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GResources: add support for resource 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 a library, without recompiling. To support this, for debugging and hacking purposes, it's now possible to define a G_RESOURCE_OVERLAYS environment variable as a colon-separated list of substitutions to perform when looking up GResources. 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. Substitutions must start with a slash, and must not have a trailing slash before the '='. It is possible to overlay the location of a single resource with an individual file. https://bugzilla.gnome.org/show_bug.cgi?id=765668
This commit is contained in:
Allison Ryan Lortie
parent
3c7c0af1c9
commit
55ab3af098
310
gio/gresource.c
310
gio/gresource.c
@ -25,6 +25,9 @@
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#include "gresource.h"
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#include <gvdb/gvdb-reader.h>
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#include <gi18n-lib.h>
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#include <gstdio.h>
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#include <gio/gfile.h>
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#include <gio/gioerror.h>
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#include <gio/gmemoryinputstream.h>
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#include <gio/gzlibdecompressor.h>
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#include <gio/gconverterinputstream.h>
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@ -132,6 +135,34 @@ G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)
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* when the library is unloaded. However, in practice this is not generally a problem, since most resource accesses
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* is for your own resources, and resource data is often used once, during parsing, and then released.
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*
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* When debugging a program or testing a change to an installed version, it is often useful to be able to
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* replace resources in the program or library, without recompiling, for debugging or quick hacking and testing
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* purposes.
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*
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* Since GLib 2.50, it is possible to use the `G_RESOURCE_OVERLAYS` environment variable to selectively overlay
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* resources with replacements from the filesystem. It is a colon-separated list of substitutions to perform
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* during resource lookups.
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*
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* A substitution has the form
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*
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* |[
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* /org/gtk/libgtk=/home/desrt/gtk-overlay
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* ]|
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*
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* The part before the `=` is the resource subpath for which the overlay applies. The part after is a
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* filesystem path which contains files and subdirectories as you would like to be loaded as resources with the
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* equivalent names.
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*
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* In the example above, if an application tried to load a resource with the resource path
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* `/org/gtk/libgtk/ui/gtkdialog.ui` then GResource would check the filesystem path
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* `/home/desrt/gtk-overlay/ui/gtkdialog.ui`. If a file was found there, it would be used instead. This is an
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* overlay, not an outright replacement, which means that if a file is not found at that path, the built-in
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* version will be used instead. Whiteouts are not currently supported.
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*
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* Substitutions must start with a slash, and must not contain a trailing slash before the '='. The path after
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* the slash should ideally be absolute, but this is not strictly required. It is possible to overlay the
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* location of a single resource with an individual file.
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*
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* Since: 2.32
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*/
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@ -141,6 +172,267 @@ G_DEFINE_BOXED_TYPE (GResource, g_resource, g_resource_ref, g_resource_unref)
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* #GStaticResource is an opaque data structure and can only be accessed
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* using the following functions.
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**/
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typedef gboolean (* CheckCandidate) (const gchar *candidate, gpointer user_data);
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static gboolean
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open_overlay_stream (const gchar *candidate,
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gpointer user_data)
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{
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GInputStream **res = (GInputStream **) user_data;
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GError *error = NULL;
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GFile *file;
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file = g_file_new_for_path (candidate);
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*res = (GInputStream *) g_file_read (file, NULL, &error);
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if (*res)
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{
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g_message ("Opened file '%s' as a resource overlay", candidate);
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}
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else
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{
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if (!g_error_matches (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
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g_warning ("Can't open overlay file '%s': %s", candidate, error->message);
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g_error_free (error);
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}
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g_object_unref (file);
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return *res != NULL;
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}
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static gboolean
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get_overlay_bytes (const gchar *candidate,
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gpointer user_data)
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{
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GBytes **res = (GBytes **) user_data;
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GMappedFile *mapped_file;
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GError *error = NULL;
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mapped_file = g_mapped_file_new (candidate, FALSE, &error);
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if (mapped_file)
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{
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g_message ("Mapped file '%s' as a resource overlay", candidate);
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*res = g_mapped_file_get_bytes (mapped_file);
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g_mapped_file_unref (mapped_file);
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}
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else
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{
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if (!g_error_matches (error, G_FILE_ERROR, G_FILE_ERROR_NOENT))
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g_warning ("Can't mmap overlay file '%s': %s", candidate, error->message);
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g_error_free (error);
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}
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return *res != NULL;
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}
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static gboolean
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enumerate_overlay_dir (const gchar *candidate,
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gpointer user_data)
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{
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GHashTable **hash = (GHashTable **) user_data;
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GError *error = NULL;
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GDir *dir;
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const gchar *name;
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dir = g_dir_open (candidate, 0, &error);
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if (dir)
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{
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if (*hash == NULL)
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/* note: keep in sync with same line below */
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*hash = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
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g_message ("Enumerating directory '%s' as resource overlay", candidate);
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while ((name = g_dir_read_name (dir)))
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{
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gchar *fullname = g_build_filename (candidate, name, NULL);
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GStatBuf buf;
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/* match gvdb behaviour by suffixing "/" on dirs */
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if (g_stat (fullname, &buf) == 0 && S_ISDIR (buf.st_mode))
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g_hash_table_add (*hash, g_strconcat (name, "/", NULL));
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else
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g_hash_table_add (*hash, g_strdup (name));
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g_free (fullname);
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}
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g_dir_close (dir);
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}
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else
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{
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if (!g_error_matches (error, G_FILE_ERROR, G_FILE_ERROR_NOENT))
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g_warning ("Can't enumerate overlay directory '%s': %s", candidate, error->message);
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g_error_free (error);
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return FALSE;
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}
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/* We may want to enumerate results from more than one overlay
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* directory.
