Checks for single bits within an integer

inc/GlobalFunctions.php

@@ -716,3 +716,22 @@ function hydrate($destination, $source, array $properties, $copyNull = true)
     }
   }
 }
+
+if(!function_exists('is_single_bit'))
+{
+  /**
+   * Check to see if an integer is a single bit, or a combination
+   *
+   * @param int $bit Bit to check
+   *
+   * @return bool
+   */
+  function is_single_bit($bit)
+  {
+    if($bit === 1)
+    {
+      return true;
+    }
+    return $bit > 0 && bcmod($bit, 2) == 0 && ($bit & ($bit - 1)) == 0;
+  }
+}

tests/GlobalFunctionsTest.php

@@ -209,6 +209,7 @@ public function testGetNamespace()
   public function testBuildPath()
   {
     $this->assertEquals("a" . DIRECTORY_SEPARATOR . "b", build_path("a", "b"));
+    $this->assertEquals("a" . DIRECTORY_SEPARATOR . "b", build_path("a", "b"));
   }
 
   public function testBuildWindowsPath()
@@ -224,6 +225,7 @@ public function testBuildUnixPath()
   public function testBuildCustomPath()
   {
     $this->assertEquals("a|b", build_path_custom("|", ["a", "b"]));
+    $this->assertEquals("a|b", build_path_custom("|", [0 => "a", 1 => "b"]));
   }
 
   public function testConcat()
@@ -397,6 +399,27 @@ public function testHydrate()
     $this->setExpectedException("Exception");
     hydrate(['' => ''], $source, []);
   }
+
+  public function testSingleBit()
+  {
+    $this->assertTrue(is_single_bit(1));
+    $this->assertTrue(is_single_bit(2));
+    $this->assertTrue(is_single_bit(4));
+
+    $fails = [3, 5, 6, 7, 9, 10, 11, 13, 14, 15];
+    foreach($fails as $checkBit)
+    {
+      $this->assertFalse(is_single_bit($checkBit));
+    }
+
+    $checkBit = 4;
+    for($i = 0; $i < 10000; $i++)
+    {
+      $checkBit = bcmul($checkBit, 2);
+      $this->assertTrue(is_single_bit($checkBit));
+      $this->assertFalse(is_single_bit(bcsub($checkBit, 3)));
+    }
+  }
 }
 
 class PropertyClass