[release/6.0-staging] Allow setting ZipArchiveEntry general-purpose flag bits

src/libraries/System.IO.Compression/src/System/IO/Compression/ZipArchiveEntry.cs

@@ -41,7 +41,7 @@ public partial class ZipArchiveEntry
         private List<ZipGenericExtraField>? _cdUnknownExtraFields;
         private List<ZipGenericExtraField>? _lhUnknownExtraFields;
         private readonly byte[]? _fileComment;
-        private readonly CompressionLevel? _compressionLevel;
+        private readonly CompressionLevel _compressionLevel;
 
         // Initializes, attaches it to archive
         internal ZipArchiveEntry(ZipArchive archive, ZipCentralDirectoryFileHeader cd)
@@ -79,7 +79,7 @@ internal ZipArchiveEntry(ZipArchive archive, ZipCentralDirectoryFileHeader cd)
             _cdUnknownExtraFields = cd.ExtraFields;
             _fileComment = cd.FileComment;
 
-            _compressionLevel = null;
+            _compressionLevel = MapCompressionLevel(_generalPurposeBitFlag, CompressionMethod);
         }
 
         // Initializes new entry
@@ -91,6 +91,7 @@ internal ZipArchiveEntry(ZipArchive archive, string entryName, CompressionLevel
             {
                 CompressionMethod = CompressionMethodValues.Stored;
             }
+            _generalPurposeBitFlag = MapDeflateCompressionOption(_generalPurposeBitFlag, _compressionLevel, CompressionMethod);
         }
 
         // Initializes new entry
@@ -104,8 +105,9 @@ internal ZipArchiveEntry(ZipArchive archive, string entryName)
             _versionMadeByPlatform = CurrentZipPlatform;
             _versionMadeBySpecification = ZipVersionNeededValues.Default;
             _versionToExtract = ZipVersionNeededValues.Default; // this must happen before following two assignment
-            _generalPurposeBitFlag = 0;
+            _compressionLevel = CompressionLevel.Optimal;
             CompressionMethod = CompressionMethodValues.Deflate;
+            _generalPurposeBitFlag = MapDeflateCompressionOption(0, _compressionLevel, CompressionMethod);
             _lastModified = DateTimeOffset.Now;
 
             _compressedSize = 0; // we don't know these yet
@@ -127,8 +129,6 @@ internal ZipArchiveEntry(ZipArchive archive, string entryName)
             _lhUnknownExtraFields = null;
             _fileComment = null;
 
-            _compressionLevel = null;
-
             if (_storedEntryNameBytes.Length > ushort.MaxValue)
                 throw new ArgumentException(SR.EntryNamesTooLong);
 
@@ -617,7 +617,7 @@ private CheckSumAndSizeWriteStream GetDataCompressor(Stream backingStream, bool
                 case CompressionMethodValues.Deflate:
                 case CompressionMethodValues.Deflate64:
                 default:
-                    compressorStream = new DeflateStream(backingStream, _compressionLevel ?? CompressionLevel.Optimal, leaveBackingStreamOpen);
+                    compressorStream = new DeflateStream(backingStream, _compressionLevel, leaveBackingStreamOpen);
                     break;
 
             }
@@ -784,6 +784,46 @@ private bool IsOpenable(bool needToUncompress, bool needToLoadIntoMemory, out st
 
         private bool SizesTooLarge() => _compressedSize > uint.MaxValue || _uncompressedSize > uint.MaxValue;
 
