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*/

#ifndef __TBB_blocked_range_H
#define __TBB_blocked_range_H

#include "tbb_stddef.h"

namespace tbb {

namespace internal {

// blocked_rangeNd_impl forward declaration in tbb::internal namespace to
// name it as a friend for a tbb::blocked_range.
template<typename Value, unsigned int N, typename>
class blocked_rangeNd_impl;

} // namespace internal

/** \page range_req Requirements on range concept
    Class \c R implementing the concept of range must define:
    - \code R::R( const R& ); \endcode               Copy constructor
    - \code R::~R(); \endcode                        Destructor
    - \code bool R::is_divisible() const; \endcode   True if range can be partitioned into two subranges
    - \code bool R::empty() const; \endcode          True if range is empty
    - \code R::R( R& r, split ); \endcode            Split range \c r into two subranges.
**/

//! A range over which to iterate.
/** @ingroup algorithms */
template<typename Value>
class blocked_range {
public:
    //! Type of a value
    /** Called a const_iterator for sake of algorithms that need to treat a blocked_range
        as an STL container. */
    typedef Value const_iterator;

    //! Type for size of a range
    typedef std::size_t size_type;

#if __TBB_DEPRECATED_BLOCKED_RANGE_DEFAULT_CTOR
    //! Construct range with default-constructed values for begin, end, and grainsize.
    /** Requires that Value have a default constructor. */
    blocked_range() : my_end(), my_begin(), my_grainsize() {}
#endif

    //! Construct range over half-open interval [begin,end), with the given grainsize.
    blocked_range( Value begin_, Value end_, size_type grainsize_=1 ) :
        my_end(end_), my_begin(begin_), my_grainsize(grainsize_)
    {
        __TBB_ASSERT( my_grainsize>0, "grainsize must be positive" );
    }

    //! Beginning of range.
    const_iterator begin() const {return my_begin;}

    //! One past last value in range.
    const_iterator end() const {return my_end;}

    //! Size of the range
    /** Unspecified if end()<begin(). */
    size_type size() const {
        __TBB_ASSERT( !(end()<begin()), "size() unspecified if end()<begin()" );
        return size_type(my_end-my_begin);
    }

    //! The grain size for this range.
    size_type grainsize() const {return my_grainsize;}

    //------------------------------------------------------------------------
    // Methods that implement Range concept
    //------------------------------------------------------------------------

    //! True if range is empty.
    bool empty() const {return !(my_begin<my_end);}

    //! True if range is divisible.
    /** Unspecified if end()<begin(). */
    bool is_divisible() const {return my_grainsize<size();}

    //! Split range.
    /** The new Range *this has the second part, the old range r has the first part.
        Unspecified if end()<begin() or !is_divisible(). */
    blocked_range( blocked_range& r, split ) :
        my_end(r.my_end),
        my_begin(do_split(r, split())),
        my_grainsize(r.my_grainsize)
    {
        // only comparison 'less than' is required from values of blocked_range objects
        __TBB_ASSERT( !(my_begin < r.my_end) && !(r.my_end < my_begin), "blocked_range has been split incorrectly" );
    }

#if __TBB_USE_PROPORTIONAL_SPLIT_IN_BLOCKED_RANGES
    //! Static field to support proportional split
    static const bool is_splittable_in_proportion = true;

    //! Split range.
    /** The new Range *this has the second part split according to specified proportion, the old range r has the first part.
        Unspecified if end()<begin() or !is_divisible(). */
    blocked_range( blocked_range& r, proportional_split& proportion ) :
        my_end(r.my_end),
        my_begin(do_split(r, proportion)),
        my_grainsize(r.my_grainsize)
    {
        // only comparison 'less than' is required from values of blocked_range objects
        __TBB_ASSERT( !(my_begin < r.my_end) && !(r.my_end < my_begin), "blocked_range has been split incorrectly" );
    }
#endif /* __TBB_USE_PROPORTIONAL_SPLIT_IN_BLOCKED_RANGES */

private:
    /** NOTE: my_end MUST be declared before my_begin, otherwise the splitting constructor will break. */
    Value my_end;
    Value my_begin;
    size_type my_grainsize;

    //! Auxiliary function used by the splitting constructor.
    static Value do_split( blocked_range& r, split )
    {
        __TBB_ASSERT( r.is_divisible(), "cannot split blocked_range that is not divisible" );
        Value middle = r.my_begin + (r.my_end - r.my_begin) / 2u;
        r.my_end = middle;
        return middle;
    }

#if __TBB_USE_PROPORTIONAL_SPLIT_IN_BLOCKED_RANGES
    static Value do_split( blocked_range& r, proportional_split& proportion )
    {
        __TBB_ASSERT( r.is_divisible(), "cannot split blocked_range that is not divisible" );

        // usage of 32-bit floating point arithmetic is not enough to handle ranges of
        // more than 2^24 iterations accurately. However, even on ranges with 2^64
        // iterations the computational error approximately equals to 0.000001% which
        // makes small impact on uniform distribution of such range's iterations (assuming
        // all iterations take equal time to complete). See 'test_partitioner_whitebox'
        // for implementation of an exact split algorithm
        size_type right_part = size_type(float(r.size()) * float(proportion.right())
                                         / float(proportion.left() + proportion.right()) + 0.5f);
        return r.my_end = Value(r.my_end - right_part);
    }
#endif /* __TBB_USE_PROPORTIONAL_SPLIT_IN_BLOCKED_RANGES */

    template<typename RowValue, typename ColValue>
    friend class blocked_range2d;

    template<typename RowValue, typename ColValue, typename PageValue>
    friend class blocked_range3d;

    template<typename DimValue, unsigned int N, typename>
    friend class internal::blocked_rangeNd_impl;
};

} // namespace tbb

#endif /* __TBB_blocked_range_H */
