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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
namespace System
{
internal sealed class ArrayEnumerator : IEnumerator, ICloneable
{
private Array array;
private int index;
private int endIndex;
private int startIndex; // Save for Reset.
private int[] _indices; // The current position in a multidim array
private bool _complete;
internal ArrayEnumerator(Array array, int index, int count)
{
this.array = array;
this.index = index - 1;
startIndex = index;
endIndex = index + count;
_indices = new int[array.Rank];
int checkForZero = 1; // Check for dimensions of size 0.
for (int i = 0; i < array.Rank; i++)
{
_indices[i] = array.GetLowerBound(i);
checkForZero *= array.GetLength(i);
}
// To make MoveNext simpler, decrement least significant index.
_indices[_indices.Length - 1]--;
_complete = (checkForZero == 0);
}
private void IncArray()
{
// This method advances us to the next valid array index,
// handling all the multiple dimension & bounds correctly.
// Think of it like an odometer in your car - we start with
// the last digit, increment it, and check for rollover. If
// it rolls over, we set all digits to the right and including
// the current to the appropriate lower bound. Do these overflow
// checks for each dimension, and if the most significant digit
// has rolled over it's upper bound, we're done.
//
int rank = array.Rank;
_indices[rank - 1]++;
for (int dim = rank - 1; dim >= 0; dim--)
{
if (_indices[dim] > array.GetUpperBound(dim))
{
if (dim == 0)
{
_complete = true;
break;
}
for (int j = dim; j < rank; j++)
_indices[j] = array.GetLowerBound(j);
_indices[dim - 1]++;
}
}
}
public object Clone()
{
return MemberwiseClone();
}
public bool MoveNext()
{
if (_complete)
{
index = endIndex;
return false;
}
index++;
IncArray();
return !_complete;
}
public object? Current
{
get
{
if (index < startIndex) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
if (_complete) ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
return array.GetValue(_indices);
}
}
public void Reset()
{
index = startIndex - 1;
int checkForZero = 1;
for (int i = 0; i < array.Rank; i++)
{
_indices[i] = array.GetLowerBound(i);
checkForZero *= array.GetLength(i);
}
_complete = (checkForZero == 0);
// To make MoveNext simpler, decrement least significant index.
_indices[_indices.Length - 1]--;
}
}
internal sealed class SZArrayEnumerator : IEnumerator, ICloneable
{
private readonly Array _array;
private int _index;
private int _endIndex; // Cache Array.Length, since it's a little slow.
internal SZArrayEnumerator(Array array)
{
Debug.Assert(array.Rank == 1 && array.GetLowerBound(0) == 0, "SZArrayEnumerator only works on single dimension arrays w/ a lower bound of zero.");
_array = array;
_index = -1;
_endIndex = array.Length;
}
public object Clone()
{
return MemberwiseClone();
}
public bool MoveNext()
{
if (_index < _endIndex)
{
_index++;
return (_index < _endIndex);
}
return false;
}
public object? Current
{
get
{
if (_index < 0)
ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumNotStarted();
if (_index >= _endIndex)
ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumEnded();
return _array.GetValue(_index);
}
}
public void Reset()
{
_index = -1;
}
}
internal sealed class SZGenericArrayEnumerator<T> : IEnumerator<T>
{
private readonly T[] _array;
private int _index;
// Array.Empty is intentionally omitted here, since we don't want to pay for generic instantiations that
// wouldn't have otherwise been used.
internal static readonly SZGenericArrayEnumerator<T> Empty = new SZGenericArrayEnumerator<T>(new T[0]);
internal SZGenericArrayEnumerator(T[] array)
{
Debug.Assert(array != null);
_array = array;
_index = -1;
}
public bool MoveNext()
{
int index = _index + 1;
if ((uint)index >= (uint)_array.Length)
{
_index = _array.Length;
return false;
}
_index = index;
return true;
}
public T Current
{
get
{
int index = _index;
T[] array = _array;
if ((uint)index >= (uint)array.Length)
{
ThrowHelper.ThrowInvalidOperationException_EnumCurrent(index);
}
return array[index];
}
}
object? IEnumerator.Current => Current;
void IEnumerator.Reset() => _index = -1;
public void Dispose()
{
}
}
}
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