Merge pull request 'add owned TLV type' (#98) from cfdp-tlv-owned-type into main

Reviewed-on: #98

CHANGELOG.md

@@ -8,10 +8,22 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 # [unreleased]
 
-# [v0.11.3] 2024-06-25
+# [v0.12.0]
 
 - Minor documentation build updates.
 
+## Added
+
+- Added new `cfdp::tlv::TlvOwned` type which erases the lifetime and is clonable.
+- Dedicated `cfdp::tlv::TlvLvDataTooLarge` error struct for APIs where this is the only possible
+  API error.
+
+## Added and Changed
+
+- Added new `ReadableTlv` to avoid some boilerplate code and have a common abstraction implemented
+  for both `Tlv` and `TlvOwned` to read the raw TLV data field and its length.
+- Replaced `cfdp::tlv::TlvLvError` by `cfdp::tlv::TlvLvDataTooLarge` where applicable.
+
 # [v0.11.2] 2024-05-19
 
 - Bumped MSRV to 1.68.2

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "spacepackets"
-version = "0.11.3"
+version = "0.12.0"
 edition = "2021"
 rust-version = "1.68.2"
 authors = ["Robin Mueller <muellerr@irs.uni-stuttgart.de>"]
@@ -60,7 +60,7 @@ chrono = "0.4"
 default = ["std"]
 std = ["chrono/std", "chrono/clock", "alloc", "thiserror"]
 serde = ["dep:serde", "chrono/serde"]
-alloc = ["postcard/alloc", "chrono/alloc"]
+alloc = ["postcard/alloc", "chrono/alloc", "defmt/alloc", "serde/alloc"]
 chrono = ["dep:chrono"]
 timelib = ["dep:time"]
 defmt = ["dep:defmt"]

src/cfdp/lv.rs

@@ -1,5 +1,4 @@
 //! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
-use crate::cfdp::TlvLvError;
 use crate::ByteConversionError;
 use core::str::Utf8Error;
 #[cfg(feature = "serde")]
@@ -7,6 +6,8 @@ use serde::{Deserialize, Serialize};
 #[cfg(feature = "std")]
 use std::string::String;
 
+use super::TlvLvDataTooLarge;
+
 pub const MIN_LV_LEN: usize = 1;
 
 /// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
@@ -63,9 +64,9 @@ pub(crate) fn generic_len_check_deserialization(
 
 impl<'data> Lv<'data> {
     #[inline]
-    pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
+    pub fn new(data: &[u8]) -> Result<Lv, TlvLvDataTooLarge> {
         if data.len() > u8::MAX as usize {
-            return Err(TlvLvError::DataTooLarge(data.len()));
+            return Err(TlvLvDataTooLarge(data.len()));
         }
         Ok(Lv {
             data,
@@ -85,7 +86,7 @@ impl<'data> Lv<'data> {
     /// Helper function to build a string LV. This is especially useful for the file or directory
     /// path LVs
     #[inline]
-    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvError> {
+    pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvDataTooLarge> {
         Self::new(str_slice.as_bytes())
     }
 
@@ -93,7 +94,7 @@ impl<'data> Lv<'data> {
     /// path LVs
     #[cfg(feature = "std")]
     #[inline]
-    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvError> {
+    pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvDataTooLarge> {
         Self::new(string.as_bytes())
     }
 
@@ -177,10 +178,10 @@ impl<'data> Lv<'data> {
 
 #[cfg(test)]
 pub mod tests {
-    use super::*;
     use alloc::string::ToString;
 
-    use crate::cfdp::TlvLvError;
+    use super::*;
+
     use crate::ByteConversionError;
     use std::string::String;
 
@@ -271,15 +272,11 @@ pub mod tests {
         let lv = Lv::new(&data_big);
         assert!(lv.is_err());
         let error = lv.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-            assert_eq!(
-                error.to_string(),
-                "data with size 256 larger than allowed 255 bytes"
-            );
-        } else {
-            panic!("invalid exception {:?}", error)
-        }
+        assert_eq!(error.0, u8::MAX as usize + 1);
+        assert_eq!(
+            error.to_string(),
+            "data with size 256 larger than allowed 255 bytes"
+        );
     }
 
