Add preamble to Snappy stream

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

@@ -0,0 +1,75 @@
+/*--------------------------------------------------------------------------
+ *  Copyright 2011 Taro L. Saito
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *--------------------------------------------------------------------------*/
+//--------------------------------------
+// XerialJ
+//
+// SnappyInputStream.java
+// Since: 2011/03/31 20:14:56
+//
+// $URL$
+// $Author$
+//--------------------------------------
+package org.xerial.snappy;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * A stream filter for reading data compressed by {@link SnappyOutputStream}.
+ * 
+ * @author leo
+ * 
+ */
+public class SnappyInputStream extends InputStream
+{
+    protected final InputStream in;
+    private int                 blockSize = SnappyOutputStream.DEFAULT_BLOCK_SIZE;
+
+    private byte[]              compressed;
+    private byte[]              uncompressed;
+
+    public SnappyInputStream(InputStream input) throws IOException {
+        this.in = input;
+        readHeader();
+    }
+
+    protected void readHeader() throws IOException {
+        byte[] header = new byte[SnappyOutputStream.PREAMBLE_SIZE];
+        int readBytes = in.read(header);
+        if (readBytes != header.length) {
+            throw new IOException("Invalid Snappy stream");
+        }
+        String headerStr = new String(header, 0, SnappyOutputStream.HEADER_SIZE, "UTF-8");
+        if (!headerStr.startsWith(SnappyOutputStream.STREAM_FORMAT_VERSION)) {
+            throw new IOException("Incompatible stream version");
+        }
+        blockSize = SnappyOutputStream.readInt(header, SnappyOutputStream.HEADER_SIZE);
+        if (blockSize < 0) {
+            throw new IOException("Invalid block size: " + blockSize);
+        }
+
+        compressed = new byte[blockSize];
+        uncompressed = new byte[blockSize];
+
+    }
+
+    @Override
+    public int read() throws IOException {
+        // TODO Auto-generated method stub
+        return 0;
+    }
+
+}

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

@@ -43,9 +43,11 @@ import java.util.Arrays;
  */
 public class SnappyOutputStream extends OutputStream
 {
-    public static final int      HEADER_SIZE        = 16 + 4; // version (16 bytes) & block size (int: 4 bytes)
+    public final static String   STREAM_FORMAT_VERSION = "snappy-1.0.1";
+    public static final int      HEADER_SIZE           = 16;             // version (16 bytes) 
+    public static final int      PREAMBLE_SIZE         = HEADER_SIZE + 4; // version (16 bytes) & block size (int: 4 bytes)
 
-    private static final int     DEFAULT_BLOCK_SIZE = 1 << 15; // use 2^15 = 32KB as block size
+    static final int             DEFAULT_BLOCK_SIZE    = 1 << 15;        // use 2^15 = 32KB as block size
 
     protected final OutputStream out;
     private final int            blockSize;
@@ -68,7 +70,7 @@ public class SnappyOutputStream extends OutputStream
     protected void writeHeader() throws IOException {
         byte[] header = new byte[16]; // header size
         Arrays.fill(header, (byte) 0);
-        byte[] version = "snappy-1.0.1".getBytes("UTF-8");
+        byte[] version = STREAM_FORMAT_VERSION.getBytes("UTF-8");
         assert (version.length <= 16);
         System.arraycopy(version, 0, header, 0, version.length);
         out.write(header);