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# iterator.c

iterator.c How to use an iterator on latitude, longitude, values.

    00001
    00010 /*
    00011  * C Implementation: iterator
    00012  *
    00013  * Description: how to use an iterator on lat/lon/values.
    00014  *
    00015  *
    00016  * Author: Enrico Fucile
    00017  *
    00018  *
    00019  */
    00020
    00021 #include <stdio.h>
    00022 #include <stdlib.h>
    00023 #include <string.h>
    00024
    00025 #include "grib_api.h"
    00026
    00027 void usage(char* prog) {
    00028   printf("Usage: %s grib_file\n",prog);
    00029   exit(1);
    00030 }
    00031
    00032 int main(int argc, char** argv) {
    00033   FILE* in = NULL;
    00034   int err = 0;
    00035   double lat,lon,value,missingValue=0;
    00036   int n=0;
    00037   char* filename = NULL;
    00038
    00039   /* Message handle. Required in all the grib_api calls acting on a message.*/
    00040   grib_handle *h = NULL;
    00041   /* Iterator on lat/lon/values.*/
    00042   grib_iterator* iter=NULL;
    00043
    00044   if (argc != 2) usage(argv[0]);
    00045
    00046   filename=strdup(argv[1]);
    00047
    00048   in = fopen(filename,"r");
    00049   if(!in) {
    00050     printf("ERROR: unable to open file %s\n",filename);
    00051     return 1;
    00052   }
    00053
    00054   /* Loop on all the messages in a file.*/
    00055   while ((h = grib_handle_new_from_file(0,in,&err)) != NULL ) {
    00056         /* Check of errors after reading a message. */
    00057     if (err != GRIB_SUCCESS) GRIB_CHECK(err,0);
    00058
    00059         /* Get the double representing the missing value in the field. */
    00060         GRIB_CHECK(grib_get_double(h,"missingValue",&missingValue),0);
    00061
    00062         /* A new iterator on lat/lon/values is created from the message handle h. */
    00063         iter=grib_iterator_new(h,0,&err);
    00064     if (err != GRIB_SUCCESS) GRIB_CHECK(err,0);
    00065
    00066     n = 0;
    00067         /* Loop on all the lat/lon/values. */
    00068     while(grib_iterator_next(iter,&lat,&lon,&value)) {
    00069           /* You can now print lat and lon,  */
    00070       printf("- %d - lat=%f lon=%f value=",n,lat,lon);
    00071           /* decide what to print if a missing value is found. */
    00072       if (value == missingValue ) printf("missing\n");
    00073           /* and print the value if is not missing. */
    00074           else printf("%f\n",value);
    00075       n++;
    00076     }
    00077
    00078         /* At the end the iterator is deleted to free memory. */
    00079     grib_iterator_delete(iter);
    00080
    00081     /* At the end the grib_handle is deleted to free memory. */
    00082     grib_handle_delete(h);
    00083   }
    00084
    00085
    00086   fclose(in);
    00087
    00088   return 0;
    00089 }