sc_temporary.hh

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/*****************************************************************************

  sc_temporary.h -- Temporary value pool classes.

  Original Author: Andy Goodrich, Forte Design Systems, Inc.

  CHANGE LOG AT END OF FILE
 *****************************************************************************/

#ifndef __SYSTEMC_EXT_DT_SC_TEMPORARY_HH__
#define __SYSTEMC_EXT_DT_SC_TEMPORARY_HH__

#include <cstddef> // std::size_t

namespace sc_core
{

//-----------------------------------------------------------------------------
// sc_byte_heap - CLASS MANAGING A TEMPORARY HEAP OF BYTES
//
// This facility implements a heap of temporary byte allocations. Once an
// request has been allocated it is not freed. However the entire heap
// wraps and the storage is reused. This means that no allocations should
// be assumed as permanent. Allocations are double-word aligned. This is
// raw storage, so objects which contain virtual methods cannot be allocated
// with this object. See the sc_vpool object for that type of storage
// allocation.
//
// char* allocate( int size )
//   This method returns a pointer to block of size bytes. The block
//   returned is the next available one in the heap. If the current heap
//   cannot fullfil the request it will be rewound and storage allocated from
//   its start. All allocations start on an 8-byte boundary.
//       size = number of bytes to be allocated.
//
// void initialize( int heap_size=0x100000 )
//   This method allocates the storage to be managed. If there is already
//   a block of storage under management it is freed. If no argument is
//   provided for the heap size, a megabyte will be allocated.
//       heap_size = number of bytes to allocate for the heap.
//
// unsigned int length()
//   This method returns the size of this object's heap in bytes.
//
// sc_byte_heap()
//   This is the non-initialized object instance constructor. It does not
//   allocate the heap storage, that is done by the initialize() method.
//
// sc_byte_heap(int)
//   This is the initializing object instance constructor. It does allocates
//   a heap of the specified number of bytes.
//       heap_size = number of bytes to allocate for the heap.
//-----------------------------------------------------------------------------
class sc_byte_heap
{
  public:
    char *m_bgn_p; // Beginning of heap storage.
    char *m_end_p; // End of heap storage.
    char *m_next_p; // Next heap location to be allocated.

    inline char *
    allocate(std::size_t bytes_n)
    {
        char *result_p;
        bytes_n = (bytes_n + 7) & ((std::size_t)(-8));
        result_p = m_next_p;
        m_next_p += bytes_n;
        if (m_next_p >= m_end_p) {
            result_p = m_bgn_p;
            m_next_p = m_bgn_p + bytes_n;
        }
        return result_p;
    }

    inline void
    initialize(std::size_t heap_size=0x100000)
    {
        delete [] m_bgn_p;
        m_bgn_p = new char[heap_size];
        m_end_p = &m_bgn_p[heap_size];
        m_next_p = m_bgn_p;
    }

    inline std::size_t
    length()
    {
        return (std::size_t)(m_end_p - m_bgn_p);
    }

    inline sc_byte_heap() : m_bgn_p(0), m_end_p(0), m_next_p(0) {}

    inline sc_byte_heap(std::size_t heap_size) :
            m_bgn_p(0), m_end_p(0), m_next_p(0)
    {
        initialize(heap_size);
    }

    inline ~sc_byte_heap() { delete [] m_bgn_p; }
};


//-----------------------------------------------------------------------------
// sc_vpool<T> - CLASS MANAGING A TEMPORARY VECTOR OF CLASS T INSTANCES
//
// This class implements a fixed pool of objects contained in a vector. These
// objects are allocated via the allocate() method. An index, m_pool_i,
// indicates the next object to be allocated. The vector is a power of 2 in
// size, and this fact is used to wrap the list when m_pool_i reaches the
// end of the vector.
//
// sc_vpool( int log2, T* pool_p=0 )
//   This is the object instance constructor for this class. It configures
//   the object to manage a vector of 2**log2 entries. If a vector is
//   not supplied one will be allocated.
//     log2   =  the log base two of the size of the vector.
//     pool_p -> vector of 2**log2 entries to be managed or 0.
//
// ~sc_vpool()
//   This is the object instance destructor for this class. It frees the
//   block of storage which was being managed.
//
// T* allocate()
//   This method returns the address of the next entry in the vector, m_pool_p,
//   pointed to by the index, m_pool_i, and updates that index. The index
//   update consists of adding 1 to m_pool_i and masking it by m_wrap.
//
// void reset()
//   This method resets the allocation index, m_pool_i, to point to the start
//   of the vector of objects under management. This call is not usually made
//   since there are a fixed number of entries and the index wraps. However,
//   for diagnostics tests it is convenient to be able to reset to the start
//   of the vector.
//
// int size()
//   This method returns the number of object instances contained in the
//   vector being managed by this object instance.
//-----------------------------------------------------------------------------
template<class T>
class sc_vpool
{
  protected:
    std::size_t m_pool_i; // Index of next entry to m_pool_m to provide.
    T *m_pool_p; // Vector of temporaries.
    std::size_t m_wrap; // Mask to wrap vector index.

  public:
    inline sc_vpool(int log2, T *pool_p=0);
    inline ~sc_vpool();
    inline T *allocate();
    inline void reset();
    inline std::size_t size();
};

template<class T>
sc_vpool<T>::sc_vpool(int log2, T *pool_p) : m_pool_i(0),
        m_pool_p(pool_p ? pool_p : new T[static_cast<std::size_t>(1) << log2]),
        m_wrap(~(static_cast<std::size_t>(-1) << log2))
{
    // if (log2 > 32) SC_REPORT_ERROR(SC_ID_POOL_SIZE_, "");
}

template<class T>
sc_vpool<T>::~sc_vpool()
{
    // delete [] m_pool_p;
}

template<class T>
T *sc_vpool<T>::allocate()
{
    T *result_p; // Entry to return.

    result_p = &m_pool_p[m_pool_i];
    m_pool_i = (m_pool_i + 1) & m_wrap;
    return result_p;
}

template<class T>
void sc_vpool<T>::reset()
{
    m_pool_i = 0;
}

template<class T>
std::size_t sc_vpool<T>::size() { return m_wrap + 1; }

} // namespace sc_core

// $Log: sc_temporary.h,v $
// Revision 1.4  2011/08/26 20:46:19  acg
//  Andy Goodrich: moved the modification log to the end of the file to
//  eliminate source line number skew when check-ins are done.
//
// Revision 1.3  2011/08/24 22:05:56  acg
//  Torsten Maehne: initialization changes to remove warnings.
//
// Revision 1.2  2011/02/18 20:38:44  acg
//  Andy Goodrich: Updated Copyright notice.
//
// Revision 1.1.1.1  2006/12/15 20:20:06  acg
// SystemC 2.3
//
// Revision 1.3  2006/01/13 18:53:11  acg
// Andy Goodrich: Added $Log command so that CVS comments are reproduced in
// the source.
//

#endif // __SYSTEMC_EXT_DT_SC_TEMPORARY_HH__