public void EvaluationBehavior(int count)
{
int index = 0;
int limit = count * 2;
var source = new DelegateIterator <int>(
moveNext: () => index++ != limit, // Stop once we go past the limit.
current: () => index, // Yield from 1 up to the limit, inclusive.
dispose: () => index ^= int.MinValue);
IEnumerator <int> iterator = source.TakeLast(count).GetEnumerator();
Assert.Equal(0, index); // Nothing should be done before MoveNext is called.
for (int i = 1; i <= count; i++)
{
Assert.True(iterator.MoveNext());
Assert.Equal(count + i, iterator.Current);
// After the first MoveNext call to the enumerator, everything should be evaluated and the enumerator
// should be disposed.
Assert.Equal(int.MinValue, index & int.MinValue);
Assert.Equal(limit + 1, index & int.MaxValue);
}
Assert.False(iterator.MoveNext());
// Unlike SkipLast, TakeLast can tell straightaway that it can return a sequence with no elements if count <= 0.
// The enumerable it returns is a specialized empty iterator that has no connections to the source. Hence,
// after MoveNext returns false under those circumstances, it won't invoke Dispose on our enumerator.
int expected = count <= 0 ? 0 : int.MinValue;
Assert.Equal(expected, index & int.MinValue);
}
public void DisposeAfterEnumeration(int sourceLength, int subLength)
{
int sourceState = 0;
int subIndex = 0; // Index within the arrays the sub-collection is supposed to be at.
int[] subState = new int[sourceLength];
bool sourceDisposed = false;
bool[] subCollectionDisposed = new bool[sourceLength];
var source = new DelegateIterator <int>(
moveNext: () => ++ sourceState <= sourceLength,
current: () => 0,
dispose: () => sourceDisposed = true);
var subCollection = new DelegateIterator <int>(
moveNext: () => ++ subState[subIndex] <= subLength, // Return true `subLength` times.
current: () => subState[subIndex],
dispose: () => subCollectionDisposed[subIndex++] = true); // Record that Dispose was called, and move on to the next index.
var iterator = source.SelectMany(_ => subCollection);
int index = 0; // How much have we gone into the iterator?
IEnumerator <int> e = iterator.GetEnumerator();
using (e)
{
while (e.MoveNext())
{
int item = e.Current;
Assert.Equal(subState[subIndex], item); // Verify Current.
Assert.Equal(index / subLength, subIndex);
Assert.False(sourceDisposed); // Not yet.
// This represents whehter the sub-collection we're iterating thru right now
// has been disposed. Also not yet.
Assert.False(subCollectionDisposed[subIndex]);
// However, all of the sub-collections before us should have been disposed.
// Their indices should also be maxed out.
Assert.All(subState.Take(subIndex), s => Assert.Equal(subLength + 1, s));
Assert.All(subCollectionDisposed.Take(subIndex), t => Assert.True(t));
index++;
}
}
Assert.True(sourceDisposed);
Assert.Equal(sourceLength, subIndex);
Assert.All(subState, s => Assert.Equal(subLength + 1, s));
Assert.All(subCollectionDisposed, t => Assert.True(t));
// Make sure the iterator's enumerator has been disposed properly.
Assert.Equal(0, e.Current); // Default value.
Assert.False(e.MoveNext());
Assert.Equal(0, e.Current);
}
public void EvaluationBehavior(int count)
{
// We want to make sure no more than `count` items are ever evaluated ahead of the current position.
