Fix writing extra data when updating Zip64 entries

src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs

@@ -2171,17 +2171,21 @@ private int WriteCentralDirectoryHeader(ZipEntry entry)
 				WriteLEInt((int)entry.Crc);
 			}
 
+			bool useExtraCompressedSize = false; //Do we want to store the compressed size in the extra data?
 			if ((entry.IsZip64Forced()) || (entry.CompressedSize >= 0xffffffff))
 			{
+				useExtraCompressedSize = true;
 				WriteLEInt(-1);
 			}
 			else
 			{
 				WriteLEInt((int)(entry.CompressedSize & 0xffffffff));
 			}
 
+			bool useExtraUncompressedSize = false; //Do we want to store the uncompressed size in the extra data?
 			if ((entry.IsZip64Forced()) || (entry.Size >= 0xffffffff))
 			{
+				useExtraUncompressedSize = true;
 				WriteLEInt(-1);
 			}
 			else
@@ -2205,12 +2209,12 @@ private int WriteCentralDirectoryHeader(ZipEntry entry)
 			{
 				ed.StartNewEntry();
 
-				if ((entry.Size >= 0xffffffff) || (useZip64_ == UseZip64.On))
+				if (useExtraUncompressedSize)
 				{
 					ed.AddLeLong(entry.Size);
 				}
 
-				if ((entry.CompressedSize >= 0xffffffff) || (useZip64_ == UseZip64.On))
+				if (useExtraCompressedSize)
 				{
 					ed.AddLeLong(entry.CompressedSize);
 				}

test/ICSharpCode.SharpZipLib.Tests/Zip/ZipFileHandling.cs

@@ -136,6 +136,57 @@ public void Zip64Useage()
 			}
 		}
 
+		/// <summary>
+		/// Test that entries can be removed from a Zip64 file
+		/// </summary>
+		[Test]
+		[Category("Zip")]
+		public void Zip64Update()
+		{
+			using (var memStream = new MemoryStream())
+			{
+				using (ZipFile f = new ZipFile(memStream, leaveOpen: true))
+				{
+					f.UseZip64 = UseZip64.On;
+
+					var m = new StringMemoryDataSource("0000000");
+					f.BeginUpdate(new MemoryArchiveStorage());
+					f.Add(m, "a.dat");
+					f.Add(m, "b.dat");
+					f.CommitUpdate();
+					Assert.That(f.TestArchive(true), Is.True, "initial archive should be valid");
+				}
+
+				memStream.Seek(0, SeekOrigin.Begin);
+
+				using (ZipFile f = new ZipFile(memStream, leaveOpen: true))
+				{
+					Assert.That(f.Count, Is.EqualTo(2), "Archive should have 2 entries");
+
+					f.BeginUpdate(new MemoryArchiveStorage());
+					f.Delete("b.dat");
+					f.CommitUpdate();
+					Assert.That(f.TestArchive(true), Is.True, "modified archive should be valid");
+				}
+
+				memStream.Seek(0, SeekOrigin.Begin);
+
+				using (ZipFile f = new ZipFile(memStream, leaveOpen: true))
+				{
+					Assert.That(f.Count, Is.EqualTo(1), "Archive should have 1 entry");
+
+					for (int index = 0; index < f.Count; ++index)
+					{
+						Stream entryStream = f.GetInputStream(index);
+						var data = new MemoryStream();
+						StreamUtils.Copy(entryStream, data, new byte[128]);
+						string contents = Encoding.ASCII.GetString(data.ToArray());
+						Assert.That(contents, Is.EqualTo("0000000"), "archive member data should be correct");
+					}
+				}
+			}
+		}
+
 		[Test]
 		[Category("Zip")]
 		[Explicit]