63 lines
1.8 KiB
C#
63 lines
1.8 KiB
C#
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namespace Azusa.Shared.Extensions;
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/// <summary>
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/// 使用Range作为参数的迭代器方法
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/// <br/>
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/// 扩展foreach关键字来实现类似<c>foreach (var i in 1..5)</c>的效果
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/// </summary>
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public static class ForeachExtensions
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{
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/// <summary>
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/// 拓展Range结构实现GetEnumerator方法供foreach读取，实现foreach(var i in x..y)
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/// </summary>
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/// <returns></returns>
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public static CustomIntEnumerator GetEnumerator(this Range range)
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{
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return new CustomIntEnumerator(range);
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}
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/// <summary>
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/// 拓展int类实现GetEnumerator方法供foreach读取，实现foreach(var i in x)
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/// </summary>
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/// <param name="end"></param>
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/// <returns></returns>
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public static CustomIntEnumerator GetEnumerator(this int end)
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{
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return new CustomIntEnumerator(end);
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return new CustomIntEnumerator(new Range(0, end));//在执行空函数时性能比上一句低10倍，Why
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}
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}
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//使用引用结构体增强性能
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public ref struct CustomIntEnumerator
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{
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private int _current;
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private readonly int _end;
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public CustomIntEnumerator(Range range)
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{
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//避免某些时候从结尾开始编制
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// x.. 时会产生Range(x,^0)
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if (range.End.IsFromEnd)
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{
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throw new NotSupportedException("不支持从结尾编制索引");
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}
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_current = range.Start.Value - 1;
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_end = range.End.Value - 1;//迭代器不包含范围的尾部
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}
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public CustomIntEnumerator(int end)
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{
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_current = -1;
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_end = end;
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}
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/* 注意，供foeach使用的迭代器不需要实现IEnumerator接口，只需要提供Current属性以及MoveNext方法即可，*/
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public int Current => _current;
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public bool MoveNext()
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{
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_current++;
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return _current <= _end;
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}
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}
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