glib/gio/gresource.c

/* GIO - GLib Input, Output and Streaming Library
 *
 * Copyright © 2011 Red Hat, Inc
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 * Authors: Alexander Larsson <alexl@redhat.com>
 */

#include "config.h"

#include <string.h>

#include "gresource.h"
#include <gvdb/gvdb-reader.h>
#include <gi18n-lib.h>
#include <gstdio.h>
#include <gio/gfile.h>
#include <gio/gioerror.h>
#include <gio/gmemoryinputstream.h>
#include <gio/gzlibdecompressor.h>
#include <gio/gconverterinputstream.h>

#include "glib-private.h"

struct _GResource
{
  int ref_count;

  GvdbTable *table;
};

static void register_lazy_static_resources (void);

G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)

/**
 * GResource:
 *
 * Applications and libraries often contain binary or textual data that is
 * really part of the application, rather than user data. For instance
 * [`GtkBuilder`](https://docs.gtk.org/gtk4/class.Builder.html) `.ui` files,
 * splashscreen images, [class@Gio.Menu] markup XML, CSS files, icons, etc.
 * These are often shipped as files in `$datadir/appname`, or manually
 * included as literal strings in the code.
 *
 * The `GResource` API and the
 * [`glib-compile-resources`](glib-compile-resources.html) program provide a
 * convenient and efficient alternative to this which has some nice properties.
 * You maintain the files as normal files, so it’s easy to edit them, but during
 * the build the files are combined into a binary bundle that is linked into the
 * executable. This means that loading the resource files are efficient (as they
 * are already in memory, shared with other instances) and simple (no need to
 * check for things like I/O errors or locate the files in the filesystem). It
 * also makes it easier to create relocatable applications.
 *
 * Resource files can also be marked as compressed. Such files will be included
 * in the resource bundle in a compressed form, but will be automatically
 * uncompressed when the resource is used. This is very useful e.g. for larger
 * text files that are parsed once (or rarely) and then thrown away.
 *
 * Resource files can also be marked to be preprocessed, by setting the value of the
 * `preprocess` attribute to a comma-separated list of preprocessing options.
 * The only options currently supported are:
 *
 *  - `xml-stripblanks` which will use the [`xmllint`](man:xmllint(1)) command
 *    to strip ignorable whitespace from the XML file. For this to work,
 *    the `XMLLINT` environment variable must be set to the full path to
 *    the xmllint executable, or xmllint must be in the `PATH`; otherwise
 *    the preprocessing step is skipped.
 *
 *  - `to-pixdata` (deprecated since gdk-pixbuf 2.32) which will use the
 *    `gdk-pixbuf-pixdata` command to convert images to the [`GdkPixdata`](https://docs.gtk.org/gdk-pixbuf/class.Pixdata.html)
 *    format, which allows you to create pixbufs directly using the data inside
 *    the resource file, rather than an (uncompressed) copy of it. For this, the
 *    `gdk-pixbuf-pixdata` program must be in the `PATH`, or the
 *    `GDK_PIXBUF_PIXDATA` environment variable must be set to the full path to
 *    the `gdk-pixbuf-pixdata` executable; otherwise the resource compiler will
 *    abort. `to-pixdata` has been deprecated since gdk-pixbuf 2.32, as
 *    `GResource` supports embedding modern image formats just as well. Instead
 *    of using it, embed a PNG or SVG file in your `GResource`.
 *
 *  - `json-stripblanks` which will use the
 *    [`json-glib-format`](man:json-glib-format(1)) command to strip ignorable
 *    whitespace from the JSON file. For this to work, the `JSON_GLIB_FORMAT`
 *    environment variable must be set to the full path to the
 *    `json-glib-format` executable, or it must be in the `PATH`; otherwise the
 *    preprocessing step is skipped. In addition, at least version 1.6 of
 *    `json-glib-format` is required.
 *
 * Resource files will be exported in the `GResource` namespace using the
 * combination of the given `prefix` and the filename from the `file` element.
 * The `alias` attribute can be used to alter the filename to expose them at a
 * different location in the resource namespace. Typically, this is used to
 * include files from a different source directory without exposing the source
 * directory in the resource namespace, as in the example below.
 *
 * Resource bundles are created by the
 * [`glib-compile-resources`](glib-compile-resources.html) program
 * which takes an XML file that describes the bundle, and a set of files that
 * the XML references. These are combined into a binary resource bundle.
 *
 * An example resource description:
 * ```xml
 * <?xml version="1.0" encoding="UTF-8"?>
 * <gresources>
 *   <gresource prefix="/org/gtk/Example">
 *     <file>data/splashscreen.png</file>
 *     <file compressed="true">dialog.ui</file>
 *     <file preprocess="xml-stripblanks">menumarkup.xml</file>
 *     <file alias="example.css">data/example.css</file>
 *   </gresource>
 * </gresources>
 * ```
 *
 * This will create a resource bundle with the following files:
 * ```
 * /org/gtk/Example/data/splashscreen.png
 * /org/gtk/Example/dialog.ui
 * /org/gtk/Example/menumarkup.xml
 * /org/gtk/Example/example.css
 * ```
 *
 * Note that all resources in the process share the same namespace, so use
 * Java-style path prefixes (like in the above example) to avoid conflicts.
 *
 * You can then use [`glib-compile-resources`](glib-compile-resources.html) to
 * compile the XML to a binary bundle that you can load with
 * [func@Gio.Resource.load]. However, it’s more common to use the
 * `--generate-source` and `--generate-header` arguments to create a source file
 * and header to link directly into your application.
 * This will generate `get_resource()`, `register_resource()` and
 * `unregister_resource()` functions, prefixed by the `--c-name` argument passed
 * to [`glib-compile-resources`](glib-compile-resources.html). `get_resource()`
 * returns the generated `GResource` object. The register and unregister
 * functions register the resource so its files can be accessed using
 * [func@Gio.resources_lookup_data].
 *
 * Once a `GResource` has been created and registered all the data in it can be
 * accessed globally in the process by using API calls like
 * [func@Gio.resources_open_stream] to stream the data or
 * [func@Gio.resources_lookup_data] to get a direct pointer to the data. You can
 * also use URIs like `resource:///org/gtk/Example/data/splashscreen.png` with
 * [iface@Gio.File] to access the resource data.
 *
 * Some higher-level APIs, such as [`GtkApplication`](https://docs.gtk.org/gtk4/class.Application.html),
 * will automatically load resources from certain well-known paths in the
 * resource namespace as a convenience. See the documentation for those APIs
 * for details.
 *
 * There are two forms of the generated source, the default version uses the
 * compiler support for constructor and destructor functions (where available)
 * to automatically create and register the `GResource` on startup or library
 * load time. If you pass `--manual-register`, two functions to
 * register/unregister the resource are created instead. This requires an
 * explicit initialization call in your application/library, but it works on all
 * platforms, even on the minor ones where constructors are not supported.
 * (Constructor support is available for at least Win32, Mac OS and Linux.)
 *
 * Note that resource data can point directly into the data segment of e.g. a
 * library, so if you are unloading libraries during runtime you need to be very
 * careful with keeping around pointers to data from a resource, as this goes
 * away when the library is unloaded. However, in practice this is not generally
 * a problem, since most resource accesses are for your own resources, and
 * resource data is often used once, during parsing, and then released.
 *
 * # Overlays
 *
 * When debugging a program or testing a change to an installed version, it is
 * often useful to be able to replace resources in the program or library,
 * without recompiling, for debugging or quick hacking and testing purposes.
 * Since GLib 2.50, it is possible to use the `G_RESOURCE_OVERLAYS` environment
 * variable to selectively overlay resources with replacements from the
 * filesystem.  It is a `G_SEARCHPATH_SEPARATOR`-separated list of substitutions
 * to perform during resource lookups. It is ignored when running in a setuid
 * process.
 *
 * A substitution has the form
 *
 * ```
 * /org/gtk/libgtk=/home/desrt/gtk-overlay
 * ```
 *
 * The part before the `=` is the resource subpath for which the overlay
 * applies.  The part after is a filesystem path which contains files and
 * subdirectories as you would like to be loaded as resources with the
 * equivalent names.
 *
 * In the example above, if an application tried to load a resource with the
 * resource path `/org/gtk/libgtk/ui/gtkdialog.ui` then `GResource` would check
 * the filesystem path `/home/desrt/gtk-overlay/ui/gtkdialog.ui`.  If a file was
 * found there, it would be used instead.  This is an overlay, not an outright
 * replacement, which means that if a file is not found at that path, the
 * built-in version will be used instead.  Whiteouts are not currently
 * supported.
 *
 * Substitutions must start with a slash, and must not contain a trailing slash
 * before the `=`.  The path after the slash should ideally be absolute, but
 * this is not strictly required.  It is possible to overlay the location of a
 * single resource with an individual file.
 *
 * Since: 2.32
 */

