h3_polygon.c

/*
 * Copyright 2018-2021 Uber Technologies, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/** @file polygon.c
 * @brief Polygon (GeoLoop) algorithms
 */

#include "h3_polygon.h"

#include <float.h>
#include <math.h>
#include <stdbool.h>

#include "h3_bbox.h"
#include "h3_constants.h"
#include "h3_h3api.h"
#include "h3_latLng.h"
#include "h3_linkedGeo.h"

// Define macros used in polygon algos for GeoLoop
#define TYPE GeoLoop
#define INIT_ITERATION INIT_ITERATION_GEOFENCE
#define ITERATE ITERATE_GEOFENCE
#define IS_EMPTY IS_EMPTY_GEOFENCE

#include "h3_polygonAlgos.h"

#undef TYPE
#undef INIT_ITERATION
#undef ITERATE
#undef IS_EMPTY

/**
 * Create a bounding box from a GeoPolygon
 * @param polygon Input GeoPolygon
 * @param bboxes  Output bboxes, one for the outer loop and one for each hole
 */
void bboxesFromGeoPolygon(const GeoPolygon *polygon, BBox *bboxes) {
    bboxFromGeoLoop(&polygon->geoloop, &bboxes[0]);
    for (int i = 0; i < polygon->numHoles; i++) {
        bboxFromGeoLoop(&polygon->holes[i], &bboxes[i + 1]);
    }
}

/**
 * pointInsidePolygon takes a given GeoPolygon data structure and
 * checks if it contains a given geo coordinate.
 *
 * @param geoPolygon The geoloop and holes defining the relevant area
 * @param bboxes     The bboxes for the main geoloop and each of its holes
 * @param coord      The coordinate to check
 * @return           Whether the point is contained
 */
bool pointInsidePolygon(const GeoPolygon *geoPolygon, const BBox *bboxes,
                        const LatLng *coord) {
    // Start with contains state of primary geoloop
    bool contains =
        pointInsideGeoLoop(&(geoPolygon->geoloop), &bboxes[0], coord);

    // If the point is contained in the primary geoloop, but there are holes in
    // the geoloop iterate through all holes and return false if the point is
    // contained in any hole
    if (contains && geoPolygon->numHoles > 0) {
        for (int i = 0; i < geoPolygon->numHoles; i++) {
            if (pointInsideGeoLoop(&(geoPolygon->holes[i]), &bboxes[i + 1],
                                   coord)) {
                return false;
            }
        }
    }

    return contains;
}