+        private static CompressionLevel MapCompressionLevel(BitFlagValues generalPurposeBitFlag, CompressionMethodValues compressionMethod)
+        {
+            // Information about the Deflate compression option is stored in bits 1 and 2 of the general purpose bit flags.
+            // If the compression method is not Deflate, the Deflate compression option is invalid - default to NoCompression.
+            if (compressionMethod == CompressionMethodValues.Deflate || compressionMethod == CompressionMethodValues.Deflate64)
+            {
+                return ((int)generalPurposeBitFlag & 0x6) switch
+                {
+                    0 => CompressionLevel.Optimal,
+                    2 => CompressionLevel.SmallestSize,
+                    4 => CompressionLevel.Fastest,
+                    6 => CompressionLevel.Fastest,
+                    _ => CompressionLevel.Optimal
+                };
+            }
+            else
+            {
+                return CompressionLevel.NoCompression;
+            }
+        }
+
+        private static BitFlagValues MapDeflateCompressionOption(BitFlagValues generalPurposeBitFlag, CompressionLevel compressionLevel, CompressionMethodValues compressionMethod)
+        {
+            ushort deflateCompressionOptions = (ushort)(
+                // The Deflate compression level is only valid if the compression method is actually Deflate (or Deflate64). If it's not, the
+                // value of the two bits is undefined and they should be zeroed out.
+                compressionMethod == CompressionMethodValues.Deflate || compressionMethod == CompressionMethodValues.Deflate64
+                    ? compressionLevel switch
+                    {
+                        CompressionLevel.Optimal => 0,
+                        CompressionLevel.SmallestSize => 2,
+                        CompressionLevel.Fastest => 6,
+                        CompressionLevel.NoCompression => 6,
+                        _ => 0
+                    }
+                    : 0);
+
+            return (BitFlagValues)(((int)generalPurposeBitFlag & ~0x6) | deflateCompressionOptions);
+        }
+
         // return value is true if we allocated an extra field for 64 bit headers, un/compressed size
         private bool WriteLocalFileHeader(bool isEmptyFile)
         {

src/libraries/System.IO.Compression/tests/ZipArchive/zip_CreateTests.cs

@@ -144,6 +144,78 @@ public static void CreateUncompressedArchive()
             }
         }
 
+        // This test checks to ensure that setting the compression level of an archive entry sets the general-purpose
+        // bit flags correctly. It verifies that these have been set by reading from the MemoryStream manually, and by
+        // reopening the generated file to confirm that the compression levels match.
+        [Theory]
+        // Special-case NoCompression: in this case, the CompressionMethod becomes Stored and the bits are unset.
+        [InlineData(CompressionLevel.NoCompression, 0)]
+        [InlineData(CompressionLevel.Optimal, 0)]
+        [InlineData(CompressionLevel.SmallestSize, 2)]
+        [InlineData(CompressionLevel.Fastest, 6)]
+        public static void CreateArchiveEntriesWithBitFlags(CompressionLevel compressionLevel, ushort expectedGeneralBitFlags)
+        {
+            var testfilename = "testfile";
+            var testFileContent = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
+            var utf8WithoutBom = new Text.UTF8Encoding(encoderShouldEmitUTF8Identifier: false);
+
+            byte[] zipFileContent;
+
+            using (var testStream = new MemoryStream())
+            {
+
+                using (var zip = new ZipArchive(testStream, ZipArchiveMode.Create))
+                {
+                    ZipArchiveEntry newEntry = zip.CreateEntry(testfilename, compressionLevel);
+                    using (var writer = new StreamWriter(newEntry.Open(), utf8WithoutBom))
+                    {
+                        writer.Write(testFileContent);
+                        writer.Flush();
+                    }
+
+                    ZipArchiveEntry secondNewEntry = zip.CreateEntry(testFileContent + "_post", CompressionLevel.NoCompression);
+                }
+
+                zipFileContent = testStream.ToArray();
+            }
+
+            // expected bit flags are at position 6 in the file header
+            var generalBitFlags = System.Buffers.Binary.BinaryPrimitives.ReadUInt16LittleEndian(zipFileContent.AsSpan(6));
+
+            Assert.Equal(expectedGeneralBitFlags, generalBitFlags);
+
+            using (var reReadStream = new MemoryStream(zipFileContent))
+            {
+                using (var reReadZip = new ZipArchive(reReadStream, ZipArchiveMode.Read))
+                {
+                    var firstArchive = reReadZip.Entries[0];
+                    var secondArchive = reReadZip.Entries[1];
+                    var compressionLevelFieldInfo = typeof(ZipArchiveEntry).GetField("_compressionLevel", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
+                    var generalBitFlagsFieldInfo = typeof(ZipArchiveEntry).GetField("_generalPurposeBitFlag", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
+
+                    var reReadCompressionLevel = (CompressionLevel)compressionLevelFieldInfo.GetValue(firstArchive);
+                    var reReadGeneralBitFlags = (ushort)generalBitFlagsFieldInfo.GetValue(firstArchive);
+
+                    Assert.Equal(compressionLevel, reReadCompressionLevel);
+                    Assert.Equal(expectedGeneralBitFlags, reReadGeneralBitFlags);
+
+                    reReadCompressionLevel = (CompressionLevel)compressionLevelFieldInfo.GetValue(secondArchive);
+                    Assert.Equal(CompressionLevel.NoCompression, reReadCompressionLevel);
+
+                    using (var strm = firstArchive.Open())
+                    {
+                        var readBuffer = new byte[firstArchive.Length];
+
+                        strm.Read(readBuffer);
+
+                        var readText = Text.Encoding.UTF8.GetString(readBuffer);
+
+                        Assert.Equal(readText, testFileContent);
+                    }
+                }
+            }
+        }
+
         [Fact]
         public static void CreateNormal_VerifyDataDescriptor()
         {

