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use crate::ByteConversionError;
use core::fmt::{Debug, Display, Formatter};
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
#[cfg(feature = "std")]
use std::error::Error;
pub trait ToBeBytes {
type ByteArray: AsRef<[u8]>;
/// Length when written to big endian bytes.
fn written_len(&self) -> usize;
fn to_be_bytes(&self) -> Self::ByteArray;
}
impl ToBeBytes for () {
type ByteArray = [u8; 0];
#[inline]
fn written_len(&self) -> usize {
0
fn to_be_bytes(&self) -> Self::ByteArray {
[]
impl ToBeBytes for u8 {
type ByteArray = [u8; 1];
1
u8::to_be_bytes(*self)
impl ToBeBytes for u16 {
type ByteArray = [u8; 2];
2
u16::to_be_bytes(*self)
impl ToBeBytes for u32 {
type ByteArray = [u8; 4];
4
u32::to_be_bytes(*self)
impl ToBeBytes for u64 {
type ByteArray = [u8; 8];
8
u64::to_be_bytes(*self)
pub trait UnsignedEnum {
/// Size of the unsigned enumeration in bytes.
fn size(&self) -> usize;
/// Write the unsigned enumeration to a raw buffer. Returns the written size on success.
fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError>;
fn value(&self) -> u64;
#[cfg(feature = "alloc")]
fn to_vec(&self) -> alloc::vec::Vec<u8> {
let mut buf = alloc::vec![0; self.size()];
self.write_to_be_bytes(&mut buf).unwrap();
buf
pub trait UnsignedEnumExt: UnsignedEnum + Debug + Copy + Clone + PartialEq + Eq {}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub enum UnsignedByteFieldError {
/// Value is too large for specified width of byte field.
ValueTooLargeForWidth {
width: usize,
value: u64,
},
/// Only 1, 2, 4 and 8 are allow width values. Optionally contains the expected width if
/// applicable, for example for conversions.
InvalidWidth {
found: usize,
expected: Option<usize>,
ByteConversionError(ByteConversionError),
impl From<ByteConversionError> for UnsignedByteFieldError {
fn from(value: ByteConversionError) -> Self {
Self::ByteConversionError(value)
impl Display for UnsignedByteFieldError {
fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
match self {
Self::ByteConversionError(e) => {
write!(f, "low level byte conversion error: {e}")
Self::InvalidWidth { found, .. } => {
write!(f, "invalid width {found}, only 1, 2, 4 and 8 are allowed.")
Self::ValueTooLargeForWidth { width, value } => {
write!(f, "value {value} too large for width {width}")
impl Error for UnsignedByteFieldError {}
/// Type erased variant.
#[cfg_attr(feature = "defmt", derive(defmt::Format))]
pub struct UnsignedByteField {
impl UnsignedByteField {
pub const fn new(width: usize, value: u64) -> Self {
Self { width, value }
pub const fn value_const(&self) -> u64 {
self.value
pub fn new_from_be_bytes(width: usize, buf: &[u8]) -> Result<Self, UnsignedByteFieldError> {
if width > buf.len() {
return Err(ByteConversionError::FromSliceTooSmall {
expected: width,
found: buf.len(),
.into());
match width {
0 => Ok(Self::new(width, 0)),
1 => Ok(Self::new(width, buf[0] as u64)),
2 => Ok(Self::new(
width,
u16::from_be_bytes(buf[0..2].try_into().unwrap()) as u64,
)),
4 => Ok(Self::new(
u32::from_be_bytes(buf[0..4].try_into().unwrap()) as u64,
8 => Ok(Self::new(
u64::from_be_bytes(buf[0..8].try_into().unwrap()),
_ => Err(UnsignedByteFieldError::InvalidWidth {
found: width,
expected: None,
}),
impl UnsignedEnum for UnsignedByteField {
fn size(&self) -> usize {
self.width
fn value(&self) -> u64 {
self.value_const()
fn write_to_be_bytes(&self, buf: &mut [u8]) -> Result<usize, ByteConversionError> {
if buf.len() < self.size() {
return Err(ByteConversionError::ToSliceTooSmall {
expected: self.size(),
});
match self.size() {
0 => Ok(0),
1 => {
let u8 = UnsignedByteFieldU8::try_from(*self).unwrap();
u8.write_to_be_bytes(buf)
2 => {
let u16 = UnsignedByteFieldU16::try_from(*self).unwrap();
u16.write_to_be_bytes(buf)
4 => {
let u32 = UnsignedByteFieldU32::try_from(*self).unwrap();
u32.write_to_be_bytes(buf)
8 => {
let u64 = UnsignedByteFieldU64::try_from(*self).unwrap();
u64.write_to_be_bytes(buf)
_ => {
// The API does not allow this.
