From a0e745fdbc4e1d638a77583ba3e75ff91aff584a Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Fri, 21 Nov 2025 11:29:36 +0000
Subject: [PATCH 1/2] feat: optimize `verify_msg_block`

---
 src/sha256.nr | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/sha256.nr b/src/sha256.nr
index 2a4cecd..0247722 100644
--- a/src/sha256.nr
+++ b/src/sha256.nr
@@ -232,25 +232,24 @@ fn verify_msg_block<let N: u32>(
         msg_end = msg_end + INT_SIZE - msg_end % INT_SIZE;
     }
 
+    let max_read_index = std::cmp::min(message_size, msg_end);
+
     // Reconstructed packed item.
     let mut msg_item: u32 = 0;
 
     // Inclusive at the end so that we can compare the last item.
-    let mut i: u32 = 0;
     for k in msg_start..=msg_end {
-        if k % INT_SIZE == 0 {
+        if (k != msg_start) & (k % INT_SIZE == 0) {
             // If we consumed some input we can compare against the block.
-            if (msg_start < message_size) & (k > msg_start) {
-                println(f"i is {i}");
-                assert_eq(msg_block[i], msg_item as u32);
-                i = i + 1;
-                msg_item = 0;
-            }
+            let msg_block_index = (k - msg_start) / INT_SIZE - 1;
+            assert_eq(msg_block[msg_block_index], msg_item);
+
+            msg_item = 0;
         }
         // Shift the accumulator
         msg_item = msg_item << 8;
         // If we have input to consume, add it at the rightmost position.
-        if k < message_size & k < msg_end {
+        if k < max_read_index {
             msg_item = msg_item + msg[k] as u32;
         }
     }

From 667ddbd590050cb9ce821ef777c544b699fb6f97 Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Fri, 21 Nov 2025 11:37:02 +0000
Subject: [PATCH 2/2] feat: remove conditional from assignment

---
 src/sha256.nr | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/sha256.nr b/src/sha256.nr
index 0247722..543b218 100644
--- a/src/sha256.nr
+++ b/src/sha256.nr
@@ -246,12 +246,10 @@ fn verify_msg_block<let N: u32>(
 
             msg_item = 0;
         }
-        // Shift the accumulator
-        msg_item = msg_item << 8;
+
         // If we have input to consume, add it at the rightmost position.
-        if k < max_read_index {
-            msg_item = msg_item + msg[k] as u32;
-        }
+        let msg_byte = if k < max_read_index { msg[k] } else { 0 };
+        msg_item = (msg_item << 8) + msg_byte as u32;
     }
 }