fix

MFR/.gitignore

@@ -0,0 +1,265 @@
+# ---> Node
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+*.lcov
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+web_modules/
+
+# TypeScript cache
+*.tsbuildinfo
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Microbundle cache
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+.env.test
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+.parcel-cache
+
+# Next.js build output
+.next
+out
+
+# Nuxt.js build / generate output
+.nuxt
+dist
+
+# Gatsby files
+.cache/
+# Comment in the public line in if your project uses Gatsby and not Next.js
+# https://nextjs.org/blog/next-9-1#public-directory-support
+# public
+
+# vuepress build output
+.vuepress/dist
+
+# Serverless directories
+.serverless/
+
+# FuseBox cache
+.fusebox/
+
+# DynamoDB Local files
+.dynamodb/
+
+# TernJS port file
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+.vscode-test
+
+# yarn v2
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.*
+
+# ---> Node
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage/
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# TypeScript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+
+# parcel-bundler cache (https://parceljs.org/)
+.cache
+
+# next.js build output
+.next
+
+# Serverless directories
+.serverless
+
+# FuseBox cache
+.fusebox/
+
+# Idea files
+.idea
+
+# VSCode files
+.vscode
+
+# DevExpress Code clean
+.cr
+
+# Build results
+[Bb]uild.[Uu]nit[Tt]est/
+[Dd]ebug/
+[Dd]ebugPublic/
+[Rr]elease/
+[Rr]eleases/
+x64/
+x86/
+[Ww][Ii][Nn]32/
+[Aa][Rr][Mm]/
+[Aa][Rr][Mm]64/
+bld/
+[Bb]uild/
+[Bb]in/
+[Oo]bj/
+[Ll]og/
+[Ll]ogs/
+.vs/
+
+# NuGet Packages
+*.nupkg
+# NuGet Symbol Packages
+*.snupkg
+# The packages folder can be ignored because of Package Restore
+**/[Pp]ackages/*
+# except build/, which is used as an MSBuild target.
+!**/[Pp]ackages/build/
+# Uncomment if necessary however generally it will be regenerated when needed
+#!**/[Pp]ackages/repositories.config
+# NuGet v3's project.json files produces more ignorable files
+*.nuget.props
+*.nuget.targets
+
+# Files built by Visual Studio
+*_i.c
+*_p.c
+*_h.h
+*.ilk
+*.meta
+*.obj
+*.iobj
+*.pch
+*.pdb
+*.ipdb
+*.pgc
+*.pgd
+*.rsp
+*.sbr
+*.tlb
+*.tli
+*.tlh
+*.tmp
+*.tmp_proj
+*_wpftmp.csproj
+*.log
+*.vspscc
+*.vssscc
+.builds
+*.pidb
+*.svclog
+*.scc
+*.user
+*.pubxml.user
+FakesAssemblies
+
+package-lock.json

MFR/MFR.sln

@@ -0,0 +1,37 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.3.32929.385
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MFR211", "MFR211\MFR211.csproj", "{E2355FDA-05E6-4F5C-B544-3AE7E1527F97}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MFR212", "MFR212\MFR212.csproj", "{388ABD3C-7D8A-47C2-B60F-5C2E40B7B3BD}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MFR213", "MFR213\MFR213.csproj", "{43900D04-E330-4EFF-990B-709374318002}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{E2355FDA-05E6-4F5C-B544-3AE7E1527F97}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E2355FDA-05E6-4F5C-B544-3AE7E1527F97}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E2355FDA-05E6-4F5C-B544-3AE7E1527F97}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E2355FDA-05E6-4F5C-B544-3AE7E1527F97}.Release|Any CPU.Build.0 = Release|Any CPU
+		{388ABD3C-7D8A-47C2-B60F-5C2E40B7B3BD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{388ABD3C-7D8A-47C2-B60F-5C2E40B7B3BD}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{388ABD3C-7D8A-47C2-B60F-5C2E40B7B3BD}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{388ABD3C-7D8A-47C2-B60F-5C2E40B7B3BD}.Release|Any CPU.Build.0 = Release|Any CPU
+		{43900D04-E330-4EFF-990B-709374318002}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{43900D04-E330-4EFF-990B-709374318002}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{43900D04-E330-4EFF-990B-709374318002}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{43900D04-E330-4EFF-990B-709374318002}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {537644CB-355C-4D29-BCAE-7C1177924702}
+	EndGlobalSection
+EndGlobal