// As an example, if Enumerable.Range(1, 6).SkipLast(2) is called, then we should read in the first 3 items,
// yield 1, read in 4, yield 2, and so on.
int index = 0;
int limit = Math.Max(0, count * 2);
var source = new DelegateIterator <int>(
moveNext: () => index++ != limit, // Stop once we go past the limit.
current: () => index, // Yield from 1 up to the limit, inclusive.
dispose: () => index ^= int.MinValue);
IEnumerator <int> iterator = source.SkipLast(count).GetEnumerator();
Assert.Equal(0, index); // Nothing should be done before MoveNext is called.
for (int i = 1; i <= count; i++)
{
Assert.True(iterator.MoveNext());
Assert.Equal(i, iterator.Current);
Assert.Equal(count + i, index);
}
Assert.False(iterator.MoveNext());
Assert.Equal(int.MinValue, index & int.MinValue);
}
public void DisposeSource(int sourceCount, int count)
{
int state = 0;
var source = new DelegateIterator <int>(
moveNext: () => ++ state <= sourceCount,
current: () => 0,
dispose: () => state = -1);
IEnumerator <int> iterator = source.Skip(count).GetEnumerator();
int iteratorCount = Math.Max(0, sourceCount - Math.Max(0, count));
Assert.All(Enumerable.Range(0, iteratorCount), _ => Assert.True(iterator.MoveNext()));
Assert.False(iterator.MoveNext());
Assert.Equal(-1, state);
}
public void DisposeSource(int sourceCount, int count)
{
int state = 0;
var source = new DelegateIterator <int>(
moveNext: () => ++ state <= sourceCount,
current: () => 0,
dispose: () => state = -1);
IEnumerator <int> iterator = source.Take(count).GetEnumerator();
int iteratorCount = Math.Min(sourceCount, Math.Max(0, count));
Assert.All(Enumerable.Range(0, iteratorCount), _ => Assert.True(iterator.MoveNext()));
Assert.False(iterator.MoveNext());
// Unlike Skip, Take can tell straightaway that it can return a sequence with no elements if count <= 0.
// The enumerable it returns is a specialized empty iterator that has no connections to the source. Hence,
// after MoveNext returns false under those circumstances, it won't invoke Dispose on our enumerator.
int expected = count <= 0 ? 0 : -1;
Assert.Equal(expected, state);
}
public void DisposeAfterEnumeration(int sourceLength, int subLength)
{
int sourceState = 0;
int subIndex = 0; // Index within the arrays the sub-collection is supposed to be at.
int[] subState = new int[sourceLength];
bool sourceDisposed = false;
bool[] subCollectionDisposed = new bool[sourceLength];
var source = new DelegateIterator <int>(
moveNext: () => ++ sourceState <= sourceLength,
current: () => 0,
dispose: () => sourceDisposed = true);
var subCollection = new DelegateIterator <int>(
moveNext: () => ++ subState[subIndex] <= subLength, // Return true `subLength` times.
current: () => subState[subIndex],
dispose: () => subCollectionDisposed[subIndex++] = true); // Record that Dispose was called, and move on to the next index.
var iterator = source.SelectMany(_ => subCollection);
int index = 0; // How much have we gone into the iterator?
IEnumerator <int> e = iterator.GetEnumerator();
using (e)
{
while (e.MoveNext())
{
int item = e.Current;
Assert.Equal(subState[subIndex], item); // Verify Current.
Assert.Equal(index / subLength, subIndex);
Assert.False(sourceDisposed); // Not yet.
// This represents whehter the sub-collection we're iterating thru right now
// has been disposed. Also not yet.
Assert.False(subCollectionDisposed[subIndex]);
// However, all of the sub-collections before us should have been disposed.
// Their indices should also be maxed out.
Assert.All(subState.Take(subIndex), s => Assert.Equal(subLength + 1, s));
Assert.All(subCollectionDisposed.Take(subIndex), t => Assert.True(t));
index++;
}
}
Assert.True(sourceDisposed);
Assert.Equal(sourceLength, subIndex);
Assert.All(subState, s => Assert.Equal(subLength + 1, s));
Assert.All(subCollectionDisposed, t => Assert.True(t));
// .NET Core fixes an oversight where we wouldn't properly dispose
// the SelectMany iterator. See https://github.com/dotnet/corefx/pull/13942.
int expectedCurrent = PlatformDetection.IsFullFramework ? subLength : 0;
Assert.Equal(expectedCurrent, e.Current);
Assert.False(e.MoveNext());
Assert.Equal(expectedCurrent, e.Current);
}