/**
 * GStaticResource:
 *
 * `GStaticResource` is an opaque data structure and can only be accessed
 * using the following functions.
 **/
typedef gboolean (* CheckCandidate) (const gchar *candidate, gpointer user_data);

static gboolean
open_overlay_stream (const gchar *candidate,
                     gpointer     user_data)
{
  GInputStream **res = (GInputStream **) user_data;
  GError *error = NULL;
  GFile *file;

  file = g_file_new_for_path (candidate);
  *res = (GInputStream *) g_file_read (file, NULL, &error);

  if (*res)
    {
      g_message ("Opened file '%s' as a resource overlay", candidate);
    }
  else
    {
      if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
        g_warning ("Can't open overlay file '%s': %s", candidate, error->message);
      g_error_free (error);
    }

  g_object_unref (file);

  return *res != NULL;
}

static gboolean
get_overlay_bytes (const gchar *candidate,
                   gpointer     user_data)
{
  GBytes **res = (GBytes **) user_data;
  GMappedFile *mapped_file;
  GError *error = NULL;

  mapped_file = g_mapped_file_new (candidate, FALSE, &error);

  if (mapped_file)
    {
      g_message ("Mapped file '%s' as a resource overlay", candidate);
      *res = g_mapped_file_get_bytes (mapped_file);
      g_mapped_file_unref (mapped_file);
    }
  else
    {
      if (!g_error_matches (error, G_FILE_ERROR, G_FILE_ERROR_NOENT))
        g_warning ("Can't mmap overlay file '%s': %s", candidate, error->message);
      g_error_free (error);
    }

  return *res != NULL;
}

static gboolean
enumerate_overlay_dir (const gchar *candidate,
                       gpointer     user_data)
{
  GHashTable **hash = (GHashTable **) user_data;
  GError *error = NULL;
  GDir *dir;
  const gchar *name;

  dir = g_dir_open (candidate, 0, &error);
  if (dir)
    {
      if (*hash == NULL)
        /* note: keep in sync with same line below */
        *hash = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);

      g_message ("Enumerating directory '%s' as resource overlay", candidate);

      while ((name = g_dir_read_name (dir)))
        {
          gchar *fullname = g_build_filename (candidate, name, NULL);

