Colon-separated paths containing plugins"), N_("PATHS")},
    {"gst-plugin-load", 0, 0, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Comma-separated list of plugins to preload in addition to the "
              "list stored in environment variable GST_PLUGIN_PATH"),
        N_("PLUGINS")},
    {"gst-disable-segtrap", 0, G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Disable trapping of segmentation faults during plugin loading"),
        NULL},
    {"gst-disable-registry-fork", 0, G_OPTION_FLAG_NO_ARG,
          G_OPTION_ARG_CALLBACK,
          (gpointer) parse_goption_arg,
          N_("Disable the use of fork() while scanning the registry"),
        NULL},
    {NULL}
  };

  /* The GLib threading system must be initialised before calling any other
   * GLib function according to the documentation; if the application hasn't
   * called gst_init() yet or initialised the threading system otherwise, we
   * better issue a warning here (since chances are high that the application
   * has already called other GLib functions such as g_option_context_new() */
  if (!g_thread_supported ()) {
    g_warning ("The GStreamer function gst_init_get_option_group() was\n"
        "\tcalled, but the GLib threading system has not been initialised\n"
        "\tyet, something that must happen before any other GLib function\n"
        "\tis called. The application needs to be fixed accordingly, please\n"
        "\tfile a bug against this application.");
    g_thread_init (NULL);
  }

  group = g_option_group_new ("gst", _("GStreamer Options"),
      _("Show GStreamer Options"), NULL, NULL);
  g_option_group_set_parse_hooks (group, (GOptionParseFunc) init_pre,
      (GOptionParseFunc) init_post);

  g_option_group_add_entries (group, gst_args);
  g_option_group_set_translation_domain (group, GETTEXT_PACKAGE);

  return group;
}

/**
 * gst_init_check:
 * @argc: pointer to application's argc
 * @argv: pointer to application's argv
 * @err: pointer to a #GError to which a message will be posted on error
 *
 * Initializes the GStreamer library, setting up internal path lists,
 * registering built-in elements, and loading standard plugins.
 *
 * This function will return %FALSE if GStreamer could not be initialized
 * for some reason.  If you want your program to fail fatally,
 * use gst_init() instead.
 *
 * This function should be called before calling any other GLib functions. If
 * this is not an option, your program must initialise the GLib thread system
 * using g_thread_init() before any other GLib functions are called.
 *
 * Returns: %TRUE if GStreamer could be initialized.
 */
gboolean
gst_init_check (int *argc, char **argv[], GError ** err)
{
  GOptionGroup *group;
  GOptionContext *ctx;
  gboolean res;

  if (!g_thread_supported ())
    g_thread_init (NULL);

  GST_INFO ("initializing GStreamer");

  if (gst_initialized) {
    GST_DEBUG ("already initialized gst");
    return TRUE;
  }

  ctx = g_option_context_new ("- GStreamer initialization");
  g_option_context_set_ignore_unknown_options (ctx, TRUE);
  group = gst_init_get_option_group ();
  g_option_context_add_group (ctx, group);
  res = g_option_context_parse (ctx, argc, argv, err);
  g_option_context_free (ctx);

  gst_initialized = res;

  if (res) {
    GST_INFO ("initialized GStreamer successfully");
  } else {
    GST_INFO ("failed to initialize GStreamer");
  }

  return res;
}

/**
 * gst_init:
 * @argc: pointer to application's argc
 * @argv: pointer to application's argv
 *
 * Initializes the GStreamer library, setting up internal path lists,
 * registering built-in elements, and loading standard plugins.
 *
 * This function should be called before calling any other GLib functions. If
 * this is not an option, your program must initialise the GLib thread system
 * using g_thread_init() before any other GLib functions are called.
 *
 * <note><para>
 * This function will terminate your program if it was unable to initialize
 * GStreamer for some reason.  If you want your program to fall back,
 * use gst_init_check() instead.
 * </para></note>
 *
 * WARNING: This function does not work in the same way as corresponding
 * functions in other glib-style libraries, such as gtk_init().  In
 * particular, unknown command line options cause this function to
 * abort program execution.
 */
void
gst_init (int *argc, char **argv[])
{
  GError *err = NULL;

  if (!gst_init_check (argc, argv, &err)) {
    g_print ("Could not initialize GStreamer: %s\n",
        err ? err->message : "unknown error occurred");
    if (err) {
      g_error_free (err);
    }
    exit (1);
  }
}

