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100 lines
2.7 KiB
C
100 lines
2.7 KiB
C
/* Copyright 2019 University Corporation for Atmospheric
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Research/Unidata. See COPYRIGHT file for conditions of use. */
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/**
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* @file
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* Read a simple file, with some of the features of netCDF-4.
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*
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* This is a very simple example which demonstrates some of the new
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* features of netCDF-4.0.
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*
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* This example reads a simple file created by simple_nc4_wr.c. This is
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* intended to illustrate the use of the netCDF-4 C API.
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*
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* This is part of the netCDF package. Full documentation of netCDF
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* can be found at https://docs.unidata.ucar.edu/netcdf-c.
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*
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* @author Ed Hartnett
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <netcdf.h>
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/* This is the name of the data file we will read. */
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#define FILE_NAME "simple_nc4.nc"
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/* We are reading 2D data, a 6 x 12 grid. */
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#define NX 6
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#define NY 12
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/* Handle errors by printing an error message and exiting with a
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* non-zero status. */
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#define ERRCODE 2
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#define ERR(e) {printf("Error: %s\n", nc_strerror(e)); exit(ERRCODE);}
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int
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main()
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{
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/* There will be netCDF IDs for the file, each group, and each
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* variable. */
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int ncid, varid1, varid2, grp1id, grp2id;
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unsigned long long data_in[NX][NY];
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/* Loop indexes, and error handling. */
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int x, y, retval;
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/* The following struct is written as a compound type. */
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struct s1
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{
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int i1;
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int i2;
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};
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struct s1 compound_data[NX][NY];
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/* Open the file. NC_NOWRITE tells netCDF we want read-only access
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* to the file.*/
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if ((retval = nc_open(FILE_NAME, NC_NOWRITE, &ncid)))
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ERR(retval);
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/* Get the group ids of our two groups. */
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if ((retval = nc_inq_ncid(ncid, "grp1", &grp1id)))
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ERR(retval);
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if ((retval = nc_inq_ncid(ncid, "grp2", &grp2id)))
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ERR(retval);
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/* Get the varid of the uint64 data variable, based on its name, in
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* grp1. */
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if ((retval = nc_inq_varid(grp1id, "data", &varid1)))
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ERR(retval);
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/* Read the data. */
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if ((retval = nc_get_var_ulonglong(grp1id, varid1, &data_in[0][0])))
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ERR(retval);
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/* Get the varid of the compound data variable, based on its name,
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* in grp2. */
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if ((retval = nc_inq_varid(grp2id, "data", &varid2)))
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ERR(retval);
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/* Read the data. */
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if ((retval = nc_get_var(grp2id, varid2, &compound_data[0][0])))
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ERR(retval);
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/* Check the data. */
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for (x = 0; x < NX; x++)
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for (y = 0; y < NY; y++)
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{
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if (data_in[x][y] != x * NY + y ||
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compound_data[x][y].i1 != 42 ||
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compound_data[x][y].i2 != -42)
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return ERRCODE;
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}
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/* Close the file, freeing all resources. */
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if ((retval = nc_close(ncid)))
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ERR(retval);
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printf("*** SUCCESS reading example file %s!\n", FILE_NAME);
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return 0;
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}
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