add SnappyOutputStream prototype

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

@@ -67,7 +67,7 @@ public class Snappy
      * High-level API for uncompressing the input byte array.
      * 
      * @param input
-     * @return
+     * @return the uncompressed byte array
      * @throws SnappyException
      */
     public static byte[] uncompress(byte[] input) throws SnappyException {
@@ -190,7 +190,7 @@ public class Snappy
      * @param inputLength
      * @param output
      * @param outputOffset
-     * @return
+     * @return the byte size of the uncompressed data
      * @throws SnappyException
      */
     public static int uncompress(byte[] input, int inputOffset, int inputLength, byte[] output, int outputOffset)

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

@@ -0,0 +1,108 @@
+/*--------------------------------------------------------------------------
+ *  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
+//
+// SnappyOutputStream.java
+// Since: 2011/03/31 17:44:10
+//
+// $URL$
+// $Author$
+//--------------------------------------
+package org.xerial.snappy;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * This class implements a stream filter for writing compressed data using
+ * Snappy.
+ * 
+ * The input data is blocked into 32KB size, and each block is compressed and
+ * then passed to the given {@link OutputStream}.
+ * 
+ * @author leo
+ * 
+ */
+public class SnappyOutputStream extends OutputStream
+{
+    protected final OutputStream out;
+
+    private int                  cursor     = 0;
+    protected byte[]             uncompressed;
+    protected byte[]             compressed;
+
+    protected final int          BLOCK_SIZE = 1 << 15; // use 2^15 = 32KB as block size
+
+    public SnappyOutputStream(OutputStream out) {
+        this.out = out;
+        uncompressed = new byte[BLOCK_SIZE];
+        compressed = new byte[Snappy.maxCompressedLength(BLOCK_SIZE)];
+    }
+
+    @Override
+    public void write(byte[] b, int off, int len) throws IOException {
+
+        for (int readBytes = 0; readBytes < len;) {
+            int copyLen = Math.min(uncompressed.length - cursor, len - readBytes);
+            System.arraycopy(b, off + readBytes, uncompressed, cursor, copyLen);
+            readBytes += copyLen;
+            cursor += copyLen;
+
+            if (cursor >= uncompressed.length) {
+                dump();
+            }
+        }
+    }
+
+    @Override
+    public void write(int b) throws IOException {
+        if (cursor >= uncompressed.length) {
+            dump();
+        }
+        uncompressed[cursor++] = (byte) b;
+    }
+
+    @Override
+    public void flush() throws IOException {
+        dump();
+        out.flush();
+    }
+
+    protected void dump() throws IOException {
+        if (cursor <= 0)
+            return; // no need to dump
+
+        // Compress and dump the buffer content
+        try {
+            int compressedSize = Snappy.compress(uncompressed, 0, cursor, compressed, 0);
+            out.write(compressed, 0, compressedSize);
+            cursor = 0;
+        }
+        catch (SnappyException e) {
+            throw new IOException(e);
+        }
+    }
+
+    @Override
+    public void close() throws IOException {
+        flush();
+
+        super.close();
+        out.close();
+    }
+
+}