Lines
97.85 %
Functions
41.79 %
Branches
100 %
//! Generic CFDP length-value (LV) abstraction as specified in CFDP 5.1.8.
use crate::ByteConversionError;
use core::str::Utf8Error;
#[cfg(feature = "serde")]
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.
///
/// Please note that this class is zero-copy and does not generate a copy of the value data for
/// both the regular [Self::new] constructor and the [Self::from_bytes] constructor.
/// # Lifetimes
/// * `data`: If the LV is generated from a raw bytestream, this will be the lifetime of
/// the raw bytestream. If the LV is generated from a raw slice or a similar data reference,
/// this will be the lifetime of that data reference.
#[derive(Debug, Copy, Clone, Eq)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub struct Lv<'data> {
data: &'data [u8],
// If the LV was generated from a raw bytestream, this will contain the start of the
// full LV.
pub(crate) raw_data: Option<&'data [u8]>,
}
impl PartialEq for Lv<'_> {
fn eq(&self, other: &Self) -> bool {
self.data == other.data
pub(crate) fn generic_len_check_data_serialization(
buf: &[u8],
data_len: usize,
min_overhead: usize,
) -> Result<(), ByteConversionError> {
if buf.len() < data_len + min_overhead {
return Err(ByteConversionError::ToSliceTooSmall {
found: buf.len(),
expected: data_len + min_overhead,
});
Ok(())
pub(crate) fn generic_len_check_deserialization(
if buf.len() < min_overhead {
return Err(ByteConversionError::FromSliceTooSmall {
expected: min_overhead,
impl<'data> Lv<'data> {
#[inline]
pub fn new(data: &[u8]) -> Result<Lv, TlvLvDataTooLarge> {
if data.len() > u8::MAX as usize {
return Err(TlvLvDataTooLarge(data.len()));
Ok(Lv {
data,
raw_data: None,
})
/// Creates a LV with an empty value field.
pub fn new_empty() -> Lv<'data> {
Lv {
data: &[],
/// Helper function to build a string LV. This is especially useful for the file or directory
/// path LVs
pub fn new_from_str(str_slice: &str) -> Result<Lv, TlvLvDataTooLarge> {
Self::new(str_slice.as_bytes())
pub fn new_from_string(string: &'data String) -> Result<Lv<'data>, TlvLvDataTooLarge> {
Self::new(string.as_bytes())
/// Returns the length of the value part, not including the length byte.
pub fn len_value(&self) -> usize {
self.data.len()
/// Returns the full raw length, including the length byte.
pub fn len_full(&self) -> usize {
self.len_value() + 1
/// Checks whether the value field is empty.
pub fn is_empty(&self) -> bool {
self.data.len() == 0
pub fn value(&self) -> &[u8] {
self.data
/// If the LV was generated from a raw bytestream using [Self::from_bytes], the raw start
/// of the LV can be retrieved with this method.
pub fn raw_data(&self) -> Option<&[u8]> {
self.raw_data
/// Convenience function to extract the value as a [str]. This is useful if the LV is
/// known to contain a [str], for example being a file name.
pub fn value_as_str(&self) -> Option<Result<&'data str, Utf8Error>> {
if self.is_empty() {
return None;
Some(core::str::from_utf8(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.len_value(), MIN_LV_LEN)?;
Ok(self.write_to_be_bytes_no_len_check(buf))
/// Reads a LV from a raw buffer.
pub fn from_bytes(buf: &'data [u8]) -> Result<Lv<'data>, ByteConversionError> {
generic_len_check_deserialization(buf, MIN_LV_LEN)?;
Self::from_be_bytes_no_len_check(buf)
pub(crate) fn write_to_be_bytes_no_len_check(&self, buf: &mut [u8]) -> usize {
buf[0] = 0;
return MIN_LV_LEN;
// 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()
pub(crate) fn from_be_bytes_no_len_check(
buf: &'data [u8],
) -> Result<Lv<'data>, ByteConversionError> {
let value_len = buf[0] as usize;
generic_len_check_deserialization(buf, value_len + MIN_LV_LEN)?;
Ok(Self {
data: &buf[MIN_LV_LEN..MIN_LV_LEN + value_len],
raw_data: Some(buf),
#[cfg(test)]
pub mod tests {
use alloc::string::ToString;
use super::*;
#[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_empty());
let val = lv.value();
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_full(), 5);
assert_eq!(lv.len_value(), 4);
fn test_empty() {
let lv_empty = Lv::new_empty();
assert_eq!(lv_empty.len_value(), 0);
assert_eq!(lv_empty.len_full(), 1);
assert!(lv_empty.is_empty());
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);
fn test_serialization() {
let mut buf: [u8; 16] = [0; 16];
let res = lv.write_to_be_bytes(&mut buf);
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);
fn test_deserialization() {
buf[0] = 4;
buf[1] = 1;
buf[2] = 2;
buf[3] = 3;
buf[4] = 4;
let lv = Lv::from_bytes(&buf);
assert!(lv.is_ok());
let lv = lv.unwrap();
assert!(lv.raw_data().is_some());
assert_eq!(lv.raw_data().unwrap(), buf);
fn test_deserialization_empty() {
let buf: [u8; 2] = [0; 2];
let lv_empty = Lv::from_bytes(&buf);
assert!(lv_empty.is_ok());
let lv_empty = lv_empty.unwrap();
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();
assert_eq!(error.0, u8::MAX as usize + 1);
assert_eq!(
error.to_string(),
"data with size 256 larger than allowed 255 bytes"
);
fn test_serialization_buf_too_small() {
let mut buf: [u8; 3] = [0; 3];
let lv = Lv::new(&lv_data).unwrap();
assert!(res.is_err());
let error = res.unwrap_err();
if let ByteConversionError::ToSliceTooSmall { found, expected } = error {
assert_eq!(expected, 5);
assert_eq!(found, 3);
} else {
panic!("invalid error {}", error);
fn test_deserialization_buf_too_small() {
let res = Lv::from_bytes(&buf);
if let ByteConversionError::FromSliceTooSmall { found, expected } = error {
fn verify_test_str_lv(lv: Lv) {
let res = res.unwrap();
assert_eq!(res, 8 + 1);
assert_eq!(buf[0], 8);
assert_eq!(buf[1], b't');
assert_eq!(buf[2], b'e');
assert_eq!(buf[3], b's');
assert_eq!(buf[4], b't');
assert_eq!(buf[5], b'.');
assert_eq!(buf[6], b'b');
assert_eq!(buf[7], b'i');
assert_eq!(buf[8], b'n');
fn test_str_helper() {
let test_str = "test.bin";
let str_lv = Lv::new_from_str(test_str);
assert!(str_lv.is_ok());
verify_test_str_lv(str_lv.unwrap());
fn test_string_helper() {
let string = String::from("test.bin");
let str_lv = Lv::new_from_string(&string);