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/*
* Copyright 2001, 2002 Adrian Thurston <thurston@complang.org>
*/
/* This file is part of Aapl.
*
* Aapl is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* Aapl 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 Lesser General Public License for
* more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Aapl; if not, write to the Free Software Foundation, Inc., 59
* Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef _AAPL_TABLE_H
#define _AAPL_TABLE_H
#ifdef AAPL_NAMESPACE
namespace Aapl {
#endif
/**
* \addtogroup vector
* @{
*/
/** \class Table
* \brief Base class for dynamic arrays.
*
* Table is used as the common data storage class for vectors. It does not
* provide any methods to operate on the data and as such it is not intended
* to be used directly. It exists so that algorithms that operatate on dynamic
* arrays can be written without knowing about the various vector classes that
* my exist.
*/
/*@}*/
/* Table class. */
template <class T> class Table
{
public:
/* Default Constructor. */
inline Table();
/**
* \brief Get the length of the vector.
*
* \returns the length of the vector.
*/
long length() const
{ return tabLen; }
/**
* \brief Table data.
*
* The pointer to the elements in the vector. Modifying the vector may
* cause this pointer to change.
*/
T *data;
/**
* \brief Table length.
*
* The number of items of type T in the table.
*/
long tabLen;
/**
* \brief Allocated length.
*
* The number of items for which there is room in the current allocation.
*/
long allocLen;
};
/**
* \brief Default constructor
*
* Initialize table data to empty.
*/
template <class T> inline Table<T>::Table()
:
data(0),
tabLen(0),
allocLen(0)
{
}
/* Default shared table header class. */
struct STabHead
{
/**
* \brief Table length.
*
* The number of items of type T in the table.
*/
long tabLen;
/**
* \brief Allocated length.
*
* The number of items for which there is room in the current allocation.
*/
long allocLen;
/**
* \brief Ref Count.
*
* The number of shared vectors referencing this data.
*/
long refCount;
};
/**
* \addtogroup vector
* @{
*/
/** \class STable
* \brief Base class for implicitly shared dynamic arrays.
*
* STable is used as the common data storage class for shared vectors. It does
* not provide any methods to operate on the data and as such it is not
* intended to be used directly. It exists so that algorithms that operatate
* on dynamic arrays can be written without knowing about the various shared
* vector classes that my exist.
*/
/*@}*/
/* STable class. */
template <class T> class STable
{
public:
/* Default Constructor. */
inline STable();
/**
* \brief Get the length of the shared vector.
*
* \returns the length of the shared vector.
*/
long length() const
{ return data == 0 ? 0 : (((STabHead*)data) - 1)->tabLen; }
/**
* \brief Get header of the shared vector.
*
* \returns the header of the shared vector.
*/
STabHead *header() const
{ return data == 0 ? 0 : (((STabHead*)data) - 1); }
/**
* \brief Table data.
*
* The pointer to the elements in the vector. The shared table header is
* located just behind the data. Modifying the vector may cause this
* pointer to change.
*/
T *data;
};
/**
* \brief Default constructor
*
* Initialize shared table data to empty.
*/
template <class T> inline STable<T>::STable()
:
data(0)
{
}
/* If needed is greater than existing, give twice needed. */
#define EXPN_UP( existing, needed ) \
needed > existing ? (needed<<1) : existing
/* If needed is less than 1 quarter existing, give twice needed. */
#define EXPN_DOWN( existing, needed ) \
needed < (existing>>2) ? (needed<<1) : existing
/**
* \addtogroup vector
* @{
*/
/** \class ResizeExpn
* \brief Exponential table resizer.
*
* ResizeExpn is the default table resizer. When an up resize is needed, space
* is doubled. When a down resize is needed, space is halved. The result is
* that when growing the vector in a linear fashion, the number of resizes of
* the allocated space behaves logarithmically.
*
* If only up resizes are done, there will never be more than 2 times the
* needed space allocated. If down resizes are done as well, there will never
* be more than 4 times the needed space allocated. ResizeExpn uses this 50%
* usage policy on up resizing and 25% usage policy on down resizing to
* improve performance when repeatedly inserting and removing a small number
* of elements relative to the size of the array. This scheme guarantees that
* repetitive inserting and removing of a small number of elements will never
* result in repetative reallocation.
*
* The sizes passed to the resizer from the vectors are in units of T.
*/
/*@}*/
/* Exponential resizer. */
class ResizeExpn
{
protected:
/**
* \brief Determine the new table size when up resizing.
*
* If the existing size is insufficient for the space needed then allocate
* twice the space needed. Otherwise use the existing size.
*
* \returns The new table size.
*/
static inline long upResize( long existing, long needed )
{ return EXPN_UP( existing, needed ); }
/**
* \brief Determine the new table size when down resizing.
*
* If the space needed is less than one quarter of the existing size then
* allocate twice the space needed. Otherwise use the exitsing size.
*
* \returns The new table size.
*/
static inline long downResize( long existing, long needed )
{ return EXPN_DOWN( existing, needed ); }
};
#undef EXPN_UP
#undef EXPN_DOWN
#ifdef AAPL_NAMESPACE
}
#endif
#endif /* _AAPL_TABLE_H */
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