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// 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};
use core::fmt::{Debug, Formatter};
/// 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.
#[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 amount of bytes, an [`EndOfStream`](Error::EndOfStream) error is returned.
pub fn take(&mut self, req: usize) -> Result<&[u8]> {
let rem = self.len;
if rem < req { return Err(Error::EndOfStream { req, rem } ) }
let start = self.data.len() - rem;
let stop = start + req;
self.len -= req;
Ok(&self.data[start..stop])
}
/// Takes a single byte from the stream.
///
/// # Errors
///
/// If the internal buffer doesn't hold at least the requested amount of bytes, an [`EndOfStream`](Error::EndOfStream) error is returned.
pub fn take_byte(&mut self) -> Result<u8> {
const LEN: usize = 0x1;
if self.len < LEN { return Err(Error::EndOfStream { req: LEN, rem: self.len } ) }
self.len -= LEN;
let index = self.data.len() - self.len;
Ok(self.data[index])
}
}
impl Debug for Dstream<'_> {
fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
self.data.fmt(f)
}
}
impl<'a, T: AsRef<[u8]>> From<&'a T> for Dstream<'a> {
fn from(value: &'a T) -> Self { Self::new(value) }
}
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