Share Library (C++)

#ifndef DEFAULT_ALLOCATOR_H
#define DEFAULT_ALLOCATOR_H
 
/**
 * @file DefaultAllocator.h
 * @brief Allocator for blocks inside shared segment
 * @author Kamil Dudka, xdudka00@gmail.com
 * @date 2007-05-15
 * @ingroup backend
 */
 
#include "sharelib.h"
 
/**
 * @brief Define @b memory @b alignment in bits that allocator work with.
 * @attention This number could not be greater then OS's alignment used in SHM API
 * @ingroup backend
 */
#define BITS_ALIGNMENT 8
 
namespace Share {
  /**
   * Template parameter bitsAlignment specifies count of bits from end to align to.
   * @brief Generic number alignmenter
   * @param input number to align
   * @return aligned number
   * @ingroup backend
   */
  template <
    unsigned char bitsAlignment,
    typename T >
  T genericAlignmenter (T input)
  {
    return
      (
       ((1 << bitsAlignment) - 1) |
       (input - 1)
      ) + 1;
  }
 
  /**
   * @brief Number alignmenter using @c BITS_ALIGNMENT macro.
   * @param input number to align
   * @return aligned number
   * @ingroup backend
   */
  template <typename T>
  inline T alignmenter (T input) {
    return genericAlignmenter <BITS_ALIGNMENT, T> (input);
  }
 
  /**
   * @brief Allocator for blocks inside shared segment
   * @note This class can be replaced with more efficient class with equivalet interface by changing Share::TSegmentAllocator
   * @ingroup backend
   */
  class DefaultAllocator/*: public AbstractAllocator*/ {
    public:
      /**
       * @brief Pointer type used inside segment
       */
      typedef RelocPtr<char> TRelocPtr;
 
      /**
       * @param atAddr Address of attached shared segment. At this addres is placed SegmentHeader object.
       * @param segmentHeaderSize Size of SegmentHeader object.
       * @param dataSize Desired size of memory for data inside shared segment.
       * @throw ShareException Library-specific exception derived from std::bad_alloc
       */
      DefaultAllocator(void *atAddr, size_t segmentHeaderSize, size_t dataSize) throw (ShareException);
      ~DefaultAllocator();
 
      /**
       * @param segmentHeaderSize Size of SegmentHeader object.
       * @param dataSize Desired size o memory for data inside shared segment.
       * @return Return computed size of shared segment to allocate.
       */
      static size_t sizeNeeded (size_t segmentHeaderSize, size_t dataSize);
 
      /**
       * Allocate block of memory inside shared segment. ShareException is thrown if not success.
       * @param size Desired size of block to allocate.
       * @return Return local address of allocated block on success.
       * @throw ShareException Library-specific exception derived from std::bad_alloc
       */
      void *alloc (size_t size) throw (ShareException);
 
      /**
       * Free block of memory previously allocated by alloc() method.
       * @param addr Address of block returned by alloc() method.
       * @attention All attached application may crash if this method is called with invalid address as parameter
       */
      void free (void *addr) throw ();
 
      /**
       * @return Return total size of memory for data inside shared segment.
       * @note Usable memory inside shared segment could be smaller due to free space fragmentation.
       */
      size_t size();
 
      /**
       * @return Return size of available memory for data inside shared segment.
       */
      size_t available();
 
    private:
      DefaultAllocator (const DefaultAllocator&);
      void operator= (const DefaultAllocator&);
 
    private:
      size_t size_;
      size_t available_;
      TRelocPtr current_;
  };
}
 
#endif // DEFAULT_ALLOCATOR_H