Chunker.h

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/*
 * LSST Data Management System
 * Copyright 2014-2015 AURA/LSST.
 *
 * This product includes software developed by the
 * LSST Project (http://www.lsst.org/).
 *
 * This program 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 LSST License Statement and
 * the GNU General Public License along with this program.  If not,
 * see <https://www.lsstcorp.org/LegalNotices/>.
 */

#ifndef LSST_SPHGEOM_CHUNKER_H_
#define LSST_SPHGEOM_CHUNKER_H_


#include <stdint.h>
#include <vector>

#include "Angle.h"
#include "Box.h"


namespace lsst {
namespace sphgeom {

struct SubChunks {
    int32_t chunkId;
    std::vector<int32_t> subChunkIds;

    SubChunks() : chunkId(-1) {}

    void swap(SubChunks & sc) {
        std::swap(chunkId, sc.chunkId);
        subChunkIds.swap(sc.subChunkIds);
    }
};


class Chunker {
public:
    Chunker(int32_t numStripes,
            int32_t numSubStripesPerStripe);

    bool operator==(Chunker const & c) const {
        return _numStripes == c._numStripes &&
               _numSubStripesPerStripe == c._numSubStripesPerStripe;
    }

    bool operator!=(Chunker const & c) const {
        return _numStripes != c._numStripes ||
               _numSubStripesPerStripe != c._numSubStripesPerStripe;
    }

    int32_t getNumStripes() const {
        return _numStripes;
    }

    int32_t getNumSubStripesPerStripe() const {
        return _numSubStripesPerStripe;
    }

    std::vector<int32_t> getChunksIntersecting(Region const & r) const;

    std::vector<SubChunks> getSubChunksIntersecting(Region const & r) const;

    std::vector<int32_t> getAllChunks() const;

    std::vector<int32_t> getAllSubChunks(int32_t chunkId) const;

    bool valid(int32_t chunkId) const;

private:
    struct Stripe {
        Angle chunkWidth;
        int32_t numChunksPerStripe;
        int32_t numSubChunksPerChunk;

        Stripe() :
            chunkWidth(0),
            numChunksPerStripe(0),
            numSubChunksPerChunk(0)
        {}
    };

    struct SubStripe {
        Angle subChunkWidth;
        int32_t numSubChunksPerChunk;

        SubStripe() : subChunkWidth(), numSubChunksPerChunk(0) {}
    };

    int32_t _getStripe(int32_t chunkId) const {
        return chunkId / (2 * _numStripes);
    }

    int32_t _getChunk(int32_t chunkId, int32_t stripe) const {
        return chunkId - stripe*2*_numStripes;
    }

    int32_t _getChunkId(int32_t stripe, int32_t chunk) const {
        return stripe * 2 * _numStripes + chunk;
    }

    int32_t _getSubChunkId(int32_t stripe, int32_t subStripe,
                           int32_t chunk, int32_t subChunk) const {
        int32_t y = subStripe - stripe * _numSubStripesPerStripe;
        int32_t x = subChunk -
                    chunk * _subStripes[subStripe].numSubChunksPerChunk;
        return y * _maxSubChunksPerSubStripeChunk + x;
    }

    void _getSubChunks(std::vector<SubChunks> & subChunks,
                       Region const & r,
                       NormalizedAngleInterval const & lon,
                       int32_t stripe,
                       int32_t chunk,
                       int32_t minSS,
                       int32_t maxSS) const;
    Box _getChunkBoundingBox(int32_t stripe, int32_t chunk) const;
    Box _getSubChunkBoundingBox(int32_t subStripe, int32_t subChunk) const;

    int32_t _numStripes;
    int32_t _numSubStripesPerStripe;
    int32_t _numSubStripes;
    int32_t _maxSubChunksPerSubStripeChunk;
    Angle _subStripeHeight;
    std::vector<Stripe> _stripes;
    std::vector<SubStripe> _subStripes;
};

}} // namespace lsst::sphgeom

#endif // LSST_SPHGEOM_CHUNKER_H_