feat: fd-commands (#4)

- [x] QueryDownstreamDevices (dc25fdf)
  - [x] test_query_downstream_devices_request_codec
  - [x] test_query_downstream_devices_response_codec
- [x] QueryDownstreamIdentifiers
(dc25fdf)
  - [x] test_query_downstream_identifiers_request_codec
  - [x] test_query_downstream_identifiers_response_codec
- [x] GetDownstreamFirmwareParameters
(b63b0f6)
  - [x] test_get_downstream_firmware_parameters_request_codec
  - [x] test_get_downstream_firmware_parameters_response_codec
  - [x] test_device_parameter_table_codec
  - [x] test_get_downstream_firmware_parameters_portion_codec
- [x] RequestDownstreamDeviceUpdate
(69aac44)
  - [x] test_request_downstream_device_update_request_codec
  - [x] test_request_downstream_device_update_response_codec
- [x] GetPackageData (ab8f458)
    - [x] test_get_package_data_request_codec
    - [x] test_get_package_data_response_codec
- [x] GetDeviceMetaData (1face4e)
    - [x] test_get_device_meta_data_request_codec
    - [x] test_get_device_meta_data_response_codec
- [x] GetMetaData (116aebd)
    - [x] test_get_metadata_request_codec
    - [x] test_get_meta_data_response_codec

---------

Signed-off-by: leongross <[email protected]>

Author: leongross

Cargo.toml

@@ -5,5 +5,5 @@ authors = ["Caliptra contributors", "OpenPRoT contributors"]
 edition = "2024"
 
 [dependencies]
-zerocopy = {version = "0.8.17", features = ["derive"]}
+zerocopy = { version = "0.8.17", features = ["derive"] }
 bitfield = "0.14.0"

src/codec.rs

@@ -6,6 +6,7 @@ use zerocopy::{FromBytes, Immutable, IntoBytes};
 pub enum PldmCodecError {
     BufferTooShort,
     Unsupported,
+    InvalidData,
 }
 
 /// A trait for encoding and decoding PLDM (Platform Level Data Model) messages.
@@ -37,7 +38,39 @@ pub trait PldmCodec: core::fmt::Debug + Sized {
     fn decode(buffer: &[u8]) -> Result<Self, PldmCodecError>;
 }
 
+/// A trait for encoding and decoding PLDM messages with explicit lifetime requirements.
+///
+/// This trait is similar to `PldmCodec` but supports types that borrow data from the buffer
+/// during decoding, requiring an explicit lifetime parameter.
+pub trait PldmCodecWithLifetime<'a>: core::fmt::Debug + Sized {
+    /// Encodes the PLDM message into the provided byte buffer.
+    ///
+    /// # Arguments
+    ///
+    /// * `buffer` - A mutable reference to a byte slice where the encoded message will be stored.
+    ///
+    /// # Returns
+    ///
+    /// A `Result` containing the size of the encoded message on success, or a `PldmCodecError` on failure.
+    fn encode(&self, buffer: &mut [u8]) -> Result<usize, PldmCodecError>;
+
+    /// Decodes a PLDM message from the provided byte buffer.
+    ///
+    /// # Arguments
+    ///
+    /// * `buffer` - A reference to a byte slice containing the encoded message. The decoded
+    ///   type may hold references to this buffer.
+    ///
+    /// # Returns
+    ///
+    /// A `Result` containing the decoded message on success, or a `PldmCodecError` on failure.
+    fn decode(buffer: &'a [u8]) -> Result<Self, PldmCodecError>;
+}
+
 // Default implementation of PldmCodec for types that can leverage zerocopy.
+// TODO: can we generalize this to use sub-struct encodes when possible?
+// There are structs like PldmFirmwareString that contain variable-length data
+// that would need special handling.
 impl<T> PldmCodec for T
 where
     T: core::fmt::Debug + Sized + FromBytes + IntoBytes + Immutable,

src/message/firmware_update/get_fw_params.rs

@@ -257,8 +257,7 @@ impl PldmCodec for GetFirmwareParametersResponse {
         offset += core::mem::size_of::<u8>();
 
         let bytes = self.parms.encode(&mut buffer[offset..])?;
-        offset += bytes;
-        Ok(offset)
+        Ok(offset + bytes)
     }
 
     fn decode(buffer: &[u8]) -> Result<Self, PldmCodecError> {
@@ -331,32 +330,71 @@ mod test {
     }
 
     #[test]
-    fn test_get_firmware_parameters_request() {
+    fn test_get_firmware_parameters_request_codec() {
         let request = GetFirmwareParametersRequest::new(0, PldmMsgType::Request);
         let mut buffer = [0u8; PLDM_MSG_HEADER_LEN];
         request.encode(&mut buffer).unwrap();
+
         let decoded_request = GetFirmwareParametersRequest::decode(&buffer).unwrap();
         assert_eq!(request, decoded_request);
+
+        // Test buffer too short error
+        let mut buffer = [0u8; PLDM_MSG_HEADER_LEN - 1];
+        assert_eq!(
+            request.encode(&mut buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
+
+        assert_eq!(
+            GetFirmwareParametersRequest::decode(&buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
     }
 
     #[test]
-    fn test_get_firmware_parameters() {
+    fn test_get_firmware_parameters_codec() {
         let firmware_parameters = construct_firmware_params();
         let mut buffer = [0u8; 1024];
         let size = firmware_parameters.encode(&mut buffer).unwrap();
         assert_eq!(size, firmware_parameters.codec_size_in_bytes());
+
         let decoded_firmware_parameters = FirmwareParameters::decode(&buffer[..size]).unwrap();
         assert_eq!(firmware_parameters, decoded_firmware_parameters);
+
+        // Test buffer too short error
+        let mut short_buffer = [0u8; 1];
+        assert_eq!(
+            firmware_parameters.encode(&mut short_buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
+
+        assert_eq!(
+            FirmwareParameters::decode(&short_buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
     }
 
     #[test]
-    fn test_get_firmware_parameters_response() {
+    fn test_get_firmware_parameters_response_codec() {
         let firmware_parameters = construct_firmware_params();
         let response = GetFirmwareParametersResponse::new(0, 0, &firmware_parameters);
         let mut buffer = [0u8; 1024];
         let size = response.encode(&mut buffer).unwrap();
         assert_eq!(size, response.codec_size_in_bytes());
+
         let decoded_response = GetFirmwareParametersResponse::decode(&buffer[..size]).unwrap();
         assert_eq!(response, decoded_response);
+
+        // Test buffer too short error
+        let mut short_buffer = [0u8; 1];
+        assert_eq!(
+            response.encode(&mut short_buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
+
+        assert_eq!(
+            GetFirmwareParametersResponse::decode(&short_buffer).unwrap_err(),
+            PldmCodecError::BufferTooShort
+        );
     }
 }