global buf size mtu based config and protocol rename

core/src/nrxp/codec/frame.rs

@@ -0,0 +1,77 @@
+use bytes::{BufMut, Bytes, BytesMut};
+
+use rand::Rng;
+
+use crate::nrxp::codec::MAX_PADDING_SIZE;
+
+pub struct Padding {
+    pub len: u16,
+    pub data: Bytes,
+}
+
+impl Padding {
+    pub fn generate_padding() -> Padding {
+        let mut rng = rand::rng();
+        let random_u32: u32 = rng.next_u32();
+        let padding_len: u16 = (random_u32 % MAX_PADDING_SIZE) as u16;
+        let mut padding = vec![0u8; padding_len as usize];
+        rng.fill_bytes(&mut padding);
+        Padding {
+            len: padding_len,
+            data: Bytes::from(padding),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum FrameType {
+    Connect = 0x00,
+    Data = 0x01,
+    Close = 0x02,
+    Heartbeat = 0x03,
+    UdpConnect = 0x04,
+    UdpData = 0x05,
+}
+#[derive(Copy, Clone)]
+pub struct FrameHeader {
+    pub auth_tag: [u8; 16],
+    pub stream_id: u32,
+    pub frame_type: FrameType,
+    pub payload_len: u16,
+    pub padding_len: u16,
+}
+
+pub struct Frame {
+    pub header: FrameHeader,
+    pub payload: Bytes,
+    pub padding: Bytes,
+}
+
+const AUTH_TAG_SIZE: u16 = 16;
+const STREAM_ID_SIZE: u16 = 4;
+const FRAME_TYPE_SIZE: u16 = 1;
+const PAYLOAD_LEN_SIZE: u16 = 2;
+const PADDING_LEN_SIZE: u16 = 2;
+
+pub const FRAME_HEADER_SIZE: u16 =
+    AUTH_TAG_SIZE + STREAM_ID_SIZE + FRAME_TYPE_SIZE + PAYLOAD_LEN_SIZE + PADDING_LEN_SIZE;
+
+impl Frame {
+    pub fn into_bytes(self, auth_key: &[u8; 16]) -> BytesMut {
+        let updated_padding = Padding::generate_padding();
+        let total_size = FRAME_HEADER_SIZE as usize + self.payload.len() + self.padding.len();
+        let mut buf = BytesMut::with_capacity(total_size);
+
+        buf.put_slice(auth_key);
+        buf.put_u32(self.header.stream_id);
+        buf.put_u8(self.header.frame_type as u8);
+        buf.put_u16(self.header.payload_len);
+        buf.put_u16(updated_padding.len);
+
+        buf.put(self.payload);
+
+        buf.put(updated_padding.data);
+
+        buf
+    }
+}