MFR/MFR211/MFR211.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <BaseIntermediateOutputPath>..\Build\obj</BaseIntermediateOutputPath>
+    <BaseOutputPath>..\Build</BaseOutputPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="obj\**" />
+    <EmbeddedResource Remove="obj\**" />
+    <None Remove="obj\**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
+  </ItemGroup>
+
+</Project>

MFR/MFR211/Program.cs

@@ -0,0 +1,299 @@
+using System.Text;
+using System.Text.Json.Serialization;
+using Newtonsoft.Json;
+
+namespace MFR211
+{
+  internal class Program
+  {
+    public class Message
+    {
+      public string From;
+      public string To;
+      public string Content;
+
+      public string AsString()
+      {
+        return JsonConvert.SerializeObject(this);
+      }
+    }
+
+    public class MessageDatabase
+    {
+      private readonly string m_sFn;
+
+      // private List<Message> MessageList = new List<Message>();
+      /// <summary>Initializes a new instance of the <see cref="T:System.Object" /> class.</summary>
+      public MessageDatabase(string sFn)
+      {
+        m_sFn = sFn;
+      }
+
+      #region low-level methods
+
+      public List<Message> LoadWhole()
+      {
+        List<Message> arList = new List<Message>();
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            string sContent = Encoding.UTF8.GetChars(btContent).ToString();
+            Message message = JsonConvert.DeserializeObject<Message>(sContent);
+            arList.Add(message);
+          }
+        }
+
+        return arList;
+      }
+
+      public Message LoadByIndex(int iIndex)
+      {
+        int ii = 0;
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            if (ii == iIndex) {
+              string sContent = Encoding.UTF8.GetChars(btContent).ToString();
+              Message message = JsonConvert.DeserializeObject<Message>(sContent);
+              return message;
+            }
+
+            ii++;
+          }
+        }
+
+        return null;
+      }
+
+      public void Save(List<Message> messageList)
+      {
+        using (Stream pStream = File.OpenWrite(m_sFn)) {
+          StreamWriter pStreamWriter = new StreamWriter(pStream);
+          foreach (Message message in messageList) {
+            string sMsg = message.AsString();
+            pStreamWriter.Write((char)sMsg.Length);
+            pStreamWriter.Write(sMsg);
+          }
+        }
+      }
+
+      public int GetCount()
+      {
+        int ii = 0;
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            ii++;
+          }
+        }
+
+        return ii;
+      }
+
+      #endregion
+
+      #region Map
+
+      /// <summary>
+      /// 1 -> 1
+      /// </summary>
+      public IEnumerable<string> Map(
+        Func<Message, string> fnMap,
+        int iTop)
+      {
+        List<string> arList = new List<string>();
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            string sContent = Encoding.UTF8.GetChars(btContent).ToString();
+            Message message = JsonConvert.DeserializeObject<Message>(sContent);
+            // -----------
+            string sResult = fnMap(message);
+            arList.Add(sResult);
+            if (arList.Count >= iTop) break;
+          }
+        }
+
+        return arList;
+      }
+
+
+      public string FnMap(Message arg)
+      {
+        return $"{arg.From} / {arg.Content.Length}";
+      }
+
+      public string FnMap2(Message arg)
+      {
+        return $"{arg.From}";
+      }
+
+
+      #endregion
+
+      #region Filter
+
+      /// <summary>
+      /// 1 -> (0-1)
+      /// </summary>
+      /// <param name="fnFilter"></param>
+      /// <param name="iTopCount"></param>
+      /// <returns></returns>
+      public IEnumerable<Message> Filter(
