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Fix List<T> to ListView<T> casting bug on .NET Framework #110

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Fix List<T> to ListView<T> casting bug on .NET Framework #110

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121 changes: 79 additions & 42 deletions src/ObservableCollections/Shims/Collections.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,70 +45,107 @@ public static void AddRange<T>(this List<T> list, ReadOnlySpan<T> source)
{
if (!source.IsEmpty)
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.ListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view, checked(view._size + source.Length));
if (!CollectionsMarshal.IsLegacyList)
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.ListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view._items, view._size, checked(view._size + source.Length));
}

source.CopyTo(view._items.AsSpan(view._size));
view._size += source.Length;
view._version++;
}
else
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.LegacyListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view._items, view._size, checked(view._size + source.Length));
}

source.CopyTo(view._items.AsSpan(view._size));
view._size += source.Length;
view._version++;
}

source.CopyTo(view._items.AsSpan(view._size));
view._size += source.Length;
view._version++;
}
}

// CollectionExtensions.InsertRange
public static void InsertRange<T>(this List<T> list, int index, ReadOnlySpan<T> source)
{
if (!source.IsEmpty)
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.ListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view, checked(view._size + source.Length));
{
if (!CollectionsMarshal.IsLegacyList)
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.ListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view._items, view._size, checked(view._size + source.Length));
}

if (index < view._size)
{
Array.Copy(view._items, index, view._items, index + source.Length, view._size - index);
}

source.CopyTo(view._items.AsSpan(index));
view._size += source.Length;
view._version++;
}
else
{
ref var view = ref Unsafe.As<List<T>, CollectionsMarshal.LegacyListView<T>>(ref list!);

if (view._items.Length - view._size < source.Length)
{
Grow(ref view._items, view._size, checked(view._size + source.Length));
}

if (index < view._size)
{
Array.Copy(view._items, index, view._items, index + source.Length, view._size - index);
}

source.CopyTo(view._items.AsSpan(index));
view._size += source.Length;
view._version++;
}

if (index < view._size)
{
Array.Copy(view._items, index, view._items, index + source.Length, view._size - index);
}

source.CopyTo(view._items.AsSpan(index));
view._size += source.Length;
view._version++;
}
}

static void Grow<T>(ref CollectionsMarshal.ListView<T> list, int capacity)
}
static void Grow<T>(ref T[] items, int size, int capacity)
{
SetCapacity(ref list, GetNewCapacity(ref list, capacity));
}

static void SetCapacity<T>(ref CollectionsMarshal.ListView<T> list, int value)
SetCapacity(ref items, size, GetNewCapacity(items.Length, capacity));
}
static void SetCapacity<T>(ref T[] items, int size, int capacity)
{
if (value != list._items.Length)
if (capacity != items.Length)
{
if (value > 0)
if (capacity > 0)
{
T[] newItems = new T[value];
if (list._size > 0)
T[] newItems = new T[capacity];
if (size > 0)
{
Array.Copy(list._items, newItems, list._size);
Array.Copy(items, newItems, size);
}
list._items = newItems;
items = newItems;
}
else
{
list._items = Array.Empty<T>();
items = Array.Empty<T>();
}
}
}

static int GetNewCapacity<T>(ref CollectionsMarshal.ListView<T> list, int capacity)
}
static int GetNewCapacity(int length, int capacity)
{
int newCapacity = list._items.Length == 0 ? 4 : 2 * list._items.Length;
int newCapacity = length == 0 ? 4 : 2 * length;

if ((uint)newCapacity > ArrayMaxLength) newCapacity = ArrayMaxLength;

Expand Down
50 changes: 43 additions & 7 deletions src/ObservableCollections/Shims/CollectionsMarshalEx.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,23 +12,59 @@ namespace System.Runtime.InteropServices;

internal static class CollectionsMarshal
{
internal static readonly bool IsLegacyList;

#if NETSTANDARD2_0 || NETSTANDARD2_1
static CollectionsMarshal()
{
int listSize = 0;
try
{
listSize = typeof(List<>).GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance).Length;
}
catch
{
listSize = 3;
}

// In .NET Framework, List<T> has a _syncRoot field, so the number of fields becomes 4.
IsLegacyList = listSize == 4;
}
#endif

/// <summary>
/// similar as AsSpan but modify size to create fixed-size span.
/// </summary>
public static Span<T> AsSpan<T>(List<T>? list)
{
if (list is null) return default;

ref var view = ref Unsafe.As<List<T>, ListView<T>>(ref list!);
return view._items.AsSpan(0, view._size);
}

if (list is null) return default;

if (IsLegacyList)
{
ref var view = ref Unsafe.As<List<T>, LegacyListView<T>>(ref list!);
return view._items.AsSpan(0, list.Count);
}
else
{
ref var view = ref Unsafe.As<List<T>, ListView<T>>(ref list!);
return view._items.AsSpan(0, list.Count);
}
}

internal sealed class ListView<T>
{
public T[] _items;
public int _size;
public int _version;
}

internal sealed class LegacyListView<T>
{
public T[] _items;
public int _size;
public int _version;
public Object _syncRoot; // in .NET Framework
}
}

#endif
#endif
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