#ifndef GST_DISABLE_REGISTRY
static void
add_path_func (gpointer data, gpointer user_data)
{
  GST_INFO ("Adding plugin path: \"%s\", will scan later", (gchar *) data);
  plugin_paths = g_list_append (plugin_paths, g_strdup (data));
}
#endif

static void
prepare_for_load_plugin_func (gpointer data, gpointer user_data)
{
  preload_plugins = g_slist_prepend (preload_plugins, g_strdup (data));
}

static void
load_plugin_func (gpointer data, gpointer user_data)
{
  GstPlugin *plugin;
  const gchar *filename;
  GError *err = NULL;

  filename = (const gchar *) data;

  plugin = gst_plugin_load_file (filename, &err);

  if (plugin) {
    GST_INFO ("Loaded plugin: \"%s\"", filename);

    gst_default_registry_add_plugin (plugin);
  } else {
    if (err) {
      /* Report error to user, and free error */
      GST_ERROR ("Failed to load plugin: %s\n", err->message);
      g_error_free (err);
    } else {
      GST_WARNING ("Failed to load plugin: \"%s\"", filename);
    }
  }
}

static void
split_and_iterate (const gchar * stringlist, gchar * separator, GFunc iterator,
    gpointer user_data)
{
  gchar **strings;
  gint j = 0;
  gchar *lastlist = g_strdup (stringlist);

  while (lastlist) {
    strings = g_strsplit (lastlist, separator, MAX_PATH_SPLIT);
    g_free (lastlist);
    lastlist = NULL;

    while (strings[j]) {
      iterator (strings[j], user_data);
      if (++j == MAX_PATH_SPLIT) {
        lastlist = g_strdup (strings[j]);
        j = 0;
        break;
      }
    }
    g_strfreev (strings);
  }
}

/* we have no fail cases yet, but maybe in the future */
static gboolean
init_pre (GOptionContext * context, GOptionGroup * group, gpointer data,
    GError ** error)
{
  if (gst_initialized) {
    GST_DEBUG ("already initialized");
    return TRUE;
  }

  /* GStreamer was built against a GLib >= 2.8 and is therefore not doing
   * the refcount hack. Check that it isn't being run against an older GLib */
  if (glib_major_version < 2 ||
      (glib_major_version == 2 && glib_minor_version < 8)) {
    g_warning ("GStreamer was compiled against GLib %d.%d.%d but is running"
        " against %d.%d.%d. This will cause reference counting issues",
        GLIB_MAJOR_VERSION, GLIB_MINOR_VERSION, GLIB_MICRO_VERSION,
        glib_major_version, glib_minor_version, glib_micro_version);
  }

  g_type_init ();

  /* we need threading to be enabled right here */
  g_assert (g_thread_supported ());
  _gst_debug_init ();

#ifdef ENABLE_NLS
  setlocale (LC_ALL, "");
  bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
#endif /* ENABLE_NLS */

#ifndef GST_DISABLE_GST_DEBUG
  {
    const gchar *debug_list;

    if (g_getenv ("GST_DEBUG_NO_COLOR") != NULL)
      gst_debug_set_colored (FALSE);

    debug_list = g_getenv ("GST_DEBUG");
    if (debug_list) {
      parse_debug_list (debug_list);
    }
  }
#endif
  /* This is the earliest we can make stuff show up in the logs.
   * So give some useful info about GStreamer here */
  GST_INFO ("Initializing GStreamer Core Library version %s", VERSION);
  GST_INFO ("Using library installed in %s", LIBDIR);

