Temporarily redirects markup data to a sub-parser.
This function may only be called from the start_element handler of
a #GMarkupParser. It must be matched with a corresponding call to
g_markup_parse_context_pop() in the matching end_element handler
(except in the case that the parser aborts due to an error).
All tags, text and other data between the matching tags is
redirected to the subparser given by @parser. @user_data is used
as the user_data for that parser. @user_data is also passed to the
error callback in the event that an error occurs. This includes
errors that occur in subparsers of the subparser.
The end tag matching the start tag for which this call was made is
handled by the previous parser (which is given its own user_data)
which is why g_markup_parse_context_pop() is provided to allow "one
last access" to the @user_data provided to this function. In the
case of error, the @user_data provided here is passed directly to
the error callback of the subparser and g_markup_parse_context_pop()
should not be called. In either case, if @user_data was allocated
then it ought to be freed from both of these locations.
This function is not intended to be directly called by users
interested in invoking subparsers. Instead, it is intended to be
used by the subparsers themselves to implement a higher-level
interface.
As an example, see the following implementation of a simple
parser that counts the number of tags encountered.
Temporarily redirects markup data to a sub-parser.
This function may only be called from the start_element handler of a #GMarkupParser. It must be matched with a corresponding call to g_markup_parse_context_pop() in the matching end_element handler (except in the case that the parser aborts due to an error).
All tags, text and other data between the matching tags is redirected to the subparser given by @parser. @user_data is used as the user_data for that parser. @user_data is also passed to the error callback in the event that an error occurs. This includes errors that occur in subparsers of the subparser.
The end tag matching the start tag for which this call was made is handled by the previous parser (which is given its own user_data) which is why g_markup_parse_context_pop() is provided to allow "one last access" to the @user_data provided to this function. In the case of error, the @user_data provided here is passed directly to the error callback of the subparser and g_markup_parse_context_pop() should not be called. In either case, if @user_data was allocated then it ought to be freed from both of these locations.
This function is not intended to be directly called by users interested in invoking subparsers. Instead, it is intended to be used by the subparsers themselves to implement a higher-level interface.
As an example, see the following implementation of a simple parser that counts the number of tags encountered.
|[<!-- language="C" --> typedef struct { gint tag_count; } CounterData;
static void counter_start_element (GMarkupParseContext *context, const gchar *element_name, const gchar **attribute_names, const gchar **attribute_values, gpointer user_data, GError **error) { CounterData *data = user_data;
data->tag_count++; }
static void counter_error (GMarkupParseContext *context, GError *error, gpointer user_data) { CounterData *data = user_data;
g_slice_free (CounterData, data); }
static GMarkupParser counter_subparser = { counter_start_element, NULL, NULL, NULL, counter_error }; ]|
In order to allow this parser to be easily used as a subparser, the following interface is provided:
|[<!-- language="C" --> void start_counting (GMarkupParseContext *context) { CounterData *data = g_slice_new (CounterData);
data->tag_count = 0; g_markup_parse_context_push (context, &counter_subparser, data); }
gint end_counting (GMarkupParseContext *context) { CounterData *data = g_markup_parse_context_pop (context); int result;
result = data->tag_count; g_slice_free (CounterData, data);
return result; } ]|
The subparser would then be used as follows:
|[<!-- language="C" --> static void start_element (context, element_name, ...) { if (strcmp (element_name, "count-these") == 0) start_counting (context);
// else, handle other tags... }
static void end_element (context, element_name, ...) { if (strcmp (element_name, "count-these") == 0) g_print ("Counted %d tags\n", end_counting (context));
// else, handle other tags... } ]|