feat: allow maximum buffer size for backpressure (#4)

src/connection_stream.rs

@@ -288,6 +288,7 @@ impl ConnectionStream {
         StreamProgress::NoInterest => {
           // Write it
           let n = self.tls.writer().write(buf).expect("Write will never fail");
+          trace!("w={n}");
           assert!(n > 0);
           // Drain what we can
           while self.poll_write_only(cx) == StreamProgress::MadeProgress {}
@@ -303,6 +304,12 @@ impl ConnectionStream {
     res
   }
 
+  /// Fully write a buffer to the TLS stream, expecting it to write fully and not fail.
+  pub(crate) fn write_buf_fully(&mut self, buf: &[u8]) {
+    let n = self.tls.writer().write(buf).expect("Write will never fail");
+    assert_eq!(n, buf.len())
+  }
+
   /// Polls for completion of all the writes in the rustls [`Connection`]. Does not progress on
   /// reads at all.
   pub fn poll_flush(&mut self, cx: &mut Context<'_>) -> Poll<io::Result<()>> {