From a917f75ce052412701213744f30be1aad9f92ecd Mon Sep 17 00:00:00 2001
From: devdesk <tami@tami.org.il>
Date: Sat, 17 Feb 2024 15:56:05 +0200
Subject: [PATCH] avoid reallocating the frame, just use a static buffer

---
 examples/live.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/examples/live.rs b/examples/live.rs
index a0d6701..e0c8b4d 100644
--- a/examples/live.rs
+++ b/examples/live.rs
@@ -67,7 +67,10 @@ fn main() -> anyhow::Result<()> {
         .unwrap();
 
     // get a packet and print its bytes
-    let mut parts = vec![];
+    const PACKET_LEN: usize = 6972;
+    const FRAME_LEN: usize = 288 * 384 * 2;
+    let mut frame = [0u8; FRAME_LEN];
+    let mut len = 0;
     let mut out = File::create(&output)?;
     while let Ok(p) = cap.next_packet() {
         let data = p.data;
@@ -80,17 +83,17 @@ fn main() -> anyhow::Result<()> {
             Err(_) => continue,
         };
         let data = &data[HDR_SIZE..];
-        if header.part == 0 && parts.len() > 0 {
-            let frame = Frame {
-                header,
-                raw: parts.concat(),
-            };
-            if frame.raw.len() == 384 * 288 * 2 {
-                out.write_all(&frame.raw)?;
+        if (header.part == 0 && len > 0)
+            // do not write out of bounds - would panic, instead just skip
+            || (data.len() + len > FRAME_LEN)
+        {
+            if len == FRAME_LEN {
+                out.write_all(&frame[..])?;
             }
-            parts.clear();
+            len = 0;
         }
-        parts.push(data.to_vec());
+        frame[len..len + data.len()].copy_from_slice(data);
+        len += data.len();
     }
     Ok(())
 }