public static void CreateUncompressedArchive()
 {
     using (var testStream = new MemoryStream())
     {
         var testfilename    = "testfile";
         var testFileContent = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
         using (var zip = new ZipArchive(testStream, ZipArchiveMode.Create))
         {
             var             utf8WithoutBom = new Text.UTF8Encoding(encoderShouldEmitUTF8Identifier: false);
             ZipArchiveEntry newEntry       = zip.CreateEntry(testfilename, CompressionLevel.NoCompression);
             using (var writer = new StreamWriter(newEntry.Open(), utf8WithoutBom))
             {
                 writer.Write(testFileContent);
                 writer.Flush();
             }
             byte[] fileContent = testStream.ToArray();
             // zip file header stores values as little-endian
             byte compressionMethod = fileContent[8];
             Assert.Equal(0, compressionMethod); // stored => 0, deflate => 8
             uint compressedSize   = BitConverter.ToUInt32(fileContent, 18);
             uint uncompressedSize = BitConverter.ToUInt32(fileContent, 22);
             Assert.Equal(uncompressedSize, compressedSize);
             byte filenamelength = fileContent[26];
             Assert.Equal(testfilename.Length, filenamelength);
             string readFileName = ReadStringFromSpan(fileContent.AsSpan(30, filenamelength));
             Assert.Equal(testfilename, readFileName);
             string readFileContent = ReadStringFromSpan(fileContent.AsSpan(30 + filenamelength, testFileContent.Length));
             Assert.Equal(testFileContent, readFileContent);
         }
     }
 }
        public void UpdateUncompressedArchive()
        {
            var utf8WithoutBom = new Text.UTF8Encoding(encoderShouldEmitUTF8Identifier: false);

            byte[] fileContent;
            using (var memStream = new MemoryStream())
            {
                using (var zip = new ZipArchive(memStream, ZipArchiveMode.Create))
                {
                    ZipArchiveEntry entry = zip.CreateEntry("testing", CompressionLevel.NoCompression);
                    using (var writer = new StreamWriter(entry.Open(), utf8WithoutBom))
                    {
                        writer.Write("hello");
                        writer.Flush();
                    }
                }
                fileContent = memStream.ToArray();
            }
            byte compressionMethod = fileContent[8];

            Assert.Equal(0, compressionMethod); // stored => 0, deflate => 8
            using (var memStream = new MemoryStream())
            {
                memStream.Write(fileContent);
                memStream.Position = 0;
                using (var archive = new ZipArchive(memStream, ZipArchiveMode.Update))
                {
                    ZipArchiveEntry entry = archive.GetEntry("testing");
                    using (var writer = new StreamWriter(entry.Open(), utf8WithoutBom))
                    {
                        writer.Write("new");
                        writer.Flush();
                    }
                }
                byte[] modifiedTestContent = memStream.ToArray();
                compressionMethod = modifiedTestContent[8];
                Assert.Equal(0, compressionMethod); // stored => 0, deflate => 8
            }
        }