     #[test]

src/cfdp/mod.rs

@@ -176,11 +176,30 @@ impl Default for ChecksumType {
 
 pub const NULL_CHECKSUM_U32: [u8; 4] = [0; 4];
 
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct TlvLvDataTooLarge(pub usize);
+
+impl Display for TlvLvDataTooLarge {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        write!(
+            f,
+            "data with size {} larger than allowed {} bytes",
+            self.0,
+            u8::MAX
+        )
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for TlvLvDataTooLarge {}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum TlvLvError {
-    DataTooLarge(usize),
+    DataTooLarge(TlvLvDataTooLarge),
     ByteConversion(ByteConversionError),
     /// First value: Found value. Second value: Expected value if there is one.
     InvalidTlvTypeField {
@@ -197,6 +216,12 @@ pub enum TlvLvError {
     InvalidFilestoreActionCode(u8),
 }
 
+impl From<TlvLvDataTooLarge> for TlvLvError {
+    fn from(value: TlvLvDataTooLarge) -> Self {
+        Self::DataTooLarge(value)
+    }
+}
+
 impl From<ByteConversionError> for TlvLvError {
     fn from(value: ByteConversionError) -> Self {
         Self::ByteConversion(value)
@@ -206,13 +231,8 @@ impl From<ByteConversionError> for TlvLvError {
 impl Display for TlvLvError {
     fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
         match self {
-            TlvLvError::DataTooLarge(data_len) => {
-                write!(
-                    f,
-                    "data with size {} larger than allowed {} bytes",
-                    data_len,
-                    u8::MAX
-                )
+            TlvLvError::DataTooLarge(e) => {
+                write!(f, "{}", e)
             }
             TlvLvError::ByteConversion(e) => {
                 write!(f, "tlv or lv byte conversion: {}", e)
@@ -240,6 +260,7 @@ impl Display for TlvLvError {
 impl Error for TlvLvError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self {
+            TlvLvError::DataTooLarge(e) => Some(e),
             TlvLvError::ByteConversion(e) => Some(e),
             _ => None,
         }

src/cfdp/pdu/finished.rs

@@ -10,6 +10,7 @@ use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
 use super::{CfdpPdu, WritablePduPacket};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, TryFromPrimitive, IntoPrimitive)]

src/cfdp/pdu/metadata.rs

@@ -11,6 +11,7 @@ use alloc::vec::Vec;
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::tlv::ReadableTlv;
 use super::{CfdpPdu, WritablePduPacket};
 
 #[derive(Default, Debug, Copy, Clone, PartialEq, Eq)]
@@ -354,7 +355,7 @@ pub mod tests {
     };
     use crate::cfdp::pdu::{CfdpPdu, PduError, WritablePduPacket};
     use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
-    use crate::cfdp::tlv::{Tlv, TlvType};
+    use crate::cfdp::tlv::{ReadableTlv, Tlv, TlvType};
     use crate::cfdp::{
         ChecksumType, CrcFlag, Direction, LargeFileFlag, PduType, SegmentMetadataFlag,
         SegmentationControl, TransmissionMode,

src/cfdp/tlv/mod.rs

@@ -9,10 +9,14 @@ use crate::ByteConversionError;
 use alloc::vec;
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
+#[cfg(feature = "alloc")]
+pub use alloc_mod::*;
 use num_enum::{IntoPrimitive, TryFromPrimitive};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+use super::TlvLvDataTooLarge;
+
 pub mod msg_to_user;
 
 pub const MIN_TLV_LEN: usize = 2;
@@ -39,6 +43,26 @@ pub trait GenericTlv {
     }
 }
 
