// Copyright 2024 Gabriel Bjørnager Jensen.
//
// This file is part of bzipper.
//
// bzipper is free software: you can redistribute
// it and/or modify it under the terms of the GNU
// Lesser General Public License as published by
// the Free Software Foundation, either version 3
// of the License, or (at your option) any later
// version.
//
// bzipper is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without
// even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Less-
// er General Public License along with bzipper. If
// not, see <https://www.gnu.org/licenses/>.
use crate::{Error, Result, Sstream};
use std::fmt::{Debug, Formatter};
/// Byte stream for deserialisation.
///
/// This type borrows a byte slice (hence [`new`](Dstream::new)), keeping track internally of the used bytes.
///
/// The stream may be converted to an [`Sstream`] using [`to_sstream`](Dstream::to_sstream).
#[derive(Clone)]
pub struct Dstream<'a> {
data: &'a [u8],
len: usize,
}
impl<'a> Dstream<'a> {
/// Constructs a new byte stream.
#[inline(always)]
#[must_use]
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 { req: len, rem: self.len } ) }
let start = self.data.len() - self.len;
let stop = start + len;
self.len -= len;
Ok(&self.data[start..stop])
}
/// Takes a single byte 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_byte(&mut self) -> Result<u8> {
const LEN: usize = 0x1;
if self.len < LEN { return Err(Error::EndOfDStream { req: LEN, rem: self.len } ) }
self.len -= LEN;
let index = self.data.len() - self.len;
Ok(self.data[index])
}
/// Takes a slice of the remaining data.
#[must_use]
pub fn as_slice(&self) -> &[u8] {
let stop = self.data.len();
let start = stop - self.len;
&self.data[start..stop]
}
/// Converts the stream to a `Sstream` object.
///
/// The returned object owns a copy of the remaining data.
#[inline(always)]
#[must_use]
pub fn to_sstream(&self) -> Sstream {
Sstream(self.as_slice().to_vec())
}
}
impl Debug for Dstream<'_> {
fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
write!(f, "[")?;
for v in self.as_slice() { 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) }
}
