src/cfdp/lv.rs

@@ -1,25 +1,30 @@
 use crate::cfdp::TlvLvError;
 use crate::{ByteConversionError, SizeMissmatch};
-use std::prelude::v1::String;
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+#[cfg(feature = "std")]
+use std::string::String;
 
 pub const MIN_LV_LEN: usize = 1;
 
-/// Generic CFDP length-value (LV) abstraction.
+/// Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
 ///
 /// This is just a thin wrapper around a raw slice which performs some additional error handling.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Lv<'a> {
-    data: &'a [u8],
+    data: Option<&'a [u8]>,
 }
 
 pub(crate) fn generic_len_check_data_serialization(
     buf: &[u8],
-    data: &[u8],
+    data_len: usize,
     min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
-    if buf.len() < data.len() + min_overhead {
+    if buf.len() < data_len + min_overhead {
         return Err(ByteConversionError::ToSliceTooSmall(SizeMissmatch {
             found: buf.len(),
-            expected: data.len() + min_overhead,
+            expected: data_len + min_overhead,
         }));
     }
     Ok(())
@@ -27,22 +32,28 @@ pub(crate) fn generic_len_check_data_serialization(
 
 pub(crate) fn generic_len_check_deserialization(
     buf: &[u8],
-    min_overheader: usize,
+    min_overhead: usize,
 ) -> Result<(), ByteConversionError> {
-    if buf.len() < min_overheader {
+    if buf.len() < min_overhead {
         return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
             found: buf.len(),
-            expected: MIN_LV_LEN,
+            expected: min_overhead,
         }));
     }
     Ok(())
 }
+
 impl<'a> Lv<'a> {
     pub fn new(data: &[u8]) -> Result<Lv, TlvLvError> {
         if data.len() > u8::MAX as usize {
             return Err(TlvLvError::DataTooLarge(data.len()));
         }
-        Ok(Lv { data })
+        Ok(Lv { data: Some(data) })
+    }
+
+    /// Creates a LV with an empty value field.
+    pub fn new_empty() -> Lv<'a> {
+        Lv { data: None }
     }
 
     /// Helper function to build a string LV. This is especially useful for the file or directory
@@ -58,14 +69,32 @@ impl<'a> Lv<'a> {
         Self::new(string.as_bytes())
     }
 
-    pub fn value(&self) -> &[u8] {
+    /// Returns the length of the value part, not including the length byte.
+    pub fn len_value(&self) -> usize {
+        if self.data.is_none() {
+            return 0;
+        }
+        self.data.unwrap().len()
+    }
+
+    /// Returns the full raw length, including the length byte.
+    pub fn len_raw(&self) -> usize {
+        self.len_value() + 1
+    }
+
+    /// Checks whether the value field is empty.
+    pub fn is_empty(&self) -> bool {
+        self.data.is_none()
+    }
+
+    pub fn value(&self) -> Option<&[u8]> {
         self.data
     }
 
     /// Writes the LV to a raw buffer. Please note that the first byte will contain the length
     /// of the value, but the values may not exceed a length of [u8::MAX].
     pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        generic_len_check_data_serialization(buf, self.data, MIN_LV_LEN)?;
+        generic_len_check_data_serialization(buf, self.len_value(), MIN_LV_LEN)?;
         Ok(self.write_to_be_bytes_no_len_check(buf))
     }
 
@@ -76,23 +105,125 @@ impl<'a> Lv<'a> {
     }
 
     pub(crate) fn write_to_be_bytes_no_len_check(&self, buf: &mut [u8]) -> usize {
+        if self.data.is_none() {
+            buf[0] = 0;
+            return MIN_LV_LEN;
+        }
+        let data = self.data.unwrap();
         // Length check in constructor ensures the length always has a valid value.
-        buf[0] = self.data.len() as u8;
-        buf[MIN_LV_LEN..self.data.len() + MIN_LV_LEN].copy_from_slice(self.data);
-        MIN_LV_LEN + self.data.len()
+        buf[0] = data.len() as u8;
+        buf[MIN_LV_LEN..data.len() + MIN_LV_LEN].copy_from_slice(data);
+        MIN_LV_LEN + data.len()
     }
 
