Add gres:// type links support for libxml2

src/astrognome.c

@@ -20,6 +20,7 @@
 GtkBuilder    *builder;
 GtkFileFilter *filter_all   = NULL;
 GtkFileFilter *filter_chart = NULL;
+GHashTable    *xinclude_positions;
 
 const char    *moonStateName[] = {
     "New Moon",
@@ -47,6 +48,100 @@ init_filters(void)
     g_object_ref_sink(filter_chart);
 }
 
+static int
+xml_match_gresource(const char *uri)
+{
+    if ((uri != NULL) && (!strncmp("gres://", uri, 7))) {
+        g_debug("Matched gres:// type link.");
+
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static void *
+xml_open_gresource(const gchar *uri)
+{
+    gchar  *path;
+    GBytes *res_location;
+    gsize  *position;
+
+    if ((uri == NULL) || (strncmp("gres://", uri, 7))) {
+        return NULL;
+    }
+
+    path = g_strdup_printf("/eu/polonkai/gergely/Astrognome/%s", uri + 7);
+    g_debug("Opening gresource %s", path);
+
+    res_location = g_resources_lookup_data(
+            path,
+            G_RESOURCE_LOOKUP_FLAGS_NONE,
+            NULL
+        );
+    g_free(path);
+
+    if ((position = g_hash_table_lookup(xinclude_positions, res_location)) == NULL) {
+        g_hash_table_insert(xinclude_positions, res_location, g_new0(gsize, 1));
+    } else {
+        g_warning("Reopening gres:// link?");
+        *position = 0;
+    }
+
+    return res_location;
+}
+
+static int
+xml_close_gresource(void *context)
+{
+    if (context == NULL) {
+        return -1;
+    }
+
+    g_debug("Closing gres:// link");
+
+    g_hash_table_remove(xinclude_positions, context);
+    g_bytes_unref((GBytes *)context);
+
+    return 0;
+}
+
+static int
+xml_read_gresource(void *context, char *buffer, int len)
+{
+    const gchar *data;
+    gsize       max_length;
+    GBytes      *data_holder = (GBytes *)context;
+    gsize       *position;
+
+    if ((context == NULL) || (buffer == NULL) || (len < 0)) {
+        return -1;
+    }
+
+    data     = g_bytes_get_data(data_holder, &max_length);
+    position = g_hash_table_lookup(xinclude_positions, data_holder);
+
+    if (position == NULL) {
+        g_warning("Trying to read non-opened gres:// link!");
+
+        return -1;
+    }
+
+    if (*position >= max_length) {
+        return 0;
+    }
+
+    if (len > max_length - *position) {
+        len = max_length - *position;
+    }
+
+    memcpy(buffer, data + *position, len);
+    g_debug("Read %d bytes", len);
+    *position += len;
+
+    return len;
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -89,10 +184,22 @@ main(int argc, char *argv[])
     LIBXML_TEST_VERSION;
     xmlSubstituteEntitiesDefault(1);
     xmlLoadExtDtdDefaultValue = 1;
+    xmlRegisterInputCallbacks(
+            xml_match_gresource,
+            xml_open_gresource,
+            xml_read_gresource,
+            xml_close_gresource
+        );
     xsltInit();
     xsltSetXIncludeDefault(1);
     exsltRegisterAll();
     gswe_init();
+    xinclude_positions = g_hash_table_new_full(
+            g_bytes_hash,
+            g_bytes_equal,
+            (GDestroyNotify)g_bytes_unref,
+            (GDestroyNotify)g_free
+        );
 
     memset(&options, 0, sizeof(AstrognomeOptions));
 
@@ -135,6 +242,7 @@ main(int argc, char *argv[])
 
     status = g_application_run(G_APPLICATION(app), argc, argv);
 
+    g_hash_table_destroy(xinclude_positions);
     g_object_unref(app);
 
     return status;