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using System;
using System.Collections.Generic;
using System.Text;
namespace Apewer
{
/// <summary>数组构建器。</summary>
public 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>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>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);
}
}