dynarray.h

hoard内存管理器

/*

  Heap Layers: An Extensible Memory Allocation Infrastructure
  
  Copyright (C) 2000-2003 by Emery Berger
  http://www.cs.umass.edu/~emery
  [e-mail]
  
  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
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  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

*/

#ifndef _DYNARRAY_H_
#define _DYNARRAY_H_

#include <assert.h>
#include <stdlib.h>

/**
 * @class DynamicArray
 * @brief A dynamic array that grows to fit any index for assignment.
 *
 * This array also features a clear() method,
 * to free the entire array, and a trim(n) method,
 * which tells the array it is no bigger than n elements.
 */

namespace HL {

template <class ObjType>
class DynamicArray {
public:
  DynamicArray (void)
    : internalArray (NULL),
      internalArrayLength (0)
  {}

  ~DynamicArray (void)
  {
    clear();
  }

  /// Clear deletes everything in the array.
  inline void clear (void) {
    if (internalArray != NULL) {
      delete internalArray;
      internalArray = NULL;
      internalArrayLength = 0;
      //printf ("\ninternalArrayLength %x = %d\n", this, internalArrayLength);
    }
  }

  /// Read-only access to an array element; asserts that index is in range.
  inline const ObjType& operator[] (int index) const {
    assert (index < internalArrayLength);
    assert (index >= 0);
    return internalArray[index];
  }

  /// Access an array index by reference, growing the array if necessary.
  inline ObjType& operator[] (int index) {
    assert (index >= 0);
    if (index >= internalArrayLength) {

      // This index is beyond the current size of the array.
      // Grow the array by doubling and copying the old array into the new.

      const int newSize = index * 2 + 1;
      ObjType * arr = new ObjType[newSize];
#if MALLOC_TRACE
      printf ("m %x %d\n", arr, newSize * sizeof(ObjType));
#endif
      if (internalArray != NULL) {
	memcpy (arr, internalArray, internalArrayLength * sizeof(ObjType));
	delete internalArray;
#if MALLOC_TRACE
	printf ("f %x\n", internalArray);
#endif
      }
      internalArray = arr;
      internalArrayLength = newSize;
      //printf ("\ninternalArrayLength %x = %d\n", this, internalArrayLength);
    }
    return internalArray[index];
  }

  /**
   * Trim informs the array that it is now only nelts long
   * as far as the client is concerned. This may trigger
   * shrinking of the array.
   */
  inline void trim (int nelts) {

    // Halve the array if the number of elements
    // drops below one-fourth of the array size.

    if (internalArray != NULL) {
      if (nelts * 4 < internalArrayLength) {
	const int newSize = nelts * 2;
	ObjType * arr = new ObjType[newSize];
#if MALLOC_TRACE
	printf ("m %x %d\n", arr, newSize * sizeof(ObjType));
#endif
	memcpy (arr, internalArray, sizeof(ObjType) * nelts);
	delete internalArray;
#if MALLOC_TRACE
	printf ("f %x\n", internalArray);
#endif
	internalArray = arr;
	internalArrayLength = newSize;
      }
      assert (nelts <= internalArrayLength);
    }
  }


private:

  /// The pointer to the current array.
  ObjType * internalArray;

  /// The length of the internal array, in elements.
  int internalArrayLength;
};

};

#endif