General Upgrade, NEW: WebServers, Better Docs

transport/src/framing.rs

@@ -0,0 +1,21 @@
+use crate::{Policy, TransportSendStream};
+use mtp_codec::CommunicationValue;
+use mtp_common::CommunicationError;
+
+/// Writes the canonical length-prefixed MTP frame used by every transport.
+pub(crate) async fn write_frame<S: TransportSendStream>(
+    stream: &mut S,
+    value: &CommunicationValue,
+    policy: &Policy,
+) -> Result<(), CommunicationError> {
+    let bytes = value.to_bytes().map_err(|_| CommunicationError::Encode)?;
+    if bytes.len() as u64 > policy.max_message_size
+        || bytes.len() as u64 >= policy.close_frame_len as u64
+    {
+        return Err(CommunicationError::MessageTooLarge);
+    }
+    stream
+        .write_all(&(bytes.len() as u32).to_be_bytes())
+        .await?;
+    stream.write_all(&bytes).await
+}