          /* match gvdb behaviour by suffixing "/" on dirs */
          if (g_file_test (fullname, G_FILE_TEST_IS_DIR))
            g_hash_table_add (*hash, g_strconcat (name, "/", NULL));
          else
            g_hash_table_add (*hash, g_strdup (name));

          g_free (fullname);
        }

      g_dir_close (dir);
    }
  else
    {
      if (!g_error_matches (error, G_FILE_ERROR, G_FILE_ERROR_NOENT))
        g_warning ("Can't enumerate overlay directory '%s': %s", candidate, error->message);
      g_error_free (error);
      return FALSE;
    }

  /* We may want to enumerate results from more than one overlay
   * directory.
   */
  return FALSE;
}

typedef struct {
  gsize size;
  guint32 flags;
} InfoData;

static gboolean
get_overlay_info (const gchar *candidate,
                  gpointer     user_data)
{
  InfoData *info = user_data;
  GStatBuf buf;

  if (g_stat (candidate, &buf) < 0)
    return FALSE;

  info->size = buf.st_size;
  info->flags = G_RESOURCE_FLAGS_NONE;

  return TRUE;
}

static gboolean
g_resource_find_overlay (const gchar    *path,
                         CheckCandidate  check,
                         gpointer        user_data)
{
  /* This is a null-terminated array of replacement strings (with '=' inside) */
  static const gchar * const *overlay_dirs;
  gboolean res = FALSE;
  size_t path_len = 0;
  gint i;

  /* We try to be very fast in case there are no overlays.  Otherwise,
   * we can take a bit more time...
   */

  if (g_once_init_enter_pointer (&overlay_dirs))
    {
      gboolean is_setuid = GLIB_PRIVATE_CALL (g_check_setuid) ();
      const gchar * const *result;
      const gchar *envvar;

      /* Don’t load overlays if setuid, as they could allow reading privileged
       * files. */
      envvar = !is_setuid ? g_getenv ("G_RESOURCE_OVERLAYS") : NULL;
      if (envvar != NULL)
        {
          gchar **parts;
          gint j;

          parts = g_strsplit (envvar, G_SEARCHPATH_SEPARATOR_S, 0);

          /* Sanity check the parts, dropping those that are invalid.
           * 'i' may grow faster than 'j'.
           */
          for (i = j = 0; parts[i]; i++)
            {
              gchar *part = parts[i];
              gchar *eq;

              eq = strchr (part, '=');
              if (eq == NULL)
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks '='.  Ignoring.", part);
                  g_free (part);
                  continue;
                }

              if (eq == part)
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks path before '='.  Ignoring.", part);
                  g_free (part);
                  continue;
                }

              if (eq[1] == '\0')
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks path after '='.  Ignoring", part);
                  g_free (part);
                  continue;
                }

              if (part[0] != '/')
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks leading '/'.  Ignoring.", part);
                  g_free (part);
                  continue;
                }

              if (eq[-1] == '/')
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' has trailing '/' before '='.  Ignoring", part);
                  g_free (part);
                  continue;
                }

              if (!g_path_is_absolute (eq + 1))
                {
                  g_critical ("G_RESOURCE_OVERLAYS segment '%s' does not have an absolute path after '='.  Ignoring", part);
                  g_free (part);
                  continue;
                }

              g_message ("Adding GResources overlay '%s'", part);
              parts[j++] = part;
            }

          parts[j] = NULL;

          result = (const gchar **) parts;
        }
      else
        {
          /* We go out of the way to avoid malloc() in the normal case
           * where the environment variable is not set.
           */
          static const gchar *const empty_strv[0 + 1] = { 0 };
          result = empty_strv;
        }

      g_once_init_leave_pointer (&overlay_dirs, result);
    }

  for (i = 0; overlay_dirs[i]; i++)
    {
      const gchar *src;
      size_t src_len;
      const gchar *dst;
      size_t dst_len;
      gchar *candidate;

      {
        gchar *eq;

        /* split the overlay into src/dst */
        src = overlay_dirs[i];
        eq = strchr (src, '=');
        g_assert (eq); /* we checked this already */
        src_len = eq - src;
        dst = eq + 1;
        /* hold off on dst_len because we will probably fail the checks below */
      }

      if (i == 0)
        path_len = strlen (path);

      /* The entire path is too short to match the source */
      if (path_len < src_len)
        continue;

      /* It doesn't match the source */
      if (memcmp (path, src, src_len) != 0)
        continue;

      /* The prefix matches, but it's not a complete path component */
      if (path[src_len] && path[src_len] != '/')
        continue;

      /* OK.  Now we need this. */
      dst_len = strlen (dst);

      /* The candidate will be composed of:
       *
       *    dst + remaining_path + nul
       */
      candidate = g_malloc (dst_len + (path_len - src_len) + 1);
      memcpy (candidate, dst, dst_len);
      memcpy (candidate + dst_len, path + src_len, path_len - src_len);
      candidate[dst_len + (path_len - src_len)] = '\0';

      /* No matter what, 'r' is what we need, including the case where
       * we are trying to enumerate a directory.
       */
      res = (* check) (candidate, user_data);
      g_free (candidate);

      if (res)
        break;
    }

  return res;
}

/**
 * g_resource_error_quark:
 *
 * Gets the [struct@Gio.Resource] Error Quark.
 *
 * Returns: a [type@GLib.Quark]
 *
 * Since: 2.32
 */
G_DEFINE_QUARK (g-resource-error-quark, g_resource_error)

/**
 * g_resource_ref:
 * @resource: A [struct@Gio.Resource]
 *
 * Atomically increments the reference count of @resource by one.
 *
 * This function is threadsafe and may be called from any thread.
 *
 * Returns: The passed in [struct@Gio.Resource]
 *
 * Since: 2.32
 **/
GResource *
g_resource_ref (GResource *resource)
{
  g_atomic_int_inc (&resource->ref_count);
  return resource;
}

