zip: finish stream async when async

src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/DeflaterOutputStream.cs

@@ -417,7 +417,7 @@ protected override void Dispose(bool disposing)
 			}
 		}
 
-#if NETSTANDARD2_1_OR_GREATER
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 		/// <summary>
 		/// Calls <see cref="FinishAsync"/> and closes the underlying
 		/// stream when <see cref="IsStreamOwner"></see> is true.

src/ICSharpCode.SharpZipLib/Zip/ZipOutputStream.cs

@@ -551,6 +551,8 @@ await baseOutputStream_.WriteProcToStreamAsync(s =>
 		/// </exception>
 		public void CloseEntry()
 		{
+			// Note: This method will run synchronously
+			FinishCompression(null).Wait();
 			WriteEntryFooter(baseOutputStream_);
 
 			// Patch the header if possible
@@ -564,9 +566,41 @@ public void CloseEntry()
 			curEntry = null;
 		}
 
+		private async Task FinishCompression(CancellationToken? ct)
+		{
+			// Compression handled externally
+			if (entryIsPassthrough) return;
+
+			// First finish the deflater, if appropriate
+			if (curMethod == CompressionMethod.Deflated)
+			{
+				if (size >= 0)
+				{
+					if (ct.HasValue) {
+						await base.FinishAsync(ct.Value).ConfigureAwait(false);
+					} else {
+						base.Finish();
+					}
+				}
+				else
+				{
+					deflater_.Reset();
+				}
+			}
+			if (curMethod == CompressionMethod.Stored)
+			{
+				// This is done by Finish() for Deflated entries, but we need to do it
+				// ourselves for Stored ones
+				base.GetAuthCodeIfAES();
+			}
+
+			return;
+		}
+
 		/// <inheritdoc cref="CloseEntry"/>
 		public async Task CloseEntryAsync(CancellationToken ct)
 		{
+			await FinishCompression(ct).ConfigureAwait(false);
 			await baseOutputStream_.WriteProcToStreamAsync(WriteEntryFooter, ct).ConfigureAwait(false);
 
 			// Patch the header if possible
@@ -600,24 +634,9 @@ internal void WriteEntryFooter(Stream stream)
 
 			long csize = size;
 
-			// First finish the deflater, if appropriate
-			if (curMethod == CompressionMethod.Deflated)
-			{
-				if (size >= 0)
-				{
-					base.Finish();
-					csize = deflater_.TotalOut;
-				}
-				else
-				{
-					deflater_.Reset();
-				}
-			}
-			else if (curMethod == CompressionMethod.Stored)
+			if (curMethod == CompressionMethod.Deflated && size >= 0)
 			{
-				// This is done by Finish() for Deflated entries, but we need to do it
-				// ourselves for Stored ones
-				base.GetAuthCodeIfAES();
+				csize = deflater_.TotalOut;
 			}
 
 			// Write the AES Authentication Code (a hash of the compressed and encrypted data)

test/ICSharpCode.SharpZipLib.Tests/TestSupport/Streams.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Threading;
+using System.Threading.Tasks;
 
 namespace ICSharpCode.SharpZipLib.Tests.TestSupport
 {
@@ -188,6 +189,77 @@ public override long Position
 
