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/* Copyright (C) 2002-2003  Mark Andrew Aikens <marka@desert.cx>
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * $Id: DataBuffer.h,v 1.7 2003/03/21 23:07:47 marka Exp $
#ifndef __DataBuffer_h
#define __DataBuffer_h

#include <sys/types.h>
#include <map>

/** \file */

/** This class implements a sparse buffer by allocating chunks of the
 * buffer only as they are needed. The maximum size that the buffer can
 * grow is \c num_chunks * \c chunk_size words. On an access to the
 * DataBuffer, new chunks will be allocated automatically when needed.
00033 class DataBuffer {
      /** The maximum number of chunks to which the buffer can grow. */
00036       static const long num_chunks = 4096;

      /** The number of words in a chunk. Must be a power of 2. */
00039       static const int chunk_size = 4096;

      /** The number of bits to represent the offset in a chunk.
       * (log2 chunk_size) */
00043       static const int chunk_size_bits = 12;

      /** Constructs a DataBuffer. When the DataBuffer is created, all the
       * locations will be cleared (all binary 1's) according to the wordsize.
       * \param wordsize The size of a word (in bits) that each location of
       *        the DataBuffer will contain.
      DataBuffer(int wordsize=16);

      /** Frees all memory and resources associated with this instance. */

      /** Clears the entire contents of the buffer. */
      void clear(void);

      /** Gets the word size that was specified to the constructor.
       * \returns The word size in bits. */
      int get_wordsize(void);

      /** Compare the contents of this DataBuffer with another.
       * \param other The DataBuffer to compare with this one.
       * \retval -1 If the DataBuffers have the same contents.
       * \retval >=0 The first address where the DataBuffers differ.
      long compare(DataBuffer& other);

      /** Checks to see if a memory location contains the blank value.
       * \param addr The offset into the DataBuffer to check.
       * \returns A boolean value indicating if the location contains
       *          a value of all binary 1's.
      bool isblank(size_t addr);

      /** The index operator used for retrieving the address of elements.
       * If the access is to a chunk which doesn't exist, the chunk will be
       * allocated and the contents of the chunk will be set to the clear
       * value.
       * \throws bad_alloc If a new chunk couldn't be allocated.
       * \throws out_of_range If the offset \c n is greater than the
       *         maximum size of the DataBuffer.
      unsigned int& operator[](size_t n);

      int wordsize;
      unsigned int clearvalue;
      unsigned int *chunktable[num_chunks];


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