/**
 * g_resource_unref:
 * @resource: A [struct@Gio.Resource]
 *
 * Atomically decrements the reference count of @resource by one.
 *
 * If the reference count drops to 0, all memory allocated by the resource is
 * released. This function is threadsafe and may be called from any
 * thread.
 *
 * Since: 2.32
 **/
void
g_resource_unref (GResource *resource)
{
  if (g_atomic_int_dec_and_test (&resource->ref_count))
    {
      gvdb_table_free (resource->table);
      g_free (resource);
    }
}

/*< internal >
 * g_resource_new_from_table:
 * @table: (transfer full): a GvdbTable
 *
 * Returns: (transfer full): a new #GResource for @table
 */
static GResource *
g_resource_new_from_table (GvdbTable *table)
{
  GResource *resource;

  resource = g_new (GResource, 1);
  resource->ref_count = 1;
  resource->table = table;

  return resource;
}

static void
g_resource_error_from_gvdb_table_error (GError **g_resource_error,
                                        GError  *gvdb_table_error  /* (transfer full) */)
{
  if (g_error_matches (gvdb_table_error, G_FILE_ERROR, G_FILE_ERROR_INVAL))
    g_set_error_literal (g_resource_error,
                         G_RESOURCE_ERROR, G_RESOURCE_ERROR_INTERNAL,
                         gvdb_table_error->message);
  else
    g_propagate_error (g_resource_error, g_steal_pointer (&gvdb_table_error));
  g_clear_error (&gvdb_table_error);
}

/**
 * g_resource_new_from_data:
 * @data: A [struct@GLib.Bytes]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Creates a [struct@Gio.Resource] from a reference to the binary resource bundle.
 *
 * This will keep a reference to @data while the resource lives, so
 * the data should not be modified or freed.
 *
 * If you want to use this resource in the global resource namespace you need
 * to register it with [func@Gio.resources_register].
 *
 * Note: @data must be backed by memory that is at least pointer aligned.
 * Otherwise this function will internally create a copy of the memory since
 * GLib 2.56, or in older versions fail and exit the process.
 *
 * If @data is empty or corrupt, %G_RESOURCE_ERROR_INTERNAL will be returned.
 *
 * Returns: (transfer full): a new [struct@Gio.Resource], or `NULL` on error
 *
 * Since: 2.32
 **/
GResource *
g_resource_new_from_data (GBytes  *data,
                          GError **error)
{
  GvdbTable *table;
  gboolean unref_data = FALSE;
  GError *local_error = NULL;

  if (((guintptr) g_bytes_get_data (data, NULL)) % sizeof (gpointer) != 0)
    {
      data = g_bytes_new (g_bytes_get_data (data, NULL),
                          g_bytes_get_size (data));
      unref_data = TRUE;
    }

  table = gvdb_table_new_from_bytes (data, TRUE, &local_error);

  if (unref_data)
    g_bytes_unref (data);

  if (table == NULL)
    {
      g_resource_error_from_gvdb_table_error (error, g_steal_pointer (&local_error));
      return NULL;
    }

  return g_resource_new_from_table (table);
}

/**
 * g_resource_load:
 * @filename: (type filename): the path of a filename to load, in the GLib filename encoding
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Loads a binary resource bundle and creates a [struct@Gio.Resource]
 * representation of it, allowing you to query it for data.
 *
 * If you want to use this resource in the global resource namespace you need
 * to register it with [func@Gio.resources_register].
 *
 * If @filename is empty or the data in it is corrupt,
 * %G_RESOURCE_ERROR_INTERNAL will be returned. If @filename doesn’t exist, or
 * there is an error in reading it, an error from [ctor@GLib.MappedFile.new]
 * will be returned.
 *
 * Returns: (transfer full): a new [struct@Gio.Resource], or `NULL` on error
 *
 * Since: 2.32
 **/
GResource *
g_resource_load (const gchar  *filename,
                 GError      **error)
{
  GvdbTable *table;
  GError *local_error = NULL;

  table = gvdb_table_new (filename, FALSE, &local_error);
  if (table == NULL)
    {
      g_resource_error_from_gvdb_table_error (error, g_steal_pointer (&local_error));
      return NULL;
    }

  return g_resource_new_from_table (table);
}

static void
set_error_not_found (GError     **error,
                     const char  *path)
{
  /* Avoid looking up the translation if it’s not going to be used. This is a hot path. */
  if (error != NULL)
    g_set_error (error, G_RESOURCE_ERROR, G_RESOURCE_ERROR_NOT_FOUND,
                 _("The resource at “%s” does not exist"),
                 path);
}

/* The only error this can return is %G_RESOURCE_ERROR_NOT_FOUND. */
static gboolean
do_lookup (GResource             *resource,
           const gchar           *path,
           GResourceLookupFlags   lookup_flags,
           gsize                 *size,
           guint32               *flags,
           const void           **data,
           gsize                 *data_size,
           GError               **error)
{
  char *free_path = NULL;
  gsize path_len;
  gboolean res = FALSE;
  GVariant *value;

  /* Drop any trailing slash. */
  path_len = strlen (path);
  if (path_len >= 1 && path[path_len-1] == '/')
    {
      path = free_path = g_strdup (path);
      free_path[path_len-1] = 0;
    }

  value = gvdb_table_get_raw_value (resource->table, path);

  if (value == NULL)
    {
      set_error_not_found (error, path);
    }
  else
    {
      guint32 _size, _flags;
      GVariant *array;

      g_variant_get (value, "(uu@ay)",
                     &_size,
                     &_flags,
                     &array);

