From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 31 Jul 2021 12:48:50 +0000 (+0100)
Subject: wip mimeswap
X-Git-Tag: hippotat/1.0.0~417
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=f991bb6a7ff2b68784f5ad11142f24bb111a7447;p=hippotat.git

wip mimeswap

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/src/bin/client.rs b/src/bin/client.rs
index 393ddf0..9ba9b80 100644
--- a/src/bin/client.rs
+++ b/src/bin/client.rs
@@ -130,7 +130,7 @@ async fn run_client<C:HCC>(
             let mut packet =
               packet.context("read from ipif")?
               .ok_or_else(|| io::Error::from(io::ErrorKind::UnexpectedEof))?;
-            if let Ok(()) = slip::check_checkmtu_mimeify(&mut packet, &ic) {
+            if let Ok(()) = slip::check_checkmtu_mimeswap(&ic, SLIP_ESC, &mut packet) {
               let new_upbound_total = packet.len() + upbound_total + 1;
               if new_upbound_total > ic.max_batch_up.sat() {
                 tx_defer = Some(packet);
diff --git a/src/prelude.rs b/src/prelude.rs
index 8407c02..c51cdba 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -53,5 +53,6 @@ pub const SLIP_END:     u8 = 0o300;
 pub const SLIP_ESC:     u8 = 0o333;
 pub const SLIP_ESC_END: u8 = 0o334;
 pub const SLIP_ESC_ESC: u8 = 0o335;
+pub const SLIP_SWAP_ESC: u8 = b'-';
 
 pub fn default<T:Default>() -> T { Default::default() }
diff --git a/src/slip.rs b/src/slip.rs
index 269c8fe..7fe3542 100644
--- a/src/slip.rs
+++ b/src/slip.rs
@@ -7,6 +7,31 @@ use crate::prelude::*;
 pub static SLIP_END_SLICE: &[u8] = &[SLIP_END];
 
 #[throws(AE)]
-pub fn check_checkmtu_mimeify(_data: &mut [u8], _ic: &InstanceConfig) {
-  // xxx
+pub fn check_checkmtu_mimeswap(ic: &InstanceConfig, input_esc: u8,
+                               mut data: &mut [u8]) {
+  let mut sofar = 0;
+  let checkmtu = |_| Ok::<_,AE>(()); // xxx
+  while let Some((i, &c)) = data.iter().enumerate().find(
+    |(_,&c)| c == SLIP_ESC || c == SLIP_SWAP_ESC
+  ) {
+    let ni; let nc;
+    if c == input_esc {
+      match data.get(i+1) {
+        Some(&SLIP_ESC_END) |
+        Some(&SLIP_ESC_ESC) => Ok(()),
+        _ => Err(anyhow!("SLIP escape not followed by ESC_END or ESC_ESC")),
+      }?;
+      ni = i+2;
+      sofar += ni;
+      nc = if input_esc == SLIP_ESC { SLIP_SWAP_ESC } else { SLIP_ESC };
+    } else {
+      ni = i+1;
+      sofar += ni;
+      checkmtu(sofar)?;
+      nc = input_esc;
+    };
+    data[i] = nc;
+    data = &mut data[ni ..];
+  }
+  checkmtu(data.len())?;
 }