Throw IOException when writing to / flushing closed SnappyOutputStreams.

src/main/java/org/xerial/snappy/SnappyOutputStream.java

@@ -232,6 +232,9 @@ public class SnappyOutputStream extends OutputStream {
      * @throws IOException
      */
     public void rawWrite(Object array, int byteOffset, int byteLength) throws IOException {
+        if (closed) {
+            throw new IOException("Stream is closed");
+        }
         int cursor = 0;
         while(cursor < byteLength) {
             int readLen = Math.min(byteLength - cursor, blockSize - inputCursor);
@@ -259,6 +262,9 @@ public class SnappyOutputStream extends OutputStream {
      */
     @Override
     public void write(int b) throws IOException {
+        if (closed) {
+            throw new IOException("Stream is closed");
+        }
         if(inputCursor >= inputBuffer.length) {
             compressInput();
         }
@@ -270,6 +276,9 @@ public class SnappyOutputStream extends OutputStream {
      */
     @Override
     public void flush() throws IOException {
+        if (closed) {
+            throw new IOException("Stream is closed");
+        }
         compressInput();
         dumpOutput();
         out.flush();

src/test/java/org/xerial/snappy/SnappyOutputStreamTest.java

@@ -29,6 +29,7 @@ import static org.junit.Assert.*;
 import java.io.BufferedInputStream;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 
 import org.junit.Test;
 import org.xerial.snappy.buffer.BufferAllocatorFactory;
@@ -193,6 +194,37 @@ public class SnappyOutputStreamTest
         in3.close();
     }
 
+    @Test
+    public void writingToClosedStreamShouldThrowIOException() throws IOException {
+        ByteArrayOutputStream b = new ByteArrayOutputStream();
+        SnappyOutputStream os = new SnappyOutputStream(b);
+        os.close();
+        try {
+            os.write(4);
+            fail("Expected write() to throw IOException");
+        } catch (IOException e) {
+            // Expected exception
+        }
+        try {
+            os.write(new int[] { 1, 2, 3, 4});
+            fail("Expected write() to throw IOException");
+        } catch (IOException e) {
+            // Expected exception
+        }
+    }
+
+    @Test
+    public void flushingClosedStreamShouldThrowIOException() throws IOException {
+        ByteArrayOutputStream b = new ByteArrayOutputStream();
+        SnappyOutputStream os = new SnappyOutputStream(b);
+        os.close();
+        try {
+            os.flush();
+        } catch (IOException e) {
+            // Expected exception
+        }
+    }
+
     @Test
     public void longArrayCompress() throws Exception {
         long[] l = new long[10];