      _size = GUINT32_FROM_LE (_size);
      _flags = GUINT32_FROM_LE (_flags);

      if (size)
        *size = _size;
      if (flags)
        *flags = _flags;
      if (data)
        *data = g_variant_get_data (array);
      if (data_size)
        {
          /* Don't report trailing newline that non-compressed files has */
          if (_flags & G_RESOURCE_FLAGS_COMPRESSED)
            *data_size = g_variant_get_size (array);
          else
            *data_size = g_variant_get_size (array) - 1;
        }
      g_variant_unref (array);
      g_variant_unref (value);

      res = TRUE;
    }

  g_free (free_path);
  return res;
}

/**
 * g_resource_open_stream:
 * @resource: A [struct@Gio.Resource]
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the resource and
 * returns a [class@Gio.InputStream] that lets you read the data.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * The only error this can return is %G_RESOURCE_ERROR_NOT_FOUND, if @path was
 * not found in @resource.
 *
 * Returns: (transfer full): [class@Gio.InputStream] or `NULL` on error
 *
 * Since: 2.32
 **/
GInputStream *
g_resource_open_stream (GResource             *resource,
                        const gchar           *path,
                        GResourceLookupFlags   lookup_flags,
                        GError               **error)
{
  const void *data;
  gsize data_size;
  guint32 flags;
  GInputStream *stream, *stream2;

  if (!do_lookup (resource, path, lookup_flags, NULL, &flags, &data, &data_size, error))
    return NULL;

  stream = g_memory_input_stream_new_from_data (data, data_size, NULL);
  g_object_set_data_full (G_OBJECT (stream), "g-resource",
                          g_resource_ref (resource),
                          (GDestroyNotify)g_resource_unref);

  if (flags & G_RESOURCE_FLAGS_COMPRESSED)
    {
      GZlibDecompressor *decompressor =
        g_zlib_decompressor_new (G_ZLIB_COMPRESSOR_FORMAT_ZLIB);

      stream2 = g_converter_input_stream_new (stream, G_CONVERTER (decompressor));
      g_object_unref (decompressor);
      g_object_unref (stream);
      stream = stream2;
    }

  return stream;
}

static GBytes *resource_to_bytes (GResource   *resource,
                                  const char  *path,
                                  size_t       size,
                                  const void  *data,
                                  size_t       data_size,
                                  guint32      flags,
                                  GError     **error);

/**
 * g_resource_lookup_data:
 * @resource: A [struct@Gio.Resource]
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the resource and
 * returns a [struct@GLib.Bytes] that lets you directly access the data in
 * memory.
 *
 * The data is always followed by a zero byte, so you
 * can safely use the data as a C string. However, that byte
 * is not included in the size of the [struct@GLib.Bytes].
 *
 * For uncompressed resource files this is a pointer directly into
 * the resource bundle, which is typically in some read-only data section
 * in the program binary. For compressed files, memory is allocated on
 * the heap and the data is automatically uncompressed.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * This can return error %G_RESOURCE_ERROR_NOT_FOUND if @path was not found in
 * @resource, or %G_RESOURCE_ERROR_INTERNAL if decompression of a compressed
 * resource failed.
 *
 * Returns: (transfer full): [struct@GLib.Bytes] or `NULL` on error
 *
 * Since: 2.32
 **/
GBytes *
g_resource_lookup_data (GResource             *resource,
                        const gchar           *path,
                        GResourceLookupFlags   lookup_flags,
                        GError               **error)
{
  const void *data;
  guint32 flags;
  gsize data_size;
  gsize size;

  if (!do_lookup (resource, path, lookup_flags, &size, &flags, &data, &data_size, error))
    return NULL;

  return resource_to_bytes (resource, path, size, data, data_size, flags, error);
}

static GBytes *
resource_to_bytes (GResource   *resource,
                   const char  *path,
                   size_t       size,
                   const void  *data,
                   size_t       data_size,
                   guint32      flags,
                   GError     **error)
{
  if (size == 0)
    return g_bytes_new_with_free_func ("", 0, (GDestroyNotify) g_resource_unref, g_resource_ref (resource));
  else if (flags & G_RESOURCE_FLAGS_COMPRESSED)
    {
      char *uncompressed, *d;
      const char *s;
      GConverterResult res;
      gsize d_size, s_size;
      gsize bytes_read, bytes_written;


      GZlibDecompressor *decompressor =
        g_zlib_decompressor_new (G_ZLIB_COMPRESSOR_FORMAT_ZLIB);

      uncompressed = g_malloc (size + 1);

      s = data;
      s_size = data_size;
      d = uncompressed;
      d_size = size;

      do
        {
          res = g_converter_convert (G_CONVERTER (decompressor),
                                     s, s_size,
                                     d, d_size,
                                     G_CONVERTER_INPUT_AT_END,
                                     &bytes_read,
                                     &bytes_written,
                                     NULL);
          if (res == G_CONVERTER_ERROR)
            {
              g_free (uncompressed);
              g_object_unref (decompressor);

              g_set_error (error, G_RESOURCE_ERROR, G_RESOURCE_ERROR_INTERNAL,
                           _("The resource at “%s” failed to decompress"),
                           path);
              return NULL;

            }
          s += bytes_read;
          s_size -= bytes_read;
          d += bytes_written;
          d_size -= bytes_written;
        }
      while (res != G_CONVERTER_FINISHED);

      uncompressed[size] = 0; /* Zero terminate */

      g_object_unref (decompressor);

      return g_bytes_new_take (uncompressed, size);
    }
  else
    return g_bytes_new_with_free_func (data, data_size, (GDestroyNotify)g_resource_unref, g_resource_ref (resource));
}

