src/adapters/a.connexity.c

   1 #include <R.h>
   2 #include <Rdefines.h>
   3 #include "sources/connexity.h"
   4
   5 // explore the connectivity of a graph (NIix = neighborhoods indices)
   6 SEXP getConnectedComponents(
   7     SEXP NIix_
   8 ) {
   9     // extract NIix list vectors in a jagged array
  10     int n = LENGTH(NIix_);
  11     int* lengthNIix = (int*)malloc(n*sizeof(int));
  12     int** NIix = (int**)malloc(n*sizeof(int*));
  13     for (int i=0; i<n; i++)
  14     {
  15         lengthNIix[i] = LENGTH(VECTOR_ELT(NIix_,i));
  16         SEXP tmp;
  17         PROTECT(tmp = AS_INTEGER(VECTOR_ELT(NIix_,i)));
  18         NIix[i] = (int*)malloc(lengthNIix[i]*sizeof(int));
  19         for (int j=0; j<lengthNIix[i]; j++)
  20             NIix[i][j] = INTEGER(tmp)[j];
  21         UNPROTECT(1);
  22         // WARNING: R indices start at 1,
  23         // so we must lower every index right now to avoid future bug
  24         for (int j=0; j<lengthNIix[i]; j++)
  25             NIix[i][j]--;
  26     }
  27
  28     // Main call (no R libraries)
  29     int* connexComps = getConnectedComponents_core(NIix, lengthNIix, n);
  30
  31     // free memory
  32     for (int i=0; i<n; i++)
  33         free(NIix[i]);
  34     free(NIix);
  35     free(lengthNIix);
  36
  37     // transfer result in an R object
  38     SEXP cc;
  39     PROTECT(cc = NEW_INTEGER(n));
  40     int* pcc = INTEGER_POINTER(cc);
  41     for (int i=0; i<n; i++)
  42         pcc[i] = connexComps[i];
  43
  44     // free remaining memory
  45     free(connexComps);
  46     UNPROTECT(1);
  47
  48     return cc;
  49 }