From 3aa84ad0696df0a59c2bfd980ef6f5f559201864 Mon Sep 17 00:00:00 2001
From: Ulf Lilleengen <ulf.lilleengen@gmail.com>
Date: Mon, 22 Apr 2024 08:59:30 +0200
Subject: [PATCH] add missing module

---
 host/src/l2cap/sar.rs | 108 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 host/src/l2cap/sar.rs

diff --git a/host/src/l2cap/sar.rs b/host/src/l2cap/sar.rs
new file mode 100644
index 00000000..d281d346
--- /dev/null
+++ b/host/src/l2cap/sar.rs
@@ -0,0 +1,108 @@
+use core::cell::RefCell;
+
+use bt_hci::param::ConnHandle;
+
+use crate::packet_pool::Packet;
+use crate::types::l2cap::L2capHeader;
+use crate::Error;
+
+pub(crate) struct AssembledPacket<'d> {
+    packet: Packet<'d>,
+    written: usize,
+}
+
+impl<'d> AssembledPacket<'d> {
+    pub(crate) fn new(packet: Packet<'d>, initial: usize) -> Self {
+        Self {
+            packet,
+            written: initial,
+        }
+    }
+
+    pub(crate) fn write(&mut self, data: &[u8]) -> Result<(), Error> {
+        if self.written + data.len() > self.packet.len() {
+            return Err(Error::InsufficientSpace);
+        }
+        self.packet.as_mut()[self.written..self.written + data.len()].copy_from_slice(data);
+        self.written += data.len();
+        Ok(())
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.written
+    }
+
+    pub(crate) fn finalize(self, header: L2capHeader) -> Result<(L2capHeader, Packet<'d>), Error> {
+        if header.length as usize != self.written {
+            return Err(Error::InvalidValue);
+        }
+        Ok((header, self.packet))
+    }
+}
+
+// Handles reassembling of packets
+pub struct PacketReassembly<'d, const CONNS: usize> {
+    handles: RefCell<[Option<(ConnHandle, L2capHeader, AssembledPacket<'d>)>; CONNS]>,
+}
+impl<'d, const CONNS: usize> Default for PacketReassembly<'d, CONNS> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<'d, const CONNS: usize> PacketReassembly<'d, CONNS> {
+    const EMPTY: Option<(ConnHandle, L2capHeader, AssembledPacket<'d>)> = None;
+    pub fn new() -> Self {
+        Self {
+            handles: RefCell::new([Self::EMPTY; CONNS]),
+        }
+    }
+
+    /// Initializes a reassembly for a given connection
+    ///
+    /// Returns InvalidState if there is already an ongoing reassembly for this connection
+    /// Returns InsufficientSpace if there is no space for this reassembly
+    pub fn init(&self, handle: ConnHandle, header: L2capHeader, p: Packet<'d>, initial: usize) -> Result<(), Error> {
+        let mut state = self.handles.borrow_mut();
+
+        // Sanity check
+        for entry in state.iter().flatten() {
+            if entry.0 == handle {
+                return Err(Error::InvalidState);
+            }
+        }
+
+        // Sanity check
+        for entry in state.iter_mut() {
+            if entry.is_none() {
+                entry.replace((handle, header, AssembledPacket::new(p, initial)));
+                return Ok(());
+            }
+        }
+        Err(Error::InsufficientSpace)
+    }
+
+    /// Updates any in progress packet assembly for the connection
+    ///
+    /// If the reassembly is complete, the l2cap header + packet is returned.
+    pub fn update(&self, handle: ConnHandle, data: &[u8]) -> Result<Option<(L2capHeader, Packet<'d>)>, Error> {
+        let mut state = self.handles.borrow_mut();
+
+        for entry in state.iter_mut() {
+            match entry {
+                Some((conn, header, packet)) if *conn == handle => {
+                    let (conn, header, mut packet) = entry.take().unwrap();
+                    packet.write(data)?;
+                    if packet.len() == header.length as usize {
+                        return Ok(Some(packet.finalize(header)?));
+                    } else {
+                        entry.replace((conn, header, packet));
+                        return Ok(None);
+                    }
+                }
+                _ => {}
+            }
+        }
+        Err(Error::NotFound)
+    }
+}