eccodes/examples/C/set_missing.c

/*
 * Copyright 2005-2019 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: set_missing
 *
 * Description: how to set a key as missing.
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "eccodes.h"

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

    FILE* in            = NULL;
    const char* infile  = "../../data/reduced_gaussian_pressure_level.grib2";
    FILE* out           = NULL;
    const char* outfile = "out_surface_level.grib2";
    codes_handle* h     = NULL;
    const void* buffer  = NULL;
    size_t size         = 0;
    char str[]          = "sfc";
    size_t str_len      = 3;
    long Ni             = 0;

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

    out = fopen(outfile, "wb");
    if (!out) {
        printf("ERROR: unable to open output file %s\n", outfile);
        fclose(in);
        return 1;
    }

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

    CODES_CHECK(codes_set_string(h, "typeOfFirstFixedSurface", str, &str_len), 0);
    CODES_CHECK(codes_set_missing(h, "scaleFactorOfFirstFixedSurface"), 0);
    CODES_CHECK(codes_set_missing(h, "scaledValueOfFirstFixedSurface"), 0);

    /* See GRIB-490 */
    CODES_CHECK(codes_get_long(h, "Ni", &Ni), 0);
    is_missing = codes_is_missing(h, "Ni", &err);
    CODES_CHECK(err, 0);
    if (is_missing != 1) assert(!"Ni should be missing");
    CODES_CHECK(codes_set_long(h, "Ni", Ni), 0);

    /* get the coded message in a buffer */
    CODES_CHECK(codes_get_message(h, &buffer, &size), 0);

    /* write the buffer in a file*/
    if (fwrite(buffer, 1, size, out) != size) {
        perror(argv[1]);
        exit(1);
    }

    /* delete handle */
    codes_handle_delete(h);

    fclose(in);
    fclose(out);

    return 0;
}