+/* Structure for defining the handling of unknown/extension fields.
+ * Usually the pb_extension_type_t structure is automatically generated,
+ * while the pb_extension_t structure is created by the user. However,
+ * if you want to catch all unknown fields, you can also create a custom
+ * pb_extension_type_t with your own callback.
+ */
+typedef struct _pb_extension_type_t pb_extension_type_t;
+typedef struct _pb_extension_t pb_extension_t;
+struct _pb_extension_type_t {
+ /* Called for each unknown field in the message.
+ * If you handle the field, read off all of its data and return true.
+ * If you do not handle the field, do not read anything and return true.
+ * If you run into an error, return false.
+ * Set to NULL for default handler.
+ */
+ bool (*decode)(pb_istream_t *stream, pb_extension_t *extension,
+ uint32_t tag, pb_wire_type_t wire_type);
+
+ /* Called once after all regular fields have been encoded.
+ * If you have something to write, do so and return true.
+ * If you do not have anything to write, just return true.
+ * If you run into an error, return false.
+ * Set to NULL for default handler.
+ */
+ bool (*encode)(pb_ostream_t *stream, const pb_extension_t *extension);
+
+ /* Free field for use by the callback. */
+ const void *arg;
+};
+
+struct _pb_extension_t {
+ /* Type describing the extension field. Usually you'll initialize
+ * this to a pointer to the automatically generated structure. */
+ const pb_extension_type_t *type;
+
+ /* Destination for the decoded data. This must match the datatype
+ * of the extension field. */
+ void *dest;
+
+ /* Pointer to the next extension handler, or NULL.
+ * If this extension does not match a field, the next handler is
+ * automatically called. */
+ pb_extension_t *next;
+
+ /* The decoder sets this to true if the extension was found.
+ * Ignored for encoding. */
+ bool found;
+};
+
+/* Memory allocation functions to use. You can define pb_realloc and
+ * pb_free to custom functions if you want. */
+#ifdef PB_ENABLE_MALLOC
+# ifndef pb_realloc
+# define pb_realloc(ptr, size) realloc(ptr, size)
+# endif
+# ifndef pb_free
+# define pb_free(ptr) free(ptr)
+# endif
+#endif
+