  /* Print some basic system details if possible (OS/architecture) */
#ifdef HAVE_SYS_UTSNAME_H
  {
    struct utsname sys_details;

    if (uname (&sys_details) == 0) {
      GST_INFO ("%s %s %s %s %s", sys_details.sysname,
          sys_details.nodename, sys_details.release, sys_details.version,
          sys_details.machine);
    }
  }
#endif

  return TRUE;
}

static gboolean
gst_register_core_elements (GstPlugin * plugin)
{
  /* register some standard builtin types */
  if (!gst_element_register (plugin, "bin", GST_RANK_PRIMARY,
          GST_TYPE_BIN) ||
      !gst_element_register (plugin, "pipeline", GST_RANK_PRIMARY,
          GST_TYPE_PIPELINE)
      )
    g_assert_not_reached ();

  return TRUE;
}

static GstPluginDesc plugin_desc = {
  GST_VERSION_MAJOR,
  GST_VERSION_MINOR,
  "staticelements",
  "core elements linked into the GStreamer library",
  gst_register_core_elements,
  VERSION,
  GST_LICENSE,
  PACKAGE,
  GST_PACKAGE_NAME,
  GST_PACKAGE_ORIGIN,

  GST_PADDING_INIT
};

#ifndef GST_DISABLE_REGISTRY

/*
 * scan_and_update_registry:
 * @default_registry: the #GstRegistry
 * @registry_file: registry filename
 * @write_changes: write registry if it has changed?
 *
 * Scans for registry changes and eventually updates the registry cache. 
 *
 * Return: %TRUE if the registry could be updated
 */
static gboolean
scan_and_update_registry (GstRegistry * default_registry,
    const gchar * registry_file, gboolean write_changes, GError ** error)
{
  const gchar *plugin_path;
  gboolean changed = FALSE;
  GList *l;

  GST_DEBUG ("reading registry cache: %s", registry_file);
  gst_registry_xml_read_cache (default_registry, registry_file);

  /* scan paths specified via --gst-plugin-path */
  GST_DEBUG ("scanning paths added via --gst-plugin-path");
  for (l = plugin_paths; l != NULL; l = l->next) {
    GST_INFO ("Scanning plugin path: \"%s\"", (gchar *) l->data);
    /* CHECKME: add changed |= here as well? */
    gst_registry_scan_path (default_registry, (gchar *) l->data);
  }
  /* keep plugin_paths around in case a re-scan is forced later on */

  /* GST_PLUGIN_PATH specifies a list of directories to scan for
   * additional plugins.  These take precedence over the system plugins */
  plugin_path = g_getenv ("GST_PLUGIN_PATH");
  if (plugin_path) {
    char **list;
    int i;

    GST_DEBUG ("GST_PLUGIN_PATH set to %s", plugin_path);
    list = g_strsplit (plugin_path, G_SEARCHPATH_SEPARATOR_S, 0);
    for (i = 0; list[i]; i++) {
      changed |= gst_registry_scan_path (default_registry, list[i]);
    }
    g_strfreev (list);
  } else {
    GST_DEBUG ("GST_PLUGIN_PATH not set");
  }

  /* GST_PLUGIN_SYSTEM_PATH specifies a list of plugins that are always
   * loaded by default.  If not set, this defaults to the system-installed
   * path, and the plugins installed in the user's home directory */
  plugin_path = g_getenv ("GST_PLUGIN_SYSTEM_PATH");
  if (plugin_path == NULL) {
    char *home_plugins;

    GST_DEBUG ("GST_PLUGIN_SYSTEM_PATH not set");

    /* plugins in the user's home directory take precedence over
     * system-installed ones */
    home_plugins = g_build_filename (g_get_home_dir (),
        ".gstreamer-" GST_MAJORMINOR, "plugins", NULL);
    changed |= gst_registry_scan_path (default_registry, home_plugins);
    g_free (home_plugins);

    /* add the main (installed) library path */
    changed |= gst_registry_scan_path (default_registry, PLUGINDIR);
  } else {
    gchar **list;
    gint i;

    GST_DEBUG ("GST_PLUGIN_SYSTEM_PATH set to %s", plugin_path);
    list = g_strsplit (plugin_path, G_SEARCHPATH_SEPARATOR_S, 0);
    for (i = 0; list[i]; i++) {
      changed |= gst_registry_scan_path (default_registry, list[i]);
    }
    g_strfreev (list);
  }

