cstring.cs

短信网关的应用开发

using System;
using System.Collections.Generic;
using System.Text;

namespace SMPP.Variable
{
	/// <summary>
	/// 定长字符串类型
	/// 有两种可能的长度：一个字节的0x00（即空字符串）或固定长度的以NULL结尾的字符串
	/// </summary>
	public class CString : Variable
	{
		/// <summary>
		/// 保存的真实数据
		/// </summary>
		protected byte[] _Value = new byte[1];

		private int FixedLength = 1;

		public override int Length
		{
			get
			{
				return _Value.Length;
			}
		}

		private System.Text.Encoding Encoding = System.Text.Encoding.ASCII;

		public string Value
		{
			get
			{
				if (_Value.Length == 0)
					return "";
				else
				{
					return Encoding.GetString(_Value, 0, Array.IndexOf(_Value, (byte)0));
				}
			}
			set
			{
				if (value == null || value == "" || Encoding.GetByteCount(value) != FixedLength - 1)
				{//如果值为空或者空字符串，或者长度不能匹配到固定长度（FixedLength - 1是为了留出最后一个字节的NULL空间）
					_Value = new byte[1];
					_Value[0] = 0;
				}
				else
				{
					_Value = new byte[FixedLength];

					byte[] data = Encoding.GetBytes(value);

					Array.Clear(_Value, 0, FixedLength);
					Array.Copy(data, _Value, data.Length);
				}
			}
		}

		public override void Parse(byte[] Datas, ref int Index)
		{
			int index = Array.IndexOf(Datas, (byte)0, Index);

			if (index == -1)
				throw new Exception("没有找到以NULL结尾的串");

			if (index - Index == 0)
			{
				Value = "";
				Index++;
			}
			else
			{
				if (index - Index != FixedLength - 1)
					throw new Exception("串长度不正确");

				_Value = new byte[FixedLength];
				Array.Copy(Datas, Index, _Value, 0, FixedLength);

				Index = index + 1;
			}
		}

		public override byte[] GetBytes()
		{
			byte[] ret = new byte[_Value.Length];

			Array.Copy(_Value, ret, ret.Length);

			return ret;
		}

		public CString(int Length)
		{
			FixedLength = Length;
		}

		public CString(int Length, System.Text.Encoding Encoding)
		{
			FixedLength = Length;
			this.Encoding = Encoding;
		}
	}
}