DmrppChunkOdometer.h

// -*- mode: c++; c-basic-offset:4 -*-
 
// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.
 
// Copyright (c) 2015 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library 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.
//
// 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
 
#ifndef DMRPP_CHUNK_ODOMETER_H_
#define DMRPP_CHUNK_ODOMETER_H_
 
#include <vector>
 
namespace dmrpp {
 
using shape = std::vector<unsigned long long>;

class DmrppChunkOdometer
{
private:
    // The state set by the ctor
    shape d_shape;
    shape d_array_shape;
 
    // The varying state of the Odometer
    shape d_indices;
 
public:
    DmrppChunkOdometer() = default;
    ~DmrppChunkOdometer() = default;

    DmrppChunkOdometer(shape chunk_shape, shape array_shape) :
        d_shape(std::move(chunk_shape)), d_array_shape(std::move(array_shape))
    {
        reset();
    }

    void reset() noexcept
    {
        d_indices.resize(d_shape.size(), 0);
    }

    inline bool next()
    {
        bool status = false;    // false indicates the last 'odometer value' has been found
        auto si = d_shape.rbegin();
        auto ai = d_array_shape.rbegin();
        for (auto i = d_indices.rbegin(), e = d_indices.rend(); i != e; ++i, ++si, ++ai) {
            *i = *i + *ai;
            if (*i >= *si) {
                *i = 0;
            }
            else {
                status = true;
                break;
            }
        }
 
        return status;
    }

    inline const shape &indices() const noexcept
    {
        return d_indices;
    }
};
 
}   // namespace libdap
 
#endif // DMRPP_CHUNK_ODOMETER_H_