sc_temporary.h

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

  sc_temporary.h -- Temporary value pool classes.

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

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

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// $Log: sc_temporary.h,v $
// Revision 1.1.1.1  2006/12/15 20:31:39  acg
// SystemC 2.2
//
// Revision 1.3  2006/01/13 18:53:11  acg
// Andy Goodrich: Added $Log command so that CVS comments are reproduced in
// the source.
//

#ifndef SC_TEMPORARY_H
#define SC_TEMPORARY_H

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()
//   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( int bytes_n )
    {
        char*   result_p;
        bytes_n = (bytes_n + 7) & 0xfffffff8;
        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( int heap_size=0x100000 )
    {
        if ( m_bgn_p ) 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 unsigned int length()
    {
        return (unsigned int)(m_end_p - m_bgn_p);
    }

    inline sc_byte_heap()
    {
        m_bgn_p = 0;
    }

    inline sc_byte_heap( int heap_size )
    {
        m_bgn_p = 0;
        initialize( heap_size );
    }

    inline ~sc_byte_heap()
    {
        if ( m_bgn_p ) 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:
    int m_pool_i;   // Index of next entry to m_pool_m to provide.
    T*  m_pool_p;   // Vector of temporaries.
    int 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 int size();
};

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

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> int sc_vpool<T>::size()
{
    return m_wrap + 1;
}

} // namespace sc_core

#endif // SC_TEMPORARY_H

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