/**
 * g_resource_get_info:
 * @resource: A [struct@Gio.Resource]
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @size:  (out) (optional): a location to place the length of the contents of the file,
 *    or `NULL` if the length is not needed
 * @flags:  (out) (optional): a location to place the flags about the file,
 *    or `NULL` if the length is not needed
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the resource and
 * if found returns information about it.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * The only error this can return is %G_RESOURCE_ERROR_NOT_FOUND, if @path was
 * not found in @resource.
 *
 * Returns: `TRUE` if the file was found, `FALSE` if there were errors
 *
 * Since: 2.32
 **/
gboolean
g_resource_get_info (GResource             *resource,
                     const gchar           *path,
                     GResourceLookupFlags   lookup_flags,
                     gsize                 *size,
                     guint32               *flags,
                     GError               **error)
{
  return do_lookup (resource, path, lookup_flags, size, flags, NULL, NULL, error);
}

static inline const char *
ensure_slash_suffix (const char  *path,
                     char        *local_str,
                     gsize        len,
                     char       **free_path)
{
  gsize path_len;

  path_len = strlen (path);

  if G_UNLIKELY (path[path_len-1] != '/')
    {
      if (path_len < len - 2)
        {
          /*
           * We got a path that does not have a trailing /. It is not the
           * ideal use of this API as we require trailing / for our lookup
           * into gvdb. Some degenerate application configurations can hit
           * this code path quite a bit, so we try to avoid using the
           * g_strconcat()/g_free().
           */
          memcpy (local_str, path, path_len);
          local_str[path_len] = '/';
          local_str[path_len+1] = 0;
          return local_str;
        }
      else
        {
          *free_path = g_strconcat (path, "/", NULL);
          return *free_path;
        }
    }
  else
    {
      return path;
    }
}

/**
 * g_resource_enumerate_children:
 * @resource: A [struct@Gio.Resource]
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Returns all the names of children at the specified @path in the resource.
 *
 * The return result is a `NULL` terminated list of strings which should
 * be released with [func@GLib.strfreev].
 *
 * If @path is invalid or does not exist in the [struct@Gio.Resource],
 * %G_RESOURCE_ERROR_NOT_FOUND will be returned.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * Returns: (array zero-terminated=1) (transfer full): an array of constant strings
 *
 * Since: 2.32
 **/
gchar **
g_resource_enumerate_children (GResource             *resource,
                               const gchar           *path,
                               GResourceLookupFlags   lookup_flags,
                               GError               **error)
{
  /* Size of 256 is arbitrarily chosen based on being large enough
   * for pretty much everything we come across, but not cumbersome
   * on the stack. It also matches common cacheline sizes.
   */
  gchar local_str[256];
  const char *path_with_slash;
  char *free_path = NULL;
  gchar **children;

  if (*path == 0)
    {
      set_error_not_found (error, path);
      return NULL;
    }

  path_with_slash = ensure_slash_suffix (path, local_str, sizeof (local_str), &free_path);

  children = gvdb_table_list (resource->table, path_with_slash);

  g_free (free_path);

  if (children == NULL)
    {
      set_error_not_found (error, path);
      return NULL;
    }

  return children;
}

/**
 * g_resource_has_children:
 * @resource: A #GResource
 * @path: A pathname inside the resource
 *
 * Returns whether the specified @path in the resource
 * has children.
 *
 * Returns: %TRUE if @path has children
 *
 * Since: 2.84
 */
gboolean
g_resource_has_children (GResource  *resource,
                         const char *path)
{
  /* Size of 256 is arbitrarily chosen based on being large enough
   * for pretty much everything we come across, but not cumbersome
   * on the stack. It also matches common cacheline sizes.
   */
  char local_str[256];
  const char *path_with_slash;
  guint n;
  char *freeme = NULL;

  if (*path == 0)
    return FALSE;

  path_with_slash = ensure_slash_suffix (path, local_str, sizeof (local_str), &freeme);

  n = gvdb_table_n_children (resource->table, path_with_slash);

  g_free (freeme);

  return n > 0;
}

static GRWLock resources_lock;
static GList *registered_resources;

/* This is updated atomically, so we can append to it and check for NULL outside the
   lock, but all other accesses are done under the write lock */
static GStaticResource *lazy_register_resources;

static void
g_resources_register_unlocked (GResource *resource)
{
  registered_resources = g_list_prepend (registered_resources, g_resource_ref (resource));
}

static void
g_resources_unregister_unlocked (GResource *resource)
{
  GList *resource_link = g_list_find (registered_resources, resource);

  if (resource_link == NULL)
    {
      g_warning ("Tried to remove not registered resource");
    }
  else
    {
      g_resource_unref (resource_link->data);
      registered_resources = g_list_delete_link (registered_resources, resource_link);
    }
}

/**
 * g_resources_register:
 * @resource: A [struct@Gio.Resource]
 *
 * Registers the resource with the process-global set of resources.
 *
 * Once a resource is registered the files in it can be accessed
 * with the global resource lookup functions like
 * [func@Gio.resources_lookup_data].
 *
 * Since: 2.32
 **/
void
g_resources_register (GResource *resource)
{
  g_rw_lock_writer_lock (&resources_lock);
  g_resources_register_unlocked (resource);
  g_rw_lock_writer_unlock (&resources_lock);
}

/**
 * g_resources_unregister:
 * @resource: A [struct@Gio.Resource]
 *
 * Unregisters the resource from the process-global set of resources.
 *
 * Since: 2.32
 **/
void
g_resources_unregister (GResource *resource)
{
  g_rw_lock_writer_lock (&resources_lock);
  g_resources_unregister_unlocked (resource);
  g_rw_lock_writer_unlock (&resources_lock);
}

