mirror of https://github.com/ecmwf/eccodes.git
113 lines
4.2 KiB
C
113 lines
4.2 KiB
C
/*
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* C Implementation: get_set
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*
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* Description:
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* Example on how to get and set values through key names
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* from a grib_handle created by an message in a file.
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* All angles are espressed in Degrees though in the
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* message can be in millidegrees or microdegrees depending
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* on the grib edition number.
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* Only angle values in Degrees should be setted and getted
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* by the user. Expert users can access the hard coded values
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* in the grib message omitting the "InDegrees" suffix, but
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* it's worth to notice that units are those appropriate for
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* the message edition.
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* WARNING: Some variables are dependent.
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* For example numberOfPointsAlongAMeridian depends on:
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* - jDirectionIncrementInDegrees
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* - latitudeOfFirstGridPointInDegrees
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* - latitudeOfLastGridPointInDegrees.
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* Thus only these last three must be set and the first will
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* be available. Inversely if numberOfPointsAlongAMeridian
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* is set then jDirectionIncrementInDegrees will be
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* automatically calculated and modified in the grib
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* message.
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* jDirectionIncrementInDegrees, latitudeOfFirstGridPointInDegrees,
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* latitudeOfLastGridPointInDegrees are required variables and
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* numberOfPointsAlongAMeridian is optional. All the required
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* variables must be set when creating a new handle, optional
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* ones can be set or not. If an optional variable is set other
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* variables are automatically set. Only required variables
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* should be set by a user. Only expert users should access
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* optional variables and only in particulare cases.
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* A list of all the available required keys for a message
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* can be obtained using the command line tool grib_dump
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* on the message file, or with the keys_iterator function
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* (see example keys_iterator.c).
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*
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* Author: Enrico Fucile <enrico.fucile@ecmwf.int>, (C) 2006
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*
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* Copyright: See COPYING file that comes with this distribution
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*
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include "grib_api.h"
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int main(int argc, char *argv[])
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{
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int ret=0;
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grib_handle* h;
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double* values;
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long numberOfPointsAlongAParallel,numberOfPointsAlongAMeridian,numberOfPoints,i,j,k;
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/* Option flags used by grib_dump.
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* Turn on:
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* GRIB_DUMP_FLAG_VALUES to dump values
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* GRIB_DUMP_FLAG_OPTIONAL to dump optional keys
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* GRIB_DUMP_FLAG_READ_ONLY to dump read_only keys
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*/
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int option_flags = GRIB_DUMP_FLAG_VALUES
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| GRIB_DUMP_FLAG_OPTIONAL
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| GRIB_DUMP_FLAG_READ_ONLY;
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h = grib_handle_new_from_template(0,"GRIB1");
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if(!h) {
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printf("ERROR: Unable to create grib handle\n");
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exit(1);
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}
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/* GRIB_CHECK is a macro that translates the error code in a message
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* printed on the standard error and exits returning the error code
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*/
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GRIB_CHECK(grib_set_double(h,"latitudeOfFirstGridPointInDegrees",10),0);
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GRIB_CHECK(grib_set_double(h,"longitudeOfFirstGridPointInDegrees",-10),0);
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GRIB_CHECK(grib_set_double(h,"latitudeOfLastGridPointInDegrees",-10),0);
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GRIB_CHECK(grib_set_double(h,"longitudeOfLastGridPointInDegrees",10),0);
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GRIB_CHECK(grib_set_double(h,"jDirectionIncrementInDegrees",0.5),0);
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GRIB_CHECK(grib_set_double(h,"iDirectionIncrementInDegrees",0.5),0);
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GRIB_CHECK(grib_get_long( h,"numberOfPointsAlongAParallel",&numberOfPointsAlongAParallel),0);
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GRIB_CHECK(grib_get_long( h,"numberOfPointsAlongAMeridian",&numberOfPointsAlongAMeridian),0);
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numberOfPoints=numberOfPointsAlongAMeridian*numberOfPointsAlongAParallel;
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values=(double*)malloc(numberOfPoints*sizeof(double));
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for (j=0;j<numberOfPointsAlongAMeridian;j++) {
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for (i=0;i<numberOfPointsAlongAParallel;i++) {
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k=i+numberOfPointsAlongAParallel*j;
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values[k]=50;
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}
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}
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GRIB_CHECK(grib_set_double_array( h,"values",values,numberOfPoints),0);
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if (h) {
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/* dump key/values pairs according the option_flags and with
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* the "serialize" style. Other available styles are:
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* - "debug" Dump all keys with octet position
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* - "c_code" Dump C code to build the grib file from scratch
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*/
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grib_dump_content(h,stdout,"serialize",option_flags,NULL);
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} else {
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printf("Error: unable to create grib_handle\n");
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}
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return ret;
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}
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