  /* Remove cached plugins so stale info is cleared. */
  changed |= _priv_gst_registry_remove_cache_plugins (default_registry);

  if (!changed) {
    GST_INFO ("Registry cache has not changed");
    return TRUE;
  }

  if (!write_changes) {
    GST_INFO ("Registry cached changed, but writing is disabled. Not writing.");
    return TRUE;
  }

  GST_INFO ("Registry cache changed. Writing new registry cache");
  if (!gst_registry_xml_write_cache (default_registry, registry_file)) {
    g_set_error (error, GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
        _("Error writing registry cache to %s: %s"),
        registry_file, g_strerror (errno));
    return FALSE;
  }

  GST_INFO ("Registry cache written successfully");
  return TRUE;
}

static gboolean
ensure_current_registry_nonforking (GstRegistry * default_registry,
    const gchar * registry_file, GError ** error)
{
  /* fork() not available */
  GST_DEBUG ("Updating registry cache in-process");
  scan_and_update_registry (default_registry, registry_file, TRUE, error);
  return TRUE;
}

/* when forking is not available this function always does nothing but return
 * TRUE immediatly */
static gboolean
ensure_current_registry_forking (GstRegistry * default_registry,
    const gchar * registry_file, GError ** error)
{
#ifdef HAVE_FORK
  pid_t pid;
  int pfd[2];
  int ret;

  /* We fork here, and let the child read and possibly rebuild the registry.
   * After that, the parent will re-read the freshly generated registry. */
  GST_DEBUG ("forking to update registry");

  if (pipe (pfd) == -1) {
    g_set_error (error, GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
        _("Error re-scanning registry %s: %s"),
        ", could not create pipes. Error", g_strerror (errno));
    return FALSE;
  }

  pid = fork ();
  if (pid == -1) {
    GST_ERROR ("Failed to fork()");
    g_set_error (error, GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
        _("Error re-scanning registry %s: %s"),
        ", failed to fork. Error", g_strerror (errno));
    return FALSE;
  }

  if (pid == 0) {
    gboolean res;
    gchar res_byte;

    /* this is the child. Close the read pipe */
    (void) close (pfd[0]);

    GST_DEBUG ("child reading registry cache");
    res =
        scan_and_update_registry (default_registry, registry_file, TRUE, NULL);

    /* need to use _exit, so that any exit handlers registered don't
     * bring down the main program */
    GST_DEBUG ("child exiting: %s", (res) ? "SUCCESS" : "FAILURE");

    /* make valgrind happy (yes, you can call it insane) */
    g_free ((char *) registry_file);

    /* write a result byte to the pipe */
    res_byte = res ? '1' : '0';
    do {
      ret = write (pfd[1], &res_byte, 1);
    } while (ret == -1 && errno == EINTR);
    /* if ret == -1 now, we could not write to pipe, probably 
     * means parent has exited before us */
    (void) close (pfd[1]);

    _exit (0);
  } else {
    gchar res_byte;

    /* parent. Close write pipe */
    (void) close (pfd[1]);

    /* Wait for result from the pipe */
    GST_DEBUG ("Waiting for data from child");
    do {
      ret = read (pfd[0], &res_byte, 1);
    } while (ret == -1 && errno == EINTR);

    if (ret == -1) {
      g_set_error (error, GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
          _("Error re-scanning registry %s: %s"),
          ", read returned error", g_strerror (errno));
      close (pfd[0]);
      return FALSE;
    }
    (void) close (pfd[0]);

    /* Wait to ensure the child is reaped, but ignore the result */
    GST_DEBUG ("parent waiting on child");
    waitpid (pid, NULL, 0);
    GST_DEBUG ("parent done waiting on child");

    if (ret == 0) {
      GST_ERROR ("child did not exit normally, terminated by signal");
      g_set_error (error, GST_CORE_ERROR, GST_CORE_ERROR_FAILED,
          _("Error re-scanning registry %s"), ", child terminated by signal");
      return FALSE;
    }

    if (res_byte == '1') {
      GST_DEBUG ("Child succeeded. Parent reading registry cache");
      gst_registry_xml_read_cache (default_registry, registry_file);
    } else {
      GST_DEBUG ("Child failed. Parent re-scanning registry, ignoring errors.");
      scan_and_update_registry (default_registry, registry_file, FALSE, NULL);
    }
  }
#endif /* HAVE_FORK */
  return TRUE;
}

static gboolean
ensure_current_registry (GError ** error)
{
  char *registry_file;
  GstRegistry *default_registry;
  gboolean ret;
  gboolean do_fork;

  default_registry = gst_registry_get_default ();
  registry_file = g_strdup (g_getenv ("GST_REGISTRY"));
  if (registry_file == NULL) {
    registry_file = g_build_filename (g_get_home_dir (),
        ".gstreamer-" GST_MAJORMINOR, "registry." HOST_CPU ".xml", NULL);
  }

