fix: correct CCSDS packet length calculation

Signed-off-by: 0rlych1kk4 <orlychikka@gmail.com>

satrs-example/types/src/ccsds.rs

@@ -54,7 +54,7 @@ impl CcsdsTcPacketOwned {
     pub fn len_written(&self) -> usize {
         ccsds_packet_len_for_user_data_len_with_checksum(
             postcard::experimental::serialized_size(&self.tc_header).unwrap() as usize
-                + postcard::experimental::serialized_size(&self.payload).unwrap() as usize,
+                + self.payload.len(),
         )
         .unwrap()
     }
@@ -116,7 +116,7 @@ impl CcsdsTmPacketOwned {
     pub fn len_written(&self) -> usize {
         ccsds_packet_len_for_user_data_len_with_checksum(
             postcard::experimental::serialized_size(&self.tm_header).unwrap() as usize
-                + postcard::experimental::serialized_size(&self.payload).unwrap() as usize,
+                + self.payload.len(),
         )
         .unwrap()
     }

satrs-example/types/tests/ccsds_len.rs

@@ -0,0 +1,49 @@
+use arbitrary_int::u11;
+use spacepackets::{SpacePacketHeader, time::cds::CdsTime};
+use types::{
+    Apid, ComponentId, MessageType, TcHeader, TmHeader,
+    ccsds::{CcsdsTcPacketOwned, CcsdsTmPacketOwned},
+};
+
+#[test]
+fn tc_len_written_matches_actual_serialized_length() {
+    let packet = CcsdsTcPacketOwned::new_with_request(
+        SpacePacketHeader::new_from_apid(u11::new(Apid::Tmtc as u16)),
+        TcHeader::new(ComponentId::Controller, MessageType::Ping),
+        types::control::request::Request::Ping,
+    );
+
+    let actual = packet.to_vec();
+
+    println!("TC len_written(): {}", packet.len_written());
+    println!("TC actual len:    {}", actual.len());
+
+    assert_eq!(packet.len_written(), actual.len());
+}
+
+#[test]
+fn tm_len_written_matches_actual_serialized_length() {
+    let timestamp = CdsTime::new_with_u16_days(0, 0);
+
+    let tm_header = TmHeader::new(
+        ComponentId::Controller,
+        ComponentId::Ground,
+        MessageType::Verification,
+        None,
+        &timestamp,
+    );
+
+    let packet = CcsdsTmPacketOwned::new_with_serde_payload(
+        SpacePacketHeader::new_from_apid(u11::new(Apid::Tmtc as u16)),
+        &tm_header,
+        &types::control::response::Response::Ok,
+    )
+    .unwrap();
+
+    let actual = packet.to_vec();
+
+    println!("TM len_written(): {}", packet.len_written());
+    println!("TM actual len:    {}", actual.len());
+
+    assert_eq!(packet.len_written(), actual.len());
+}