From 366c2422abbeeb314edc20a82e20cf54931c2c04 Mon Sep 17 00:00:00 2001
From: caobug <7737673+caobug@users.noreply.github.com>
Date: Thu, 19 Jun 2025 22:32:05 +0800
Subject: [PATCH 1/3] Optimize checksum calculation

Replace slice iteration with indexed access to reduce overhead and improve performance - CPU usage dropped by 8% on Apple M1.
---
 src/wire/ip.rs | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/wire/ip.rs b/src/wire/ip.rs
index 5c2b0cde8..334b11b1c 100644
--- a/src/wire/ip.rs
+++ b/src/wire/ip.rs
@@ -688,11 +688,12 @@ pub mod checksum {
         // For each 32-byte chunk...
         const CHUNK_SIZE: usize = 32;
         while data.len() >= CHUNK_SIZE {
-            let mut d = &data[..CHUNK_SIZE];
+            let chunk = &data[..CHUNK_SIZE];
+            let mut i = 0;
             // ... take by 2 bytes and sum them.
-            while d.len() >= 2 {
-                accum += NetworkEndian::read_u16(d) as u32;
-                d = &d[2..];
+            while i + 1 < CHUNK_SIZE {
+                accum += u16::from_be_bytes([chunk[i], chunk[i + 1]]) as u32;
+                i += 2;
             }
 
             data = &data[CHUNK_SIZE..];
@@ -700,14 +701,15 @@ pub mod checksum {
 
         // Sum the rest that does not fit the last 32-byte chunk,
         // taking by 2 bytes.
-        while data.len() >= 2 {
-            accum += NetworkEndian::read_u16(data) as u32;
-            data = &data[2..];
+        let mut i = 0;
+        while i + 1 < data.len() {
+            accum += u16::from_be_bytes([data[i], data[i + 1]]) as u32;
+            i += 2;
         }
 
         // Add the last remaining odd byte, if any.
-        if let Some(&value) = data.first() {
-            accum += (value as u32) << 8;
+        if i < data.len() {
+            accum += (data[i] as u32) << 8;
         }
 
         propagate_carries(accum)

From 7d5b4bbc9e4284b86805f0afb03b2e156cad262d Mon Sep 17 00:00:00 2001
From: caobug <7737673+caobug@users.noreply.github.com>
Date: Fri, 20 Jun 2025 12:57:01 +0800
Subject: [PATCH 2/3] Replaced manual indexing with chunks_exact

---
 src/wire/ip.rs | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/src/wire/ip.rs b/src/wire/ip.rs
index 334b11b1c..a5deaf4d1 100644
--- a/src/wire/ip.rs
+++ b/src/wire/ip.rs
@@ -682,34 +682,30 @@ pub mod checksum {
     }
 
     /// Compute an RFC 1071 compliant checksum (without the final complement).
-    pub fn data(mut data: &[u8]) -> u16 {
+    pub fn data(data: &[u8]) -> u16 {
         let mut accum = 0;
 
         // For each 32-byte chunk...
         const CHUNK_SIZE: usize = 32;
-        while data.len() >= CHUNK_SIZE {
-            let chunk = &data[..CHUNK_SIZE];
-            let mut i = 0;
+        const WORD_SIZE: usize = 2;
+        for chunk in data.chunks_exact(CHUNK_SIZE) {
             // ... take by 2 bytes and sum them.
-            while i + 1 < CHUNK_SIZE {
-                accum += u16::from_be_bytes([chunk[i], chunk[i + 1]]) as u32;
-                i += 2;
+            for pair in chunk.chunks_exact(WORD_SIZE) {
+                accum += u16::from_be_bytes([pair[0], pair[1]]) as u32;
             }
-
-            data = &data[CHUNK_SIZE..];
         }
 
         // Sum the rest that does not fit the last 32-byte chunk,
         // taking by 2 bytes.
-        let mut i = 0;
-        while i + 1 < data.len() {
-            accum += u16::from_be_bytes([data[i], data[i + 1]]) as u32;
-            i += 2;
+        let remainder = data.chunks_exact(CHUNK_SIZE).remainder();
+        for pair in remainder.chunks_exact(WORD_SIZE) {
+            accum += u16::from_be_bytes([pair[0], pair[1]]) as u32;
         }
 
         // Add the last remaining odd byte, if any.
-        if i < data.len() {
-            accum += (data[i] as u32) << 8;
+        let last = remainder.chunks_exact(WORD_SIZE).remainder();
+        if !last.is_empty() {
+            accum += (last[0] as u32) << 8;
         }
 
         propagate_carries(accum)

From 6f649b0c7107a0f1bf670198c03dea42c059907f Mon Sep 17 00:00:00 2001
From: caobug <7737673+caobug@users.noreply.github.com>
Date: Fri, 20 Jun 2025 14:07:22 +0800
Subject: [PATCH 3/3] Improve readability

---
 src/wire/ip.rs | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/wire/ip.rs b/src/wire/ip.rs
index a5deaf4d1..998aeb01d 100644
--- a/src/wire/ip.rs
+++ b/src/wire/ip.rs
@@ -688,7 +688,8 @@ pub mod checksum {
         // For each 32-byte chunk...
         const CHUNK_SIZE: usize = 32;
         const WORD_SIZE: usize = 2;
-        for chunk in data.chunks_exact(CHUNK_SIZE) {
+        let mut chunks = data.chunks_exact(CHUNK_SIZE);
+        for chunk in &mut chunks {
             // ... take by 2 bytes and sum them.
             for pair in chunk.chunks_exact(WORD_SIZE) {
                 accum += u16::from_be_bytes([pair[0], pair[1]]) as u32;
@@ -697,15 +698,15 @@ pub mod checksum {
 
         // Sum the rest that does not fit the last 32-byte chunk,
         // taking by 2 bytes.
-        let remainder = data.chunks_exact(CHUNK_SIZE).remainder();
-        for pair in remainder.chunks_exact(WORD_SIZE) {
+        let remainder = chunks.remainder();
+        let mut word_pairs = remainder.chunks_exact(WORD_SIZE);
+        for pair in &mut word_pairs {
             accum += u16::from_be_bytes([pair[0], pair[1]]) as u32;
         }
 
         // Add the last remaining odd byte, if any.
-        let last = remainder.chunks_exact(WORD_SIZE).remainder();
-        if !last.is_empty() {
-            accum += (last[0] as u32) << 8;
+        if let Some(&byte) = word_pairs.remainder().first() {
+            accum += (byte as u32) << 8;
         }
 
         propagate_carries(accum)