+        Func<Message, bool> fnFilter,
+        int iTopCount)
+      {
+        List<Message> arList = new List<Message>();
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            string sContent = Encoding.UTF8.GetChars(btContent).ToString();
+            Message message = JsonConvert.DeserializeObject<Message>(sContent);
+            // -----------
+            bool bAdd = fnFilter(message);
+            if (bAdd) {
+              arList.Add(message);
+            }
+
+            if (arList.Count >= iTopCount) break;
+          }
+        }
+
+        return arList;
+      }
+
+      /// <summary>
+      /// 1->1
+      /// </summary>
+      /// <param name="arg"></param>
+      /// <returns></returns>
+      public bool FnFilter(Message arg)
+      {
+        return true;
+      }
+
+      /// <summary>
+      /// by condition
+      /// </summary>
+      /// <param name="arg"></param>
+      /// <returns></returns>
+      public bool FnFilterSelf(Message arg)
+      {
+        return (arg.From == arg.To);
+      }
+
+      #endregion
+
+      #region Reduce
+
+      public int Reduce(
+        Func<Message, int, int> fnReduce)
+      {
+        int acc = 0;
+        using (Stream pStream = File.OpenRead(m_sFn)) {
+          while (pStream.Position < pStream.Length) {
+            byte[] btHeader = new byte[0] { };
+            pStream.Read(btHeader, 0, 1);
+            byte[] btContent = new byte[btHeader[0]];
+            pStream.Read(btContent, 0, btContent.Length);
+            string sContent = Encoding.UTF8.GetChars(btContent).ToString();
+            Message message = JsonConvert.DeserializeObject<Message>(sContent);
+            // -----------
+            acc = fnReduce(message, acc);
+            if (acc < 0) {
+              return -acc;
+            }
+          }
+        }
+
+        return acc;
+      }
+
+      private Dictionary<string, int> arCounter = new Dictionary<string, int>() {
+        { "0", 0 },
+        { "1", 0 },
+        { "2", 0 },
+        { "3", 0 },
+        { "4", 0 },
+      };
+
+      /// <summary>
+      /// Подсчет сообщений от заданных отправителей,
+      /// но при нахождении больше
+      /// трех от любого из них прекращает счет
+      /// </summary>
+      /// <param name="arg1"></param>
+      /// <param name="iAcc"></param>
+      /// <returns></returns>
+      public int FnReduce(
+        Message arg1, int iAcc)
+      {
+        if (arCounter.ContainsKey(arg1.From)) {
+          arCounter[arg1.From]++;
+          iAcc++;
+          if (arCounter[arg1.From] > 3) {
+            return -iAcc;
+          }
+        }
+        return iAcc;
+      }
+
+
+      public int FnReduce2(
+        Message arg1, int iAcc)
+      {
+        return iAcc + arg1.Content.Length;
+      }
+
+      #endregion
+    }
+
+    static void Main(string[] args)
+    {
+      const string sFn = "1.txt";
+      MessageDatabase md = new MessageDatabase(sFn);
+      // 1. Whole load
+      //List<Message> arList = md.LoadWhole(sFn);
+      // 2. load one by one
+      int iiCount = md.GetCount();
+      for (int ii = 0; ii < iiCount; ii++) {
+        Message msg = md.LoadByIndex(ii);
+        Console.WriteLine($"[loaded msg] {msg.From}");
+      }
+      // 3. Map - Filter - Reduce
+      // 3.1. MAP
+      IEnumerable<string> ar =
+        md.Map(md.FnMap, 100);
+      foreach (string str in ar) {
+        Console.WriteLine($"[map msg] {str}");
+      }
+
+      // 3.2. FILTER
+      IEnumerable<Message> ar2 =
+        md.Filter(md.FnFilterSelf, 100);
+      foreach (Message msg in ar2) {
+        Console.WriteLine($"[filter msg] {msg.Content.Length}");
+      }
+
+      // 3.3. REDUCE
+      int iCnt =
+        md.Reduce(md.FnReduce);
+      Console.WriteLine($"[reducemsg] {iCnt}");
+    }
+  }
+}

