Initial commit

vs4win/Chapter09/WorkingWithStreams/Program.Compress.cs

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+using System.IO.Compression; // BrotliStream, GZipStream, CompressionMode
+using System.Xml; // XmlWriter, XmlReader
+
+using static System.Environment; // CurrentDirectory
+using static System.IO.Path; // Combine
+
+partial class Program
+{
+  static void Compress(string algorithm = "gzip")
+  {
+    // define a file path using algorithm as file extension
+    string filePath = Combine(
+      CurrentDirectory, $"streams.{algorithm}");
+
+    FileStream file = File.Create(filePath);
+    Stream compressor;
+    if (algorithm == "gzip")
+    {
+      compressor = new GZipStream(file, CompressionMode.Compress);
+    }
+    else
+    {
+      compressor = new BrotliStream(file, CompressionMode.Compress);
+    }
+
+    using (compressor)
+    {
+      using (XmlWriter xml = XmlWriter.Create(compressor))
+      {
+        xml.WriteStartDocument();
+        xml.WriteStartElement("callsigns");
+        foreach (string item in Viper.Callsigns)
+        {
+          xml.WriteElementString("callsign", item);
+        }
+      }
+    } // also closes the underlying stream
+
+    // output all the contents of the compressed file
+    WriteLine("{0} contains {1:N0} bytes.",
+      filePath, new FileInfo(filePath).Length);
+
+    WriteLine($"The compressed contents:");
+    WriteLine(File.ReadAllText(filePath));
+
+    // read a compressed file
+    WriteLine("Reading the compressed XML file:");
+    file = File.Open(filePath, FileMode.Open);
+    Stream decompressor;
+    if (algorithm == "gzip")
+    {
+      decompressor = new GZipStream(
+        file, CompressionMode.Decompress);
+    }
+    else
+    {
+      decompressor = new BrotliStream(
+        file, CompressionMode.Decompress);
+    }
+
+    using (decompressor)
+    {
+      using (XmlReader reader = XmlReader.Create(decompressor))
+      {
+        while (reader.Read())
+        {
+          // check if we are on an element node named callsign
+          if ((reader.NodeType == XmlNodeType.Element)
+            && (reader.Name == "callsign"))
+          {
+            reader.Read(); // move to the text inside element
+            WriteLine($"{reader.Value}"); // read its value
+          }
+        }
+      }
+    }
+  }
+}