panic!("unexpected written length");
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct GenericUnsignedByteField<TYPE: Copy + Into<u64>> {
value: TYPE,
impl<TYPE: Copy + Into<u64>> GenericUnsignedByteField<TYPE> {
pub const fn new(val: TYPE) -> Self {
Self { value: val }
pub const fn value_typed(&self) -> TYPE {
impl<TYPE: Copy + ToBeBytes + Into<u64>> UnsignedEnum for GenericUnsignedByteField<TYPE> {
self.value.written_len()
buf[..self.size()].copy_from_slice(self.value.to_be_bytes().as_ref());
Ok(self.value.written_len())
self.value_typed().into()
pub type UnsignedByteFieldEmpty = GenericUnsignedByteField<()>;
pub type UnsignedByteFieldU8 = GenericUnsignedByteField<u8>;
pub type UnsignedByteFieldU16 = GenericUnsignedByteField<u16>;
pub type UnsignedByteFieldU32 = GenericUnsignedByteField<u32>;
pub type UnsignedByteFieldU64 = GenericUnsignedByteField<u64>;
pub type UbfU8 = UnsignedByteFieldU8;
pub type UbfU16 = UnsignedByteFieldU16;
pub type UbfU32 = UnsignedByteFieldU32;
pub type UbfU64 = UnsignedByteFieldU64;
impl From<UnsignedByteFieldU8> for UnsignedByteField {
fn from(value: UnsignedByteFieldU8) -> Self {
Self::new(1, value.value as u64)
impl TryFrom<UnsignedByteField> for UnsignedByteFieldU8 {
type Error = UnsignedByteFieldError;
fn try_from(value: UnsignedByteField) -> Result<Self, Self::Error> {
if value.width != 1 {
return Err(UnsignedByteFieldError::InvalidWidth {
found: value.width,
expected: Some(1),
Ok(Self::new(value.value as u8))
impl From<UnsignedByteFieldU16> for UnsignedByteField {
fn from(value: UnsignedByteFieldU16) -> Self {
Self::new(2, value.value as u64)
impl TryFrom<UnsignedByteField> for UnsignedByteFieldU16 {
if value.width != 2 {
expected: Some(2),
Ok(Self::new(value.value as u16))
impl From<UnsignedByteFieldU32> for UnsignedByteField {
fn from(value: UnsignedByteFieldU32) -> Self {
Self::new(4, value.value as u64)
impl TryFrom<UnsignedByteField> for UnsignedByteFieldU32 {
if value.width != 4 {
expected: Some(4),
Ok(Self::new(value.value as u32))
impl From<UnsignedByteFieldU64> for UnsignedByteField {
fn from(value: UnsignedByteFieldU64) -> Self {
Self::new(8, value.value)
impl TryFrom<UnsignedByteField> for UnsignedByteFieldU64 {
if value.width != 8 {
expected: Some(8),
Ok(Self::new(value.value))
#[cfg(test)]
pub mod tests {
use crate::util::{
UnsignedByteField, UnsignedByteFieldError, UnsignedByteFieldU16, UnsignedByteFieldU32,
UnsignedByteFieldU64, UnsignedByteFieldU8, UnsignedEnum,
};
use std::format;
#[test]
fn test_simple_u8() {
let u8 = UnsignedByteFieldU8::new(5);
assert_eq!(u8.size(), 1);
let mut buf: [u8; 8] = [0; 8];
let len = u8
.write_to_be_bytes(&mut buf)
.expect("writing to raw buffer failed");
assert_eq!(len, 1);
assert_eq!(buf[0], 5);
for val in buf.iter().skip(1) {
