Properly compute size of messages with long packed field fields

Fix issue #281

protobuf-test/src/common/v2/test_repeated_packed.rs

@@ -70,3 +70,14 @@ fn test_read_packed_to_packed() {
     test.set_sfixed32s([17i32, 1000].to_vec());
     test_deserialize("2a 08 11 00 00 00 e8 03 00 00", &test);
 }
+
+#[test]
+fn test_issue_281() {
+    // Data len len was incorrectly computed.
+    // For 100 elements, bytes len is 400
+    // and varint len of 400 is 2,
+    // while varint len of 100 is 1.
+    let mut test = TestIssue281::new();
+    test.set_values((0..100).collect());
+    test_serialize_deserialize_no_hex(&test);
+}

protobuf-test/src/common/v2/test_repeated_packed_pb.proto

@@ -7,3 +7,7 @@ message TestUnpacked {
     repeated int32 varints = 4 [packed=false];
     repeated sfixed32 sfixed32s = 5 [packed=false];
 }
+
+message TestIssue281 {
+    repeated fixed32 values = 1 [packed=true];
+}

protobuf/src/codegen/field.rs

@@ -1318,9 +1318,9 @@ impl<'a> FieldGen<'a> {
     fn self_field_vec_packed_fixed_size(&self) -> String {
         // zero is filtered outside
         format!(
-            "{} + ::protobuf::rt::compute_raw_varint32_size({}.len() as u32) + {}",
+            "{} + ::protobuf::rt::compute_raw_varint32_size({}) + {}",
             self.tag_size(),
-            self.self_field(),
+            self.self_field_vec_packed_fixed_data_size(),
             self.self_field_vec_packed_fixed_data_size()
         )
     }