src/libraries/System.IO.Packaging/src/System/IO/Packaging/ZipPackage.cs

@@ -404,7 +404,11 @@ internal static void GetZipCompressionMethodFromOpcCompressionOption(
                     break;
                 case CompressionOption.Maximum:
                     {
+#if NET
+                        compressionLevel = CompressionLevel.SmallestSize;
+#else
                         compressionLevel = CompressionLevel.Optimal;
+#endif
                     }
                     break;
                 case CompressionOption.Fast:

src/libraries/System.IO.Packaging/tests/ReflectionTests.cs

@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.IO.Compression;
+using System.Reflection;
+using Xunit;
+
+namespace System.IO.Packaging.Tests;
+
+public class ReflectionTests
+{
+    [Fact]
+    public void Verify_GeneralPurposeBitFlag_NotSetTo_Unicode()
+    {
+        using MemoryStream ms = new();
+
+        using (ZipPackage package = (ZipPackage)Package.Open(ms, FileMode.Create, FileAccess.Write))
+        {
+            Uri uri = PackUriHelper.CreatePartUri(new Uri("document.xml", UriKind.Relative));
+            ZipPackagePart part = (ZipPackagePart)package.CreatePart(uri, Tests.Mime_MediaTypeNames_Text_Xml, CompressionOption.NotCompressed);
+            using (Stream partStream = part.GetStream())
+            {
+                using StreamWriter sw = new(partStream);
+                sw.Write(Tests.s_DocumentXml);
+            }
+            package.CreateRelationship(part.Uri, TargetMode.Internal, "http://packageRelType", "rId1234");
+        }
+
+        ms.Position = 0;
+        using (ZipArchive archive = new ZipArchive(ms, ZipArchiveMode.Read, leaveOpen: false))
+        {
+            FieldInfo archiveEncodingFieldInfo = typeof(ZipArchive).GetField("_entryNameAndCommentEncoding", BindingFlags.Instance | BindingFlags.NonPublic);
+            System.Text.Encoding archiveEncoding = (archiveEncodingFieldInfo.GetValue(archive) as System.Text.Encoding) ?? System.Text.Encoding.UTF8;
+
+            foreach (ZipArchiveEntry entry in archive.Entries)
+            {
+                FieldInfo fieldInfo = typeof(ZipArchiveEntry).GetField("_generalPurposeBitFlag", BindingFlags.Instance | BindingFlags.NonPublic);
+                object fieldObject = fieldInfo.GetValue(entry);
+                ushort shortField = (ushort)fieldObject;
+                Assert.Equal(0, shortField & 0x800); // If it was UTF8, we would set the general purpose bit flag to 0x800 (UnicodeFileNameAndComment)
+                CheckCharacters(entry.Name);
+                fieldInfo = typeof(ZipArchiveEntry).GetField("_fileComment", BindingFlags.Instance | BindingFlags.NonPublic);
+                byte[]? commentBytes = (byte[]?)fieldInfo.GetValue(entry);
+
+                CheckCharacters(archiveEncoding.GetString(commentBytes));
+            }
+        }
+
+        void CheckCharacters(string value)
+        {
+            for (int i = 0; i < value.Length; i++)
+            {
+                char c = value[i];
+                Assert.True(c >= 32 && c <= 126, $"ZipArchiveEntry name character {c} requires UTF8");
+            }
+        }
+    }
+
+}

