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