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GVariant: add g_variant_check_format_string()
For some time now people have been asking for a way to check for type compatibility between GVariant instances and format strings. There are several APIs inside of GLib itself that would benefit from this. This patch introduces a way to do that.
This commit is contained in:
Ryan Lortie
parent
6a6b64ef4d
commit
34653169e5
@ -3061,6 +3061,7 @@ g_variant_classify
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GVariantClass
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<SUBSECTION>
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g_variant_check_format_string
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g_variant_get
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g_variant_get_va
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g_variant_new
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@ -1560,6 +1560,7 @@ g_variant_builder_end
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g_variant_builder_new
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g_variant_builder_unref
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g_variant_builder_ref
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g_variant_check_format_string
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g_variant_new_va
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g_variant_get_va
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g_variant_new
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104
glib/gvariant.c
104
glib/gvariant.c
@ -3741,6 +3741,110 @@ g_variant_format_string_scan (const gchar *string,
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return TRUE;
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}
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/**
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* g_variant_check_format_string:
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* @value: a #GVariant
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* @format_string: a valid #GVariant format string
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* @copy_only: %TRUE to ensure the format string makes deep copies
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*
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* Checks if calling g_variant_get() with @format_string on @value would
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* be valid from a type-compatibility standpoint. @format_string is
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* assumed to be a valid format string (from a syntactic standpoint).
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*
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* If @copy_only is %TRUE then this function additionally checks that it
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* would be safe to call g_variant_unref() on @value immediately after
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* the call to g_variant_get() without invalidating the result. This is
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* only possible if deep copies are made (ie: there are no pointers to
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* the data inside of the soon-to-be-freed #GVariant instance). If this
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* check fails then a g_critical() is printed and %FALSE is returned.
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*
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* This function is meant to be used by functions that wish to provide
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* varargs accessors to #GVariant values of uncertain values (eg:
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* g_variant_lookup() or g_menu_model_get_item_attribute()).
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*
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* Returns: %TRUE if @format_string is safe to use
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*
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* Since: 2.34
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*/
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gboolean
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g_variant_check_format_string (GVariant *value,
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const gchar *format_string,
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gboolean copy_only)
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{
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const gchar *original_format = format_string;
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const gchar *type_string;
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/* Interesting factoid: assuming a format string is valid, it can be
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* converted to a type string by removing all '@' '&' and '^'
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* characters.
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*
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* Instead of doing that, we can just skip those characters when
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* comparing it to the type string of @value.
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*
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* For the copy-only case we can just drop the '&' from the list of
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* characters to skip over. A '&' will never appear in a type string
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* so we know that it won't be possible to return %TRUE if it is in a
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* format string.
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*/
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type_string = g_variant_get_type_string (value);
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while (*type_string || *format_string)
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{
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gchar format = *format_string++;
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switch (format)
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{
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case '&':
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if G_UNLIKELY (copy_only)
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{
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/* for the love of all that is good, please don't mark this string for translation... */
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g_critical ("g_variant_check_format_string() is being called by a function with a GVariant varargs "
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"interface to validate the passed format string for type safety. The passed format "
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"(%s) contains a '&' character which would result in a pointer being returned to the "
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"data inside of a GVariant instance that may no longer exist by the time the function "
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"returns. Modify your code to use a format string without '&'.", original_format);
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return FALSE;
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}
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/* fall through */
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case '^':
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case '@':
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/* ignore these 2 (or 3) */
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continue;
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case '?':
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/* attempt to consume one of 'bynqiuxthdsog' */
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{
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char s = *type_string++;