     pub(crate) fn from_be_bytes_no_len_check(buf: &'a [u8]) -> Result<Lv<'a>, TlvLvError> {
         let value_len = buf[0] as usize;
-        if buf.len() < value_len + MIN_LV_LEN {
-            return Err(ByteConversionError::FromSliceTooSmall(SizeMissmatch {
-                found: buf.len(),
-                expected: MIN_LV_LEN + value_len,
-            })
-            .into());
+        generic_len_check_deserialization(buf, value_len + MIN_LV_LEN)?;
+        let mut data = None;
+        if value_len > 0 {
+            data = Some(&buf[MIN_LV_LEN..MIN_LV_LEN + value_len])
+        }
+        Ok(Self { data })
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::cfdp::lv::Lv;
+    use crate::cfdp::TlvLvError;
+
+    #[test]
+    fn test_basic() {
+        let lv_data: [u8; 4] = [1, 2, 3, 4];
+        let lv_res = Lv::new(&lv_data);
+        assert!(lv_res.is_ok());
+        let lv = lv_res.unwrap();
+        assert!(lv.value().is_some());
+        let val = lv.value().unwrap();
+        assert_eq!(val[0], 1);
+        assert_eq!(val[1], 2);
+        assert_eq!(val[2], 3);
+        assert_eq!(val[3], 4);
+        assert!(!lv.is_empty());
+        assert_eq!(lv.len_raw(), 5);
+        assert_eq!(lv.len_value(), 4);
+    }
+
+    #[test]
+    fn test_empty() {
+        let lv_empty = Lv::new_empty();
+        assert_eq!(lv_empty.len_value(), 0);
+        assert_eq!(lv_empty.len_raw(), 1);
+        assert!(lv_empty.is_empty());
+        assert_eq!(lv_empty.value(), None);
+        let mut buf: [u8; 4] = [0xff; 4];
+        let res = lv_empty.write_to_be_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, 1);
+        assert_eq!(buf[0], 0);
+    }
+
+    #[test]
+    fn test_serialization() {
+        let lv_data: [u8; 4] = [1, 2, 3, 4];
+        let lv_res = Lv::new(&lv_data);
+        assert!(lv_res.is_ok());
+        let lv = lv_res.unwrap();
+        let mut buf: [u8; 16] = [0; 16];
+        let res = lv.write_to_be_bytes(&mut buf);
+        assert!(res.is_ok());
+        let written = res.unwrap();
+        assert_eq!(written, 5);
+        assert_eq!(buf[0], 4);
+        assert_eq!(buf[1], 1);
+        assert_eq!(buf[2], 2);
+        assert_eq!(buf[3], 3);
+        assert_eq!(buf[4], 4);
+    }
+
+    #[test]
+    fn test_deserialization() {
+        let mut buf: [u8; 16] = [0; 16];
+        buf[0] = 4;
+        buf[1] = 1;
+        buf[2] = 2;
+        buf[3] = 3;
+        buf[4] = 4;
+        let lv = Lv::from_be_bytes(&buf);
+        assert!(lv.is_ok());
+        let lv = lv.unwrap();
+        assert!(!lv.is_empty());
+        assert!(lv.value().is_some());
+        assert_eq!(lv.len_value(), 4);
+        assert_eq!(lv.len_raw(), 5);
+        let val = lv.value().unwrap();
+        assert_eq!(val[0], 1);
+        assert_eq!(val[1], 2);
+        assert_eq!(val[2], 3);
+        assert_eq!(val[3], 4);
+    }
+
+    #[test]
+    fn test_deserialization_empty() {
+        let buf: [u8; 2] = [0; 2];
+        let lv_empty = Lv::from_be_bytes(&buf);
+        assert!(lv_empty.is_ok());
+        let lv_empty = lv_empty.unwrap();
+        assert!(lv_empty.is_empty());
+        assert!(lv_empty.value().is_none());
+    }
+
+    #[test]
+    fn test_data_too_large() {
+        let data_big: [u8; u8::MAX as usize + 1] = [0; u8::MAX as usize + 1];
+        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);
+        } else {
+            panic!("invalid exception {:?}", error)
         }
-        Ok(Self {
-            data: &buf[MIN_LV_LEN..MIN_LV_LEN + value_len],
-        })
     }
 }

src/cfdp/pdu/metadata.rs

@@ -1,3 +1,4 @@
+#![allow(dead_code)]
 use crate::cfdp::lv::Lv;
 use crate::cfdp::pdu::{FileDirectiveType, PduHeader};
 use crate::cfdp::ChecksumType;

src/cfdp/tlv.rs

@@ -21,6 +21,9 @@ pub enum TlvType {
     EntityId = 0x06,
 }
 
+/// Generic CFDP type-length-value (TLV) abstraction as specified in CFDP 5.1.9.
+///
+/// This is just a thin wrapper around a length-value (LV) object, which add the [TlvType].
 pub struct Tlv<'a> {
     tlv_type: TlvType,
     lv: Lv<'a>,
@@ -37,17 +40,40 @@ impl<'a> Tlv<'a> {
         })
     }
 
-    pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
-        generic_len_check_data_serialization(buf, self.value(), MIN_TLV_LEN)?;
-        buf[0] = self.tlv_type as u8;
-        self.lv.write_to_be_bytes_no_len_check(&mut buf[1..]);
-        Ok(MIN_TLV_LEN + self.value().len())
+    /// Creates a TLV with an empty value field.
+    pub fn new_empty(tlv_type: TlvType) -> Tlv<'a> {
+        Tlv {
+            tlv_type,
+            lv: Lv::new_empty(),
+        }
     }
 
-    pub fn value(&self) -> &[u8] {
+    pub fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
+        generic_len_check_data_serialization(buf, self.len_value(), MIN_TLV_LEN)?;
+        buf[0] = self.tlv_type as u8;
+        self.lv.write_to_be_bytes_no_len_check(&mut buf[1..]);
+        Ok(self.len_full())
+    }
+
+    pub fn value(&self) -> Option<&[u8]> {
         self.lv.value()
     }
 
+    /// Returns the length of the value part, not including the length byte.
+    pub fn len_value(&self) -> usize {
+        self.lv.len_value() + 1
+    }
+
+    /// Returns the full raw length, including the length byte.
+    pub fn len_full(&self) -> usize {
+        self.lv.len_raw() + 1
+    }
+
+    /// Checks whether the value field is empty.
+    pub fn is_empty(&self) -> bool {
+        self.lv.is_empty()
+    }
+
     pub fn from_be_bytes(buf: &'a [u8]) -> Result<Tlv<'a>, TlvLvError> {
         generic_len_check_deserialization(buf, MIN_TLV_LEN)?;
         let tlv_type_res = TlvType::try_from(buf[0]);