diff --git a/.vscode/settings.json b/.vscode/settings.json
index b89b4b1c..bb9e1222 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,5 +1,4 @@
 {
-    "nxunitExplorer.nunit": "/Users/dean/.nuget/packages/nunit.consolerunner/3.10.0/tools/nunit3-console.exe",
     "nxunitExplorer.modules": [
         "LibZipSharp.UnitTest/bin/Debug/net471/LibZipSharp.UnitTest.dll",
     ]
diff --git a/LibZipSharp.UnitTest/LibZipSharp.UnitTest.csproj b/LibZipSharp.UnitTest/LibZipSharp.UnitTest.csproj
index be5bb1d6..18f619f5 100644
--- a/LibZipSharp.UnitTest/LibZipSharp.UnitTest.csproj
+++ b/LibZipSharp.UnitTest/LibZipSharp.UnitTest.csproj
@@ -42,6 +42,15 @@
     <None Include="packaged_resources">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Include="info.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Include="characters_players.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Include="object_spawn.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
   <Target Name="RunNunitTests" DependsOnTargets="Build">
diff --git a/LibZipSharp.UnitTest/ZipTests.cs b/LibZipSharp.UnitTest/ZipTests.cs
index 39ea5956..f5b2b2fd 100644
--- a/LibZipSharp.UnitTest/ZipTests.cs
+++ b/LibZipSharp.UnitTest/ZipTests.cs
@@ -257,6 +257,54 @@ public void CheckForUnknownCompressionMethods ()
 			}
 		}
 
+		[Test]
+		public void InMemoryZipFile ()
+		{
+			string filePath = Path.GetFullPath ("info.json");
+			if (!File.Exists (filePath)) {
+				filePath = Path.GetFullPath (Path.Combine ("LibZipSharp.UnitTest", "info.json"));
+			}
+			string fileRoot = Path.GetDirectoryName (filePath);
+			using (var stream = new MemoryStream ()) {
+				using (var zip = ZipArchive.Create (stream)) {
+					zip.AddFile (filePath, "info.json");
+					zip.AddFile (Path.Combine (fileRoot, "characters_players.json"), "characters_players.json");
+					zip.AddFile (Path.Combine (fileRoot, "object_spawn.json"), "object_spawn.json");
+				}
+
+				stream.Position = 0;
+				using (var zip = ZipArchive.Open (stream)) {
+					Assert.AreEqual (3, zip.EntryCount);
+					foreach (var e in zip) {
+						Console.WriteLine (e.FullName);
+					}
+					zip.DeleteEntry ("info.json");
+				}
+
+				stream.Position = 0;
+				using (var zip = ZipArchive.Open (stream)) {
+					Assert.AreEqual (2, zip.EntryCount);
+					zip.AddEntry ("info.json", File.ReadAllText (filePath), Encoding.UTF8, CompressionMethod.Deflate);
+				}
+
+				stream.Position = 0;
+				using (var zip = ZipArchive.Open (stream)) {
+					Assert.AreEqual (3, zip.EntryCount);
+					Assert.IsTrue (zip.ContainsEntry ("info.json"));
+					var entry1 = zip.ReadEntry ("info.json");
+					using (var s = new MemoryStream ()) {
+						entry1.Extract (s);
+						s.Position = 0;
+						using (var sr = new StreamReader (s)) {
+							var t = sr.ReadToEnd ();
+							Assert.AreEqual (File.ReadAllText (filePath), t);
+						}
+
+					}
+				}
+			}
+		}
+
 		[TestCase (false)]
 		[TestCase (true)]
 		public void EnumerateSkipDeletedEntries (bool deleteFromExistingFile)
diff --git a/LibZipSharp.UnitTest/characters_players.json b/LibZipSharp.UnitTest/characters_players.json
new file mode 100644
index 00000000..443d47cf
--- /dev/null
+++ b/LibZipSharp.UnitTest/characters_players.json
@@ -0,0 +1,3 @@
+{
+	"players": []
+}
\ No newline at end of file
diff --git a/LibZipSharp.UnitTest/info.json b/LibZipSharp.UnitTest/info.json
new file mode 100644
index 00000000..864a321e
--- /dev/null
+++ b/LibZipSharp.UnitTest/info.json
@@ -0,0 +1,21 @@
+{
+	"version": 22,
+	"type": "Object",
+	"id": "c9bb1a03-cb8a-4f9f-b298-49ee26fa1fd9",
+	"ownerId": "47b9d124-6421-4055-abf4-b5fc8fbfe784",
+	"name": "OBJECT NAME",
+	"description": "",
+	"blockCount": 9,
+	"created": "2019-06-21T14:20:42.000Z",
+	"lastChanged": "0001-01-01T00:00:00.000Z",
+	"tags": [
+		{
+			"value": "some_tag",
+			"origin": "category"
+		},
+		{
+			"value": "some_other_tag",
+			"origin": "category"
+		}
+	]
+}
diff --git a/LibZipSharp.UnitTest/object_spawn.json b/LibZipSharp.UnitTest/object_spawn.json
new file mode 100644
index 00000000..940507c0
--- /dev/null
+++ b/LibZipSharp.UnitTest/object_spawn.json
@@ -0,0 +1,30 @@
+{
+	"spawnRotationOffset":
+	{
+		"pitch": -16.274194717407227,
+		"yaw": -34.644023895263672,
+		"roll": 65.772232055664063
+	},
+	"spawnScaleOffset":
+	{
+		"x": 0.52916890382766724,
+		"y": 0.52916890382766724,
+		"z": 0.52916890382766724
+	},
+	"bounds":
+	{
+		"origin":
+		{
+			"x": -9086.74609375,
+			"y": -6475.60498046875,
+			"z": 1128.5997314453125
+		},
+		"boxExtent":
+		{
+			"x": 400.17755126953125,
+			"y": 474.9906005859375,
+			"z": 502.65240478515625
+		},
+		"sphereRadius": 530.2637939453125
+	}
+}
\ No newline at end of file
diff --git a/LibZipSharp.props b/LibZipSharp.props
index 22ce3b43..80dc1906 100644
--- a/LibZipSharp.props
+++ b/LibZipSharp.props
@@ -1,6 +1,6 @@
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <_LibZipSharpAssemblyVersion>2.0.1</_LibZipSharpAssemblyVersion>
+    <_LibZipSharpAssemblyVersion>2.0.2</_LibZipSharpAssemblyVersion>
     <!--
       Nuget Version. You can append things like -alpha-1 etc to this value.
       But always leave the $(_LibZipSharpAssemblyVersion) value at the start.
diff --git a/LibZipSharp/Xamarin.Tools.Zip/Native.cs b/LibZipSharp/Xamarin.Tools.Zip/Native.cs
index ad58fab6..a0e4b05a 100644
--- a/LibZipSharp/Xamarin.Tools.Zip/Native.cs
+++ b/LibZipSharp/Xamarin.Tools.Zip/Native.cs
@@ -356,7 +356,7 @@ public static extern IntPtr zip_source_function_create (
 			[MarshalAs (UnmanagedType.FunctionPtr)]zip_source_callback callback, IntPtr user_data, out zip_error_t errorp);
 
