Fix bug in Calculator::twosComplement()

The code forgot to prepend the carry bit when all bytes have been zeroed. This bug affected bitwise operations AND, OR, XOR for all but the GMP calculator.
brick · Aug 18, 2020 · e6f8e7d · e6f8e7d
1 parent fadf080
commit e6f8e7d
Show file tree

Hide file tree

Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/src/Internal/Calculator.php b/src/Internal/Calculator.php
@@ -695,7 +695,11 @@ private function twosComplement(string $number) : string
                 break;
             }
 
-            $number[$i] = \chr(0);
+            $number[$i] = "\x00";
+
+            if ($i === 0) {
+                $number = "\x01" . $number;
+            }
         }
 
         return $number;

diff --git a/tests/BigIntegerTest.php b/tests/BigIntegerTest.php
@@ -2389,6 +2389,8 @@ public function providerXor() : array
             ['1', '-2', '-1'],
             ['-1', '2', '-3'],
             ['0', '1', '1'],
+            ['-83', '173', '-256'],
+            ['-18771', '46765', '-65536'],
             ['123456789', '123456787', '6'],
             ['123456789012345678901234567890', '123456789012345678901234567880', '26'],