Implement slicing operator

src/main/php/util/Bytes.class.php

@@ -43,6 +43,19 @@ public function getIterator(): Traversable {
     }
   }
 
+  /**
+   * Slicing
+   *
+   * @param  string|array $slice
+   * @return self
+   */
+  public function __invoke($slice) {
+    list($start, $stop)= is_array($slice) ? $slice : explode(':', $slice, 2);
+    $offset= (int)$start;
+    $end= (int)$stop ?: $this->size;
+    return new self(substr($this->buffer, $offset, ($end < 0 ? $this->size + $end : $end) - $offset));
+  }
+
   /**
    * = list[] overloading
    *

src/test/php/util/unittest/BytesTest.class.php

@@ -6,6 +6,25 @@
 
 class BytesTest {
 
+  /** @return iterable */
+  private function slices() {
+    yield ['0:4', 'This'];         // start:stop
+    yield ['5:7', 'is'];           // start:stop - with non-zero start
+    yield ['5:-5', 'is a'];        // start:stop - with negative offset
+    yield ['-4:-2', 'test'];       // start:stop - with negative offsets
+
+    yield [':4', 'This'];          // :stop
+    yield [':-5', 'This is a'];    // :stop - with negative offset
+    yield ['5:', 'is a test'];     // start:
+    yield ['-4:', 'test'];         // start: - at negative offset
+    yield [':', 'This is a test']; // : - copy
+
+    yield [[0, 4], 'This'];        // start:stop
+    yield [[5, 7], 'is'];          // start:stop - with non-zero start
+    yield [[5, -5], 'is a'];       // start:stop - with negative offset
+    yield [[-4, -2], 'test'];      // start:stop - with negative offsets
+  }
+
   /** @return iterable */
   private function comparing() {
     yield [new Bytes('Test'), 0];
@@ -338,6 +357,12 @@ public function iteration() {
     Assert::equals($i, sizeof($c)- 1);
   }
 
+  #[Test, Values(from: 'slices')]
+  public function slice($slice, $expected) {
+    $b= new Bytes('This is a test');
+    Assert::equals(new Bytes($expected), $b($slice));
+  }
+
   #[Test, Values(from: 'comparing')]
   public function compare($value, $expected) {
     Assert::equals($expected, (new Bytes('Test'))->compareTo($value));