using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication10
{
    class Program//总之就是问题多多，求抱大腿，看了几小时了
    {
        static void Main(string[] args)
        {
            FileStream fs = new CzCryptStream("EncyptLetter.txt", FileMode.Create, "rose");//rose是干什么的，这个txt会被创建出来吗
            StreamWriter sw = new StreamWriter(fs);
            sw.WriteLine("this is a letter from hollywood.外公家");
            sw.Close();
            fs = new FileStream("EncyptLetter.txt", FileMode.Open);
            StreamReader sr = new StreamReader(fs);
            Console.WriteLine("加密文件内容：");
            while (!sr.EndOfStream)
                Console.WriteLine(sr.ReadLine());
            sr.Close();
            fs = new CzCryptStream("EncyptLetter.txt", FileMode.Open,"rose");
            sr = new StreamReader(fs);
            Console.WriteLine("\n解密文件内容：");
            while(!sr.EndOfStream)
               Console.WriteLine(sr.ReadLine());
            sr.Close();
            fs.Close();
        }
    }
    public class CzCryptStream : FileStream
    {
        private byte[] mkey;
        public CzCryptStream(string spath, FileMode fmode, string skey)//fmode干嘛吃的？各种搞不懂啊！
            : base(spath, fmode)
        {
            mkey = new byte[skey.Length];
            for (int i = 0; i < skey.Length; i++)
                mkey[i] = (byte)skey[i];
        }
        public override int ReadByte()
        {
            return base.ReadByte() ^ mkey[this.Position % mkey.Length];//Position我问度娘还是不知道什么意思啊，求解
        }
        public override void WriteByte(byte value)//这么多事件，主方法里没见调用，这是为什么？
        {
            value ^= mkey[this.Position % mkey.Length];
            base.WriteByte(value);
        }
        public override int Read(byte[] buffer, int offset, int count)
        {
            int iLen= base.Read(buffer, offset, count);
            for (int i = 0; i < iLen; i++)
            {
                buffer[i]^=mkey[(offset+i)%mkey.Length];
            }
            return iLen;
        }
        public override void Write(byte[] buffer, int offset, int count)
        {
            for (int i = 0; i < buffer.Length; i++)
            {
                buffer[i] ^= mkey[(offset + i) % mkey.Length];
            }
            base.Write(buffer, offset, count);
        }

    }
}