+pub trait ReadableTlv {
+    fn value(&self) -> &[u8];
+
+    /// Checks whether the value field is empty.
+    fn is_empty(&self) -> bool {
+        self.value().is_empty()
+    }
+
+    /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
+    /// [Self::value]
+    fn len_value(&self) -> usize {
+        self.value().len()
+    }
+
+    /// Returns the full raw length, including the length byte.
+    fn len_full(&self) -> usize {
+        self.len_value() + 2
+    }
+}
+
 pub trait WritableTlv {
     fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
     fn len_written(&self) -> usize;
@@ -129,14 +153,14 @@ pub struct Tlv<'data> {
 }
 
 impl<'data> Tlv<'data> {
-    pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Tlv, TlvLvError> {
+    pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Tlv, TlvLvDataTooLarge> {
         Ok(Tlv {
             tlv_type_field: TlvTypeField::Standard(tlv_type),
             lv: Lv::new(data)?,
         })
     }
 
-    pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Tlv, TlvLvError> {
+    pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Tlv, TlvLvDataTooLarge> {
         Ok(Tlv {
             tlv_type_field: TlvTypeField::Custom(tlv_type),
             lv: Lv::new(data)?,
@@ -151,26 +175,6 @@ impl<'data> Tlv<'data> {
         }
     }
 
-    pub fn value(&self) -> &[u8] {
-        self.lv.value()
-    }
-
-    /// Checks whether the value field is empty.
-    pub fn is_empty(&self) -> bool {
-        self.value().is_empty()
-    }
-
-    /// Helper method to retrieve the length of the value. Simply calls the [slice::len] method of
-    /// [Self::value]
-    pub fn len_value(&self) -> usize {
-        self.value().len()
-    }
-
-    /// Returns the full raw length, including the length byte.
-    pub fn len_full(&self) -> usize {
-        self.len_value() + 2
-    }
-
     /// Creates a TLV give a raw bytestream. Please note that is is not necessary to pass the
     /// bytestream with the exact size of the expected TLV. This function will take care
     /// of parsing the length byte, and the length of the parsed TLV can be retrieved using
@@ -192,6 +196,27 @@ impl<'data> Tlv<'data> {
     pub fn raw_data(&self) -> Option<&[u8]> {
         self.lv.raw_data()
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        TlvOwned {
+            tlv_type_field: self.tlv_type_field,
+            data: self.value().to_vec(),
+        }
+    }
+}
+
+#[cfg(feature = "alloc")]
+impl PartialEq<TlvOwned> for Tlv<'_> {
+    fn eq(&self, other: &TlvOwned) -> bool {
+        self.tlv_type_field == other.tlv_type_field && self.value() == other.value()
+    }
+}
+
+impl ReadableTlv for Tlv<'_> {
+    fn value(&self) -> &[u8] {
+        self.lv.value()
+    }
 }
 
 impl WritableTlv for Tlv<'_> {
@@ -212,18 +237,98 @@ impl GenericTlv for Tlv<'_> {
     }
 }
 
