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// Copyright 2022-2024 Gabriel Bjørnager Jensen.
use crate::error::{Error, Result};
use std::fmt::{Debug, Formatter};
/// A byte stream for deserialisation.
///
/// This type borrows a byte slice (hence [`new`](DStream::new)), keeping track internally of the used bytes.
#[derive(Clone)]
pub struct DStream<'a> {
data: &'a [u8],
len: usize,
}
impl<'a> DStream<'a> {
/// Constructs a new byte stream.
pub fn new<T: AsRef<[u8]> + ?Sized>(buf: &'a T) -> Self { Self {
data: buf.as_ref(),
len: buf.as_ref().len(),
} }
/// Takes bytes from the stream.
///
/// # Errors
///
/// If the internal buffer doesn't hold at least the requested ammount of bytes, an [`EndOfDStream`](Error::EndOfDStream) error is returned.
pub fn take(&mut self, len: usize) -> Result<&[u8]> {
if self.len < len { return Err(Error::EndOfDStream { len: self.len, ok_len: len } ) }
let start = self.data.len() - self.len;
let stop = start + len;
self.len -= len;
Ok(&self.data[start..stop])
}
}
impl Debug for DStream<'_> {
fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
let stop = self.data.len();
let start = self.data.len() - self.len;
write!(f, "[")?;
for v in &self.data[start..stop] { write!(f, "{v:#02X},")? };
write!(f, "]")?;
Ok(())
}
}
impl<'a> From<&'a [u8]> for DStream<'a> {
fn from(value: &'a [u8]) -> Self { Self::new(value) }
}
impl<'a, const N: usize> From<&'a [u8; N]> for DStream<'a> {
fn from(value: &'a [u8; N]) -> Self { Self::new(value) }
}
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