speed up multiplication

1 files changed, 16 insertions, 11 deletions

diff --git a/src/block.rs b/src/block.rs
index abd7ff7..e9ba527 100644
--- a/src/block.rs
+++ b/src/block.rs
@@ -134,19 +134,24 @@ impl IndexMut<usize> for Block {
 
 impl Mul<u32> for Block {
     type Output = Block;
-    fn mul(self, rhs: u32) -> Block {
-        match rhs {
-            0 => Block::NULL,
-            1 => self,
-            2 => {
-                let mut result = self << 1;
-                if self[0] & 0x80 != 0 {
-                    result[15] ^= 135;
+    fn mul(mut self, mut rhs: u32) -> Block {
+        loop {
+            match rhs {
+                0 => break Block::NULL,
+                1 => break self,
+                2 => {
+                    let mut result = self << 1;
+                    if self[0] & 0x80 != 0 {
+                        result[15] ^= 135;
+                    }
+                    break result;
                 }
-                result
+                _ if rhs % 2 == 0 => {
+                    self = self * 2;
+                    rhs = rhs / 2;
+                }
+                _ => break self * (rhs - 1) ^ self,
             }
-            _ if rhs % 2 == 0 => self * 2 * (rhs / 2),
-            _ => self * (rhs - 1) ^ self,
         }
     }
 }