 	}
 
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
+	/// <summary>
+	/// A <see cref="Stream"/> that does not support non-async operations.
+	/// </summary>
+	/// <remarks>
+	/// This could not be done by extending MemoryStream itself, since other instances of MemoryStream tries to us a faster (non-async) method of copying
+	///  if it detects that it's a (subclass of) MemoryStream.
+	/// </remarks>
+	public class MemoryStreamWithoutSync : Stream
+	{
+		MemoryStream _inner = new MemoryStream();
+
+		public override bool CanRead => _inner.CanRead;
+		public override bool CanSeek => _inner.CanSeek;
+		public override bool CanWrite => _inner.CanWrite;
+		public override long Length => _inner.Length;
+		public override long Position { get => _inner.Position; set => _inner.Position = value; }
+
+		public byte[] ToArray() => _inner.ToArray();
+
+		public override void Flush() => throw new NotSupportedException($"Non-async call to {nameof(Flush)}");
+
+
+		public override void CopyTo(Stream destination, int bufferSize) => throw new NotSupportedException($"Non-async call to {nameof(CopyTo)}");
+		public override void Write(ReadOnlySpan<byte> buffer) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
+		public override int Read(Span<byte> buffer) => throw new NotSupportedException($"Non-async call to {nameof(Read)}");
+
+		public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
+		public override void WriteByte(byte value) => throw new NotSupportedException($"Non-async call to {nameof(Write)}");
+
+		public override int Read(byte[] buffer, int offset, int count)  => throw new NotSupportedException($"Non-async call to {nameof(Read)}");
+		public override int ReadByte() => throw new NotSupportedException($"Non-async call to {nameof(ReadByte)}");
+
+		// Even though our mock stream is writing synchronously, this should not fail the tests
+		public override async Task CopyToAsync(Stream destination, int bufferSize, CancellationToken cancellationToken) 
+		{
+			var buf = new byte[bufferSize];
+			while(_inner.Read(buf, 0, bufferSize) > 0) {
+				await destination.WriteAsync(buf, cancellationToken);
+			}
+		}
+		public override Task FlushAsync(CancellationToken cancellationToken) => TaskFromBlocking(() => _inner.Flush());
+		public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) => TaskFromBlocking(() => _inner.Write(buffer, offset, count));
+		public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) => Task.FromResult(_inner.Read(buffer, offset, count));
+		public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default) => ValueTaskFromBlocking(() => _inner.Write(buffer.Span));
+		public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default) => ValueTask.FromResult(_inner.Read(buffer.Span));
+
+		static Task TaskFromBlocking(Action action)
+		{
+			action();
+			return Task.CompletedTask;
+		}
+
+		static ValueTask ValueTaskFromBlocking(Action action)
+		{
+			action();
+			return ValueTask.CompletedTask;
+		}
+
+		public override long Seek(long offset, SeekOrigin origin)
+		{
+			return _inner.Seek(offset, origin);
+		}
+
+		public override void SetLength(long value)
+		{
+			_inner.SetLength(value);
+		}
+	}
+#endif
+
 	/// <summary>
 	/// A <see cref="Stream"/> that cannot be read but supports infinite writes.
 	/// </summary>

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

@@ -15,7 +15,7 @@ public class ZipStreamAsyncTests
 		[Category("Async")]
 		public async Task WriteZipStreamUsingAsync()
 		{
-#if NETCOREAPP3_1_OR_GREATER
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
 			await using var ms = new MemoryStream();
 
 			await using (var outStream = new ZipOutputStream(ms){IsStreamOwner = false})
@@ -121,5 +121,32 @@ public async Task WriteReadOnlyZipStreamAsync ()
 			ZipTesting.AssertValidZip(new MemoryStream(ms.ToArray()));
 		}
 
+		[Test]
+		[Category("Zip")]
+		[Category("Async")]
+		public async Task WriteZipStreamToAsyncOnlyStream ()
+		{
+#if NETSTANDARD2_1 || NETCOREAPP3_0_OR_GREATER
+			await using(var ms = new MemoryStreamWithoutSync()){
+				await using(var outStream = new ZipOutputStream(ms) { IsStreamOwner = false })
+				{
+					await outStream.PutNextEntryAsync(new ZipEntry("FirstFile"));
+					await Utils.WriteDummyDataAsync(outStream, 12);
+
+					await outStream.PutNextEntryAsync(new ZipEntry("SecondFile"));
+					await Utils.WriteDummyDataAsync(outStream, 12);
+
+					await outStream.FinishAsync(CancellationToken.None);
+					await outStream.DisposeAsync();
+				}
+
+				ZipTesting.AssertValidZip(new MemoryStream(ms.ToArray()));
+			}
+#else
+			await Task.CompletedTask;
+			Assert.Ignore("AsyncDispose is not supported");
+#endif
+		}
+
 	}
 }