Fixed an unwanted infinite loop (#8)

kodecocodes · Jul 10, 2023 · ee30e0c · ee30e0c
1 parent cb5e501
commit ee30e0c
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Showing 2 changed files with 54 additions and 8 deletions.
diff --git a/06-queues/projects/final/lib/ring_buffer.dart b/06-queues/projects/final/lib/ring_buffer.dart
@@ -20,9 +20,7 @@ class RingBuffer<E> {
     _size++;
   }
 
-  int _advance(int index) {
-    return (index == _list.length - 1) ? 0 : index + 1;
-  }
+  int _advance(int index) => (index + 1) % _list.length;
 
   E? read() {
     if (isEmpty) return null;
@@ -38,13 +36,12 @@ class RingBuffer<E> {
   String toString() {
     final text = StringBuffer();
     text.write('[');
-    int index = _readIndex;
-    while (index != _writeIndex) {
+    for (int i = 0; i < _size; i++) {
+      final index = (_readIndex + i) % _list.length;
       if (index != _readIndex) {
         text.write(', ');
       }
-      text.write(_list[index % _list.length]);
-      index++;
+      text.write(_list[index]);
     }
     text.write(']');
     return text.toString();

diff --git a/06-queues/projects/final/test/ring_buffer_test.dart b/06-queues/projects/final/test/ring_buffer_test.dart
@@ -83,13 +83,62 @@ void main() {
       expect(buffer.read(), isNull);
     });
 
+    // https://github.com/kodecocodes/dsad-materials/pull/8
     test('toString contains no infinite loop', () {
-      final buffer = RingBuffer<int>(5);
+      final buffer = RingBuffer<int>(3);
       buffer.write(1);
       buffer.write(2);
       buffer.write(3);
       buffer.read();
       expect(buffer.toString(), '[2, 3]');
+
+      final rb = RingBuffer<String>(3);
+      rb.write('Ray');
+      rb.write('Brian');
+      rb.write('Noah');
+      expect(rb.read(), 'Ray');
+      expect(rb.toString(), '[Brian, Noah]');
+    });
+
+// https://github.com/kodecocodes/dsad-materials/pull/8
+    test('toString not empty when read and write index equal', () {
+      final rb = RingBuffer<String>(3);
+      rb.write('Ray');
+      rb.write('Brian');
+      rb.write('Noah');
+      expect(rb.toString(), '[Ray, Brian, Noah]');
+    });
+
+    test('toString variations', () {
+      var buffer = RingBuffer<int>(3);
+      expect(buffer.toString(), '[]');
+
+      buffer.write(1);
+      expect(buffer.toString(), '[1]');
+
+      buffer.write(2);
+      expect(buffer.toString(), '[1, 2]');
+
+      buffer.write(3);
+      expect(buffer.toString(), '[1, 2, 3]');
+
+      buffer.read();
+      expect(buffer.toString(), '[2, 3]');
+
+      buffer.write(4);
+      expect(buffer.toString(), '[2, 3, 4]');
+
+      buffer.read();
+      expect(buffer.toString(), '[3, 4]');
+
+      buffer.read();
+      expect(buffer.toString(), '[4]');
+
+      buffer.read();
+      expect(buffer.toString(), '[]');
+
+      buffer.read();
+      expect(buffer.toString(), '[]');
     });
   });
 }