using System; using System.Collections.Generic; using System.Text; namespace Apewer { /// <summary>数组构建器。</summary> public sealed class ArrayBuilder<T> { private T[] _array; private int _capacity; private int _count; private int _step; /// <summary>创建构建程序实例。</summary> /// <param name="step">每次扩容的增量,最小值:1,默认值:256。</param> /// <exception cref="ArgumentNullException"></exception> public ArrayBuilder(int step = 256) { if (step < 1) throw new ArgumentOutOfRangeException(nameof(step)); _step = step; _capacity = step; _count = 0; _array = new T[step]; } private ArrayBuilder(ArrayBuilder<T> old) { _step = old._step; _capacity = old._capacity; _count = old._count; _array = new T[_capacity]; if (_count > 0) Array.Copy(old._array, _array, _count); } /// <summary>获取或设置指定位置的元素,索引器范围为 [0, Length)。</summary> /// <exception cref="ArgumentOutOfRangeException"></exception> public T this[int index] { get { if (index < 0 || index >= _count) throw new ArgumentOutOfRangeException("索引超出了当前数组的范围。"); return _array[index]; } set { if (index < 0 || index >= _count) throw new ArgumentOutOfRangeException("索引超出了当前数组的范围。"); _array[index] = value; } } /// <summary>缓冲区的容量。</summary> public int Capacity { get => _capacity; } /// <summary>当前的元素数量。</summary> public int Length { get => _count; } /// <summary>当前的元素数量。</summary> public int Count { get => _count; } /// <summary>添加元素。</summary> public void Add(T item) { if (_count >= _capacity) { var capacity = _capacity + _step; var array = new T[capacity]; Array.Copy(_array, array, _count); _array = array; } _array[_count] = item; _count++; } /// <summary>添加多个元素。</summary> public void Add(params T[] items) { if (items == null) return; var length = items.Length; if (length < 1) return; if (_capacity - _count < length) { _capacity = _count + length; var temp = new T[_capacity]; Array.Copy(_array, temp, _count); _array = temp; } Array.Copy(items, _array, length); _count += length; } /// <summary>添加多个元素。</summary> public void Add(ICollection<T> items) { if (items == null) return; var length = items.Count; if (length < 1) return; if (_capacity - _count < length) { _capacity = _count + length; var temp = new T[_capacity]; Array.Copy(_array, temp, _count); _array = temp; } items.CopyTo(_array, _count); _count += length; } /// <summary>添加多个元素。</summary> public void Add(IEnumerable<T> items) { if (items == null) return; foreach (var item in items) Add(item); } /// <summary>清空所有元素。</summary> public void Clear() { _capacity = 0; _count = 0; _array = new T[0]; } // 修剪数组,去除剩余空间。 void Trim() { if (_count == 0) { if (_capacity > 0) { _capacity = 0; _array = new T[0]; } return; } if (_count == _capacity) return; var array = new T[_count]; Array.Copy(_array, array, _count); _capacity = _count; } /// <summary></summary> /// <param name="clear"></param> /// <returns></returns> public T[] Export(bool clear = false) { if (_count == 0) return new T[0]; if (_count == _capacity) return _array; var array = new T[_count]; Array.Copy(_array, array, _count); return array; } /// <summary>克隆当前实例,生成新实例。</summary> public ArrayBuilder<T> Clone() => new ArrayBuilder<T>(this); /// <summary>使用 Export 方法实现从 ArrayBuilder<T> 到 T[] 的隐式转换。</summary> public static implicit operator T[](ArrayBuilder<T> instance) => instance == null ? null : instance.Export(); } }