refactor: fix broken gfmil algo

src/tasks/tasks01/gfmul.rs

@@ -48,4 +48,64 @@ mod tests {
         );
         Ok(())
     }
+
+    #[test]
+    fn gfmul_task02() -> Result<()> {
+        let args: Value = json!({"a": "AwEAAAAAAAAAAAAAAAAAgA==", "b": "gBAAAAAAAAAAAAAAAAAAAA=="});
+
+        let poly1_text: String = serde_json::from_value(args["a"].clone())?;
+        let poly_a = BASE64_STANDARD.decode(poly1_text)?;
+
+        let poly2_text: String = serde_json::from_value(args["b"].clone())?;
+        let poly_b = BASE64_STANDARD.decode(poly2_text)?;
+
+        let result = BASE64_STANDARD.encode(gfmul(poly_a, poly_b, "xex")?);
+
+        assert_eq!(
+            result, "QKgUAAAAAAAAAAAAAAAAAA==",
+            "Failure. Calulated result was: {}",
+            result
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn gfmul_task03() -> Result<()> {
+        let args: Value = json!({"a": "AwEAAAAAAAAAAAAAAAAAgA==", "b": "oBAAAAAAAAAAAAAAAAAAAA=="});
+
+        let poly1_text: String = serde_json::from_value(args["a"].clone())?;
+        let poly_a = BASE64_STANDARD.decode(poly1_text)?;
+
+        let poly2_text: String = serde_json::from_value(args["b"].clone())?;
+        let poly_b = BASE64_STANDARD.decode(poly2_text)?;
+
+        let result = BASE64_STANDARD.encode(gfmul(poly_a, poly_b, "xex")?);
+
+        assert_eq!(
+            result, "UIAUAAAAAAAAAAAAAAAAAA==",
+            "Failure. Calulated result was: {}",
+            result
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn gfmul_task04() -> Result<()> {
+        let args: Value = json!({"a": "ARIAAAAAAAAAAAAAAAAAgA==", "b": "AgAAAAAAAAAAAAAAAAAAAA=="});
+
+        let poly1_text: String = serde_json::from_value(args["a"].clone())?;
+        let poly_a = BASE64_STANDARD.decode(poly1_text)?;
+
+        let poly2_text: String = serde_json::from_value(args["b"].clone())?;
+        let poly_b = BASE64_STANDARD.decode(poly2_text)?;
+
+        let result = BASE64_STANDARD.encode(gfmul(poly_a, poly_b, "xex")?);
+
+        assert_eq!(
+            result, "hSQAAAAAAAAAAAAAAAAAAA==",
+            "Failure. Calulated result was: {}",
+            result
+        );
+        Ok(())
+    }
 }

src/utils/math.rs

@@ -92,6 +92,10 @@ impl ByteArray {
         (self.0.first().unwrap() & 1) == 1
     }
 
+    pub fn msb_is_one(&self) -> bool {
+        (self.0.last().unwrap() & 1) == 1
+    }
+
     pub fn is_empty(&self) -> bool {
         for i in self.0.iter() {
             if *i != 0 {

src/utils/poly.rs

@@ -19,20 +19,20 @@ pub fn gfmul(poly_a: Vec<u8>, poly_b: Vec<u8>, semantic: &str) -> Result<Vec<u8>
 
     if poly2.LSB_is_one() {
         result.xor_byte_arrays(&poly1);
-        poly2.right_shift(semantic)?;
-    } else {
-        poly2.right_shift(semantic)?;
     }
+    poly2.right_shift(semantic)?;
 
     while !poly2.is_empty() {
-        if poly2.LSB_is_one() {
-            poly1.left_shift(semantic)?;
-            poly1.xor_byte_arrays(&red_poly_bytes);
-            result.xor_byte_arrays(&poly1);
-        } else {
         poly1.left_shift(semantic)?;
+
+        if poly1.msb_is_one() {
             poly1.xor_byte_arrays(&red_poly_bytes);
         }
+
+        if poly2.LSB_is_one() {
+            result.xor_byte_arrays(&poly1);
+        }
+
         poly2.right_shift(semantic)?;
     }