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if (s == '\0' || strchr ("bynqiuxthdsog", s) == NULL)
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return FALSE;
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}
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continue;
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case 'r':
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/* ensure it's a tuple */
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if (*type_string != '(')
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return FALSE;
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/* fall through */
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case '*':
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/* consume a full type string for the '*' or 'r' */
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if (!g_variant_type_string_scan (type_string, NULL, &type_string))
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return FALSE;
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continue;
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default:
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/* attempt to consume exactly one character equal to the format */
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if (format != *type_string++)
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return FALSE;
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}
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}
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return TRUE;
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}
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/*< private >
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* g_variant_format_string_scan_type:
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* @string: a string that may be prefixed with a format string
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@ -265,7 +265,9 @@ void g_variant_get_va (GVarian
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const gchar *format_string,
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const gchar **endptr,
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va_list *app);
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gboolean g_variant_check_format_string (GVariant *value,
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const gchar *format_string,
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gboolean copy_only);
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GVariant * g_variant_parse (const GVariantType *type,
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const gchar *text,
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@ -4123,6 +4123,59 @@ test_fixed_array (void)
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g_variant_unref (a);
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}
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static void
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test_check_format_string (void)
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{
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GVariant *value;
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value = g_variant_new ("(sas)", "foo", NULL);
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g_variant_ref_sink (value);
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g_assert (g_variant_check_format_string (value, "(s*)", TRUE));
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g_assert (g_variant_check_format_string (value, "(s*)", FALSE));
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g_assert (!g_variant_check_format_string (value, "(u*)", TRUE));
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g_assert (!g_variant_check_format_string (value, "(u*)", FALSE));
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g_assert (g_variant_check_format_string (value, "(&s*)", FALSE));
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g_test_expect_message ("GLib", G_LOG_LEVEL_CRITICAL, "*contains a '&' character*");
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g_assert (!g_variant_check_format_string (value, "(&s*)", TRUE));
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g_test_assert_expected_messages ();
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g_assert (g_variant_check_format_string (value, "(s^as)", TRUE));
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g_assert (g_variant_check_format_string (value, "(s^as)", FALSE));
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g_test_expect_message ("GLib", G_LOG_LEVEL_CRITICAL, "*contains a '&' character*");
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g_assert (!g_variant_check_format_string (value, "(s^a&s)", TRUE));
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g_test_assert_expected_messages ();
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g_assert (g_variant_check_format_string (value, "(s^a&s)", FALSE));
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g_variant_unref (value);
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/* Do it again with a type that will let us put a '&' after a '^' */
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value = g_variant_new ("(say)", "foo", NULL);
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g_variant_ref_sink (value);
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g_assert (g_variant_check_format_string (value, "(s*)", TRUE));
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g_assert (g_variant_check_format_string (value, "(s*)", FALSE));
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g_assert (!g_variant_check_format_string (value, "(u*)", TRUE));
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g_assert (!g_variant_check_format_string (value, "(u*)", FALSE));
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g_assert (g_variant_check_format_string (value, "(&s*)", FALSE));
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g_test_expect_message ("GLib", G_LOG_LEVEL_CRITICAL, "*contains a '&' character*");
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g_assert (!g_variant_check_format_string (value, "(&s*)", TRUE));
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g_test_assert_expected_messages ();
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g_assert (g_variant_check_format_string (value, "(s^ay)", TRUE));
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g_assert (g_variant_check_format_string (value, "(s^ay)", FALSE));
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g_test_expect_message ("GLib", G_LOG_LEVEL_CRITICAL, "*contains a '&' character*");
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g_assert (!g_variant_check_format_string (value, "(s^&ay)", TRUE));
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g_test_assert_expected_messages ();
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g_assert (g_variant_check_format_string (value, "(s^&ay)", FALSE));
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g_variant_unref (value);
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}
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int
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main (int argc, char **argv)
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{
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@ -4167,6 +4220,7 @@ main (int argc, char **argv)
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g_test_add_func ("/gvariant/lookup", test_lookup);
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g_test_add_func ("/gvariant/compare", test_compare);
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g_test_add_func ("/gvariant/fixed-array", test_fixed_array);
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g_test_add_func ("/gvariant/check-format-string", test_check_format_string);
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return g_test_run ();
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}
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