C#统计文本文件中的行数，用3中方法对一个300k 的文件进行统计的结果

青旅半醒 2024-02-17 17:48 14阅读 0赞

统计文本文件中的行数，用3中方法对一个300k 的文件进行统计的结果：  
第一次：  
StreamReader.Read()：共2761行,耗时：6.08  
FileStream.Read()：共2761行,耗时：11.23  
StreamReader.ReadLine()：共2761行,耗时：3.61  
第二次：  
StreamReader.Read()：共2761行,耗时：8.87  
FileStream.Read()：共2761行,耗时：14.74  
StreamReader.ReadLine()：共2761行,耗时：4.14  
第三次：  
StreamReader.Read()：共2761行,耗时：6.39  
FileStream.Read()：共2761行,耗时：14.1  
StreamReader.ReadLine()：共2761行,耗时：4.76

本以为 StreamReader.ReadLine() 方法统计会很慢，结果.....。如果有快速统计算法分享下

http://blog.csdn.net/xxj\_jing/article/details/52063883

测试代码如下：

using Microsoft.VisualStudio.TestTools.UnitTesting;
    using System;
    using System.Diagnostics;
    using System.IO;
    using System.Linq;
    using System.Text;
    
    namespace TestGrass.Log
    {
        [TestClass]
        public class TestTxtRead
        {
            public string _minFile = @"D:\temp\logs\***.txt";
            public string _maxFile = @"D:\temp\logs\***.log";
            /// <summary>
            /// 回车符 \n=13=0x0D
            /// </summary>
            public byte _enter = 0x0D;
            /// <summary>
            /// 换行符 \r=10=0x0A
            /// </summary>
            public byte _return = 0x0A;
            [TestMethod]
            public void TestStream()
            {
                /*
                 * 读取300k文件耗时
                 * StreamReader.Read() 用时 8.19s
                 * FileStream.Read() 用时
                 * StreamReader.ReadLine() 用时 2.83s
                 */
                byte n = 0xD;
                byte r = 0xA;
                StringBuilder msg = new StringBuilder();
                Stopwatch sw = new Stopwatch();
                var path = _minFile;
                int lines1 = 0;
                int lines2 = 0;
                int lines3 = 0;
                //单个字符读取
                sw.Start();
                using (var sr = new StreamReader(path))
                {
                    int val = 0;
                    val = sr.Read();
                    //while ((val=sr.Read()) != -1)
                    while(val!=-1)
                    {
                        if (val == n)
                            lines1++;
                        val = sr.Read();
                    }
                }
                sw.Stop();
                msg.AppendLine(string.Format("StreamReader.Read()：共{0}行,耗时：{1}"
                    ,lines1
                    ,Math.Round(sw.ElapsedTicks*1.0/1000,2)));
    
    
                //使用缓冲读取
                Action<byte[]> totalizer = (arr)=>
                {
                    lines2 += arr.Count(x => { return x == n; });
                };
                sw.Restart();
                
                using (var fs = new FileStream(path,FileMode.Open))
                {
                    var buffer = new byte[1024];
                    var rc = fs.Read(buffer, 0, buffer.Length);
                    totalizer(buffer);
                    
                    while (rc!=0)
                    {
                        buffer = new byte[1024];
                        rc = fs.Read(buffer, 0, buffer.Length);
                        totalizer(buffer);
                    }
                }
                sw.Stop();
                msg.AppendLine(string.Format("FileStream.Read()：共{0}行,耗时：{1}"
                    , lines2
                    , Math.Round(sw.ElapsedTicks * 1.0 / 1000, 2)));
    
                //按行读取
                sw.Restart();
                using (var sr = new StreamReader(path))
                {
                    var ls = "";
                    while ((ls=sr.ReadLine()) != null)
                    {
                        lines3++;
                    }
                }
                sw.Stop();
                msg.AppendLine(string.Format("StreamReader.ReadLine()：共{0}行,耗时：{1}"
                    , lines3
                    , Math.Round(sw.ElapsedTicks * 1.0 / 1000, 2)));
                string str = msg.ToString();
                Assert.IsTrue(true);
            }
        }
    
    }