 		[DllImport (ZIP_LIBNAME, SetLastError = true, CallingConvention = CallingConvention.Cdecl)]
-		public static extern UInt64 zip_source_seek_compute_offset (UInt64 offset, UInt64 length, IntPtr data, UInt64 data_length, out zip_error_t error);
+		public static extern Int64 zip_source_seek_compute_offset (UInt64 offset, UInt64 length, IntPtr data, UInt64 data_length, out zip_error_t error);
 
 		[DllImport (ZIP_LIBNAME, CallingConvention = CallingConvention.Cdecl)]
 		public static extern Int64 zip_dir_add (IntPtr archive, IntPtr name, OperationFlags flags);
diff --git a/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs b/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs
index 8d13cd53..0a31df73 100644
--- a/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs
+++ b/LibZipSharp/Xamarin.Tools.Zip/ZipArchive.cs
@@ -40,6 +40,11 @@ namespace Xamarin.Tools.Zip
 	/// </summary>
 	public abstract partial class ZipArchive : IDisposable, IEnumerable <ZipEntry>
 	{
+		internal class CallbackContext {
+			public Stream Source { get; set; } = null;
+			public Stream Destination {get; set;} = null;
+			public string DestinationFileName {get; set; } = null;
+		}
 		public const EntryPermissions DefaultFilePermissions = EntryPermissions.OwnerRead | EntryPermissions.OwnerWrite | EntryPermissions.GroupRead | EntryPermissions.WorldRead;
 		public const EntryPermissions DefaultDirectoryPermissions = EntryPermissions.OwnerAll | EntryPermissions.GroupRead | EntryPermissions.GroupExecute |  EntryPermissions.WorldRead | EntryPermissions.WorldExecute;
 
