1 files changed, 115 insertions, 0 deletions
diff --git a/src/dstream/mod.rs b/src/dstream/mod.rs
new file mode 100644
index 0000000..a9cfa89
--- /dev/null
+++ b/src/dstream/mod.rs
@@ -0,0 +1,115 @@
+// 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) }
+}