Struct xaynet_core::message::LengthValueBuffer

pub struct LengthValueBuffer<T> { /* fields omitted */ }

A helper for encoding and decoding Length-Value (LV) fields.

Note that the 4 bytes length() field gives the length of the total Length-Value field, i.e. the length of the value, plus the 4 extra bytes of the length field itself.

Examples

Decoding a LV field

let bytes = vec![
    0x00, 0x00, 0x00, 0x05, // Length = 5
    0xff, // Value = 0xff
    0x11, 0x22, // Extra bytes
];
let buffer = LengthValueBuffer::new(&bytes).unwrap();
assert_eq!(buffer.length(), 5);
assert_eq!(buffer.value_length(), 1);
assert_eq!(buffer.value(), &[0xff][..]);

Encoding a LV field

let mut bytes = vec![0xff; 9];
let mut buffer = LengthValueBuffer::new_unchecked(&mut bytes);
// It is important to set the length field before setting the value, otherwise, `value_mut()` will panic.
buffer.set_length(8);
buffer.value_mut().copy_from_slice(&[0, 1, 2, 3][..]);
let expected = vec![
    0x00, 0x00, 0x00, 0x08, // Length = 8
    0x00, 0x01, 0x02, 0x03, // Value
    0xff, // unchanged
];

assert_eq!(bytes, expected);

Implementations

impl<T: AsRef<[u8]>> LengthValueBuffer<T>

pub fn new(bytes: T) -> Result<Self, DecodeError>

Returns a new LengthValueBuffer.

Errors

This method performs bound checks and returns an error if the given buffer is not a valid Length-Value item.

Examples

// truncated length:
assert!(LengthValueBuffer::new(&vec![0x00, 0x00, 0x00]).is_err());

// truncated value:
let bytes = vec![
    0x00, 0x00, 0x00, 0x08, // length: 8
    0x11, 0x22, 0x33, // value
];
assert!(LengthValueBuffer::new(&bytes).is_err());

// valid Length-Value item
let bytes = vec![
    0x00, 0x00, 0x00, 0x08, // length: 8
    0x11, 0x22, 0x33, 0x44, // value
    0xaa, 0xbb, // extra bytes are ignored
];
let buf = LengthValueBuffer::new(&bytes).unwrap();
assert_eq!(buf.length(), 8);
assert_eq!(buf.value(), &[0x11, 0x22, 0x33, 0x44][..]);

pub fn new_unchecked(bytes: T) -> Self

Create a new LengthValueBuffer without any bound checks.

pub fn check_buffer_length(&self) -> Result<(), DecodeError>

Check that the buffer is a valid Length-Value item.

pub fn length(&self) -> u32

Returns the length field. Note that the value of the length field includes the length of the field itself (4 bytes).

Panics

This method may panic if buffer is not a valid Length-Value item.

pub fn value_length(&self) -> usize

Returns the length of the value.

impl<T: AsMut<[u8]>> LengthValueBuffer<T>

pub fn set_length(&mut self, value: u32)

Sets the length field to the given value.

Panics

This method may panic if buffer is not a valid Length-Value item.

impl<'a, T: AsRef<[u8]> + AsMut<[u8]> + ?Sized> LengthValueBuffer<&'a mut T>

pub fn value_mut(&mut self) -> &mut [u8]

Gets a mutable reference to the value field.

Panics

This method may panic if buffer is not a valid Length-Value item.

pub fn bytes_mut(&mut self) -> &mut [u8]

Gets a mutable reference to the underlying buffer.

Panics

This method may panic if buffer is not a valid Length-Value item.

impl<'a, T: AsRef<[u8]> + ?Sized> LengthValueBuffer<&'a T>

pub fn value(&self) -> &'a [u8]

Gets a reference to the value field.

Panics

This method may panic if buffer is not a valid Length-Value item.

pub fn bytes(self) -> &'a [u8]

Gets a reference to the underlying buffer.

Panics

This method may panic if buffer is not a valid Length-Value item.