statistical encoding

brouter-codec/src/main/java/btools/codec/LinkedListContainer.java

@@ -0,0 +1,87 @@
+package btools.codec;
+
+/**
+ * Simple container for a list of lists of integers
+ */
+public class LinkedListContainer
+{
+  private int[] ia; // prev, data, prev, data, ...
+  private int size;
+  private int[] startpointer; // 0=void, odd=head-data-cell
+  private int listpointer;
+
+  /**
+   * Construct a container for the given number of lists
+   *
+   * If no default-buffer is given, an int[nlists*4] is constructed,
+   * able to hold 2 entries per list on average
+   *
+   * @param nlists the number of lists
+   * @param defaultbuffer an optional data array for re-use (gets replaced if too small)
+   */
+  public LinkedListContainer( int nlists, int[] defaultbuffer )
+  {
+    ia = defaultbuffer == null ? new int[nlists*4] : defaultbuffer;
+    startpointer = new int[nlists]; 
+  }
+  
+  /**
+   * Add a data element to the given list
+   *
+   * @param listNr the list to add the data to
+   * @param data the data value
+   */
+  public void addDataElement( int listNr, int data )
+  {
+    if ( size + 2 > ia.length )
+    {
+      resize();
+    }
+    ia[size++] = startpointer[ listNr ];
+    startpointer[ listNr ] = size;
+    ia[size++] = data;
+  }
+  
+  /**
+   * Initialize a list for reading
+   *
+   * @param listNr the list to initialize
+   * @return the number of entries in that list
+   */
+  public int initList( int listNr )
+  {
+    int cnt = 0;
+    int lp = listpointer = startpointer[ listNr ];
+    while( lp != 0 )
+    {
+      lp = ia[ lp-1 ];
+      cnt++;
+    }
+    return cnt;
+  }
+
+  /**
+   * Get a data element from the list previously initialized.
+   * Data elements are return in reverse order (lifo)
+   *
+   * @return the data element
+   * @throws IllegalArgumentException if no more element
+   */
+  public int getDataElement()
+  {
+    if ( listpointer == 0 )
+    {
+      throw new IllegalArgumentException( "no more element!" );
+    }
+    int data = ia[ listpointer ];
+    listpointer = ia[ listpointer-1 ];
+    return data;
+  }
+  
+  private void resize()
+  {
+    int[] ia2 = new int[2*ia.length];
+    System.arraycopy( ia, 0, ia2, 0, ia.length );
+    ia = ia2;
+  }
+}