/
Range.cs
75 lines (63 loc) · 2.11 KB
/
Range.cs
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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.
using System.Collections.Generic;
using System.Diagnostics;
namespace System.Linq
{
public static partial class Enumerable
{
public static IEnumerable<int> Range(int start, int count)
{
long max = ((long)start) + count - 1;
if (count < 0 || max > int.MaxValue)
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.count);
}
if (count == 0)
{
return Empty<int>();
}
return new RangeIterator(start, count);
}
/// <summary>
/// An iterator that yields a range of consecutive integers.
/// </summary>
[DebuggerDisplay("Count = {CountForDebugger}")]
private sealed partial class RangeIterator : Iterator<int>
{
private readonly int _start;
private readonly int _end;
public RangeIterator(int start, int count)
{
Debug.Assert(count > 0);
_start = start;
_end = unchecked(start + count);
}
private int CountForDebugger => _end - _start;
public override Iterator<int> Clone() => new RangeIterator(_start, _end - _start);
public override bool MoveNext()
{
switch (_state)
{
case 1:
Debug.Assert(_start != _end);
_current = _start;
_state = 2;
return true;
case 2:
if (unchecked(++_current) == _end)
{
break;
}
return true;
}
_state = -1;
return false;
}
public override void Dispose()
{
_state = -1; // Don't reset current
}
}
}
}