Fix chunk type for stream identifier

Motivation:
The problem with the current snappy implementation is that it does
not comply with framing format definition found on
https://code.google.com/p/snappy/source/browse/trunk/framing_format.txt

The document describes that chunk type of the stream identifier is defined
as 0xff. The current implentation uses 0x80.

Modifications:
This patch replaces the first byte of the chunk type of the stream identifier
with 0xff.

Result:
After this modification the snappy implementation is compliant to the
framing format described at
https://code.google.com/p/snappy/source/browse/trunk/framing_format.txt.
This results in a better compatibility with other implementations.

codec/src/main/java/io/netty/handler/codec/compression/SnappyFramedDecoder.java

@@ -198,7 +198,7 @@ public class SnappyFramedDecoder extends ByteToMessageDecoder {
             return ChunkType.COMPRESSED_DATA;
         } else if (type == 1) {
             return ChunkType.UNCOMPRESSED_DATA;
-        } else if (type == -0x80) {
+        } else if (type == (byte) 0xff) {
             return ChunkType.STREAM_IDENTIFIER;
         } else if ((type & 0x80) == 0x80) {
             return ChunkType.RESERVED_SKIPPABLE;

codec/src/main/java/io/netty/handler/codec/compression/SnappyFramedEncoder.java

@@ -40,7 +40,7 @@ public class SnappyFramedEncoder extends MessageToByteEncoder<ByteBuf> {
      * type 0xff, a length field of 0x6, and 'sNaPpY' in ASCII.
      */
     private static final byte[] STREAM_START = {
-        -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59
+        (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59
     };
 
     private final Snappy snappy = new Snappy();

codec/src/test/java/io/netty/handler/codec/compression/SnappyFramedDecoderTest.java

@@ -53,7 +53,7 @@ public class SnappyFramedDecoderTest {
     @Test(expected = DecompressionException.class)
     public void testInvalidStreamIdentifierValue() throws Exception {
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-            -0x80, 0x06, 0x00, 0x00, 's', 'n', 'e', 't', 't', 'y'
+            (byte) 0xff, 0x06, 0x00, 0x00, 's', 'n', 'e', 't', 't', 'y'
         });
 
         channel.writeInbound(in);
@@ -89,7 +89,7 @@ public class SnappyFramedDecoderTest {
     @Test
     public void testReservedSkippableSkipsInput() throws Exception {
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-           -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+           (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
            -0x7f, 0x05, 0x00, 0x00, 'n', 'e', 't', 't', 'y'
         });
 
@@ -102,7 +102,7 @@ public class SnappyFramedDecoderTest {
     @Test
     public void testUncompressedDataAppendsToOut() throws Exception {
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-           -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+           (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
             0x01, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 'n', 'e', 't', 't', 'y'
         });
 
@@ -115,7 +115,7 @@ public class SnappyFramedDecoderTest {
     @Test
     public void testCompressedDataDecodesAndAppendsToOut() throws Exception {
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-           -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+           (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
             0x00, 0x0B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                   0x05, // preamble length
                   0x04 << 2, // literal tag + length
@@ -137,7 +137,7 @@ public class SnappyFramedDecoderTest {
 
         // checksum here is presented as 0
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-           -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+           (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
             0x01, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 'n', 'e', 't', 't', 'y'
         });
 
@@ -150,7 +150,7 @@ public class SnappyFramedDecoderTest {
 
         // checksum here is presented as a282986f (little endian)
         ByteBuf in = Unpooled.wrappedBuffer(new byte[] {
-           -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+           (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
             0x01, 0x09, 0x00, 0x00, 0x6f, -0x68, -0x7e, -0x5e, 'n', 'e', 't', 't', 'y'
         });
 

codec/src/test/java/io/netty/handler/codec/compression/SnappyFramedEncoderTest.java

@@ -43,7 +43,7 @@ public class SnappyFramedEncoderTest {
         assertTrue(channel.finish());
 
         ByteBuf expected = Unpooled.wrappedBuffer(new byte[] {
-            -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+            (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
              0x01, 0x09, 0x00, 0x00, 0x6f, -0x68, -0x7e, -0x5e, 'n', 'e', 't', 't', 'y'
         });
 
@@ -61,7 +61,7 @@ public class SnappyFramedEncoderTest {
         assertTrue(channel.finish());
 
         ByteBuf expected = Unpooled.wrappedBuffer(new byte[] {
-            -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+            (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
              0x00, 0x0E, 0x00, 0x00, 0x3b, 0x36, -0x7f, 0x37,
                    0x14, 0x10,
                    'n', 'e', 't', 't', 'y',
@@ -83,7 +83,7 @@ public class SnappyFramedEncoderTest {
         assertTrue(channel.finish());
 
         ByteBuf expected = Unpooled.wrappedBuffer(new byte[] {
-            -0x80, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
+            (byte) 0xff, 0x06, 0x00, 0x00, 0x73, 0x4e, 0x61, 0x50, 0x70, 0x59,
              0x01, 0x09, 0x00, 0x00, 0x6f, -0x68, -0x7e, -0x5e, 'n', 'e', 't', 't', 'y',
              0x01, 0x09, 0x00, 0x00, 0x6f, -0x68, -0x7e, -0x5e, 'n', 'e', 't', 't', 'y',
         });