MFR/MFR212/MFR212.csproj

@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <BaseIntermediateOutputPath>..\Build\obj</BaseIntermediateOutputPath>
+    <BaseOutputPath>..\Build</BaseOutputPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="obj\**" />
+    <EmbeddedResource Remove="obj\**" />
+    <None Remove="obj\**" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
+  </ItemGroup>
+
+</Project>

MFR/MFR212/Program.cs

@@ -0,0 +1,316 @@
+using System.Diagnostics.Metrics;
+using System.Diagnostics.Tracing;
+using System.Reflection.Metadata;
+using System.Security.Cryptography.X509Certificates;
+using System.Text;
+using Newtonsoft.Json;
+
+namespace MFR212
+{
+  public class Event
+  {
+    public DateTime EventDate;
+    public string Message;
+    public int Type;
+  }
+
+
+  // 1. Данных много: они не умещаются в память
+  // 2. Возможность распараллеливания обработки
+  // 3. 
+  public class EventManager
+  {
+    private readonly string m_sFilename;
+
+    public EventManager(string sFilename)
+    {
+      m_sFilename = sFilename;
+    }
+
+    public void SaveEvents(List<Event> arEvents)
+    {
+      using (Stream pOutputStream =
+             File.OpenWrite(m_sFilename)) {
+        using (StreamWriter pSw =
+               new StreamWriter(pOutputStream, Encoding.UTF8)) {
+          foreach (Event pEvent in arEvents) {
+            string sEvent = JsonConvert.SerializeObject(pEvent);
+            pSw.Write((byte)sEvent.Length);
+            pSw.Write(sEvent);
+          }
+        }
+      }
+    }
+
+    public List<Event> LoadEvents()
+    {
+      List<Event> ar = new List<Event>();
+      using (Stream pStream =
+             File.OpenRead(m_sFilename)) {
+        while (pStream.Length > pStream.Position) {
+          byte[] btHeader = new byte[1];
+          pStream.Read(btHeader, 0, 1);
+
+          byte[] btContent = new byte[btHeader[0]];
+          pStream.Read(btContent, 0, btContent.Length);
+          string sContent = Encoding.UTF8.GetString(btContent);
+          Event pEvent = JsonConvert.DeserializeObject<Event>(sContent);
+          ar.Add(pEvent);
+        }
+      }
+
+      return ar;
+    }
+
+    /// <summary>
+    /// 1 -> 1 (конвертация)
+    /// </summary>
+    /// <param name="fnMap"></param>
+    /// <param name="iTopCount"></param>
+    /// <returns></returns>
+    public List<string> Map(
+      Func<Event, string> fnMap,
+      int iTopCount)
+    {
+      List<string> ar = new List<string>();
+      using (Stream pStream =
+             File.OpenRead(m_sFilename)) {
+        while (pStream.Length > pStream.Position) {
+          byte[] btHeader = new byte[1];
+          pStream.Read(btHeader, 0, 1);
+
+          byte[] btContent = new byte[btHeader[0]];
+          pStream.Read(btContent, 0, btContent.Length);
+          string sContent = Encoding.UTF8.GetString(btContent);