assert_eq!(*val, 0);
assert_eq!(u8.value_typed(), 5);
assert_eq!(u8.value(), 5);
fn test_simple_u16() {
let u16 = UnsignedByteFieldU16::new(3823);
assert_eq!(u16.size(), 2);
let len = u16
assert_eq!(len, 2);
let raw_val = u16::from_be_bytes(buf[0..2].try_into().unwrap());
assert_eq!(raw_val, 3823);
for val in buf.iter().skip(2) {
assert_eq!(u16.value_typed(), 3823);
assert_eq!(u16.value(), 3823);
fn test_simple_u32() {
let u32 = UnsignedByteFieldU32::new(80932);
assert_eq!(u32.size(), 4);
let len = u32
assert_eq!(len, 4);
let raw_val = u32::from_be_bytes(buf[0..4].try_into().unwrap());
assert_eq!(raw_val, 80932);
(4..8).for_each(|i| {
assert_eq!(buf[i], 0);
assert_eq!(u32.value_typed(), 80932);
assert_eq!(u32.value(), 80932);
fn test_simple_u64() {
let u64 = UnsignedByteFieldU64::new(5999999);
assert_eq!(u64.size(), 8);
let len = u64
assert_eq!(len, 8);
let raw_val = u64::from_be_bytes(buf[0..8].try_into().unwrap());
assert_eq!(raw_val, 5999999);
assert_eq!(u64.value_typed(), 5999999);
assert_eq!(u64.value(), 5999999);
fn conversions_u8() {
let u8_type_erased = UnsignedByteField::from(u8);
assert_eq!(u8_type_erased.width, 1);
assert_eq!(u8_type_erased.value, 5);
let u8_conv_back =
UnsignedByteFieldU8::try_from(u8_type_erased).expect("conversion failed for u8");
assert_eq!(u8, u8_conv_back);
assert_eq!(u8_conv_back.value, 5);
fn conversion_u8_fails() {
let field = UnsignedByteField::new(2, 60000);
let conv_fails = UnsignedByteFieldU8::try_from(field);
assert!(conv_fails.is_err());
let err = conv_fails.unwrap_err();
match err {
UnsignedByteFieldError::InvalidWidth {
found,
expected: Some(expected),
} => {
assert_eq!(found, 2);
assert_eq!(expected, 1);
panic!("{}", format!("invalid error {err}"))
fn conversions_u16() {
let u16 = UnsignedByteFieldU16::new(64444);
let u16_type_erased = UnsignedByteField::from(u16);
assert_eq!(u16_type_erased.width, 2);
assert_eq!(u16_type_erased.value, 64444);
let u16_conv_back =
UnsignedByteFieldU16::try_from(u16_type_erased).expect("conversion failed for u16");
assert_eq!(u16, u16_conv_back);
assert_eq!(u16_conv_back.value, 64444);
fn conversion_u16_fails() {
let field = UnsignedByteField::new(4, 75000);
let conv_fails = UnsignedByteFieldU16::try_from(field);
assert_eq!(found, 4);
assert_eq!(expected, 2);
fn conversions_u32() {
let u32 = UnsignedByteFieldU32::new(75000);
let u32_type_erased = UnsignedByteField::from(u32);
assert_eq!(u32_type_erased.width, 4);
assert_eq!(u32_type_erased.value, 75000);
let u32_conv_back =
UnsignedByteFieldU32::try_from(u32_type_erased).expect("conversion failed for u32");
assert_eq!(u32, u32_conv_back);
assert_eq!(u32_conv_back.value, 75000);
fn conversion_u32_fails() {
let field = UnsignedByteField::new(8, 75000);
let conv_fails = UnsignedByteFieldU32::try_from(field);
