Create base class for codebooks.

src/main/java/cz/it4i/qcmp/quantization/Codebook.java

+package cz.it4i.qcmp.quantization;
+
+import cz.it4i.qcmp.huffman.HuffmanDecoder;
+import cz.it4i.qcmp.huffman.HuffmanEncoder;
+import cz.it4i.qcmp.huffman.HuffmanNode;
+import cz.it4i.qcmp.huffman.HuffmanTreeBuilder;
+
+public class Codebook {
+
+    /**
+     * Huffman tree root.
+     */
+    private final HuffmanNode huffmanRoot;
+
+    // Cached encoder and decoder.
+    private HuffmanEncoder huffmanEncoder;
+    private HuffmanDecoder huffmanDecoder;
+
+    /**
+     * Create base codebook with huffman tree symbol coder.
+     *
+     * @param huffmanRoot Root of the huffman tree.
+     */
+    protected Codebook(final HuffmanNode huffmanRoot) {
+        this.huffmanRoot = huffmanRoot;
+    }
+
+
+    /**
+     * Get huffman decoder of this codebook.
+     *
+     * @return Symbol decoder.
+     */
+    public HuffmanDecoder getHuffmanDecoder() {
+        if (huffmanDecoder == null)
+            huffmanDecoder = new HuffmanDecoder(huffmanRoot);
+        return huffmanDecoder;
+    }
+
+    /**
+     * Get huffman encoder of this codebook.
+     *
+     * @return Symbol encoder.
+     */
+    public HuffmanEncoder getHuffmanEncoder() {
+        if (huffmanEncoder == null)
+            huffmanEncoder = new HuffmanEncoder(huffmanRoot, HuffmanTreeBuilder.createSymbolCodes(huffmanRoot));
+        return huffmanEncoder;
+    }
+}