refactor(nix-compat/wire): move BytesPacketPosition into writer r/8013

We don't use it in the reader anymore.

Change-Id: I98fe204a747711464e9e7ca17df06fa9854eb344
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11519
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

1 files changed, 17 insertions, 1 deletions

diff --git a/tvix/nix-compat/src/wire/bytes/writer.rs b/tvix/nix-compat/src/wire/bytes/writer.rs
index 347934b3dc..f5632771e9 100644
--- a/tvix/nix-compat/src/wire/bytes/writer.rs
+++ b/tvix/nix-compat/src/wire/bytes/writer.rs
@@ -3,7 +3,7 @@ use std::task::{ready, Poll};
 
 use tokio::io::AsyncWrite;
 
-use super::{padding_len, BytesPacketPosition, EMPTY_BYTES, LEN_SIZE};
+use super::{padding_len, EMPTY_BYTES, LEN_SIZE};
 
 pin_project! {
     /// Writes a "bytes wire packet" to the underlying writer.
@@ -41,6 +41,22 @@ pin_project! {
     }
 }
 
+/// Models the position inside a "bytes wire packet" that the writer is in.
+/// It can be in three different stages, inside size, payload or padding fields.
+/// The number tracks the number of bytes written inside the specific field.
+/// There shall be no ambiguous states, at the end of a stage we immediately
+/// move to the beginning of the next one:
+/// - Size(LEN_SIZE) must be expressed as Payload(0)
+/// - Payload(self.payload_len) must be expressed as Padding(0)
+///
+/// Padding(padding_len) means we're at the end of the bytes wire packet.
+#[derive(Clone, Debug, PartialEq, Eq)]
+enum BytesPacketPosition {
+    Size(usize),
+    Payload(u64),
+    Padding(usize),
+}
+
 impl<W> BytesWriter<W>
 where
     W: AsyncWrite,