@@ -87,9 +92,12 @@ internal ZipArchive (Stream stream, IPlatformOptions options, OpenFlags flags =
 				throw new ArgumentNullException (nameof (options));
 			Options = options;
 			Native.zip_error_t errorp;
-			var streamHandle = GCHandle.Alloc (stream, GCHandleType.Normal);
-			IntPtr h = GCHandle.ToIntPtr (streamHandle);
-			IntPtr source = Native.zip_source_function_create (callback, h, out errorp);
+			CallbackContext context = new CallbackContext () {
+				Source = stream,
+				Destination = null,
+			};
+			var contextHandle = GCHandle.Alloc (context, GCHandleType.Normal);
+			IntPtr source = Native.zip_source_function_create (callback, GCHandle.ToIntPtr (contextHandle), out errorp);
 			archive = Native.zip_open_from_source (source, flags, out errorp);
 			if (archive == IntPtr.Zero) {
 				// error;
@@ -323,7 +331,10 @@ public ZipEntry AddStream (Stream stream, string archivePath, EntryPermissions p
 				throw new ArgumentNullException (nameof (stream));
 			sources.Add (stream);
 			string destPath = EnsureArchivePath (archivePath);
-			var handle = GCHandle.Alloc (stream, GCHandleType.Normal);
+			var context = new CallbackContext () {
+				Source = stream,
+			};
+			var handle = GCHandle.Alloc (context, GCHandleType.Normal);
 			IntPtr h = GCHandle.ToIntPtr (handle);
 			IntPtr source = Native.zip_source_function (archive, callback, h);
 			long index = Native.zip_file_add (archive, destPath, source, overwriteExisting ? OperationFlags.Overwrite : OperationFlags.None);
@@ -758,9 +769,13 @@ internal static unsafe Int64 stream_callback (IntPtr state, IntPtr data, UInt64
 			var handle = GCHandle.FromIntPtr (state);
 			if (!handle.IsAllocated)
 				return -1;
-			var stream = handle.Target as Stream;
+			var context = handle.Target as CallbackContext;
+			if (context == null)
+				return -1;
+			var stream = context.Source;
 			if (stream == null)
 				return -1;
+			var destination = context.Destination ?? context.Source;
 			switch (cmd) {
 				case SourceCommand.Stat:
 					if (len < (UInt64)sizeof (Native.zip_stat_t))
@@ -773,34 +788,68 @@ internal static unsafe Int64 stream_callback (IntPtr state, IntPtr data, UInt64
 					return (Int64)sizeof (Native.zip_stat_t);
 
 				case SourceCommand.Tell:
-				case SourceCommand.TellWrite:
 					return (Int64)stream.Position;
+				case SourceCommand.TellWrite:
+					return (Int64)destination.Position;
 
 				case SourceCommand.Write:
 					buffer = ArrayPool<byte>.Shared.Rent (length);
 					try {
 						Marshal.Copy (data, buffer, 0, length);
-						stream.Write (buffer, 0, length);
+						destination.Write (buffer, 0, length);
 						return length;
 					} finally {
 						ArrayPool<byte>.Shared.Return (buffer);
 					}
 
 				case SourceCommand.SeekWrite:
-				case SourceCommand.Seek:
 					Native.zip_error_t error;
-					UInt64 offset = Native.zip_source_seek_compute_offset ((UInt64)stream.Position, (UInt64)stream.Length, data, len, out error);
-					stream.Seek ((long)offset, SeekOrigin.Begin);
+					Int64 offset = Native.zip_source_seek_compute_offset ((UInt64)destination.Position, (UInt64)destination.Length, data, len, out error);
+					if (offset < 0) {
+						return offset;
+					}
+					if (offset != stream.Seek (offset, SeekOrigin.Begin)) {
+						return -1;
+					}
+					break;
+				case SourceCommand.Seek:
+					offset = Native.zip_source_seek_compute_offset ((UInt64)stream.Position, (UInt64)stream.Length, data, len, out error);
+					if (offset < 0) {
+						return offset;
+					}
+					if (offset != stream.Seek (offset, SeekOrigin.Begin)) {
+						return -1;
+					}
 					break;
 
 				case SourceCommand.CommitWrite:
+					destination.Flush ();
+					stream.Position = 0;
+					destination.Position = 0;
+					stream.SetLength (destination.Length);
+					destination.CopyTo (stream);
 					stream.Flush ();
+					stream.Position = 0;
+					destination.Dispose ();
+					context.Destination = null;
+					if (!string.IsNullOrEmpty (context.DestinationFileName)&& File.Exists (context.DestinationFileName)) {
+						try {
+							File.Delete (context.DestinationFileName);
+						} catch (Exception) {
+							// we are deleting a temp file. So we can ignore any error.
+							// it will get cleaned up eventually.
+							Console.WriteLine ($"warning: Could not delete {context.DestinationFileName}.");
+						}
+						context.DestinationFileName = null;
+					}
+					break;
+				case SourceCommand.RollbackWrite:
+					destination.Dispose ();
+					context.Destination = null;
 					break;
 
 				case SourceCommand.Read:
-					if (length > stream.Length - stream.Position) {
-						length = (int)(stream.Length - stream.Position);
-					}
+					length = (int)Math.Min (stream.Length - stream.Position, length);
 					buffer = ArrayPool<byte>.Shared.Rent (length);
 					try {
 						int bytesRead = stream.Read (buffer, 0, length);
@@ -809,8 +858,18 @@ internal static unsafe Int64 stream_callback (IntPtr state, IntPtr data, UInt64
 					} finally {
 						ArrayPool<byte>.Shared.Return (buffer);
 					}
-
 				case SourceCommand.BeginWrite:
+					try {
+						string tempFile = Path.GetTempFileName ();
+						context.Destination = File.Open (tempFile, FileMode.OpenOrCreate, FileAccess.ReadWrite);
+						context.DestinationFileName = tempFile;
+					} catch (IOException) {
+						// ok use a memory stream as a backup
+						context.Destination = new MemoryStream ();
+					}
+					destination = context.Destination;
+					destination.Position = 0;
+					break;
 				case SourceCommand.Open:
 					stream.Position = 0;
 					return 0;