-pub(crate) fn verify_tlv_type(raw_type: u8, expected_tlv_type: TlvType) -> Result<(), TlvLvError> {
-    let tlv_type = TlvType::try_from(raw_type).map_err(|_| TlvLvError::InvalidTlvTypeField {
-        found: raw_type,
-        expected: Some(expected_tlv_type.into()),
-    })?;
-    if tlv_type != expected_tlv_type {
-        return Err(TlvLvError::InvalidTlvTypeField {
-            found: tlv_type as u8,
-            expected: Some(expected_tlv_type as u8),
-        });
+#[cfg(feature = "alloc")]
+pub mod alloc_mod {
+    use crate::cfdp::TlvLvDataTooLarge;
+
+    use super::*;
+
+    /// Owned variant of [Tlv] which is consequently [Clone]able and does not have a lifetime
+    /// associated to a data slice.
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+    #[cfg_attr(feature = "defmt", derive(defmt::Format))]
+    pub struct TlvOwned {
+        pub(crate) tlv_type_field: TlvTypeField,
+        pub(crate) data: Vec<u8>,
+    }
+
+    impl TlvOwned {
+        pub fn new(tlv_type: TlvType, data: &[u8]) -> Result<Self, TlvLvDataTooLarge> {
+            if data.len() > u8::MAX as usize {
+                return Err(TlvLvDataTooLarge(data.len()));
+            }
+            Ok(Self {
+                tlv_type_field: TlvTypeField::Standard(tlv_type),
+                data: data.to_vec(),
+            })
+        }
+
+        pub fn new_with_custom_type(tlv_type: u8, data: &[u8]) -> Result<Self, TlvLvDataTooLarge> {
+            if data.len() > u8::MAX as usize {
+                return Err(TlvLvDataTooLarge(data.len()));
+            }
+            Ok(Self {
+                tlv_type_field: TlvTypeField::Custom(tlv_type),
+                data: data.to_vec(),
+            })
+        }
+
+        /// Creates a TLV with an empty value field.
+        pub fn new_empty(tlv_type: TlvType) -> Self {
+            Self {
+                tlv_type_field: TlvTypeField::Standard(tlv_type),
+                data: Vec::new(),
+            }
+        }
+
+        pub fn as_tlv(&self) -> Tlv<'_> {
+            Tlv {
+                tlv_type_field: self.tlv_type_field,
+                // The API should ensure that the data length is never to large, so the unwrap for the
+                // LV creation should never be an issue.
+                lv: Lv::new(&self.data).expect("lv creation failed unexpectedly"),
+            }
+        }
+    }
+
+    impl ReadableTlv for TlvOwned {
+        fn value(&self) -> &[u8] {
+            &self.data
+        }
+    }
+
+    impl WritableTlv for TlvOwned {
+        fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+            generic_len_check_data_serialization(buf, self.data.len(), MIN_TLV_LEN)?;
+            buf[0] = self.tlv_type_field.into();
+            buf[1] = self.data.len() as u8;
+            buf[2..2 + self.data.len()].copy_from_slice(&self.data);
+            Ok(self.len_written())
+        }
+
+        fn len_written(&self) -> usize {
+            self.data.len() + 2
+        }
+    }
+
+    impl GenericTlv for TlvOwned {
+        fn tlv_type_field(&self) -> TlvTypeField {
+            self.tlv_type_field
+        }
+    }
+
+    impl From<Tlv<'_>> for TlvOwned {
+        fn from(value: Tlv<'_>) -> Self {
+            value.to_owned()
+        }
+    }
+
+    impl PartialEq<Tlv<'_>> for TlvOwned {
+        fn eq(&self, other: &Tlv) -> bool {
+            self.tlv_type_field == other.tlv_type_field && self.data == other.value()
+        }
     }
-    Ok(())
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -238,7 +343,7 @@ impl EntityIdTlv {
         Self { entity_id }
     }
 
-    fn len_check(buf: &[u8]) -> Result<(), ByteConversionError> {
+    fn check_min_len(buf: &[u8]) -> Result<(), ByteConversionError> {
         if buf.len() < 2 {
             return Err(ByteConversionError::ToSliceTooSmall {
                 found: buf.len(),
@@ -261,7 +366,7 @@ impl EntityIdTlv {
     }
 
     pub fn from_bytes(buf: &[u8]) -> Result<Self, TlvLvError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         verify_tlv_type(buf[0], TlvType::EntityId)?;
         let len = buf[1];
         if len != 1 && len != 2 && len != 4 && len != 8 {
@@ -272,22 +377,31 @@ impl EntityIdTlv {
         Ok(Self { entity_id })
     }
 
