1 files changed, 82 insertions, 0 deletions
diff --git a/net/src/stream/buffer.rs b/net/src/stream/buffer.rs
new file mode 100644
index 0000000..f211600
--- /dev/null
+++ b/net/src/stream/buffer.rs
@@ -0,0 +1,82 @@
+#[derive(Debug)]
+pub struct Buffer<B> {
+    inner: B,
+    len: usize,
+    cap: usize,
+}
+
+impl<B> Buffer<B>
+where
+    B: AsMut<[u8]> + AsRef<[u8]>,
+{
+    /// Constructs a new, empty Buffer<B>.
+    pub fn new(b: B) -> Self {
+        Self {
+            cap: b.as_ref().len(),
+            inner: b,
+            len: 0,
+        }
+    }
+
+    /// Returns the number of elements in the buffer.
+    #[allow(dead_code)]
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Resizes the buffer in-place so that `len` is equal to `new_size`.
+    pub fn resize(&mut self, new_size: usize) {
+        assert!(self.cap > new_size);
+        self.len = new_size;
+    }
+
+    /// Appends all elements in a slice to the buffer.
+    pub fn extend_from_slice(&mut self, bytes: &[u8]) {
+        let old_len = self.len;
+        self.resize(self.len + bytes.len());
+        self.inner.as_mut()[old_len..bytes.len() + old_len].copy_from_slice(bytes);
+    }
+
+    /// Shortens the buffer, dropping the first `cnt` bytes and keeping the
+    /// rest.
+    pub fn advance(&mut self, cnt: usize) {
+        assert!(self.len >= cnt);
+        self.inner.as_mut().rotate_left(cnt);
+        self.resize(self.len - cnt);
+    }
+
+    /// Returns `true` if the buffer contains no elements.
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+}
+
+impl<B> AsMut<[u8]> for Buffer<B>
+where
+    B: AsMut<[u8]> + AsRef<[u8]>,
+{
+    fn as_mut(&mut self) -> &mut [u8] {
+        &mut self.inner.as_mut()[..self.len]
+    }
+}
+
+impl<B> AsRef<[u8]> for Buffer<B>
+where
+    B: AsMut<[u8]> + AsRef<[u8]>,
+{
+    fn as_ref(&self) -> &[u8] {
+        &self.inner.as_ref()[..self.len]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_buffer_advance() {
+        let mut buf = Buffer::new([0u8; 32]);
+        buf.extend_from_slice(&[1, 2, 3]);
+        assert_eq!([1, 2, 3], buf.as_ref());
+    }
+}