Fix Request::pdu_len

Author: flosse

CHANGELOG.md

@@ -14,6 +14,7 @@
 - Add `Coils::from_iter`
 - Removed `modbus_core::packed_coils_len`, it is now implemented via `CoilQuantity::packed_len`.
 - `modbus_core::pack_coils` now takes an iterator over coils instead of a slice of coils, and it returns a `CoilQuantity` instead of a `usize`.
+- Fixed `Request::pdu_len` for `Request::WriteMultipleRegisters` and `Request::ReadWriteMultipleRegisters`
 
 ## v0.2.0 (2025-09-30)
 

src/frame/mod.rs

@@ -387,8 +387,8 @@ impl Request<'_> {
             | Self::WriteSingleRegister(_, _)
             | Self::WriteSingleCoil(_, _) => 5,
             Self::WriteMultipleCoils(_, coils) => 6 + coils.packed_len(),
-            Self::WriteMultipleRegisters(_, words) => 6 + words.data.len(),
-            Self::ReadWriteMultipleRegisters(_, _, _, words) => 10 + words.data.len(),
+            Self::WriteMultipleRegisters(_, data) => 6 + data.len() * 2,
+            Self::ReadWriteMultipleRegisters(_, _, _, data) => 10 + data.len() * 2,
             Self::Custom(_, data) => 1 + data.len(),
             #[cfg(feature = "rtu")]
             _ => todo!(), // TODO
@@ -406,9 +406,9 @@ impl Response<'_> {
             Self::WriteMultipleCoils(_, _)
             | Self::WriteMultipleRegisters(_, _)
             | Self::WriteSingleRegister(_, _) => 5,
-            Self::ReadInputRegisters(words)
-            | Self::ReadHoldingRegisters(words)
-            | Self::ReadWriteMultipleRegisters(words) => 2 + words.len() * 2,
+            Self::ReadInputRegisters(data)
+            | Self::ReadHoldingRegisters(data)
+            | Self::ReadWriteMultipleRegisters(data) => 2 + data.len() * 2,
             Self::Custom(_, data) => 1 + data.len(),
             #[cfg(feature = "rtu")]
             Self::ReadExceptionStatus(_) => 2,
@@ -548,6 +548,25 @@ mod tests {
                 .pdu_len(),
             7
         );
+        let mut big_buffer = [0; 200];
+        assert_eq!(
+            Request::WriteMultipleRegisters(
+                0,
+                Data::from_words(&[0x23, 0x24], &mut big_buffer).unwrap()
+            )
+            .pdu_len(),
+            10
+        );
+        assert_eq!(
+            Request::ReadWriteMultipleRegisters(
+                0,
+                3,
+                2,
+                Data::from_words(&[0x23, 0x24], &mut big_buffer).unwrap()
+            )
+            .pdu_len(),
+            14
+        );
         // TODO: extend test
     }