slice_array.h

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// The template and inlines for the -*- C++ -*- slice_array class.

// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2004
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library 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 General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

// Written by Gabriel Dos Reis <[e-mail]>

/** @file slice_array.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _SLICE_ARRAY_H
#define _SLICE_ARRAY_H 1

//#pragma GCC system_header

namespace std
{
    /**
     *  @brief  Class defining one-dimensional subset of an array.
     *
     *  The slice class represents a one-dimensional subset of an array,
     *  specified by three parameters: start offset, size, and stride.  The
     *  start offset is the index of the first element of the array that is part
     *  of the subset.  The size is the total number of elements in the subset.
     *  Stride is the distance between each successive array element to include
     *  in the subset.
     *
     *  For example, with an array of size 10, and a slice with offset 1, size 3
     *  and stride 2, the subset consists of array elements 1, 3, and 5.
     */
    class slice
    {
        public:
            ///  Construct an empty slice.
            slice();

            /**
             *  @brief  Construct a slice.
             *
             *  @param  o  Offset in array of first element.
             *  @param  d  Number of elements in slice.
             *  @param  s  Stride between array elements.
             */
            slice(size_t, size_t, size_t);

            ///  Return array offset of first slice element.
            size_t start() const;
            ///  Return size of slice.
            size_t size() const;
            ///  Return array stride of slice.
            size_t stride() const;

        private:
            size_t _M_off;                      // offset
            size_t _M_sz;			// size
            size_t _M_st;			// stride unit
    };

    // The default constructor constructor is not required to initialize
    // data members with any meaningful values, so we choose to do nothing.
    inline
        slice::slice() {}

    inline
        slice::slice(size_t __o, size_t __d, size_t __s)
        : _M_off(__o), _M_sz(__d), _M_st(__s) {}

    inline size_t
        slice::start() const
        { return _M_off; }

    inline size_t
        slice::size() const
        { return _M_sz; }

    inline size_t
        slice::stride() const
        { return _M_st; }

    /**
     *  @brief  Reference to one-dimensional subset of an array.
     *
     *  A slice_array is a reference to the actual elements of an array
     *  specified by a slice.  The way to get a slice_array is to call
     *  operator[](slice) on a valarray.  The returned slice_array then permits
     *  carrying operations out on the referenced subset of elements in the
     *  original valarray.  For example, operator+=(valarray) will add values
     *  to the subset of elements in the underlying valarray this slice_array
     *  refers to.
     *
     *  @param  Tp  Element type.
     */
    template<typename _Tp>
        class slice_array
        {
            public:
                typedef _Tp value_type;

                // _GLIBCXX_RESOLVE_LIB_DEFECTS
                // 253. valarray helper functions are almost entirely useless

                ///  Copy constructor.  Both slices refer to the same underlying array.
                slice_array(const slice_array&);

                ///  Assignment operator.  Assigns slice elements to corresponding
                ///  elements of @a a.
                slice_array& operator=(const slice_array&);

                ///  Assign slice elements to corresponding elements of @a v.
                void operator=(const valarray<_Tp>&) const;
                ///  Multiply slice elements by corresponding elements of @a v.
                void operator*=(const valarray<_Tp>&) const;
                ///  Divide slice elements by corresponding elements of @a v.
                void operator/=(const valarray<_Tp>&) const;
                ///  Modulo slice elements by corresponding elements of @a v.
                void operator%=(const valarray<_Tp>&) const;
                ///  Add corresponding elements of @a v to slice elements.
                void operator+=(const valarray<_Tp>&) const;
                ///  Subtract corresponding elements of @a v from slice elements.
                void operator-=(const valarray<_Tp>&) const;
                ///  Logical xor slice elements with corresponding elements of @a v.
                void operator^=(const valarray<_Tp>&) const;
                ///  Logical and slice elements with corresponding elements of @a v.
                void operator&=(const valarray<_Tp>&) const;
                ///  Logical or slice elements with corresponding elements of @a v.
                void operator|=(const valarray<_Tp>&) const;
                ///  Left shift slice elements by corresponding elements of @a v.
                void operator<<=(const valarray<_Tp>&) const;
                ///  Right shift slice elements by corresponding elements of @a v.
                void operator>>=(const valarray<_Tp>&) const;
                ///  Assign all slice elements to @a t.
                void operator=(const _Tp &) const;
                //        ~slice_array ();