+          Event pEvent = JsonConvert.DeserializeObject<Event>(sContent);
+          ar.Add(fnMap(pEvent));
+          if (ar.Count >= iTopCount) break;
+        }
+      }
+
+      return ar;
+
+
+    }
+
+    public string fnMap(Event arg)
+    {
+      return arg.Message;
+    }
+
+    public string fnMap2(Event arg)
+    {
+      return arg.EventDate.ToShortTimeString();
+    }
+
+    /// <summary>
+    /// * -> мало (фильтрация)
+    /// </summary>
+    /// <param name="fnFilter"></param>
+    /// <param name="iTopCount"></param>
+    /// <returns></returns>
+    public List<Event> Filter(
+      Func<Event, bool> fnFilter,
+      int iTopCount)
+    {
+
+      List<Event> ar = new List<Event>();
+      using (Stream pStream =
+             File.OpenRead(m_sFilename)) {
+        while (pStream.Length > pStream.Position) {
+          byte[] btHeader = new byte[1];
+          pStream.Read(btHeader, 0, 1);
+
+          byte[] btContent = new byte[btHeader[0]];
+          pStream.Read(btContent, 0, btContent.Length);
+          string sContent = Encoding.UTF8.GetString(btContent);
+          Event pEvent = JsonConvert.DeserializeObject<Event>(sContent);
+          if (fnFilter(pEvent)) {
+            ar
+              .Add(pEvent);
+            if (ar.Count >= iTopCount) break;
+          }
+        }
+      }
+
+      return ar;
+    }
+
+    public bool fnFilter(Event arg)
+    {
+      return true;
+    }
+
+    public bool fnFilterToday(Event arg)
+    {
+      return (arg.EventDate >= DateTime.Today);
+    }
+
+    /// <summary>
+    /// * -> 1 (свод)
+    /// </summary>
+    /// <param name="fnReduce"></param>
+    /// <returns></returns>
+    public int Reduce(
+      Func<Event, int, int> fnReduce)
+    {
+      int iCounter = 0;
+      using (Stream pStream =
+             File.OpenRead(m_sFilename)) {
+        while (pStream.Length > pStream.Position) {
+          byte[] btHeader = new byte[1];
+          pStream.Read(btHeader, 0, 1);
+
+          byte[] btContent = new byte[btHeader[0]];
+          pStream.Read(btContent, 0, btContent.Length);
+          string sContent = Encoding.UTF8.GetString(btContent);
+          Event pEvent = JsonConvert.DeserializeObject<Event>(sContent);
+
+          iCounter = fnReduce(pEvent, iCounter);
+        }
+      }
+
+      return iCounter;
+    }
+
+
+    /// <summary>
+    /// * -> 1 (свод)
+    /// </summary>
+    /// <param name="fnReduce"></param>
+    /// <returns></returns>
+    public int ReduceWithBreak(
+      Func<Event, int, int> fnReduce)
+    {
+      int iCounter = 0;
+      using (Stream pStream =
+             File.OpenRead(m_sFilename)) {
+        while (pStream.Length > pStream.Position) {
+          byte[] btHeader = new byte[1];
+          pStream.Read(btHeader, 0, 1);
+
+          byte[] btContent = new byte[btHeader[0]];
+          pStream.Read(btContent, 0, btContent.Length);
