From 4749964f06a7aa20ee19c5f7b3c97079e5c67911 Mon Sep 17 00:00:00 2001
From: edef <edef@edef.eu>
Date: Fri, 9 May 2025 22:31:45 +0000
Subject: [PATCH] refactor(nix-daemon/framed): simplify partial header read

Rather than having separate branches, just make it part of the state
machine discipline.

Change-Id: Ib21456227515506495ca06ac2a8a529d04f95fde
Reviewed-on: https://cl.snix.dev/c/snix/+/30496
Reviewed-by: Brian Olsen <brian@maven-group.org>
Tested-by: besadii
Reviewed-by: Florian Klink <flokli@flokli.de>
---
 .../src/nix_daemon/framing/framed_read.rs           | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/snix/nix-compat/src/nix_daemon/framing/framed_read.rs b/snix/nix-compat/src/nix_daemon/framing/framed_read.rs
index 333924e07..62e584e6d 100644
--- a/snix/nix-compat/src/nix_daemon/framing/framed_read.rs
+++ b/snix/nix-compat/src/nix_daemon/framing/framed_read.rs
@@ -70,6 +70,12 @@ impl<R: AsyncRead> AsyncRead for NixFramedReader<R> {
                 State::Eof => {
                     return Ok(()).into();
                 }
+                State::Length { buf, filled: 8 } => {
+                    *this.state = match NonZeroU64::new(u64::from_le_bytes(*buf)) {
+                        None => State::Eof,
+                        Some(remaining) => State::Chunk { remaining },
+                    };
+                }
                 State::Length { buf, filled } => {
                     let bytes_read = {
                         let mut b = ReadBuf::new(&mut buf[*filled as usize..]);
@@ -82,13 +88,6 @@ impl<R: AsyncRead> AsyncRead for NixFramedReader<R> {
                     }
 
                     *filled += bytes_read;
-
-                    if *filled == 8 {
-                        *this.state = match NonZeroU64::new(u64::from_le_bytes(*buf)) {
-                            None => State::Eof,
-                            Some(remaining) => State::Chunk { remaining },
-                        };
-                    }
                 }
                 State::Chunk { remaining } => {
                     let bytes_read = ready!(with_limited(buf, remaining.get(), |buf| {