  /* first see if forking is enabled */
  do_fork = _gst_enable_registry_fork;
  if (do_fork) {
    const gchar *fork_env;

    /* forking enabled, see if it is disabled with an env var */
    if ((fork_env = g_getenv ("GST_REGISTRY_FORK"))) {
      /* fork enabled for any value different from "no" */
      do_fork = strcmp (fork_env, "no") != 0;
    }
  }

  /* now check registry with or without forking */
  if (do_fork) {
    GST_DEBUG ("forking for registry rebuild");
    ret = ensure_current_registry_forking (default_registry, registry_file,
        error);
  } else {
    GST_DEBUG ("requested not to fork for registry rebuild");
    ret = ensure_current_registry_nonforking (default_registry, registry_file,
        error);
  }

  g_free (registry_file);

  return ret;
}
#endif /* GST_DISABLE_REGISTRY */

/*
 * this bit handles:
 * - initalization of threads if we use them
 * - log handler
 * - initial output
 * - initializes gst_format
 * - registers a bunch of types for gst_objects
 *
 * - we don't have cases yet where this fails, but in the future
 *   we might and then it's nice to be able to return that
 */
static gboolean
init_post (GOptionContext * context, GOptionGroup * group, gpointer data,
    GError ** error)
{
  GLogLevelFlags llf;

#ifndef GST_DISABLE_TRACE
  GstTrace *gst_trace;
#endif /* GST_DISABLE_TRACE */

  if (gst_initialized) {
    GST_DEBUG ("already initialized");
    return TRUE;
  }

  llf = G_LOG_LEVEL_CRITICAL | G_LOG_LEVEL_ERROR | G_LOG_FLAG_FATAL;
  g_log_set_handler (g_log_domain_gstreamer, llf, debug_log_handler, NULL);

  _priv_gst_quarks_initialize ();
  _gst_format_initialize ();
  _gst_query_initialize ();
  gst_object_get_type ();
  gst_pad_get_type ();
  gst_element_factory_get_type ();
  gst_element_get_type ();
  gst_type_find_factory_get_type ();
  gst_bin_get_type ();

#ifndef GST_DISABLE_INDEX
  gst_index_factory_get_type ();
#endif /* GST_DISABLE_INDEX */
#ifndef GST_DISABLE_URI
  gst_uri_handler_get_type ();
#endif /* GST_DISABLE_URI */

  gst_structure_get_type ();
  _gst_value_initialize ();
  gst_caps_get_type ();
  _gst_event_initialize ();
  _gst_buffer_initialize ();
  _gst_message_initialize ();
  _gst_tag_initialize ();

  /* register core plugins */
  _gst_plugin_register_static (&plugin_desc);

  _gst_plugin_initialize ();

  /*
   * Any errors happening below this point are non-fatal, we therefore mark
   * gstreamer as being initialized, since it is the case from a plugin point of
   * view.
   *
   * If anything fails, it will be put back to FALSE in gst_init_check().
   * This allows some special plugins that would call gst_init() to not cause a
   * looping effect (i.e. initializing GStreamer twice).
   */
  gst_initialized = TRUE;

#ifndef GST_DISABLE_REGISTRY
  if (!ensure_current_registry (error))
    return FALSE;
#endif /* GST_DISABLE_REGISTRY */

  /* if we need to preload plugins, do so now */
  g_slist_foreach (preload_plugins, load_plugin_func, NULL);
  /* keep preload_plugins around in case a re-scan is forced later on */

