# usecases/c/UsesCase_MEDfield_3.c

    /*  This file is part of MED.
     *
     *  COPYRIGHT (C) 1999 - 2012  EDF R&D, CEA/DEN
     *  MED is free software: you can redistribute it and/or modify
     *  it under the terms of the GNU Lesser General Public License as published by
     *  the Free Software Foundation, either version 3 of the License, or
     *  (at your option) any later version.
     *
     *  MED 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 Lesser General Public License for more details.
     *
     *  You should have received a copy of the GNU Lesser General Public License
     *  along with MED.  If not, see <http://www.gnu.org/licenses/>.
     */

    #include <med.h>
    #define MESGERR 1
    #include <med_utils.h>

    #include <string.h>

    #include <med.h>
    #define MESGERR 1
    #include <med_utils.h>

    #include <string.h>

    /*
     * Field use case 3 : read a field (generic approach)
     */

    int main (int argc, char **argv) {
      med_idt fid;
      med_idt nfield, i, j;
      char meshname[MED_NAME_SIZE+1]="";
      med_bool localmesh;
      char fieldname[MED_NAME_SIZE+1]="";
      med_field_type fieldtype;
      char *componentname = NULL;
      char *componentunit = NULL;
      char dtunit[MED_SNAME_SIZE+1]="";
      med_float *values = NULL;
      med_int nstep, nvalues;
      med_int ncomponent;
      med_geometry_type geotype;
      med_geometry_type *geotypes = MED_GET_CELL_GEOMETRY_TYPE;
      int ret=-1;

      /* file creation */
      fid = MEDfileOpen("UsesCase_MEDfield_1.med",MED_ACC_RDONLY);
      if (fid < 0) {
        MESSAGE("ERROR : open file ...");
        goto ERROR;
      }

      /*
       * generic approach : how many fields in the file and identification
       * of each field.
       */
      if ((nfield = MEDnField(fid)) < 0) {
        MESSAGE("ERROR : How many fields in the file ...");
        goto ERROR;
      }

      for (i=0; i<nfield; i++) {

        /* field information
         * ... we know that the field has no computation step
         * and that the field values type is MED_FLOAT64, a real code working would check ...
         */
        if ((ncomponent = MEDfieldnComponent(fid,i+1)) < 0) {
          MESSAGE("ERROR : number of field component ...");
          goto ERROR;
        }

        if ((componentname = (char *) malloc(ncomponent*MED_SNAME_SIZE+1)) == NULL) {
          MESSAGE("ERROR : memory allocation ...");
          goto ERROR;
        }

        if ((componentunit = (char *) malloc(ncomponent*MED_SNAME_SIZE+1)) == NULL) {
          MESSAGE("ERROR : memory allocation ...");
          goto ERROR;
        }

        if (MEDfieldInfo(fid, i+1, fieldname, meshname, &localmesh, &fieldtype,
                         componentname, componentunit, dtunit, &nstep) < 0) {
          MESSAGE("ERROR : Field info ...");
          free(componentname); free(componentunit);
          goto ERROR;
        }
        free(componentname); free(componentunit);

        /* read field values for nodes and cells */

        /* MED_NODE */
        if ((nvalues = MEDfieldnValue(fid, fieldname, MED_NO_DT, MED_NO_IT, MED_NODE, MED_NONE)) < 0) {
          MESSAGE("ERROR : read number of values ...");
          goto ERROR;
        }

        if (nvalues) {
          if ((values = (med_float *) malloc(sizeof(med_float)*nvalues*ncomponent)) == NULL) {
            MESSAGE("ERROR : memory allocation ...");
            goto ERROR;
          }
          if (MEDfieldValueRd(fid, fieldname, MED_NO_DT, MED_NO_IT, MED_NODE, MED_NONE,
                              MED_FULL_INTERLACE, MED_ALL_CONSTITUENT, (unsigned char*) values) < 0) {
            MESSAGE("ERROR : read fields values defined on vertices ...");
            free(values);
            goto ERROR;
          }
          free(values);
        }

        /* MED_CELL */
        for (j=1; j<=MED_N_CELL_FIXED_GEO; j++) {
          geotype = geotypes[j];

          if ((nvalues = MEDfieldnValue(fid, fieldname, MED_NO_DT, MED_NO_IT, MED_CELL,
                                        geotype)) < 0) {
            MESSAGE("ERROR : read number of values ...");
            goto ERROR;
          }

          if (nvalues) {
            if ((values = (med_float *) malloc(sizeof(med_float)*nvalues*ncomponent)) == NULL) {
              MESSAGE("ERROR : memory allocation ...");
              goto ERROR;
            }
            if (MEDfieldValueRd(fid, fieldname, MED_NO_DT, MED_NO_IT, MED_CELL, geotype,
                                MED_FULL_INTERLACE, MED_ALL_CONSTITUENT, (unsigned char*) values) < 0) {
              MESSAGE("ERROR : read fields values for cells ...");
              free(values);
              goto ERROR;
            }
            free(values);
          }
        }
      }

      ret=0;
     ERROR:

      /* close file */
      if (MEDfileClose(fid) < 0) {
        MESSAGE("ERROR : close file ...");
        ret=-1;
      }

      return ret;
    }