Add test for isValidCompressedBuffer. Add a comment on the usage of SnappyOutputStream

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

@@ -34,8 +34,14 @@ import java.io.OutputStream;
  * The input data is blocked into 32kb size (in default), and each block is
  * compressed and then passed to the given {@link OutputStream}.
  * 
- * The output data format is a sequence of (compressed chunk size, compressed
+ * The output data format is a sequence of (compressed data size, compressed
- * data chunk binary...) pair.
+ * data...) pair.
+ * 
+ * Note that the compressed data created by {@link SnappyOutputStream} cannot be
+ * uncompressed by {@link Snappy#uncompress(byte[])} since the output formats of
+ * {@link Snappy#compress(byte[])} and {@link SnappyOutputStream} are different.
+ * Use {@link SnappyInputStream} for uncompress the data generated by
+ * {@link SnappyOutputStream}.
  * 
  * @author leo
  * 

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

@@ -283,4 +283,14 @@ public class SnappyTest
         assertEquals(s, uncompressedString);
     }
 
+    @Test
+    public void isValidCompressedData() throws Exception {
+
+        byte[] b = new byte[] { (byte) 91, (byte) 34, (byte) 80, (byte) 73, (byte) 34, (byte) 93 };
+        if (Snappy.isValidCompressedBuffer(b, 0, b.length)) {
+            byte[] uncompressed = Snappy.uncompress(b);
+        }
+
+    }
+
 }