public void DoWriter(Stream stream, Encoding encoding) {

     if (_data == null || _data.Count == )

         return;

     BinaryWriter bw = new BinaryWriter(stream, encoding);

     //设置偏移量在开头预留写入NumberInfoCompress的总数

     this.WriteCount(bw, , _phoneInfoCompressCount);

     //设置偏移量在开头预留号码类型的总数

     this.WriteCount(bw, , );

     //先读取第一条号码数据

     var enumerator = this._data.GetEnumerator();

     if (!enumerator.MoveNext())

         return;

     //为什么要预先读取一条数据呢？获取第一条数据是为了和下一条进行对比

     var phoneInfo = enumerator.Current;

     //增加城市信息，并且返回集合所在索引位置

     var cityIdx = this.AddCity(phoneInfo.City);

     //增加号码类型信息，并且返回集合所在索引位置

     var cardIdx = this.AddCard(phoneInfo.CardType);

     //构造一个8字节存储的结构体

     var pre = new NumberInfoCompress(phoneInfo.Code, , cityIdx, cardIdx);

     while (enumerator.MoveNext()) {

         //读取下一条数据，准备和上一条比较

         phoneInfo = enumerator.Current;

         cityIdx = this.AddCity(phoneInfo.City);

         cardIdx = this.AddCard(phoneInfo.CardType);

         //和上个号码对比是否连续的，比如 1370875 1370876 1370877。

         //1370875开头有3个，表示13708 375:从75开始有3个连续的号码

         if (phoneInfo.Code - (pre.GetBegin() + pre.GetSkip()) ==  && cityIdx == pre.GetCityIndex()) {

             //设置号码段连续位置

             pre.SetSkip((ushort)(phoneInfo.Code - pre.GetBegin()));

         } else {

             //递增一个

             ++_phoneInfoCompressCount;

             //写入13708号码段的数据

             this.Write(bw, pre);

             //继续构造一个8字节存储的结构体等待下次循环比较

             pre = new NumberInfoCompress(phoneInfo.Code, , cityIdx, cardIdx);

         }

     }

     //写入最后的号码数据

     this.Write(bw, pre);

     ++_phoneInfoCompressCount;//记录总数

     //写入NumberInfoCompress的总数

     this.WriteCount(bw, , _phoneInfoCompressCount);

     //写入号码类型的总数

     this.WriteCount(bw, , (uint)(_listCard.Count));

     //结尾写入城市地区数据

     this.WriteCity(bw, encoding);

     //结尾写入号码类型数据

     this.WriteCard(bw, encoding);

     bw.Close();

     bw.Dispose();

 }

 public PhoneInfo GetPhoneInfo(Stream stream, Encoding encoding, int number) {

     PhoneInfo result = new PhoneInfo();

     result.Code = number;

     BinaryReader br = new BinaryReader(stream, encoding);

     //获取索引总数

     int phoneInfoCompressCount = br.ReadInt32();

     //号码类型总数

     int cardCount = br.ReadInt32();

     int left = , right = phoneInfoCompressCount - ;

     var per = new NumberInfoCompress();

     var perSize = Marshal.SizeOf(per);

     //使用折半查询（二分法）

     while (left <= right) {

         //折半

         int middle = (left + right) / ;

         //索引总数8字节 + middle * NumberInfoCompress字节数

         stream.Position = sizeof(int) *  + middle * perSize;

         //读取NumberInfoCompress数据

         per.Before = br.ReadUInt16();

         per.After = br.ReadUInt16();

         per.CityIndex = br.ReadUInt16();

         per.CardIndex = br.ReadUInt16();

         //判断号码是否匹配

         if (number < per.GetBegin()) {

             right = middle - ;//在左半区间找

         } else if (number > (per.GetBegin() + per.GetSkip())) {

             left = middle + ;//在右半区间找

         } else {

             //已找到，直接查询城市和号码类型

             result.City = DoFindCityThing(br, phoneInfoCompressCount, per);

             result.CardType = DoFindCardThing(br, cardCount, per);

             return result;

         }

     }

     br.Close();

     br.Dispose();

     return result;

 }

 private string DoFindCityThing(BinaryReader br, int phoneInfoCompressCount, NumberInfoCompress infoMiddle) {

     //计算城市区域信息位置

     //sizeof(int) * 2 开头位置储存了一个4字节的NumberInfoCompress总数和类型总数

     //phoneInfoCompressCount NumberInfoCompress总数

     //Marshal.SizeOf(infoMiddle) NumberInfoCompress占用空间

     //infoMiddle.GetCityIndex() 城市的所在位置

     //_maxCityLength 城市总数

     //偏移量 = 索引总数8字节 + 索引总数 * NumberInfoCompress字节数 + 城市的所在位置 * 城市大小

     long totalOffset = sizeof(int) *  + phoneInfoCompressCount * Marshal.SizeOf(infoMiddle)

         + infoMiddle.GetCityIndex() * this._maxCityLength;

     br.BaseStream.Position = totalOffset;//设置偏移量

     char[] charCity = br.ReadChars(this._maxCityLength);

     return new string(charCity, , Array.IndexOf(charCity, '\0'));

 }

 private string DoFindCardThing(BinaryReader br, int cardCount, NumberInfoCompress infoMiddle) {

     //号码类型存储在尾端

     //所以偏移量 = （流的总长度 - 类型总数 * 类型大小） + 所在位置 * 类型大小

     long totalOffset = (br.BaseStream.Length - cardCount * this._maxCardLength) + infoMiddle.GetCardIndex() * this._maxCardLength;

     br.BaseStream.Position = totalOffset;//设置偏移量

     char[] charCard = br.ReadChars(this._maxCardLength);

     return new string(charCard, , Array.IndexOf(charCard, '\0'));

 }