/* table_offset.h
 * Copyright (C) 2008, Francisco Claude, all rights reserved.
 *
 * Table for offsets definition.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#ifndef _TABLE_OFFSET_H
#define	_TABLE_OFFSET_H

#include <basics.h>
#include <iostream>

using namespace std;

/** Universal table required for static_bitsequence_rrr02, Raman, Raman and Rao's [1] 
 *  proposal for rank/select capable data structures, it achieves space nH_0, 
 *  O(sample_rate) time for rank and O(log len) for select. The practial implementation 
 *  is based on [2]
 * 
 *  [1] R. Raman, V. Raman and S. Rao. Succinct indexable dictionaries with applications 
 *     to encoding $k$-ary trees and multisets. SODA02.
 *  [2] F. Claude and G. Navarro. Practical Rank/Select over Arbitrary Sequences. SPIRE08.
 *
 *  @author Francisco Claude
 */
class table_offset {

public:
  /** builds a universal table, designed for u<=15 */
	table_offset(uint u);
	~table_offset();
	
	/** Increments the counter of users for the table */
	inline void use() {
		users_count++;
	}
	
	/** Tells the object that the user is not going to need the table anymore. */
	inline table_offset * unuse() {
		users_count--;
		if(!users_count) {
			delete this;
      return NULL;
    }
    return this;
	}
	
	/** Computes binomial(n,k) for n,k<=u */
	inline uint get_binomial(uint n, uint k) {
		return binomial[n][k];
	}
	
	/** Computes ceil(log2(binomial(n,k))) for n,k<=u */
	inline ushort get_log2binomial(uint n, uint k) {
		return log2binomial[n][k];
	}
	
	/** Returns the bitmap represented by the given class and inclass offsets */
	inline ushort short_bitmap(uint class_offset, uint inclass_offset) {
		if(class_offset==0) return 0;
		if(class_offset==u) return (ushort)(((uint)1<<u)-1);
		return short_bitmaps[offset_class[class_offset]+inclass_offset];
	}
	
	/** Returns u */
	inline uint get_u() {
		return u;
	}
	
	/** Computes the offset of the first u bits of a given bitstring */
	inline ushort compute_offset(ushort v) {
		return rev_offset[v];
	}
	
	/** Returns the size of the bitmap in bytes */
	uint size();

protected:
	int users_count;
	uint u;
	uint ** binomial;
	ushort * rev_offset;
	ushort ** log2binomial;
	ushort * offset_class;
	ushort * short_bitmaps;
	
	void fill_tables();
};

#endif
