1 files changed, 175 insertions, 0 deletions
diff --git a/src/bytes_buf.rs b/src/bytes_buf.rs
new file mode 100644
index 0000000..931be82
--- /dev/null
+++ b/src/bytes_buf.rs
@@ -0,0 +1,175 @@
+use std::collections::VecDeque;
+
+use bytes::BytesMut;
+
+pub use bytes::Bytes;
+
+/// A circular buffer of bytes, internally represented as a list of Bytes
+/// for optimization, but that for all intent and purposes acts just like
+/// a big byte slice which can be extended on the right and from which
+/// stuff can be taken on the left.
+pub struct BytesBuf {
+	buf: VecDeque<Bytes>,
+	buf_len: usize,
+}
+
+impl BytesBuf {
+	/// Creates a new empty BytesBuf
+	pub fn new() -> Self {
+		Self {
+			buf: VecDeque::new(),
+			buf_len: 0,
+		}
+	}
+
+	/// Returns the number of bytes stored in the BytesBuf
+	#[inline]
+	pub fn len(&self) -> usize {
+		self.buf_len
+	}
+
+	/// Returns true iff the BytesBuf contains zero bytes
+	#[inline]
+	pub fn is_empty(&self) -> bool {
+		self.buf_len == 0
+	}
+
+	/// Adds some bytes to the right of the buffer
+	pub fn extend(&mut self, b: Bytes) {
+		if !b.is_empty() {
+			self.buf_len += b.len();
+			self.buf.push_back(b);
+		}
+	}
+
+	/// Takes the whole content of the buffer and returns it as a single Bytes unit
+	pub fn take_all(&mut self) -> Bytes {
+		if self.buf.len() == 0 {
+			Bytes::new()
+		} else if self.buf.len() == 1 {
+			self.buf_len = 0;
+			self.buf.pop_back().unwrap()
+		} else {
+			let mut ret = BytesMut::with_capacity(self.buf_len);
+			for b in self.buf.iter() {
+				ret.extend_from_slice(&b[..]);
+			}
+			self.buf.clear();
+			self.buf_len = 0;
+			ret.freeze()
+		}
+	}
+
+	/// Takes at most max_len bytes from the left of the buffer
+	pub fn take_max(&mut self, max_len: usize) -> Bytes {
+		if self.buf_len <= max_len {
+			self.take_all()
+		} else {
+			self.take_exact_ok(max_len)
+		}
+	}
+
+	/// Take exactly len bytes from the left of the buffer, returns None if
+	/// the BytesBuf doesn't contain enough data
+	pub fn take_exact(&mut self, len: usize) -> Option<Bytes> {
+		if self.buf_len < len {
+			None
+		} else {
+			Some(self.take_exact_ok(len))
+		}
+	}
+
+	fn take_exact_ok(&mut self, len: usize) -> Bytes {
+		assert!(len <= self.buf_len);
+		let front = self.buf.pop_front().unwrap();
+		if front.len() > len {
+			self.buf.push_front(front.slice(len..));
+			self.buf_len -= len;
+			front.slice(..len)
+		} else if front.len() == len {
+			self.buf_len -= len;
+			front
+		} else {
+			let mut ret = BytesMut::with_capacity(len);
+			ret.extend_from_slice(&front[..]);
+			self.buf_len -= front.len();
+			while ret.len() < len {
+				let front = self.buf.pop_front().unwrap();
+				if front.len() > len - ret.len() {
+					let take = len - ret.len();
+					ret.extend_from_slice(&front[..take]);
+					self.buf.push_front(front.slice(take..));
+					self.buf_len -= take;
+					break;
+				} else {
+					ret.extend_from_slice(&front[..]);
+					self.buf_len -= front.len();
+				}
+			}
+			ret.freeze()
+		}
+	}
+
+	/// Return the internal sequence of Bytes slices that make up the buffer
+	pub fn into_slices(self) -> VecDeque<Bytes> {
+		self.buf
+	}
+}
+
+impl From<Bytes> for BytesBuf {
+	fn from(b: Bytes) -> BytesBuf {
+		let mut ret = BytesBuf::new();
+		ret.extend(b);
+		ret
+	}
+}
+
+impl From<BytesBuf> for Bytes {
+	fn from(mut b: BytesBuf) -> Bytes {
+		b.take_all()
+	}
+}
+
+#[cfg(test)]
+mod test {
+	use super::*;
+
+	#[test]
+	fn test_bytes_buf() {
+		let mut buf = BytesBuf::new();
+		assert!(buf.len() == 0);
+		assert!(buf.is_empty());
+
+		buf.extend(Bytes::from(b"Hello, world!".to_vec()));
+		assert!(buf.len() == 13);
+		assert!(!buf.is_empty());
+
+		buf.extend(Bytes::from(b"1234567890".to_vec()));
+		assert!(buf.len() == 23);
+		assert!(!buf.is_empty());
+
+		assert_eq!(
+			buf.take_all(),
+			Bytes::from(b"Hello, world!1234567890".to_vec())
+		);
+		assert!(buf.len() == 0);
+		assert!(buf.is_empty());
+
+		buf.extend(Bytes::from(b"1234567890".to_vec()));
+		buf.extend(Bytes::from(b"Hello, world!".to_vec()));
+		assert!(buf.len() == 23);
+		assert!(!buf.is_empty());
+
+		assert_eq!(buf.take_max(12), Bytes::from(b"1234567890He".to_vec()));
+		assert!(buf.len() == 11);
+
+		assert_eq!(buf.take_exact(12), None);
+		assert!(buf.len() == 11);
+		assert_eq!(
+			buf.take_exact(11),
+			Some(Bytes::from(b"llo, world!".to_vec()))
+		);
+		assert!(buf.len() == 0);
+		assert!(buf.is_empty());
+	}
+}