Commit 4808a957 authored by Colin Walters's avatar Colin Walters Committed by Philip Withnall

GFile: Add g_file_peek_path()

This is a variant of g_file_get_path() which returns a const string to
the caller, rather than transferring ownership.

I've been carrying `gs_file_get_path_cached()` in libgsystem and it
has seen a lot of use in the ostree and flatpak codebases.  There are
probably others too.

I think language bindings like Python/Gjs could also use this to avoid
an extra malloc (i.e. we could transparently replace
`g_file_get_path()` with `g_file_peek_path()`.

(Originally by Colin Walters. Tweaked by Philip Withnall to update to
2.56, change the function name and drop the locking.)

https://bugzilla.gnome.org/show_bug.cgi?id=767976
parent 261cb8ea
......@@ -91,6 +91,7 @@ g_file_hash
g_file_equal
g_file_get_basename
g_file_get_path
g_file_peek_path
g_file_get_uri
g_file_get_parse_name
g_file_get_parent
......
......@@ -534,6 +534,107 @@ g_file_get_path (GFile *file)
return (* iface->get_path) (file);
}
/* Original commit introducing this in libgsystem:
*
* fileutil: Handle recent: and trash: URIs
*
* The gs_file_get_path_cached() was rather brittle in its handling
* of URIs. It would assert() when a GFile didn't have a backing path
* (such as when handling trash: or recent: URIs), and didn't know
* how to get the target URI for those items either.
*
* Make sure that we do not assert() when a backing path cannot be
* found, and handle recent: and trash: URIs.
*
* https://bugzilla.gnome.org/show_bug.cgi?id=708435
*/
static char *
file_get_target_path (GFile *file)
{
GFileInfo *info;
const char *target;
char *path;
info = g_file_query_info (file, G_FILE_ATTRIBUTE_STANDARD_TARGET_URI, G_FILE_QUERY_INFO_NONE, NULL, NULL);
if (info == NULL)
return NULL;
target = g_file_info_get_attribute_string (info, G_FILE_ATTRIBUTE_STANDARD_TARGET_URI);
path = g_filename_from_uri (target, NULL, NULL);
g_object_unref (info);
return path;
}
static const char *
file_peek_path_generic (GFile *file)
{
const char *path;
static GQuark _file_path_quark = 0;
if (G_UNLIKELY (_file_path_quark) == 0)
_file_path_quark = g_quark_from_static_string ("gio-file-path");
/* We need to be careful about threading, as two threads calling
* g_file_peek_path() on the same file could race: both would see
* (g_object_get_qdata(…) == NULL) to begin with, both would generate and add
* the path, but the second thread to add it would end up freeing the path
* set by the first thread. The first thread would still return the pointer
* to that freed path, though, resulting an a read-after-free. Handle that
* with a compare-and-swap loop. The g_object_*_qdata() functions are atomic. */
while (TRUE)
{
gchar *new_path = NULL;
path = g_object_get_qdata ((GObject*)file, _file_path_quark);
if (path != NULL)
break;
if (g_file_has_uri_scheme (file, "trash") ||
g_file_has_uri_scheme (file, "recent"))
new_path = file_get_target_path (file);
else
new_path = g_file_get_path (file);
if (new_path == NULL)
return NULL;
/* By passing NULL here, we ensure we never replace existing data: */
if (g_object_replace_qdata ((GObject *) file, _file_path_quark,
NULL, (gpointer) new_path,
(GDestroyNotify) g_free, NULL))
break;
else
g_free (new_path);
}
return path;
}
/**
* g_file_peek_path:
* @file: input #GFile
*
* Exactly like g_file_get_path(), but caches the result via
* g_object_set_qdata_full(). This is useful for example in C
* applications which mix `g_file_*` APIs with native ones. It
* also avoids an extra duplicated string when possible, so will be
* generally more efficient.
*
* This call does no blocking I/O.
*
* Returns: (type filename) (nullable): string containing the #GFile's path,
* or %NULL if no such path exists. The returned string is owned by @file.
* Since: 2.56
*/
const char *
g_file_peek_path (GFile *file)
{
if (G_IS_LOCAL_FILE (file))
return _g_local_file_get_filename ((GLocalFile *) file);
return file_peek_path_generic (file);
}
/**
* g_file_get_uri:
* @file: input #GFile
......
......@@ -620,6 +620,8 @@ GLIB_AVAILABLE_IN_ALL
char * g_file_get_basename (GFile *file);
GLIB_AVAILABLE_IN_ALL
char * g_file_get_path (GFile *file);
GLIB_AVAILABLE_IN_2_56
const char * g_file_peek_path (GFile *file);
GLIB_AVAILABLE_IN_ALL
char * g_file_get_uri (GFile *file);
GLIB_AVAILABLE_IN_ALL
......
......@@ -169,9 +169,12 @@ monitor_changed (GFileMonitor *monitor,
{
CreateDeleteData *data = user_data;
gchar *path;
const gchar *peeked_path;
path = g_file_get_path (file);
peeked_path = g_file_peek_path (file);
g_assert_cmpstr (data->monitor_path, ==, path);
g_assert_cmpstr (path, ==, peeked_path);
g_free (path);
if (event_type == G_FILE_MONITOR_EVENT_CREATED)
......@@ -619,7 +622,7 @@ static void
test_replace_load (void)
{
ReplaceLoadData *data;
gchar *path;
const gchar *path;
GFileIOStream *iostream;
data = g_new0 (ReplaceLoadData, 1);
......@@ -631,7 +634,7 @@ test_replace_load (void)
g_assert (data->file != NULL);
g_object_unref (iostream);
path = g_file_get_path (data->file);
path = g_file_peek_path (data->file);
remove (path);
g_assert (!g_file_query_exists (data->file, NULL));
......@@ -653,7 +656,6 @@ test_replace_load (void)
g_main_loop_unref (data->loop);
g_object_unref (data->file);
g_free (data);
free (path);
}
static void
......
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