don't allocate in pad_to_blocks

This saves around 6% on my machine.

1 files changed, 10 insertions, 13 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 5a2e205..908cc1f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -579,16 +579,13 @@ fn cipher_aez_core(mode: Mode, aez: &Aez, tweaks: Tweak, message: &mut [u8]) {
     blocks.set_m_y(c_y);
 }
 
-fn pad_to_blocks(value: &[u8]) -> Vec<Block> {
-    let mut blocks = Vec::new();
-    for chunk in value.chunks(16) {
-        if chunk.len() == 16 {
-            blocks.push(Block::from_slice(chunk));
+fn pad_to_blocks(value: &[u8]) -> impl Iterator<Item=Block> {
+    value.chunks(16)
+        .map(|chunk| if chunk.len() == 16 {
+            Block::from_slice(chunk)
         } else {
-            blocks.push(Block::from_slice(chunk).pad(chunk.len() * 8));
-        }
-    }
-    blocks
+            Block::from_slice(chunk).pad(chunk.len() * 8)
+        })
 }
 
 fn aez_hash(aez: &Aez, tweaks: Tweak) -> Block {
@@ -609,12 +606,12 @@ fn aez_hash(aez: &Aez, tweaks: Tweak) -> Block {
             }
         } else {
             let blocks = pad_to_blocks(tweak);
-            for (l, chunk) in blocks.iter().enumerate() {
+            for (l, chunk) in blocks.enumerate() {
                 ej.advance();
-                if l == blocks.len() - 1 {
-                    hash = hash ^ e(j.try_into().unwrap(), 0, aez, *chunk);
+                if l == tweak.len() / 16 {
+                    hash = hash ^ e(j.try_into().unwrap(), 0, aez, chunk);
                 } else {
-                    hash = hash ^ ej.eval(*chunk);
+                    hash = hash ^ ej.eval(chunk);
                 }
             }
         }