form1.cs

简单介绍base64,UTF8编码解码原理

using System;
using System.IO;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Text;

namespace Base64example
{
	/// <summary>
	/// Form1 的摘要说明。
	/// </summary>
	public class Form1 : System.Windows.Forms.Form
	{
		private System.Windows.Forms.Button button1;
		/// <summary>
		/// 必需的设计器变量。
		/// </summary>
		private System.ComponentModel.Container components = null;

		public Form1()
		{
			//
			// Windows 窗体设计器支持所必需的
			//
			InitializeComponent();

			//
			// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
			//
		}

		/// <summary>
		/// 清理所有正在使用的资源。
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows 窗体设计器生成的代码
		/// <summary>
		/// 设计器支持所需的方法 - 不要使用代码编辑器修改
		/// 此方法的内容。
		/// </summary>
		private void InitializeComponent()
		{
			this.button1 = new System.Windows.Forms.Button();
			this.SuspendLayout();
			// 
			// button1
			// 
			this.button1.Location = new System.Drawing.Point(192, 144);
			this.button1.Name = "button1";
			this.button1.TabIndex = 0;
			this.button1.Text = "button1";
			this.button1.Click += new System.EventHandler(this.button1_Click);
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
			this.ClientSize = new System.Drawing.Size(536, 349);
			this.Controls.Add(this.button1);
			this.Name = "Form1";
			this.Text = "Form1";
			this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		/// 应用程序的主入口点。
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}

		//将gb2312转成base64
		private String tobase64(String source)
		{
			
			byte [] buf = Encoding.GetEncoding(936).GetBytes(source);
			char [] cBase = {'A', 'B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T',
								'U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m',
								'n','o','p','q','r','s','t','u','v','w','x','y','z','0','1',
								'2','3','4','5','6','7','8','9','+','/'};

			String szStr = Convert.ToBase64String( buf);
			String Result="";
			int ntmp;
			for ( int n = 0; n < buf.Length;)
			{
				#region 填充代码
				if ( buf.Length - n  == 2)
				{
					ntmp = (0xfc & buf[n]) >> 2;
					Result = String.Format("{0}{1}", Result, cBase[ntmp]);
					ntmp = ((0x03 & buf[n]) << 4) | (buf[n+1] >> 4) ;
					Result = String.Format("{0}{1}", Result, cBase[ntmp]);
					ntmp = (0x0f & buf[n+1]) << 2;
					Result = String.Format("{0}{1}=", Result, cBase[ntmp]);
					break;
				}
				if ( buf.Length - n  == 1)
				{
					ntmp = (0xfc & buf[n]) >> 2;
					Result = String.Format("{0}{1}", Result, cBase[ntmp]);
					ntmp = ((0x03 & buf[n]) << 4) ;
					Result = String.Format("{0}{1}==", Result, cBase[ntmp]);
					break;
				}
				#endregion

				ntmp = (0xfc & buf[n]) >> 2;
				Result = String.Format("{0}{1}", Result, cBase[ntmp]);
				ntmp = ((0x03 & buf[n]) << 4) | (buf[n+1] >> 4) ;
				Result = String.Format("{0}{1}", Result, cBase[ntmp]);
				ntmp = ((0x0f & buf[n+1]) << 2) | ((0xc0 & buf[n+2]) >> 6);
				Result = String.Format("{0}{1}", Result, cBase[ntmp]);
				ntmp = (0x3f & buf[n+2]);
				Result = String.Format("{0}{1}", Result, cBase[ntmp]);

				n += 3;
			}


			return Result;
			
		
		}


		//将base64转成gb2312
		private String frombase64(String Source)
		{
			char [] buf = Source.ToCharArray();
			String szBase = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
			MemoryStream sb=new MemoryStream();

			byte btmp;
			for (int n = 0; n < buf.Length; )
			{
				#region 填充代码
				if (buf.Length - n == 4)
				{
					if ('=' == buf[n+2])
					{
						btmp = (byte)(((szBase.IndexOf(buf[n]) << 2) | ((szBase.IndexOf(buf[n+1]) & 0x30) >> 4)));
						sb.WriteByte(btmp);
						break;
					}
					if ('=' == buf[n+3])
					{
						btmp = (byte)(((szBase.IndexOf(buf[n]) << 2) | ((szBase.IndexOf(buf[n+1]) & 0x30) >> 4)));
						sb.WriteByte(btmp);
						btmp = (byte)((szBase.IndexOf(buf[n+1]) & 0x0f) << 4 | ((szBase.IndexOf(buf[n+2]) & 0x3c) >> 2));
						sb.WriteByte(btmp);
						break;
					}
				}
				#endregion
				btmp = (byte)(((szBase.IndexOf(buf[n]) << 2) | ((szBase.IndexOf(buf[n+1]) & 0x30) >> 4)));
				sb.WriteByte(btmp);
				btmp = (byte)((szBase.IndexOf(buf[n+1]) & 0x0f) << 4 | ((szBase.IndexOf(buf[n+2]) & 0x3c) >> 2));
				sb.WriteByte(btmp);
				btmp = (byte)(((szBase.IndexOf(buf[n+2]) & 0x03) << 6) | szBase.IndexOf(buf[n+3]));
				sb.WriteByte(btmp);

				n += 4;
			}
			return Encoding.GetEncoding(936).GetString(sb.ToArray());
		
		}


		//转成utf8
		private byte[] toutf8(String source)
		{
			StringBuilder buf = new StringBuilder(source);

			byte [] dest = Encoding.UTF8.GetBytes(source);
			MemoryStream sb=new MemoryStream();

			for ( int n = 0; n < buf.Length; n++)
			{
				if (0x7F >= buf[n])
					sb.WriteByte((byte)buf[n]);
				else if (buf[n] <= 0x07ff)
				{
					sb.WriteByte((byte)(((buf[n] & 0x7c0) >> 6) | 0xc0));
					sb.WriteByte((byte)((buf[n] & 0x3f) | 0x80));
				}
				else if (buf[n] <= 0xffff)
				{
					sb.WriteByte((byte)(((buf[n] & 0xf000) >> 12) | 0xe0));
					sb.WriteByte((byte)(((buf[n] & 0xfc0) >> 6) | 0x80));
					sb.WriteByte((byte)((buf[n] & 0x3f) | 0x80));
				}
			}
			return sb.ToArray();
		}


		
		private void button1_Click(object sender, System.EventArgs e)
		{
			//String base64 = tobase64("测试工！");
			//String gb2312 = frombase64(base64);
			byte [] utf8 = toutf8("as测sa试！");
			

		}
	}
}