assert_eq!(found, 8);
assert_eq!(expected, 4);
fn conversions_u64() {
let u64_type_erased = UnsignedByteField::from(u64);
assert_eq!(u64_type_erased.width, 8);
assert_eq!(u64_type_erased.value, 5999999);
let u64_conv_back =
UnsignedByteFieldU64::try_from(u64_type_erased).expect("conversion failed for u64");
assert_eq!(u64, u64_conv_back);
assert_eq!(u64_conv_back.value, 5999999);
fn conversion_u64_fails() {
let field = UnsignedByteField::new(4, 60000);
let conv_fails = UnsignedByteFieldU64::try_from(field);
assert_eq!(expected, 8);
fn type_erased_u8_write() {
let u8 = UnsignedByteField::new(1, 5);
u8.write_to_be_bytes(&mut buf)
(1..8).for_each(|i| {
fn type_erased_u16_write() {
let u16 = UnsignedByteField::new(2, 3823);
u16.write_to_be_bytes(&mut buf)
fn type_erased_u32_write() {
let u32 = UnsignedByteField::new(4, 80932);
u32.write_to_be_bytes(&mut buf)
fn type_erased_u64_write() {
let u64 = UnsignedByteField::new(8, 5999999);
u64.write_to_be_bytes(&mut buf)
fn type_erased_u8_construction() {
let buf: [u8; 2] = [5, 10];
let u8 = UnsignedByteField::new_from_be_bytes(1, &buf).expect("construction failed");
assert_eq!(u8.width, 1);
assert_eq!(u8.value, 5);
fn type_erased_u16_construction() {
let buf: [u8; 2] = [0x10, 0x15];
let u16 = UnsignedByteField::new_from_be_bytes(2, &buf).expect("construction failed");
assert_eq!(u16.width, 2);
assert_eq!(u16.value, 0x1015);
fn type_erased_u32_construction() {
let buf: [u8; 4] = [0x01, 0x02, 0x03, 0x04];
let u32 = UnsignedByteField::new_from_be_bytes(4, &buf).expect("construction failed");
assert_eq!(u32.width, 4);
assert_eq!(u32.value, 0x01020304);
fn type_erased_u64_construction() {
let buf: [u8; 8] = [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08];
let u64 = UnsignedByteField::new_from_be_bytes(8, &buf).expect("construction failed");
assert_eq!(u64.width, 8);
assert_eq!(u64.value, 0x0102030405060708);
fn type_u16_target_buf_too_small() {
let u16 = UnsignedByteFieldU16::new(500);
let mut buf: [u8; 1] = [0; 1];
let res = u16.write_to_be_bytes(&mut buf);
assert!(res.is_err());
let err = res.unwrap_err();
ByteConversionError::ToSliceTooSmall { found, expected } => {
assert_eq!(found, 1);
panic!("invalid exception")
fn type_erased_u16_target_buf_too_small() {
let u16 = UnsignedByteField::new(2, 500);
panic!("invalid exception {}", err)
let u16 = UnsignedByteField::new_from_be_bytes(2, &buf);
assert!(u16.is_err());
let err = u16.unwrap_err();
if let UnsignedByteFieldError::ByteConversionError(
ByteConversionError::FromSliceTooSmall { found, expected },
) = err
{
} else {
panic!("unexpected exception {}", err);
fn type_u32_target_buf_too_small() {
let u16 = UnsignedByteFieldU32::new(500);
let mut buf: [u8; 3] = [0; 3];
assert_eq!(found, 3);