+          string sContent = Encoding.UTF8.GetString(btContent);
+          Event pEvent = JsonConvert.DeserializeObject<Event>(sContent);
+
+          iCounter = fnReduce(pEvent, iCounter);
+          if (iCounter < 0) return -iCounter;
+        }
+      }
+
+      return iCounter;
+    }
+
+
+    public int fnReduceErrorsToday(
+      Event pObject,
+      int iAccumulator)
+    {
+      if (pObject.Type == 2
+          && pObject.EventDate > DateTime.Today
+          && pObject.EventDate < DateTime.Today.AddDays(+1)) {
+        return iAccumulator + 1;
+      }
+
+      return iAccumulator;
+    }
+
+
+    public int fnReduceErrorsTodayMax(
+      Event pObject,
+      int iAccumulator,
+      int iMax)
+    {
+      if (pObject.Type == 2
+          && pObject.EventDate > DateTime.Today
+          && pObject.EventDate < DateTime.Today.AddDays(+1)) {
+
+        if (iAccumulator >= iMax - 1) {
+          return -(iAccumulator + 1);
+        }
+
+        return iAccumulator + 1;
+      }
+
+      return iAccumulator;
+    }
+
+    private Dictionary<int, int> arCount = new Dictionary<int, int>() {
+      { 0, 0 },
+      { 1, 0 },
+      { 2, 0 },
+    };
+
+
+    public int fnReduceBreak(
+      Event pObject,
+      int iAccumulator)
+    {
+      if (arCount.ContainsKey(pObject.Type)) {
+        arCount[pObject.Type]++;
+        if (arCount[pObject.Type] > 3) {
+          return -pObject.Type;
+        }
+      }
+
+      return iAccumulator;
+    }
+
+
+    public int fnReduce(
+        Event pObject,
+        int iAccumulator,
+        int iMax)
+    {
+      if (pObject.Type == 2
+          && pObject.EventDate > DateTime.Today
+          && pObject.EventDate < DateTime.Today.AddDays(+1)) {
+
+        if (iAccumulator >= iMax - 1) {
+          return -(iAccumulator + 1);
+        }
+
+        return iAccumulator + 1;
+      }
+
+      return iAccumulator;
+    }
+
+
+  }
+
+
+  internal class Program
+  {
+    static void Main(string[] args)
+    {
+      // 1. Working with whole content in memory
+      EventManager ev = new EventManager("1.txt");
+      List<Event> ar = ev.LoadEvents();
+      foreach (Event pEvent in ar) {
+        Console.WriteLine($"{pEvent.Message}");
+      }
+      // 2. Map, Filter, Reduce
+      // 2.1. MAP
+      List<string> ar2 = ev.Map(ev.fnMap, 100);
+      foreach (string str in ar2) {
+        Console.WriteLine($"{str}, ");
+      }
+
+      // 2.2. FILTER
+      List<Event> ar3 = ev.Filter(
+        ev.fnFilterToday, 100);
+      foreach (Event pEvent in ar3) {
+        Console.WriteLine($"{pEvent.Message}, ");
+      }
+
+      // 2.3. REDUCE
+      int iCount = ev.Reduce(ev.fnReduceErrorsToday);
+      Console.WriteLine($"{iCount}");
+      int iCount2 = ev.ReduceWithBreak(
+        ev.fnReduceBreak);
+      Console.WriteLine($"{iCount2}");
+    }
+  }
+}

