eccodes/examples/C/grib_list.c

/*
 * (C) Copyright 2005- 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: grib_list
 *
 * Description: how to get values using keys.
 *
 */
#include <stdio.h>
#include <assert.h>

#include "eccodes.h"

int main(int argc, char** argv)
{
    int err = 0;

    size_t i = 0;
    size_t count;
    size_t size;

    long numberOfContributingSpectralBands;
    long values[1024];
    long new_values[1024];

    FILE* in             = NULL;
    const char* filename = "../../data/satellite.grib";
    codes_handle* h      = NULL;

    in = fopen(filename, "rb");
    if (!in) {
        fprintf(stderr, "Error: unable to open input file %s\n", filename);
        return 1;
    }

    /* create new handle from a message in a file*/
    h = codes_handle_new_from_file(0, in, PRODUCT_GRIB, &err);
    if (h == NULL) {
        fprintf(stderr, "Error: unable to create handle from file %s\n", filename);
        return 1;
    }

    CODES_CHECK(codes_get_long(h, "numberOfContributingSpectralBands", &numberOfContributingSpectralBands), 0);
    assert(numberOfContributingSpectralBands == 3);

    /* shrink NB to 2 */
    numberOfContributingSpectralBands = 2;
    CODES_CHECK(codes_set_long(h, "numberOfContributingSpectralBands", numberOfContributingSpectralBands), 0);

    /* expand NB to 9 */
    numberOfContributingSpectralBands = 9;
    CODES_CHECK(codes_set_long(h, "numberOfContributingSpectralBands", numberOfContributingSpectralBands), 0);

    /* get as a long*/
    CODES_CHECK(codes_get_long(h, "numberOfContributingSpectralBands", &numberOfContributingSpectralBands), 0);
    printf("numberOfContributingSpectralBands=%ld\n", numberOfContributingSpectralBands);

    /* get as a long*/
    CODES_CHECK(codes_get_size(h, "scaledValueOfCentralWaveNumber", &count), 0);
    printf("count=%zu\n", count);

    assert(count < sizeof(values) / sizeof(values[0]));

    size = count;
    CODES_CHECK(codes_get_long_array(h, "scaledValueOfCentralWaveNumber", values, &size), 0);
    assert(size == count);

    for (i = 0; i < count; i++) {
        printf("scaledValueOfCentralWaveNumber %zu = %ld\n", i, values[i]);
        if (i == 0) assert(values[i] == 26870);
        if (i == 1) assert(values[i] == 9272);
    }

    for (i = 0; i < count; i++)
        values[i] = i + 1000;

    size = count;
    /* size--; */
    CODES_CHECK(codes_set_long_array(h, "scaledValueOfCentralWaveNumber", values, size), 0);
    assert(size == count);

    /* check what we set */
    CODES_CHECK(codes_get_long_array(h, "scaledValueOfCentralWaveNumber", new_values, &size), 0);
    assert(size == count);
    for (i = 0; i < count; i++) {
        printf("Now scaledValueOfCentralWaveNumber %zu = %ld\n", i, new_values[i]);
        assert(new_values[i] == (i + 1000));
    }

    codes_handle_delete(h);

    fclose(in);
    return 0;
}