/**
 * g_resources_open_stream:
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the set of
 * globally registered resources and returns a [class@Gio.InputStream]
 * that lets you read the data.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * Returns: (transfer full): [class@Gio.InputStream] or `NULL` on error
 *
 * Since: 2.32
 **/
GInputStream *
g_resources_open_stream (const gchar           *path,
                         GResourceLookupFlags   lookup_flags,
                         GError               **error)
{
  GInputStream *res = NULL;
  GList *l;
  GInputStream *stream;

  if (g_resource_find_overlay (path, open_overlay_stream, &res))
    return res;

  register_lazy_static_resources ();

  g_rw_lock_reader_lock (&resources_lock);

  for (l = registered_resources; l != NULL; l = l->next)
    {
      GResource *r = l->data;

      stream = g_resource_open_stream (r, path, lookup_flags, NULL);
      if (stream == NULL)
        {
          /* g_resource_open_stream() guarantees it only fails with
           * %G_RESOURCE_ERROR_NOT_FOUND */
        }
      else
        {
          res = stream;
          break;
        }
    }

  if (l == NULL)
    set_error_not_found (error, path);

  g_rw_lock_reader_unlock (&resources_lock);

  return res;
}

/**
 * g_resources_lookup_data:
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the set of
 * globally registered resources and returns a [struct@GLib.Bytes] that
 * lets you directly access the data in memory.
 *
 * The data is always followed by a zero byte, so you
 * can safely use the data as a C string. However, that byte
 * is not included in the size of the [struct@GLib.Bytes].
 *
 * For uncompressed resource files this is a pointer directly into
 * the resource bundle, which is typically in some read-only data section
 * in the program binary. For compressed files we allocate memory on
 * the heap and automatically uncompress the data.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * Returns: (transfer full): [struct@GLib.Bytes] or `NULL` on error
 *
 * Since: 2.32
 **/
GBytes *
g_resources_lookup_data (const gchar           *path,
                         GResourceLookupFlags   lookup_flags,
                         GError               **error)
{
  GBytes *res = NULL;
  GList *l;

  if (g_resource_find_overlay (path, get_overlay_bytes, &res))
    return res;

  register_lazy_static_resources ();

  g_rw_lock_reader_lock (&resources_lock);

  for (l = registered_resources; l != NULL; l = l->next)
    {
      GResource *r = l->data;
      const void *data;
      guint32 flags;
      gsize data_size;
      gsize size;

      /* This is essentially g_resource_lookup_data(), but split up so we can
       * avoid allocating a #GError if the resource is not found. */
      if (do_lookup (r, path, lookup_flags, &size, &flags, &data, &data_size, NULL))
        {
          res = resource_to_bytes (r, path, size, data, data_size, flags, error);
          break;
        }
    }

  if (l == NULL)
    set_error_not_found (error, path);

  g_rw_lock_reader_unlock (&resources_lock);

  return res;
}

/**
 * g_resources_enumerate_children:
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Returns all the names of children at the specified @path in the set of
 * globally registered resources.
 *
 * The return result is a `NULL` terminated list of strings which should
 * be released with [func@GLib.strfreev].
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * Returns: (array zero-terminated=1) (transfer full): an array of constant strings
 *
 * Since: 2.32
 **/
gchar **
g_resources_enumerate_children (const gchar           *path,
                                GResourceLookupFlags   lookup_flags,
                                GError               **error)
{
  GHashTable *hash = NULL;
  GList *l;
  char **children;
  int i;

  /* This will enumerate actual files found in overlay directories but
   * will not enumerate the overlays themselves.  For example, if we
   * have an overlay "/org/gtk=/path/to/files" and we enumerate "/org"
   * then we will not see "gtk" in the result set unless it is provided
   * by another resource file.
   *
   * This is probably not going to be a problem since if we are doing
   * such an overlay, we probably will already have that path.
   */
  g_resource_find_overlay (path, enumerate_overlay_dir, &hash);

  register_lazy_static_resources ();

  g_rw_lock_reader_lock (&resources_lock);

  for (l = registered_resources; l != NULL; l = l->next)
    {
      GResource *r = l->data;

      children = g_resource_enumerate_children (r, path, 0, NULL);

      if (children != NULL)
        {
          if (hash == NULL)
            /* note: keep in sync with same line above */
            hash = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);

          for (i = 0; children[i] != NULL; i++)
            g_hash_table_add (hash, children[i]);
          g_free (children);
        }
    }

  g_rw_lock_reader_unlock (&resources_lock);

  if (hash == NULL)
    {
      set_error_not_found (error, path);
      return NULL;
    }
  else
    {
      children = (gchar **) g_hash_table_get_keys_as_array (hash, NULL);
      g_hash_table_steal_all (hash);
      g_hash_table_destroy (hash);

      return children;
    }
}

/**
 * g_resources_has_children:
 * @path: A pathname
 *
 * Returns whether the specified @path in the set of
 * globally registered resources has children.
 *
 * Returns: %TRUE if @patch has children
 *
 * Since: 2.84
 */
gboolean
g_resources_has_children (const char *path)
{
  register_lazy_static_resources ();

  g_rw_lock_reader_lock (&resources_lock);

  for (GList *l = registered_resources; l != NULL; l = l->next)
    {
      GResource *r = l->data;

      if (g_resource_has_children (r, path))
        {
          g_rw_lock_reader_unlock (&resources_lock);
          return TRUE;
        }
    }