MFR/MFR213/HardWorkProcessor.cs

@@ -0,0 +1,129 @@
+using System.Text;
+
+namespace ConsoleApp1
+{
+
+  #region CRecordCollection
+
+  public class CRecordCollection
+  {
+    private List<CRecord> RecordList;
+
+    public void Serialize(Stream pOutStream)
+    {
+      foreach (CRecord pRecord in RecordList) {
+        byte[] btRecord = pRecord.GetBytes();
+        pOutStream.Write(btRecord);
+      }
+    }
+
+    public void Deserialize(Stream pInStream)
+    {
+      pInStream.Seek(0, SeekOrigin.Begin);
+      while (pInStream.Position < pInStream.Length) {
+        byte[] btHeader = new byte[1];
+        pInStream.Read(btHeader, 0, 1);
+        byte[] btContent = new byte[btHeader[0]];
+        pInStream.Read(btContent, 0, btContent.Length);
+        string sName = Encoding.UTF8.GetChars(btContent).ToString();
+        RecordList.Add(new CRecord() { Name = sName });
+      }
+    }
+
+    public CRecord Deserialize2(Stream pInStream, int iRecordId)
+    {
+      pInStream.Seek(0, SeekOrigin.Begin);
+      int ii = 0;
+      while (pInStream.Position < pInStream.Length) {
+        byte[] btHeader = new byte[1];
+        pInStream.Read(btHeader, 0, 1);
+        byte[] btContent = new byte[btHeader[0]];
+        pInStream.Read(btContent, 0, btContent.Length);
+        string sName = Encoding.UTF8.GetChars(btContent).ToString();
+        if (ii == iRecordId) return new CRecord() { Name = sName };
+        ii++;
+      }
+
+      return null;
+    }
+
+    public int DeserializeCount(Stream pInStream)
+    {
+      pInStream.Seek(0, SeekOrigin.Begin);
+      int ii = 0;
+      while (pInStream.Position < pInStream.Length) {
+        byte[] btHeader = new byte[1];
+        pInStream.Read(btHeader, 0, 1);
+        byte[] btContent = new byte[btHeader[0]];
+        pInStream.Read(btContent, 0, btContent.Length);
+        ii++;
+      }
+
+      return ii;
+    }
+  }
+
+  #endregion
+
+  #region Record
+
+  public class CRecord
+  {
+    public string Name;
+
+    public byte[] GetBytes()
+    {
+      byte[] btInnerContent = Encoding.UTF8.GetBytes(Name);
+      byte[] btHeader = new byte[] { (byte)btInnerContent.Length };
+      byte[] btOut = new byte[btInnerContent.Length + btHeader.Length];
+      for (int ii = 0; ii < btHeader.Length; ii++) {
+        btOut[ii] = btHeader[ii];
+      }
+
+      int iShift = btHeader.Length;
+      for (int ii = 0; ii < btInnerContent.Length; ii++) {
+        btOut[ii + iShift] = btInnerContent[ii];
+      }
+
+      return btOut;
+    }
+
+
+
+  }
+
+
+
+  #endregion
+
+  #region CHardWorkProcessor
+
+  public class CHardWorkProcessor
+  {
+    #region public methods
+
+    public void StepThrough()
+    {
+      using (Stream pIn = File.OpenRead("1.txt")) {
+        CRecordCollection pR = new CRecordCollection();
+        int iCount = pR.DeserializeCount(pIn);
+        for (int ii = 0; ii < iCount; ii++) {
+          CRecord pRecord = pR.Deserialize2(pIn, ii);
+          Console.WriteLine(pRecord.Name);
+        }
+      }
+    }
+
+    public void GetWhole()
+    {
+      using (Stream pIn = File.OpenRead("1.txt")) {
+        CRecordCollection pR = new CRecordCollection();
+        pR.Deserialize(pIn);
+      }
+    }
+
+    #endregion
+  }
+
+  #endregion
+}

MFR/MFR213/MFR213.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <BaseIntermediateOutputPath>..\Build\obj\</BaseIntermediateOutputPath>
+    <BaseOutputPath>..\Build</BaseOutputPath>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Remove="obj\**" />
+    <EmbeddedResource Remove="obj\**" />
+    <None Remove="obj\**" />
+  </ItemGroup>
+
+</Project>