                template<class _Dom>
                    void operator=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator*=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator/=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator%=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator+=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator-=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator^=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator&=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator|=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator<<=(const _Expr<_Dom,_Tp>&) const;
                template<class _Dom>
                    void operator>>=(const _Expr<_Dom,_Tp>&) const;

            private:
                friend class valarray<_Tp>;
                slice_array(_Array<_Tp>, const slice&);

                const size_t     _M_sz;
                const size_t     _M_stride;
                const _Array<_Tp> _M_array;

                // not implemented
                slice_array();
        };

    template<typename _Tp>
        inline
        slice_array<_Tp>::slice_array(_Array<_Tp> __a, const slice& __s)
        : _M_sz(__s.size()), _M_stride(__s.stride()),
        _M_array(__a.begin() + __s.start()) {}

    template<typename _Tp>
        inline
        slice_array<_Tp>::slice_array(const slice_array<_Tp>& a)
        : _M_sz(a._M_sz), _M_stride(a._M_stride), _M_array(a._M_array) {}

    //    template<typename _Tp>
    //    inline slice_array<_Tp>::~slice_array () {}

    template<typename _Tp>
        inline slice_array<_Tp>&
        slice_array<_Tp>::operator=(const slice_array<_Tp>& __a)
        {
            std::__valarray_copy(__a._M_array, __a._M_sz, __a._M_stride,
                    _M_array, _M_stride);
            return *this;
        }

    template<typename _Tp>
        inline void
        slice_array<_Tp>::operator=(const _Tp& __t) const
        { std::__valarray_fill(_M_array, _M_sz, _M_stride, __t); }

    template<typename _Tp>
        inline void
        slice_array<_Tp>::operator=(const valarray<_Tp>& __v) const
        { std::__valarray_copy(_Array<_Tp>(__v), _M_array, _M_sz, _M_stride); }

    template<typename _Tp>
        template<class _Dom>
        inline void
        slice_array<_Tp>::operator=(const _Expr<_Dom,_Tp>& __e) const
        { std::__valarray_copy(__e, _M_sz, _M_array, _M_stride); }

#undef _DEFINE_VALARRAY_OPERATOR
#define _DEFINE_VALARRAY_OPERATOR(_Op,_Name)				\
    template<typename _Tp>						\
    inline void								\
    slice_array<_Tp>::operator _Op##=(const valarray<_Tp>& __v) const	\
    {									\
        _Array_augmented_##_Name(_M_array, _M_sz, _M_stride, _Array<_Tp>(__v));\
    }									\
    \
    template<typename _Tp>                                                \
    template<class _Dom>				                \
    inline void							\
    slice_array<_Tp>::operator _Op##=(const _Expr<_Dom,_Tp>& __e) const\
    {									\
        _Array_augmented_##_Name(_M_array, _M_stride, __e, _M_sz);	\
    }


    _DEFINE_VALARRAY_OPERATOR(*, __multiplies)
        _DEFINE_VALARRAY_OPERATOR(/, __divides)
        _DEFINE_VALARRAY_OPERATOR(%, __modulus)
        _DEFINE_VALARRAY_OPERATOR(+, __plus)
        _DEFINE_VALARRAY_OPERATOR(-, __minus)
        _DEFINE_VALARRAY_OPERATOR(^, __bitwise_xor)
        _DEFINE_VALARRAY_OPERATOR(&, __bitwise_and)
        _DEFINE_VALARRAY_OPERATOR(|, __bitwise_or)
        _DEFINE_VALARRAY_OPERATOR(<<, __shift_left)
        _DEFINE_VALARRAY_OPERATOR(>>, __shift_right)

#undef _DEFINE_VALARRAY_OPERATOR

} // std::

#endif /* _SLICE_ARRAY_H */

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