refactor(proto): centralize packet envelope handling

crates/irtt-proto/src/close.rs

@@ -1,6 +1,8 @@
 use crate::{
-    flags::{FLAG_CLOSE, FLAG_HMAC},
-    hmac, write_header, Result, HMAC_SIZE,
+    envelope::{self, FlagRule},
+    flags::{FLAG_CLOSE, FLAG_OPEN, FLAG_REPLY},
+    layout::PacketLayout,
+    Result,
 };
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -9,27 +11,24 @@ pub struct CloseRequest {
 }
 
 pub fn encode_close_request(request: &CloseRequest, hmac_key: Option<&[u8]>) -> Result<Vec<u8>> {
-    let mut flags = FLAG_CLOSE;
-    if hmac_key.is_some() {
-        flags |= FLAG_HMAC;
-    }
-
-    let mut out = Vec::new();
-    write_header(&mut out, flags);
-    if hmac_key.is_some() {
-        out.extend_from_slice(&[0; HMAC_SIZE]);
-    }
+    let mut out = envelope::begin(
+        FLAG_CLOSE,
+        hmac_key,
+        &[
+            FlagRule::Require(FLAG_CLOSE),
+            FlagRule::Reject(FLAG_OPEN),
+            FlagRule::Reject(FLAG_REPLY),
+        ],
+        PacketLayout::close_request(hmac_key.is_some()).header_len(),
+    )?;
     out.extend_from_slice(&request.token.to_le_bytes());
-    if let Some(key) = hmac_key {
-        hmac::compute_hmac_in_place(key, &mut out, hmac::hmac_offset())?;
-    }
-    Ok(out)
+    envelope::finish(out, hmac_key)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::{hmac, FLAG_HMAC};
+    use crate::{hmac, FLAG_HMAC, HMAC_SIZE};
 
     #[test]
     fn hmac_close_request_places_token_after_hmac() {