MFR/MFR213/MFRProcessor.cs

@@ -0,0 +1,111 @@
+
+namespace ConsoleApp1
+{
+  public class CMFRProcessor
+  {
+    #region Map-Filter-Reduce
+    public void Filter(
+      Stream pInStream,
+      Stream pOutStream,
+      Func<byte, bool> fnFilter)
+    {
+      pInStream.Seek(0, SeekOrigin.Begin);
+
+      byte[] bt = new byte[1];
+      while (pInStream.Position < pInStream.Length) {
+        pInStream.Read(bt, 0, 1);
+        bool bIsNeeded = fnFilter(bt[0]);
+        if (bIsNeeded) {
+          pOutStream.Write(bt, 0, 1);
+        }
+      }
+    }
+
+
+    public void Map(
+      Stream pInStream,
+      Stream pOutStream,
+
+      Func<byte, byte> fnMap)
+    {
+
+      pInStream.Seek(0, SeekOrigin.Begin);
+
+      byte[] bt = new byte[1];
+      while (pInStream.Position < pInStream.Length) {
+        pInStream.Read(bt, 0, 1);
+        byte[] btOut = new[] { fnMap(bt[0]) };
+        pOutStream.Write(btOut, 0, 1);
+      }
+    }
+
+    public int Reduce(
+      Stream pStream,
+      Func<int, byte, int> fnReduce)
+    {
+      pStream.Seek(0, SeekOrigin.Begin);
+
+      byte[] bt = new byte[1];
+      int ii = 0;
+      while (pStream.Position < pStream.Length) {
+        pStream.Read(bt, 0, 1);
+        ii = fnReduce(ii, bt[0]);
+        if (ii < 0) return -ii;
+      }
+
+      return ii;
+    }
+
+
+    #endregion
+
+    #region delegates "implementation"
+
+    private Dictionary<char, int> ar =
+      new Dictionary<char, int>() {
+        { '0', 0 },
+        { '1', 0 },
+        { '2', 0 },
+        { '3', 0 },
+      };
+
+
+    public int FnReduceDictionary(int iCounter, byte btValue)
+    {
+      char ch = (char)btValue;
+      if (ar.ContainsKey(ch)) {
+        ar[ch]++;
+        if (ar[ch] > 3) {
+          return -btValue;
+        }
+      }
+      return iCounter;
+    }
+
+
+    public int FnReduce(int iCounter, byte btValue)
+    {
+      if (btValue == '0') {
+        iCounter++;
+      }
+
+      if (iCounter >= 3) {
+        return -iCounter;
+      }
+      return iCounter;
+    }
+
+    public bool FnFilter(byte arg)
+    {
+      return arg == '0';
+    }
+
+    public byte FnMap(byte arg)
+    {
+      return arg;
+    }
+    
+
+    #endregion
+  }
+}

MFR/MFR213/Program.cs

@@ -0,0 +1,72 @@
+using System.IO.Pipes;
+using System.Reflection.Metadata;
+using System.Text;
+
+namespace ConsoleApp1
+{
+
+  public class Program
+  {
+    public static void Main()
+    {
+      //// hard work demo
+      //CHardWorkProcessor pProc = new CHardWorkProcessor();
+      //pProc.GetWhole();
+      //pProc.StepThrough();
+
+      // map - filter - reduce demo
+      h_StepMap();
+      h_StepFilter();
+      h_StepReduce();
+
+
+    }
+
+    #region demo methods
+
+    /// <summary>
+    /// 1 -> (acc++)
+    /// </summary>
+    private static void h_StepReduce()
+    {
+      using (Stream pIn = File.OpenRead("1.txt")) {
+        CMFRProcessor pProc = new CMFRProcessor();
+        int iCount = pProc.Reduce(pIn, pProc.FnReduceDictionary);
+        Console.WriteLine($"{iCount}");
+      }
+    }
+
+    /// <summary>
+    /// 1 -> (0..1)
+    /// </summary>
+    private static void h_StepFilter()
+    {
+      using (Stream pIn = File.OpenRead("1.txt")) {
+        using (Stream poUT = File.OpenWrite("2.txt")) {
+          CMFRProcessor pProc = new CMFRProcessor();
+          pProc.Filter(pIn, poUT, pProc.FnFilter);
+          Console.WriteLine($"Done");
+        }
+      }
+    }
+
+    /// <summary>
+    /// 1 -> 1
+    /// </summary>
+    private static void h_StepMap()
+    {
+      using (Stream pIn = File.OpenRead("1.txt")) {
+        using (Stream poUT = File.OpenWrite("2.txt")) {
+          CMFRProcessor pProc = new CMFRProcessor();
+          pProc.Map(pIn, poUT, pProc.FnMap);
+          Console.WriteLine($"Done");
+        }
+      }
+    }
+
+    #endregion
+
+
+  }
+
+}