-    /// Convert to a generic [Tlv], which also erases the programmatic type information.
+    /// Convert to a generic [Tlv], which also erases the type information.
     pub fn to_tlv(self, buf: &mut [u8]) -> Result<Tlv, ByteConversionError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         self.entity_id
             .write_to_be_bytes(&mut buf[2..2 + self.entity_id.size()])?;
-        Tlv::new(TlvType::EntityId, &buf[2..2 + self.entity_id.size()]).map_err(|e| match e {
-            TlvLvError::ByteConversion(e) => e,
-            // All other errors are impossible.
-            _ => panic!("unexpected TLV error"),
-        })
+        if buf.len() < self.len_value() {
+            return Err(ByteConversionError::ToSliceTooSmall {
+                found: buf.len(),
+                expected: self.len_value(),
+            });
+        }
+        // We performed all checks necessary to ensure this call never panics.
+        Ok(Tlv::new(TlvType::EntityId, &buf[2..2 + self.entity_id.size()]).unwrap())
+    }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // Unwrap is okay here, entity ID should never be larger than maximum allowed size.
+        TlvOwned::new(TlvType::EntityId, &self.entity_id.to_vec()).unwrap()
     }
 }
 
 impl WritableTlv for EntityIdTlv {
     fn write_to_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        Self::len_check(buf)?;
+        Self::check_min_len(buf)?;
         buf[0] = TlvType::EntityId as u8;
         buf[1] = self.entity_id.size() as u8;
         Ok(2 + self.entity_id.write_to_be_bytes(&mut buf[2..])?)
@@ -526,6 +640,12 @@ impl<'first_name, 'second_name> FilestoreRequestTlv<'first_name, 'second_name> {
             },
         })
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // The API should ensure the data field is never too large, so unwrapping here is okay.
+        TlvOwned::new(TlvType::FilestoreRequest, &self.to_vec()[2..]).unwrap()
+    }
 }
 
 impl WritableTlv for FilestoreRequestTlv<'_, '_> {
@@ -711,6 +831,12 @@ impl<'first_name, 'second_name, 'fs_msg> FilestoreResponseTlv<'first_name, 'seco
             filestore_message,
         })
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        // The API should ensure the data field is never too large, so unwrap is okay here.
+        TlvOwned::new(TlvType::FilestoreResponse, &self.to_vec()[2..]).unwrap()
+    }
 }
 
 impl WritableTlv for FilestoreResponseTlv<'_, '_, '_> {
@@ -752,6 +878,20 @@ impl GenericTlv for FilestoreResponseTlv<'_, '_, '_> {
     }
 }
 
+pub(crate) fn verify_tlv_type(raw_type: u8, expected_tlv_type: TlvType) -> Result<(), TlvLvError> {
+    let tlv_type = TlvType::try_from(raw_type).map_err(|_| TlvLvError::InvalidTlvTypeField {
+        found: raw_type,
+        expected: Some(expected_tlv_type.into()),
+    })?;
+    if tlv_type != expected_tlv_type {
+        return Err(TlvLvError::InvalidTlvTypeField {
+            found: tlv_type as u8,
+            expected: Some(expected_tlv_type as u8),
+        });
+    }
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -939,15 +1079,11 @@ mod tests {
         let tlv_res = Tlv::new(TlvType::MsgToUser, &buf_too_large);
         assert!(tlv_res.is_err());
         let error = tlv_res.unwrap_err();
-        if let TlvLvError::DataTooLarge(size) = error {
-            assert_eq!(size, u8::MAX as usize + 1);
-            assert_eq!(
-                error.to_string(),
-                "data with size 256 larger than allowed 255 bytes"
-            );
-        } else {
-            panic!("unexpected error {:?}", error);
-        }
+        assert_eq!(error.0, u8::MAX as usize + 1);
+        assert_eq!(
+            error.to_string(),
+            "data with size 256 larger than allowed 255 bytes"
+        );
     }
 
