bbox.cpp

#include <Rcpp.h>

#include "bbox.h"

// [[Rcpp::export(rng=false)]]
Rcpp::NumericVector CPL_get_bbox(Rcpp::List sf, int depth = 0) {
	Rcpp::NumericVector bb(4);
	bb[0] = bb[1] = bb[2] = bb[3] = NA_REAL;
	auto n = sf.size();

	switch(depth) {
		case 0: // points:
		for (decltype(n) i = 0; i < n; i++) {
			Rcpp::NumericVector pt = sf[i];
			if (i == 0) {
				bb[0] = bb[2] = pt[0];
				bb[1] = bb[3] = pt[1];
			} else {
				bb[0] = std::min(pt[0],bb[0]);
				bb[1] = std::min(pt[1],bb[1]);
				bb[2] = std::max(pt[0],bb[2]);
				bb[3] = std::max(pt[1],bb[3]);
			}
		}
		break;

		case 1: { // list of matrices:
			bool initialised = false;
			for (decltype(n) i = 0; i < n; i++) {
				Rcpp::NumericMatrix m = sf[i];
				auto rows = m.nrow();
	
				if (rows > 0) { // non-empty:
					if (! initialised) { // initialize:
						bb[0] = bb[2] = m(0,0);
						bb[1] = bb[3] = m(0,1);
						initialised = true;
					}
					for (decltype(rows) j = 0; j < rows; j++) {
						bb[0] = std::min(m(j,0),bb[0]);
						bb[1] = std::min(m(j,1),bb[1]);
						bb[2] = std::max(m(j,0),bb[2]);
						bb[3] = std::max(m(j,1),bb[3]);
					}
				}
			}
		}
		break;

		default: // recursive list
		for (decltype(n) i = 0; i < n; i++) {
			Rcpp::NumericVector bbi = CPL_get_bbox(sf[i], depth - 1); // recurse
			if (! Rcpp::NumericVector::is_na(bbi[0])) {
				if (i == 0) {
					bb[0] = bbi[0];
					bb[1] = bbi[1];
					bb[2] = bbi[2];
					bb[3] = bbi[3];
				} else {
					bb[0] = std::min(bbi[0],bb[0]);
					bb[1] = std::min(bbi[1],bb[1]);
					bb[2] = std::max(bbi[2],bb[2]);
					bb[3] = std::max(bbi[3],bb[3]);
				}
			}
		}
		break;
	}
	return bb;
}