文本二叉树折半查询及其截取值

using System;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Collections;
using System.IO;
namespace CS_ScanSample1
{
/// <summary>
/// Logic 的摘要说明。
/// </summary>
public class Logic
{
  /// <summary>
  /// 从排序文本中查找指定关键字的行
  /// </summary>
  /// <param name="path">路径</param>
  /// <param name="keyString">关键字</param>
  /// <param name="rowLength">一行的长度</param>
  /// <param name="keyStart">开始位置</param>
  /// <param name="keyLength">取的长度</param>
  public static DataTable Find(string path, string keyString, int rowLength, int keyStart, int keyLength)
  {
   DataTable ddt=new DataTable();
   ddt.Columns.Add("Titlex");
   ddt.Columns.Add("BookNum");
   long s = DateTime.Now.Ticks;

ArrayList list = new ArrayList();
   FileStream fs = File.Open(path, FileMode.Open, FileAccess.Read);
   long fileLength = fs.Length;
   int recCount = (int)(fileLength / rowLength);
   int recStart = 0;
   int recEnd = recCount;
   string rowKeyString;
   int curRowNo = 0;
   int result;
   curRowNo = (recStart + recEnd) / 2;
   int seekCount = 0;
      byte[] rowBytes;

do
   {
    seekCount++;
    rowBytes = ReadRow(fs, curRowNo, rowLength);
    rowKeyString = Encoding.Default.GetString(rowBytes, keyStart, keyLength).Trim();
    result = rowKeyString.CompareTo(keyString);
    if (result == 0)
    {
     // 提取该记录前后相同的数据
     int recMore = curRowNo;
     do
     {
     // list.Add(Encoding.Default.GetString(rowBytes));
      ddt = InStrOutTable(Encoding.Default.GetString(rowBytes,0,rowBytes.Length),ddt);
      recMore++;

rowBytes = ReadRow(fs, recMore, rowLength);
rowKeyString = Encoding.Default.GetString(rowBytes, keyStart, keyLength).Trim();
result = rowKeyString.CompareTo(keyString);

} while (result == 0 && recMore <= recCount);
     recMore = curRowNo - 1;
     do
     {
      rowBytes = ReadRow(fs, recMore, rowLength);
      rowKeyString = Encoding.Default.GetString(rowBytes, keyStart, keyLength).Trim();
      result = rowKeyString.CompareTo(keyString);
      recMore--;
      if (result == 0)
      {
      // list.Add(Encoding.Default.GetString(rowBytes));
       ddt = InStrOutTable( Encoding.Default.GetString(rowBytes,0,rowBytes.Length),ddt);
      }

} while (result == 0 && recMore >= 0);
     break;
    }
    else if (result > 0)    // 当前记录Key大于要查找的Key，则向前查找
    {
     if (recEnd <= recStart) break;
     recEnd = curRowNo - 1;
    }
    else                    // 当前记录Key小于要查找的Key，则向后查找
    {
     if (recStart >= recEnd) break;
     recStart = curRowNo + 1;
    }
    curRowNo = (recStart + recEnd) / 2;
   } while (true);

fs.Close();
long e = DateTime.Now.Ticks;
//Console.WriteLine("Time={0},Times={1}", TimeSpan.FromTicks(e - s), seekCount);

return ddt;
   // return list;

  }

private static byte[] ReadRow(FileStream fs, int recno, int rowLength)
  {

   byte[] rowBytes = new byte[rowLength - 2];
   if(recno <0) return rowBytes;
   int position = recno * rowLength;
   fs.Seek(position, SeekOrigin.Begin);
   fs.Read(rowBytes, 0, rowLength - 2);
   return rowBytes;
  }
  public static DataTable InStrOutTable( string arowStr,DataTable Dt)
  {
   string ztm = MySubstring(arowStr, 20, 60).Trim().Replace("'", "’");
   int fbs = Convert.ToInt32((MySubstring(arowStr, 120, 10).Trim().Replace("'", "’")=="") ? "0" :MySubstring(arowStr, 120, 10).Trim().Replace("'", "’"));
   return InputDataTable( ztm, fbs,Dt);

}

/// <summary>
  /// 把一行加入DataTable里
  /// </summary>
  /// <param name="ZykDt1">DataTable</param>
  /// <param name="idxstr">IdxStr</param>
  /// <param name="Titlexstr">Title</param>
  /// <param name="booknumstr">nCopies</param>
  /// <returns></returns>
  private static DataTable InputDataTable( string Titlexstr, int booknumstr,DataTable ZykDt1)
  {

string Titlex = Titlexstr;
   int BookNum = booknumstr;
   DataRow row = ZykDt1.NewRow();
   row["Titlex"] = Titlex;
   row["BookNum"] = BookNum;
   ZykDt1.Rows.Add(row);
   return ZykDt1;

}
  /// <summary>
  /// 取字符
  /// </summary>
  /// <param name="string1">字符串</param>
  /// <param name="start">开始位置</param>
  /// <param name="length">长度</param>
  /// <returns></returns>
  private static string MySubstring(string string1, int start, int length)
  {

if (string1 == "" || string1 == null)
   {
    return "";
   }
   else
   {
    byte[] s = Encoding.Default.GetBytes(string1);
    if (s.Length >= start + length)
    {
     return Encoding.Default.GetString(s, start, length);
    }
    else
    {
     if (s.Length > start)
     {
      return Encoding.Default.GetString(s, start, s.Length - start);
     }
     else
     {
      return "";
     }
    }
   }

}

}
}

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