When growing a BitList make sure all newly exposed values are properl…

…y initialized.
renggli · Sep 3, 2023 · 71a4f80 · 71a4f80
1 parent 5a8f72d
commit 71a4f80
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Showing 2 changed files with 45 additions and 20 deletions.
diff --git a/lib/src/collection/bitlist.dart b/lib/src/collection/bitlist.dart
@@ -107,26 +107,7 @@ abstract class BitList extends ListBase<bool> {
  @override
  void fillRange(int start, int end, [bool? fill]) {
  RangeError.checkValidRange(start, end, length);
- if (start == end) return;
- final startIndex = start >> bitShift, startBit = start & bitOffset;
- final endIndex = (end - 1) >> bitShift, endBit = (end - 1) & bitOffset;
- if (startIndex == endIndex) {
- if (fill == true) {
- buffer[startIndex] |= ((1 << (endBit - startBit + 1)) - 1) << startBit;
- } else {
- buffer[startIndex] &= ((1 << startBit) - 1) | (bitMask << (endBit + 1));
- }
- } else {
- if (fill == true) {
- buffer[startIndex] |= bitMask << startBit;
- buffer.fillRange(startIndex + 1, endIndex, bitMask);
- buffer[endIndex] |= (1 << (endBit + 1)) - 1;
- } else {
- buffer[startIndex] &= (1 << startBit) - 1;
- buffer.fillRange(startIndex + 1, endIndex, 0);
- buffer[endIndex] &= bitMask << (endBit + 1);
- }
- }
+ _fillRange(buffer, start, end, fill ?? false);
  }
 
  /// Sets the bit at the specified [index] to the complement of its current
@@ -332,6 +313,10 @@ class GrowableBitList extends BitList {
  newBuffer.setRange(0, newBuffer.length, buffer);
  buffer = newBuffer;
  }
+ if (_length < length) {
+ // When growing, make sure we always have predictable state.
+ _fillRange(buffer, _length, length, false);
+ }
  _length = length;
  }
 }
@@ -425,3 +410,26 @@ const List<int> bitClearMask = [
  -1073741825,
  -2147483649
 ];
+
+void _fillRange(Uint32List buffer, int start, int end, bool? fill) {
+ if (start == end) return;
+ final startIndex = start >> bitShift, startBit = start & bitOffset;
+ final endIndex = (end - 1) >> bitShift, endBit = (end - 1) & bitOffset;
+ if (startIndex == endIndex) {
+ if (fill == true) {
+ buffer[startIndex] |= ((1 << (endBit - startBit + 1)) - 1) << startBit;
+ } else {
+ buffer[startIndex] &= ((1 << startBit) - 1) | (bitMask << (endBit + 1));
+ }
+ } else {
+ if (fill == true) {
+ buffer[startIndex] |= bitMask << startBit;
+ buffer.fillRange(startIndex + 1, endIndex, bitMask);
+ buffer[endIndex] |= (1 << (endBit + 1)) - 1;
+ } else {
+ buffer[startIndex] &= (1 << startBit) - 1;
+ buffer.fillRange(startIndex + 1, endIndex, 0);
+ buffer[endIndex] &= bitMask << (endBit + 1);
+ }
+ }
+}
diff --git a/test/collection_test.dart b/test/collection_test.dart
@@ -607,6 +607,23 @@ void main() {
  target.length -= 2;
  expect(target.buffer, same(buffer));
  });
+ test('length (cleared)', () {
+ final generator = Random(584);
+ for (var i = 0; i < 0xff; i++) {
+ final original = 1 + generator.nextInt(0xff);
+ final smaller = generator.nextInt(original);
+ final larger = original + generator.nextInt(0xff);
+ final target = BitList.filled(original, true, growable: growable);
+ target.length = smaller;
+ target.length = larger;
+ for (var i = 0; i < smaller; i++) {
+ expect(target[i], isTrue);
+ }
+ for (var i = smaller; i < larger; i++) {
+ expect(target[i], isFalse);
+ }
+ }
+ });
  test('removeLast', () {
  final source = randomBooleans(453, 500);
  final target = BitList.of(source, growable: growable);