BitArray.setWhere and clearWhere.

Author: isoos

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 2.3.0
 
 - Updated SDK constraint, lints and format.
+- `BitArray.setWhere` and `BitArray.clearWhere` for callback-driven updates.
 
 ## 2.2.1
 

lib/src/bit_array.dart

@@ -121,6 +121,28 @@ class BitArray extends BitSet {
     indexes.forEach(clearBit);
   }
 
+  /// Sets the bits where the [fn] returns true, to false.
+  ///
+  /// Calls [fn] only for index values where the bit is true.
+  void clearWhere(bool Function(int index) fn) {
+    var index = 0;
+    for (var i = 0; i < _data.length; i++) {
+      var d = _data[i];
+      if (d == 0) {
+        index += 32;
+        continue;
+      }
+      for (var j = 0; j < _bitMask.length; j++) {
+        final bm = _bitMask[j];
+        if ((d & bm) != 0 && fn(index)) {
+          d = d & _clearMask[j];
+        }
+        index++;
+      }
+      _data[i] = d;
+    }
+  }
+
   /// Sets all of the bits in the current [BitArray] to false.
   void clearAll() {
     for (var i = 0; i < _data.length; i++) {
@@ -138,6 +160,28 @@ class BitArray extends BitSet {
     indexes.forEach(setBit);
   }
 
+  /// Sets the bits where the [fn] returns true, to true.
+  ///
+  /// Calls [fn] only for index values where the bit is false.
+  void setWhere(bool Function(int index) fn) {
+    var index = 0;
+    for (var i = 0; i < _data.length; i++) {
+      var d = _data[i];
+      if (d == -1) {
+        index += 32;
+        continue;
+      }
+      for (var j = 0; j < _bitMask.length; j++) {
+        final bm = _bitMask[j];
+        if ((d & bm) == 0 && fn(index)) {
+          d = d | bm;
+        }
+        index++;
+      }
+      _data[i] = d;
+    }
+  }
+
   /// Sets all the bit values in the current [BitArray] to true.
   void setAll() {
     for (var i = 0; i < _data.length; i++) {

test/bit_array_test.dart

@@ -135,6 +135,59 @@ void main() {
       expect((oioi ^ oooo).toBinaryString().substring(0, 4), '0101');
       expect((oioi ^ ioio).toBinaryString().substring(0, 4), '1111');
     });
+
+    test('setWhere calling one', () {
+      for (var i = 0; i < 128; i++) {
+        final array = BitArray(128);
+        array.setAll();
+        array.clearBit(i);
+        final called = [];
+        array.setWhere((i) {
+          called.add(i);
+          return false;
+        });
+        expect(called, [i]);
+        for (var j = 0; j < 128; j++) {
+          expect(array[j], j != i);
+        }
+
+        called.clear();
+        array.setWhere((i) {
+          called.add(i);
+          return true;
+        });
+        expect(called, [i]);
+        for (var j = 0; j < 128; j++) {
+          expect(array[j], true);
+        }
+      }
+    });
+
+    test('clearWhere calling one', () {
+      for (var i = 0; i < 128; i++) {
+        final array = BitArray(128);
+        array.setBit(i);
+        final called = [];
+        array.clearWhere((i) {
+          called.add(i);
+          return false;
+        });
+        expect(called, [i]);
+        for (var j = 0; j < 128; j++) {
+          expect(array[j], j == i);
+        }
+
+        called.clear();
+        array.clearWhere((i) {
+          called.add(i);
+          return true;
+        });
+        expect(called, [i]);
+        for (var j = 0; j < 128; j++) {
+          expect(array[j], false);
+        }
+      }
+    });
   });
 
   group('BitArray equals and hashCode', () {