src/libraries/System.IO.Packaging/tests/System.IO.Packaging.Tests.csproj

@@ -5,6 +5,9 @@
   <ItemGroup>
     <Compile Include="Tests.cs" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETFramework'">
+    <Compile Include="ReflectionTests.cs" />
+  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="System.IO.Packaging.TestData" Version="$(SystemIOPackagingTestDataVersion)" />
     <ProjectReference Include="..\src\System.IO.Packaging.csproj" />

src/libraries/System.IO.Packaging/tests/Tests.cs

@@ -12,9 +12,9 @@ namespace System.IO.Packaging.Tests
 {
     public class Tests : FileCleanupTestBase
     {
-        private const string Mime_MediaTypeNames_Text_Xml = "text/xml";
+        internal const string Mime_MediaTypeNames_Text_Xml = "text/xml";
         private const string Mime_MediaTypeNames_Image_Jpeg = "image/jpeg"; // System.Net.Mime.MediaTypeNames.Image.Jpeg
-        private const string s_DocumentXml = @"<Hello>Test</Hello>";
+        internal const string s_DocumentXml = @"<Hello>Test</Hello>";
         private const string s_ResourceXml = @"<Resource>Test</Resource>";
 
         private FileInfo GetTempFileInfoFromExistingFile(string existingFileName, [CallerMemberName] string memberName = null, [CallerLineNumber] int lineNumber = 0)
@@ -3988,6 +3988,47 @@ public void CreatePackUriWithFragment()
 
         }
 
+        [Theory]
+#if NET
+        [InlineData(CompressionOption.NotCompressed, CompressionOption.Normal, 0)]
+        [InlineData(CompressionOption.Normal, CompressionOption.Normal, 0)]
+        [InlineData(CompressionOption.Maximum, CompressionOption.Normal, 2)]
+        [InlineData(CompressionOption.Fast, CompressionOption.Normal, 6)]
+        [InlineData(CompressionOption.SuperFast, CompressionOption.Normal, 6)]
+#else
+        [InlineData(CompressionOption.NotCompressed, CompressionOption.NotCompressed, 0)]
+        [InlineData(CompressionOption.Normal, CompressionOption.Normal, 0)]
+        [InlineData(CompressionOption.Maximum, CompressionOption.Maximum, 2)]
+        [InlineData(CompressionOption.Fast, CompressionOption.Fast, 4)]
+        [InlineData(CompressionOption.SuperFast, CompressionOption.SuperFast, 6)]
+#endif
+        public void Roundtrip_Compression_Option(CompressionOption createdCompressionOption, CompressionOption expectedCompressionOption, ushort expectedZipFileBitFlags)
+        {
+            var documentPath = "untitled.txt";
+            Uri partUriDocument = PackUriHelper.CreatePartUri(new Uri(documentPath, UriKind.Relative));
+
+            using (MemoryStream ms = new MemoryStream())
+            {
+                Package package = Package.Open(ms, FileMode.Create, FileAccess.ReadWrite);
+                PackagePart part = package.CreatePart(partUriDocument, "application/text", createdCompressionOption);
+
+                package.Flush();
+                package.Close();
+                (package as IDisposable).Dispose();
+
+                ms.Seek(0, SeekOrigin.Begin);
+
+                var zipBytes = ms.ToArray();
+                var generalBitFlags = System.Buffers.Binary.BinaryPrimitives.ReadUInt16LittleEndian(zipBytes.AsSpan(6));
+
+                package = Package.Open(ms, FileMode.Open, FileAccess.Read);
+                part = package.GetPart(partUriDocument);
+
+                Assert.Equal(expectedZipFileBitFlags, generalBitFlags);
+                Assert.Equal(expectedCompressionOption, part.CompressionOption);
+            }
+        }
+
         private const string DocumentRelationshipType = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument";
     }