libgofigure-dev 0.9.0-3 / usr / include / gofigure2 / Allocator.h

/*=========================================================================
 Authors: Michael Kazhdan and Matthew Bolitho
 at Johns Hopkins University, 2006-10

 Copyright (c) 2006-10, Michael Kazhdan and Matthew Bolitho,
 Johns Hopkins University.
 All rights reserved.

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 this list of conditions and the following disclaimer.
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 and/or other materials provided with the distribution.
 Neither the name of the Johns Hopkins University nor the names of its
 contributors may be used to endorse or promote products derived from this
 software without specific prior written permission.

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 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
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=========================================================================*/
#ifndef ALLOCATOR_INCLUDED
#define ALLOCATOR_INCLUDED
#include <vector>
#include <cstdio>

class AllocatorState
{
public:
  int index, remains;
};
/** This templated class assists in memory allocation and is well suited
 * for instances when it is known that the sequence of memory allocations
 * is performed in a stack-based manner, so that memory allocated last is
 * released first. It also preallocates memory in chunks so that multiple
 * requests for small chunks of memory do not require separate system calls
 *  to the memory manager.
  * The allocator is templated off of the class of objects that we would
  * like it to allocate, ensuring that appropriate constructors and
  * destructors are called as necessary.
  *
  * \ingroup PoissonReconstruction
  */
template< class T >
class Allocator
{
  int                blockSize;
  int                index, remains;
  std::vector< T * > memory;
public:
  Allocator(void)
  {
    blockSize = index = remains = 0;
  }

  ~Allocator(void)
  {
    reset();
  }

  /** This method is the allocators destructor.
 * It frees up any of the memory that it has allocated. */
  void reset(void)
  {
    for ( size_t i = 0; i < memory.size(); i++ ) { delete[] memory[i]; }
    memory.clear();
    blockSize = index = remains = 0;
  }

  /** This method returns the memory state of the allocator. */
  AllocatorState getState(void) const
  {
    AllocatorState s;

    s.index = index;
    s.remains = remains;
    return s;
  }

  /** This method rolls back the allocator so that it makes all of the
 * memory previously allocated available for re-allocation. Note that it
 * does it not call the constructor again, so after this method has been
 * called, assumptions about the state of the values in memory are no
 * longer valid. */
  void rollBack(void)
  {
    if ( memory.size() )
      {
      for ( size_t i = 0; i < memory.size(); i++ )
        {
        for ( int j = 0; j < blockSize; j++ )
          {
          memory[i][j].~T();
          new ( &memory[i][j] )T();
          }
        }
      index = 0;
      remains = blockSize;
      }
  }

  /** This method rolls back the allocator to the previous memory state
 * and makes all of the memory previously allocated available for
 * re-allocation. Note that it does it not call the constructor again,
 * so after this method has been called, assumptions about the state of
 * the values in memory are no longer valid. */
  void rollBack(const AllocatorState & state)
  {
    if ( state.index < index || ( state.index == index && state.remains < remains ) )
      {
      if ( state.index < index )
        {
        for ( int j = state.remains; j < blockSize; j++ )
          {
          memory[state.index][j].~T();
          new ( &memory[state.index][j] )T();
          }
        for ( int i = state.index + 1; i < index - 1; i++ )
          {
          for ( int j = 0; j < blockSize; j++ )
            {
            memory[i][j].~T();
            new ( &memory[i][j] )T();
            }
          }
        for ( int j = 0; j < remains; j++ )
          {
          memory[index][j].~T();
          new ( &memory[index][j] )T();
          }
        index = state.index;
        remains = state.remains;
        }
      else
        {
        for ( int j = 0; j < state.remains; j++ )
          {
          memory[index][j].~T();
          new ( &memory[index][j] )T();
          }
        remains = state.remains;
        }
      }
  }

  /** This method initiallizes the constructor and the blockSize variable
 * specifies the the number of objects that should be pre-allocated at a
 * time. */
  void set(const int & iBlockSize)
  {
    reset();
    this->blockSize = iBlockSize;
    index = -1;
    remains = 0;
  }

  /** This method returns a pointer to an array of elements objects. If
 * there is left over pre-allocated memory, this method simply returns a
 * pointer to the next free piece of memory, otherwise it pre-allocates
 * more memory. Note that if the number of objects requested is larger
 * than the value blockSize with which the allocator was initialized, the
 * request for memory will fail.
    */
  T * newElements(const int & elements = 1)
  {
    T *mem;

    if ( !elements ) { return NULL; }
    if ( elements > blockSize )
      {
      fprintf(stderr, "Allocator Error, elements bigger than block-size: %d>%d\n", elements, blockSize);
      return NULL;
      }
    if ( remains < elements )
      {
      if ( index == static_cast< int >( memory.size() - 1 ) )
        {
        mem = new T[blockSize];
        if ( !mem ) { fprintf(stderr, "Failed to allocate memory\n"); exit(0); }
        memory.push_back(mem);
        }
      index++;
      remains = blockSize;
      }
    mem = &( memory[index][blockSize - remains] );
    remains -= elements;
    return mem;
  }
};
#endif // ALLOCATOR_INCLUDE