+ break;
+
+ default:
+ PB_RETURN_ERROR(stream, "invalid field type");
+ }
+
+ return true;
+}
+
+/* Encode a field with callback semantics. This means that a user function is
+ * called to provide and encode the actual data. */
+static bool checkreturn encode_callback_field(pb_ostream_t *stream,
+ const pb_field_t *field, const void *pData)
+{
+ const pb_callback_t *callback = (const pb_callback_t*)pData;
+
+#ifdef PB_OLD_CALLBACK_STYLE
+ const void *arg = callback->arg;
+#else
+ void * const *arg = &(callback->arg);
+#endif
+
+ if (callback->funcs.encode != NULL)
+ {
+ if (!callback->funcs.encode(stream, field, arg))
+ PB_RETURN_ERROR(stream, "callback error");
+ }
+ return true;
+}
+
+/* Encode a single field of any callback or static type. */
+static bool checkreturn encode_field(pb_ostream_t *stream,
+ const pb_field_t *field, const void *pData)
+{
+ switch (PB_ATYPE(field->type))
+ {
+ case PB_ATYPE_STATIC:
+ case PB_ATYPE_POINTER:
+ return encode_basic_field(stream, field, pData);
+
+ case PB_ATYPE_CALLBACK:
+ return encode_callback_field(stream, field, pData);
+
+ default:
+ PB_RETURN_ERROR(stream, "invalid field type");
+ }
+}
+
+/* Default handler for extension fields. Expects to have a pb_field_t
+ * pointer in the extension->type->arg field. */
+static bool checkreturn default_extension_encoder(pb_ostream_t *stream,
+ const pb_extension_t *extension)
+{
+ const pb_field_t *field = (const pb_field_t*)extension->type->arg;