src/adapters/a.dijkstra.c

   1 #include <R.h>
   2 #include <Rdefines.h>
   3 #include "sources/dijkstra.h"
   4
   5 // Dijkstra from index start : return vector of distances to every other vertex
   6 // NOTE [space VS perf]: passing neighborhoods infos would be enough, but
   7 //                     require extra computation to translate R list argument
   8 SEXP dijkstra(
   9     SEXP distances_,
  10     SEXP start_
  11 ) {
  12     // get arguments
  13     SEXP dim = getAttrib(distances_, R_DimSymbol);
  14     int n = INTEGER(dim)[0];
  15     double* pDistsIn = REAL(distances_);
  16     int start = INTEGER_VALUE(start_) - 1; // R indices start at 1
  17
  18     // Main call to core algorithm
  19     double* distances = dijkstra_core(pDistsIn, start, n);
  20
  21     // allocate vector output and obtain R vector object
  22     SEXP distsOut;
  23     PROTECT(distsOut = allocVector(REALSXP, n));
  24     double* pDistsOut = NUMERIC_POINTER(distsOut);
  25     for (int i=0; i<n; i++)
  26         pDistsOut[i] = distances[i];
  27
  28     free(distances);
  29     UNPROTECT(1);
  30
  31     return distsOut;
  32 }