     #[test]
@@ -1300,4 +1436,71 @@ mod tests {
         assert_eq!(tlv_as_vec[0], 20);
         assert_eq!(tlv_as_vec[1], 0);
     }
+
+    #[test]
+    fn test_tlv_to_owned() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
+        assert!(tlv_res.is_ok());
+        let tlv_res = tlv_res.unwrap();
+        let tlv_owned = tlv_res.to_owned();
+        assert_eq!(tlv_res, tlv_owned);
+        let tlv_owned_from_conversion: TlvOwned = tlv_res.into();
+        assert_eq!(tlv_owned_from_conversion, tlv_owned);
+        assert_eq!(tlv_owned_from_conversion, tlv_res);
+    }
+
+    #[test]
+    fn test_owned_tlv() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = TlvOwned::new(TlvType::EntityId, &buf[0..1]).expect("creating TLV failed");
+        assert_eq!(
+            tlv_res.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::EntityId)
+        );
+        assert_eq!(tlv_res.len_full(), 3);
+        assert_eq!(tlv_res.value().len(), 1);
+        assert_eq!(tlv_res.len_value(), 1);
+        assert!(!tlv_res.is_empty());
+        assert_eq!(tlv_res.value()[0], 5);
+    }
+
+    #[test]
+    fn test_owned_tlv_empty() {
+        let tlv_res = TlvOwned::new_empty(TlvType::FlowLabel);
+        assert_eq!(
+            tlv_res.tlv_type_field(),
+            TlvTypeField::Standard(TlvType::FlowLabel)
+        );
+        assert_eq!(tlv_res.len_full(), 2);
+        assert_eq!(tlv_res.value().len(), 0);
+        assert_eq!(tlv_res.len_value(), 0);
+        assert!(tlv_res.is_empty());
+    }
+
+    #[test]
+    fn test_owned_tlv_custom_type() {
+        let tlv_res = TlvOwned::new_with_custom_type(32, &[]).unwrap();
+        assert_eq!(tlv_res.tlv_type_field(), TlvTypeField::Custom(32));
+        assert_eq!(tlv_res.len_full(), 2);
+        assert_eq!(tlv_res.value().len(), 0);
+        assert_eq!(tlv_res.len_value(), 0);
+        assert!(tlv_res.is_empty());
+    }
+
+    #[test]
+    fn test_owned_tlv_conversion_to_bytes() {
+        let entity_id = UbfU8::new(5);
+        let mut buf: [u8; 4] = [0; 4];
+        assert!(entity_id.write_to_be_bytes(&mut buf).is_ok());
+        let tlv_res = Tlv::new(TlvType::EntityId, &buf[0..1]);
+        assert!(tlv_res.is_ok());
+        let tlv_res = tlv_res.unwrap();
+        let tlv_owned_from_conversion: TlvOwned = tlv_res.into();
+        assert_eq!(tlv_res.to_vec(), tlv_owned_from_conversion.to_vec());
+    }
 }

src/cfdp/tlv/msg_to_user.rs

@@ -1,6 +1,8 @@
 //! Abstractions for the Message to User CFDP TLV subtype.
-use super::{GenericTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
-use crate::ByteConversionError;
+#[cfg(feature = "alloc")]
+use super::TlvOwned;
+use super::{GenericTlv, ReadableTlv, Tlv, TlvLvError, TlvType, TlvTypeField, WritableTlv};
+use crate::{cfdp::TlvLvDataTooLarge, ByteConversionError};
 use delegate::delegate;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -10,7 +12,7 @@ pub struct MsgToUserTlv<'data> {
 
 impl<'data> MsgToUserTlv<'data> {
     /// Create a new message to user TLV where the type field is set correctly.
-    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvError> {
+    pub fn new(value: &'data [u8]) -> Result<MsgToUserTlv<'data>, TlvLvDataTooLarge> {
         Ok(Self {
             tlv: Tlv::new(TlvType::MsgToUser, value)?,
         })
@@ -75,6 +77,11 @@ impl<'data> MsgToUserTlv<'data> {
         }
         Ok(msg_to_user)
     }
+
+    #[cfg(feature = "alloc")]
+    pub fn to_owned(&self) -> TlvOwned {
+        self.tlv.to_owned()
+    }
 }
 
 impl WritableTlv for MsgToUserTlv<'_> {