#ifndef GST_DISABLE_TRACE
  _gst_trace_on = 0;
  if (_gst_trace_on) {
    gst_trace = gst_trace_new ("gst.trace", 1024);
    gst_trace_set_default (gst_trace);
  }
#endif /* GST_DISABLE_TRACE */

  return TRUE;
}

#ifndef GST_DISABLE_GST_DEBUG
static gboolean
select_all (GstPlugin * plugin, gpointer user_data)
{
  return TRUE;
}

static gint
sort_by_category_name (gconstpointer a, gconstpointer b)
{
  return strcmp (gst_debug_category_get_name ((GstDebugCategory *) a),
      gst_debug_category_get_name ((GstDebugCategory *) b));
}
static void
gst_debug_help (void)
{
  GSList *list, *walk;
  GList *list2, *g;

  /* Need to ensure the registry is loaded to get debug categories */
  if (!init_post (NULL, NULL, NULL, NULL))
    exit (1);

  list2 = gst_registry_plugin_filter (gst_registry_get_default (),
      select_all, FALSE, NULL);

  /* FIXME this is gross.  why don't debug have categories PluginFeatures? */
  for (g = list2; g; g = g_list_next (g)) {
    GstPlugin *plugin = GST_PLUGIN_CAST (g->data);

    gst_plugin_load (plugin);
  }
  g_list_free (list2);

  list = gst_debug_get_all_categories ();
  walk = list = g_slist_sort (list, sort_by_category_name);

  g_print ("\n");
  g_print ("name                  level    description\n");
  g_print ("---------------------+--------+--------------------------------\n");

  while (walk) {
    GstDebugCategory *cat = (GstDebugCategory *) walk->data;

    if (gst_debug_is_colored ()) {
      gchar *color = gst_debug_construct_term_color (cat->color);

      g_print ("%s%-20s\033[00m  %1d %s  %s%s\033[00m\n",
          color,
          gst_debug_category_get_name (cat),
          gst_debug_category_get_threshold (cat),
          gst_debug_level_get_name (gst_debug_category_get_threshold (cat)),
          color, gst_debug_category_get_description (cat));
      g_free (color);
    } else {
      g_print ("%-20s  %1d %s  %s\n", gst_debug_category_get_name (cat),
          gst_debug_category_get_threshold (cat),
          gst_debug_level_get_name (gst_debug_category_get_threshold (cat)),
          gst_debug_category_get_description (cat));
    }
    walk = g_slist_next (walk);
  }
  g_slist_free (list);
  g_print ("\n");
}
#endif

static gboolean
parse_one_option (gint opt, const gchar * arg, GError ** err)
{
  switch (opt) {
    case ARG_VERSION:
      g_print ("GStreamer Core Library version %s\n", PACKAGE_VERSION);
      exit (0);
    case ARG_FATAL_WARNINGS:{
      GLogLevelFlags fatal_mask;

      fatal_mask = g_log_set_always_fatal (G_LOG_FATAL_MASK);
      fatal_mask |= G_LOG_LEVEL_WARNING | G_LOG_LEVEL_CRITICAL;
      g_log_set_always_fatal (fatal_mask);
      break;
    }
#ifndef GST_DISABLE_GST_DEBUG
    case ARG_DEBUG_LEVEL:{
      gint tmp = 0;

      tmp = strtol (arg, NULL, 0);
      if (tmp >= 0 && tmp < GST_LEVEL_COUNT) {
        gst_debug_set_default_threshold (tmp);
      }
      break;
    }
    case ARG_DEBUG:
      parse_debug_list (arg);
      break;
    case ARG_DEBUG_NO_COLOR:
      gst_debug_set_colored (FALSE);
      break;
    case ARG_DEBUG_DISABLE:
      gst_debug_set_active (FALSE);
      break;
    case ARG_DEBUG_HELP:
      gst_debug_help ();
      exit (0);
#endif
    case ARG_PLUGIN_SPEW:
      break;
    case ARG_PLUGIN_PATH:
#ifndef GST_DISABLE_REGISTRY
      split_and_iterate (arg, G_SEARCHPATH_SEPARATOR_S, add_path_func, NULL);
#endif /* GST_DISABLE_REGISTRY */
      break;
    case ARG_PLUGIN_LOAD:
      split_and_iterate (arg, ",", prepare_for_load_plugin_func, NULL);
      break;
    case ARG_SEGTRAP_DISABLE:
      _gst_disable_segtrap = TRUE;
      break;
    case ARG_REGISTRY_FORK_DISABLE:
      _gst_enable_registry_fork = FALSE;
      break;
    default:
      g_set_error (err, G_OPTION_ERROR, G_OPTION_ERROR_UNKNOWN_OPTION,
          _("Unknown option"));
      return FALSE;
  }

