eccodes/examples/C/grib_index.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_index
 *
 * Description: How to create and use an index to access GRIB messages from a file
 *
 */

#include "eccodes.h"

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

int main(int argc, char* argv[])
{
    codes_index* index = NULL;
    codes_handle* h    = NULL;
    char* inputfile       = NULL;
    char* indexfile       = NULL;
    long *steps, *levels, *numbers; /* arrays */
    char** shortName = NULL;
    int i, j, k, l;
    size_t stepSize, levelSize, shortNameSize, numberSize;
    long ostep, olevel, onumber;
    char oshortName[200];
    size_t lenshortName = sizeof(oshortName);
    int ret = 0, count = 0;

    if (argc != 3) usage(argv[0]);
    inputfile = argv[1];
    indexfile = argv[2];

    printf("indexing...\n");

    /* create an index given set of keys*/
    index = codes_index_new(0, "shortName,level,number,step", &ret);
    if (ret) {
        fprintf(stderr, "Error: %s\n", codes_get_error_message(ret));
        exit(ret);
    }

    /* indexes a file */
    ret = codes_index_add_file(index, inputfile);
    if (ret) {
        fprintf(stderr, "Error: %s\n", codes_get_error_message(ret));
        exit(ret);
    }
    printf("end indexing...\n");

    /* get the number of distinct values of "step" in the index */
    CODES_CHECK(codes_index_get_size(index, "step", &stepSize), 0);
    steps = (long*)malloc(sizeof(long) * stepSize);
    if (!steps) exit(1);
    /* get the list of distinct steps from the index */
    /* the list is in ascending order */
    CODES_CHECK(codes_index_get_long(index, "step", steps, &stepSize), 0);
    printf("stepSize=%zu\n", stepSize);
    for (i = 0; i < stepSize; i++)
        printf("%ld ", steps[i]);
    printf("\n");

    /*same as for "step"*/
    CODES_CHECK(codes_index_get_size(index, "level", &levelSize), 0);
    levels = (long*)malloc(sizeof(long) * levelSize);
    if (!levels) exit(1);
    /*same as for "step"*/
    CODES_CHECK(codes_index_get_long(index, "level", levels, &levelSize), 0);
    printf("levelSize=%zu\n", levelSize);
    for (i = 0; i < levelSize; i++)
        printf("%ld ", levels[i]);
    printf("\n");

    /*same as for "step"*/
    CODES_CHECK(codes_index_get_size(index, "number", &numberSize), 0);
    numbers = (long*)malloc(sizeof(long) * numberSize);
    if (!numbers) exit(1);
    /*same as for "step"*/
    CODES_CHECK(codes_index_get_long(index, "number", numbers, &numberSize), 0);
    printf("numberSize=%zu\n", numberSize);
    for (i = 0; i < numberSize; i++)
        printf("%ld ", numbers[i]);
    printf("\n");

    /*same as for "step"*/
    CODES_CHECK(codes_index_get_size(index, "shortName", &shortNameSize), 0);
    shortName = (char**)malloc(sizeof(char*) * shortNameSize);
    if (!shortName) exit(1);
    /*same as for "step"*/
    CODES_CHECK(codes_index_get_string(index, "shortName", shortName, &shortNameSize), 0);
    printf("shortNameSize=%zu\n", shortNameSize);
    for (i = 0; i < shortNameSize; i++)
        printf("%s ", shortName[i]);
    printf("\n");

    count = 0;
    /* nested loops on the keys values of the index */
    /* different order of the nested loops doesn't affect performance*/
    for (i = 0; i < shortNameSize; i++) {
        /* select the GRIB with shortName=shortName[i] */
        codes_index_select_string(index, "shortName", shortName[i]);

        for (l = 0; l < levelSize; l++) {
            /* select the GRIB with level=levels[l] */
            codes_index_select_long(index, "level", levels[l]);

            for (j = 0; j < numberSize; j++) {
                /* select the GRIB with number=numbers[j] */
                codes_index_select_long(index, "number", numbers[j]);

                for (k = 0; k < stepSize; k++) {
                    /* select the GRIB with step=steps[k] */
                    codes_index_select_long(index, "step", steps[k]);

                    /* create a new codes_handle from the index with the constraints
                       imposed by the select statements. It is a loop because
                       in the index there could be more than one GRIB with those
                       constraints */
                    while ((h = codes_handle_new_from_index(index, &ret)) != NULL) {
                        count++;
                        if (ret) {
                            fprintf(stderr, "Error: %s\n", codes_get_error_message(ret));
                            exit(ret);
                        }
                        lenshortName = sizeof(oshortName);
                        codes_get_string(h, "shortName", oshortName, &lenshortName);
                        codes_get_long(h, "level", &olevel);
                        codes_get_long(h, "number", &onumber);
                        codes_get_long(h, "step", &ostep);
                        printf("shortName=%s ", oshortName);
                        printf("level=%ld ", olevel);
                        printf("number=%ld ", onumber);
                        printf("step=%ld \n", ostep);
                        codes_handle_delete(h);
                    }
                    if (ret && ret != GRIB_END_OF_INDEX) {
                        fprintf(stderr, "Error: %s\n", codes_get_error_message(ret));
                        exit(ret);
                    }
                }
            }
        }
    }
    printf("  %d messages selected\n", count);

    codes_index_write(index, indexfile);
    codes_index_delete(index);

    return 0;
}