Fix flushing GZipOutputStream so all data is written to the underlying stream

src/ICSharpCode.SharpZipLib/GZip/GzipInputStream.cs

@@ -139,6 +139,9 @@ public override int Read(byte[] buffer, int offset, int count)
 				if (inf.IsFinished)
 				{
 					ReadFooter();
+				} else if (inf.RemainingInput == 0) {
+					// If the stream is not finished but we have no more data to read, don't keep looping forever
+					throw new GZipException("Unexpected EOF");
 				}
 
 				if (bytesRead > 0)

src/ICSharpCode.SharpZipLib/Zip/Compression/DeflaterEngine.cs

@@ -643,7 +643,7 @@ private bool DeflateStored(bool flush, bool finish)
 
 				huffman.FlushStoredBlock(window, blockStart, storedLength, lastBlock);
 				blockStart += storedLength;
-				return !lastBlock;
+				return !(lastBlock || storedLength == 0);
 			}
 			return true;
 		}

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

@@ -241,7 +241,12 @@ protected void InitializeAESPassword(ZipEntry entry, string rawPassword,
 		/// </summary>
 		protected void Deflate()
 		{
-			while (!deflater_.IsNeedingInput)
+			Deflate(false);
+		}
+
+		private void Deflate(bool flushing)
+		{
+			while (flushing || !deflater_.IsNeedingInput)
 			{
 				int deflateCount = deflater_.Deflate(buffer_, 0, buffer_.Length);
 
@@ -380,7 +385,7 @@ public override int Read(byte[] buffer, int offset, int count)
 		public override void Flush()
 		{
 			deflater_.Flush();
-			Deflate();
+			Deflate(true);
 			baseOutputStream_.Flush();
 		}
 

test/ICSharpCode.SharpZipLib.Tests/GZip/GZipTests.cs

@@ -289,6 +289,61 @@ public void TrailingGarbage()
 			}
 		}
 
+		/// <summary>
+		/// Test that if we flush a GZip output stream then all data that has been written
+		/// is flushed through to the underlying stream and can be successfully read back
+		/// even if the stream is not yet finished.
+		/// </summary>
+		[Test]
+		[Category("GZip")]
+		public void FlushToUnderlyingStream()
+		{
+			var ms = new MemoryStream();
+			var outStream = new GZipOutputStream(ms);
+
+			byte[] buf = new byte[100000];
+			var rnd = new Random();
+			rnd.NextBytes(buf);
+
+			outStream.Write(buf, 0, buf.Length);
+			// Flush output stream but don't finish it yet
+			outStream.Flush();
+
+			ms.Seek(0, SeekOrigin.Begin);
+
+			var inStream = new GZipInputStream(ms);
+			byte[] buf2 = new byte[buf.Length];
+			int currentIndex = 0;
+			int count = buf2.Length;
+
+			while (true)
+			{
+				try
+				{
+					int numRead = inStream.Read(buf2, currentIndex, count);
+					if (numRead <= 0)
+					{
+						break;
+					}
+					currentIndex += numRead;
+					count -= numRead;
+				}
+				catch (GZipException)
+				{
+					// We should get an unexpected EOF exception once we've read all
+					// data as the stream isn't yet finished.
+					break;
+				}
+			}
+
+			Assert.AreEqual(0, count);
+
+			for (int i = 0; i < buf.Length; ++i)
+			{
+				Assert.AreEqual(buf2[i], buf[i]);
+			}
+		}
+
 		[Test]
 		[Category("GZip")]
 		[Category("Performance")]