  return TRUE;
}

static gboolean
parse_goption_arg (const gchar * opt,
    const gchar * arg, gpointer data, GError ** err)
{
  static const struct
  {
    gchar *opt;
    int val;
  } options[] = {
    {
    "--gst-version", ARG_VERSION}, {
    "--gst-fatal-warnings", ARG_FATAL_WARNINGS},
#ifndef GST_DISABLE_GST_DEBUG
    {
    "--gst-debug-level", ARG_DEBUG_LEVEL}, {
    "--gst-debug", ARG_DEBUG}, {
    "--gst-debug-disable", ARG_DEBUG_DISABLE}, {
    "--gst-debug-no-color", ARG_DEBUG_NO_COLOR}, {
    "--gst-debug-help", ARG_DEBUG_HELP},
#endif
    {
    "--gst-plugin-spew", ARG_PLUGIN_SPEW}, {
    "--gst-plugin-path", ARG_PLUGIN_PATH}, {
    "--gst-plugin-load", ARG_PLUGIN_LOAD}, {
    "--gst-disable-segtrap", ARG_SEGTRAP_DISABLE}, {
    "--gst-disable-registry-fork", ARG_REGISTRY_FORK_DISABLE}, {
    NULL}
  };
  gint val = 0, n;

  for (n = 0; options[n].opt; n++) {
    if (!strcmp (opt, options[n].opt)) {
      val = options[n].val;
      break;
    }
  }

  return parse_one_option (val, arg, err);
}

extern GstRegistry *_gst_registry_default;

/**
 * gst_deinit:
 *
 * Clean up any resources created by GStreamer in gst_init().
 *
 * It is normally not needed to call this function in a normal application
 * as the resources will automatically be freed when the program terminates.
 * This function is therefore mostly used by testsuites and other memory
 * profiling tools.
 *
 * After this call GStreamer (including this method) should not be used anymore. 
 */
void
gst_deinit (void)
{
  GstClock *clock;

  GST_INFO ("deinitializing GStreamer");

  if (!gst_initialized) {
    GST_DEBUG ("already deinitialized");
    return;
  }

  g_slist_foreach (preload_plugins, (GFunc) g_free, NULL);
  g_slist_free (preload_plugins);
  preload_plugins = NULL;

  g_list_foreach (plugin_paths, (GFunc) g_free, NULL);
  g_list_free (plugin_paths);
  plugin_paths = NULL;

  clock = gst_system_clock_obtain ();
  gst_object_unref (clock);
  gst_object_unref (clock);

  _priv_gst_registry_cleanup ();

  gst_initialized = FALSE;
  GST_INFO ("deinitialized GStreamer");
}

/**
 * gst_version:
 * @major: pointer to a guint to store the major version number
 * @minor: pointer to a guint to store the minor version number
 * @micro: pointer to a guint to store the micro version number
 * @nano:  pointer to a guint to store the nano version number
 *
 * Gets the version number of the GStreamer library.
 */
void
gst_version (guint * major, guint * minor, guint * micro, guint * nano)
{
  g_return_if_fail (major);
  g_return_if_fail (minor);
  g_return_if_fail (micro);
  g_return_if_fail (nano);

  *major = GST_VERSION_MAJOR;
  *minor = GST_VERSION_MINOR;
  *micro = GST_VERSION_MICRO;
  *nano = GST_VERSION_NANO;
}