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*/
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return FALSE;
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}
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static gboolean
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g_resource_find_overlay (const gchar *path,
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CheckCandidate check,
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gpointer user_data)
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{
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/* This is a null-terminated array of replacement strings (with '=' inside) */
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static const gchar * const *overlay_dirs;
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gboolean res = FALSE;
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gint path_len = -1;
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gint i;
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/* We try to be very fast in case there are no overlays. Otherwise,
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* we can take a bit more time...
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*/
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if (g_once_init_enter (&overlay_dirs))
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{
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const gchar * const *result;
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const gchar *envvar;
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envvar = g_getenv ("G_RESOURCE_OVERLAYS");
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if (envvar != NULL)
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{
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gchar **parts;
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gint i, j;
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parts = g_strsplit (envvar, ":", 0);
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/* Sanity check the parts, dropping those that are invalid.
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* 'i' may grow faster than 'j'.
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*/
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for (i = j = 0; parts[i]; i++)
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{
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gchar *part = parts[i];
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gchar *eq;
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eq = strchr (part, '=');
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if (eq == NULL)
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks '='. Ignoring.", part);
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g_free (part);
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continue;
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}
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if (eq == part)
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks path before '='. Ignoring.", part);
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g_free (part);
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continue;
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}
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if (eq[1] == '\0')
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks path after '='. Ignoring", part);
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g_free (part);
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continue;
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}
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if (part[0] != '/')
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks leading '/'. Ignoring.", part);
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g_free (part);
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continue;
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}
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if (eq[-1] == '/')
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' has trailing '/' before '='. Ignoring", part);
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g_free (part);
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continue;
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}
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if (eq[1] != '/')
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{
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g_critical ("G_RESOURCE_OVERLAYS segment '%s' lacks leading '/' after '='. Ignoring", part);
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g_free (part);
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continue;
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}
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g_message ("Adding GResources overlay '%s'", part);
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parts[j++] = part;
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}
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parts[j] = NULL;
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result = (const gchar **) parts;
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}
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else
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{
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/* We go out of the way to avoid malloc() in the normal case
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* where the environment variable is not set.
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*/
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static const gchar * const empty_strv[0 + 1];
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result = empty_strv;
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}
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g_once_init_leave (&overlay_dirs, result);
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}
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for (i = 0; overlay_dirs[i]; i++)
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{
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const gchar *src;
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gint src_len;
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const gchar *dst;
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gint dst_len;
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gchar *candidate;
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{
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gchar *eq;
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/* split the overlay into src/dst */
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src = overlay_dirs[i];
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eq = strchr (src, '=');
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g_assert (eq); /* we checked this already */
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src_len = eq - src;
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dst = eq + 1;
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/* hold off on dst_len because we will probably fail the checks below */
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}
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if (path_len == -1)
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path_len = strlen (path);
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/* The entire path is too short to match the source */
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if (path_len < src_len)
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continue;
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/* It doesn't match the source */
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if (memcmp (path, src, src_len) != 0)
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continue;
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/* The prefix matches, but it's not a complete path component */
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if (path[src_len] && path[src_len] != '/')
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continue;
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/* OK. Now we need this. */
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dst_len = strlen (dst);
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/* The candidate will be composed of:
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*
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* dst + remaining_path + nul
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*/
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candidate = g_malloc (dst_len + (path_len - src_len) + 1);
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memcpy (candidate, dst, dst_len);
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memcpy (candidate + dst_len, path + src_len, path_len - src_len);
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candidate[dst_len + (path_len - src_len)] = '\0';
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/* No matter what, 'r' is what we need, including the case where
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* we are trying to enumerate a directory.
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*/
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res = (* check) (candidate, user_data);
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g_free (candidate);
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if (res)
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break;
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}
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return res;
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}
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/**
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* g_resource_error_quark:
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@ -664,6 +956,9 @@ g_resources_open_stream (const gchar *path,
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GList *l;
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GInputStream *stream;
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if (g_resource_find_overlay (path, open_overlay_stream, &res))
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return res;
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register_lazy_static_resources ();
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g_rw_lock_reader_lock (&resources_lock);
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@ -733,6 +1028,9 @@ g_resources_lookup_data (const gchar *path,
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GList *l;
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GBytes *data;
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if (g_resource_find_overlay (path, get_overlay_bytes, &res))
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return res;
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register_lazy_static_resources ();
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g_rw_lock_reader_lock (&resources_lock);
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@ -794,6 +1092,17 @@ g_resources_enumerate_children (const gchar *path,
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char **children;
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int i;
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/* This will enumerate actual files found in overlay directories but
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* will not enumerate the overlays themselves. For example, if we
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* have an overlay "/org/gtk=/path/to/files" and we enumerate "/org"
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* then we will not see "gtk" in the result set unless it is provided
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* by another resource file.
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*
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* This is probably not going to be a problem since if we are doing
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* such an overlay, we probably will already have that path.
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*/
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g_resource_find_overlay (path, enumerate_overlay_dir, &hash);
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register_lazy_static_resources ();
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g_rw_lock_reader_lock (&resources_lock);
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@ -807,6 +1116,7 @@ g_resources_enumerate_children (const gchar *path,
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if (children != NULL)
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{
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if (hash == NULL)
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/* note: keep in sync with same line above */
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hash = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, NULL);
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for (i = 0; children[i] != NULL; i++)
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