  g_rw_lock_reader_unlock (&resources_lock);
  return FALSE;
}

/**
 * g_resources_get_info:
 * @path: A path name inside the resource
 * @lookup_flags: A [flags@Gio.ResourceLookupFlags]
 * @size:  (out) (optional): a location to place the length of the contents of the file,
 *    or `NULL` if the length is not needed
 * @flags:  (out) (optional): a location to place the [flags@Gio.ResourceFlags] about the file,
 *    or `NULL` if the flags are not needed
 * @error: return location for a [type@GLib.Error], or `NULL`
 *
 * Looks for a file at the specified @path in the set of
 * globally registered resources and if found returns information about it.
 *
 * @lookup_flags controls the behaviour of the lookup.
 *
 * Returns: `TRUE` if the file was found, `FALSE` if there were errors
 *
 * Since: 2.32
 **/
gboolean
g_resources_get_info (const gchar           *path,
                      GResourceLookupFlags   lookup_flags,
                      gsize                 *size,
                      guint32               *flags,
                      GError               **error)
{
  gboolean res = FALSE;
  GList *l;
  InfoData info;

  if (g_resource_find_overlay (path, get_overlay_info, &info))
    {
      if (size)
        *size = info.size;
      if (flags)
        *flags = info.flags;

      return TRUE;
    }

  register_lazy_static_resources ();

  g_rw_lock_reader_lock (&resources_lock);

  for (l = registered_resources; l != NULL; l = l->next)
    {
      GResource *r = l->data;

      if (g_resource_get_info (r, path, lookup_flags, size, flags, NULL))
        {
          res = TRUE;
          break;
        }
    }

  if (l == NULL)
    set_error_not_found (error, path);

  g_rw_lock_reader_unlock (&resources_lock);

  return res;
}

/* This code is to handle registration of resources very early, from a constructor.
 * At that point we'd like to do minimal work, to avoid ordering issues. For instance,
 * we're not allowed to use g_malloc, as the user need to be able to call g_mem_set_vtable
 * before the first call to g_malloc.
 *
 * So, what we do at construction time is that we just register a static structure on
 * a list of resources that need to be initialized, and then later, when doing any lookups
 * in the global list of registered resources, or when getting a reference to the
 * lazily initialized resource we lazily create and register all the GResources on
 * the lazy list.
 *
 * To avoid having to use locks in the constructor, and having to grab the writer lock
 * when checking the lazy registering list we update lazy_register_resources in
 * a lock-less fashion (atomic prepend-only, atomic replace with NULL). However, all
 * operations except:
 *  * check if there are any resources to lazily initialize
 *  * Add a static resource to the lazy init list
 * Do use the full writer lock for protection.
 */

static void
register_lazy_static_resources_unlocked (void)
{
  GStaticResource *list = g_atomic_pointer_get (&lazy_register_resources);

  while (!g_atomic_pointer_compare_and_exchange_full (&lazy_register_resources, list, NULL, &list))
    ;

  while (list != NULL)
    {
      GBytes *bytes = g_bytes_new_static (list->data, list->data_len);
      GResource *resource = g_resource_new_from_data (bytes, NULL);
      if (resource)
        {
          g_resources_register_unlocked (resource);
          g_atomic_pointer_set (&list->resource, resource);
        }
      g_bytes_unref (bytes);

      list = list->next;
    }
}

static void
register_lazy_static_resources (void)
{
  if (g_atomic_pointer_get (&lazy_register_resources) == NULL)
    return;

  g_rw_lock_writer_lock (&resources_lock);
  register_lazy_static_resources_unlocked ();
  g_rw_lock_writer_unlock (&resources_lock);
}

/**
 * g_static_resource_init:
 * @static_resource: pointer to a static [struct@Gio.StaticResource]
 *
 * Initializes a [struct@Gio.Resource] from static data using a
 * [struct@Gio.StaticResource].
 *
 * This is normally used by code generated by
 * [`glib-compile-resources`](glib-compile-resources.html)
 * and is not typically used by other code.
 *
 * Since: 2.32
 **/
void
g_static_resource_init (GStaticResource *static_resource)
{
  GStaticResource *next;

  g_return_if_fail (static_resource != NULL);
  g_return_if_fail (static_resource->next == NULL);
  g_return_if_fail (static_resource != g_atomic_pointer_get (&lazy_register_resources));

  do
    {
      next = g_atomic_pointer_get (&lazy_register_resources);
      static_resource->next = next;
    }
  while (!g_atomic_pointer_compare_and_exchange (&lazy_register_resources, next, static_resource));
}

/**
 * g_static_resource_fini:
 * @static_resource: pointer to a static [struct@Gio.StaticResource]
 *
 * Finalizes a [struct@Gio.Resource] initialized by
 * [method@Gio.StaticResource.init].
 *
 * This is normally used by code generated by
 * [`glib-compile-resources`](glib-compile-resources.html)
 * and is not typically used by other code.
 *
 * Since: 2.32
 **/
void
g_static_resource_fini (GStaticResource *static_resource)
{
  GResource *resource;

  g_rw_lock_writer_lock (&resources_lock);

  register_lazy_static_resources_unlocked ();

  resource = g_atomic_pointer_exchange (&static_resource->resource, NULL);
  if (resource)
    {
      /* There should be at least two references to the resource now: one for
       * static_resource->resource, and one in the registered_resources list. */
      g_assert (g_atomic_int_get (&resource->ref_count) >= 2);

      g_resources_unregister_unlocked (resource);
      g_resource_unref (resource);
    }

  g_rw_lock_writer_unlock (&resources_lock);
}

/**
 * g_static_resource_get_resource:
 * @static_resource: pointer to a static [struct@Gio.StaticResource]
 *
 * Gets the [struct@Gio.Resource] that was registered by a call to
 * [method@Gio.StaticResource.init].
 *
 * This is normally used by code generated by
 * [`glib-compile-resources`](glib-compile-resources.html)
 * and is not typically used by other code.
 *
 * Returns:  (transfer none): a [struct@Gio.Resource]
 *
 * Since: 2.32
 **/
GResource *
g_static_resource_get_resource (GStaticResource *static_resource)
{
  register_lazy_static_resources ();

  return g_atomic_pointer_get (&static_resource->resource);
}