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List Clear+Remove #9540

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jkotas merged 3 commits into from
Feb 12, 2017
Merged

List Clear+Remove #9540

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8bd9545
List Clear+Remove
benaadams Feb 12, 2017
8f00485
Tail call Array.Clear
benaadams Feb 12, 2017
ac68ad3
Only Array.Clear List for ref types
benaadams Feb 12, 2017
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49 changes: 35 additions & 14 deletions src/mscorlib/src/System/Collections/Generic/List.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,14 +12,13 @@
**
**
===========================================================*/
namespace System.Collections.Generic {

namespace System.Collections.Generic
{
using System;
using System.Runtime;
using System.Runtime.Versioning;
using System.Diagnostics;
using System.Diagnostics.Contracts;
using System.Collections.ObjectModel;
using Runtime.CompilerServices;

// Implements a variable-size List that uses an array of objects to store the
// elements. A List has a capacity, which is the allocated length
Expand Down Expand Up @@ -291,13 +290,23 @@ public int BinarySearch(T item, IComparer<T> comparer)


// Clears the contents of List.
public void Clear() {
if (_size > 0)
public void Clear()
{
if (JitHelpers.ContainsReferences<T>())
{
Array.Clear(_items, 0, _size); // Don't need to doc this but we clear the elements so that the gc can reclaim the references.
int size = _size;
_size = 0;
_version++;
if (size > 0)
{
Array.Clear(_items, 0, size); // Clear the elements so that the gc can reclaim the references.
}
}
else
{
_size = 0;
_version++;
}
_version++;
}

// Contains returns true if the specified element is in the List.
Expand Down Expand Up @@ -852,9 +861,13 @@ public int RemoveAll(Predicate<T> match) {
// copy item to the free slot.
_items[freeIndex++] = _items[current++];
}
}

Array.Clear(_items, freeIndex, _size - freeIndex);
}

if (JitHelpers.ContainsReferences<T>())
{
Array.Clear(_items, freeIndex, _size - freeIndex); // Clear the elements so that the gc can reclaim the references.
}

int result = _size - freeIndex;
_size = freeIndex;
_version++;
Expand All @@ -870,10 +883,14 @@ public void RemoveAt(int index) {
}
Contract.EndContractBlock();
_size--;
if (index < _size) {
if (index < _size)
{
Array.Copy(_items, index + 1, _items, index, _size - index);
}
_items[_size] = default(T);
if (JitHelpers.ContainsReferences<T>())
{
_items[_size] = default(T);
}
_version++;
}

Expand All @@ -898,8 +915,12 @@ public void RemoveRange(int index, int count) {
if (index < _size) {
Array.Copy(_items, index + count, _items, index, _size - index);
}
Array.Clear(_items, _size, count);

_version++;
if (JitHelpers.ContainsReferences<T>())
{
Array.Clear(_items, _size, count);
}
}
}

Expand Down