eccodes/examples/C/iterator.c

/*
 * Copyright 2005-2015 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

/*
 * C Implementation: iterator
 *
 * Description: how to use an iterator on lat/lon/values.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "eccodes.h"  

void usage(const char* prog) {
    printf("Usage: %s grib_file\n",prog);
    exit(1);
}

int main(int argc, char** argv)
{
    FILE* in = NULL;
    int err = 0;
    double lat,lon,value,missingValue=0;
    int n=0;
    char* filename = NULL;

    /* Message handle. Required in all the grib_api calls acting on a message.*/
    codes_handle *h = NULL;
    /* Iterator on lat/lon/values.*/
    codes_iterator* iter=NULL;

    if (argc != 2) usage(argv[0]);

    filename=argv[1];

    in = fopen(filename,"r");
    if(!in) {
        printf("ERROR: unable to open file %s\n", filename);
        return 1;
    }

    /* Loop on all the messages in a file.*/
    while ((h = codes_handle_new_from_file(0,in,&err)) != NULL ) {
        /* Check of errors after reading a message. */
        if (err != CODES_SUCCESS) CODES_CHECK(err,0);

        /* Get the double representing the missing value in the field. */
        CODES_CHECK(codes_get_double(h,"missingValue",&missingValue),0);

        /* A new iterator on lat/lon/values is created from the message handle h. */
        iter=codes_iterator_new(h,0,&err);
        if (err != CODES_SUCCESS) CODES_CHECK(err,0);

        n = 0;
        /* Loop on all the lat/lon/values. */
        while(codes_iterator_next(iter,&lat,&lon,&value)) {
            /* You can now print lat and lon,  */
            printf("- %d - lat=%f lon=%f value=",n,lat,lon);
            /* decide what to print if a missing value is found. */
            if (value == missingValue ) printf("missing\n");
            /* and print the value if is not missing. */
            else printf("%f\n",value);
            n++;
        }

        /* At the end the iterator is deleted to free memory. */
        codes_iterator_delete(iter);

        /* At the end the codes_handle is deleted to free memory. */
        codes_handle_delete(h);
    }

    fclose(in);

    return 0;
}