/**
 * gst_version_string:
 *
 * This function returns a string that is useful for describing this version
 * of GStreamer to the outside world: user agent strings, logging, ...
 *
 * Returns: a newly allocated string describing this version of GStreamer.
 */

gchar *
gst_version_string ()
{
  guint major, minor, micro, nano;

  gst_version (&major, &minor, &micro, &nano);
  if (nano == 0)
    return g_strdup_printf ("GStreamer %d.%d.%d", major, minor, micro);
  else if (nano == 1)
    return g_strdup_printf ("GStreamer %d.%d.%d (CVS)", major, minor, micro);
  else
    return g_strdup_printf ("GStreamer %d.%d.%d (prerelease)", major, minor,
        micro);
}

/**
 * gst_segtrap_is_enabled:
 *
 * Some functions in the GStreamer core might install a custom SIGSEGV handler
 * to better catch and report errors to the application. Currently this feature
 * is enabled by default when loading plugins.
 *
 * Applications might want to disable this behaviour with the
 * gst_segtrap_set_enabled() function. This is typically done if the application
 * wants to install its own handler without GStreamer interfering.
 *
 * Returns: %TRUE if GStreamer is allowed to install a custom SIGSEGV handler.
 *
 * Since: 0.10.10
 */
gboolean
gst_segtrap_is_enabled (void)
{
  /* yeps, it's enabled when it's not disabled */
  return !_gst_disable_segtrap;
}

/**
 * gst_segtrap_set_enabled:
 * @enabled: whether a custom SIGSEGV handler should be installed.
 *
 * Applications might want to disable/enable the SIGSEGV handling of
 * the GStreamer core. See gst_segtrap_is_enabled() for more information.
 *
 * Since: 0.10.10
 */
void
gst_segtrap_set_enabled (gboolean enabled)
{
  _gst_disable_segtrap = !enabled;
}

/**
 * gst_registry_fork_is_enabled:
 *
 * By default GStreamer will perform a fork() when scanning and rebuilding the
 * registry file. 
 *
 * Applications might want to disable this behaviour with the
 * gst_registry_fork_set_enabled() function. 
 *
 * Returns: %TRUE if GStreamer will use fork() when rebuilding the registry. On
 * platforms without fork(), this function will always return %FALSE.
 *
 * Since: 0.10.10
 */
gboolean
gst_registry_fork_is_enabled (void)
{
  return _gst_enable_registry_fork;
}

/**
 * gst_registry_fork_set_enabled:
 * @enabled: whether rebuilding the registry may fork
 *
 * Applications might want to disable/enable the usage of fork() when rebuilding
 * the registry. See gst_registry_fork_is_enabled() for more information.
 *
 * On platforms without fork(), this function will have no effect on the return
 * value of gst_registry_fork_is_enabled().
 *
 * Since: 0.10.10
 */
void
gst_registry_fork_set_enabled (gboolean enabled)
{
#ifdef HAVE_FORK
  _gst_enable_registry_fork = enabled;
#endif /* HAVE_FORK */
}


/**
 * gst_update_registry:
 *
 * Forces GStreamer to re-scan its plugin paths and update the default
 * plugin registry.
 *
 * Applications will almost never need to call this function, it is only
 * useful if the application knows new plugins have been installed (or old
 * ones removed) since the start of the application (or, to be precise, the
 * first call to gst_init()) and the application wants to make use of any
 * newly-installed plugins without restarting the application.
 *
 * Applications should assume that the registry update is neither atomic nor
 * thread-safe and should therefore not have any dynamic pipelines running
 * (including the playbin and decodebin elements) and should also not create
 * any elements or access the GStreamer registry while the update is in
 * progress.
 *
 * Note that this function may block for a significant amount of time.
 *
 * Returns: %TRUE if the registry has been updated successfully (does not
 *          imply that there were changes), otherwise %FALSE.
 *
 * Since: 0.10.12
 */
gboolean
gst_update_registry (void)
{
  gboolean res = FALSE;

#ifndef GST_DISABLE_REGISTRY
  GError *err = NULL;

  res = ensure_current_registry (&err);
  if (err) {
    GST_WARNING ("registry update failed: %s", err->message);
    g_error_free (err);
  } else {
    GST_LOG ("registry update succeeded");
  }

  if (preload_plugins) {
    g_slist_foreach (preload_plugins, load_plugin_func, NULL);
  }
#else
  GST_WARNING ("registry update failed: %s", "registry disabled");
#endif /* GST_DISABLE_REGISTRY */

  return res;
}