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129 lines
4.0 KiB
C
129 lines
4.0 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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* Write a file demonstrating some of the features of netCDF-4.
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*
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* We create two shared dimensions, "x" and "y", in a parent group, and
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* some netCDF variables in different subgroups. The variables will
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* include a compound and an enum type, as well as some of the new atomic
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* types, like the unsigned 64-bit integer.
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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 http://www.unidata.ucar.edu/software/netcdf/docs.
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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 create. */
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#define FILE_NAME "simple_nc4.nc"
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/* We are writing 2D data, a 6 x 12 grid. */
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#define NDIMS 2
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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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/* When we create netCDF variables, groups, dimensions, or types,
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* we get back an ID for each one. */
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int ncid, x_dimid, y_dimid, varid1, varid2, grp1id, grp2id, typeid;
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int dimids[NDIMS];
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/* This is the data array we will write. It will be filled with a
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* progression of numbers for this example. */
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unsigned long long data_out[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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/* Create some pretend 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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data_out[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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}
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/* Create the file. The NC_NETCDF4 flag tells netCDF to
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* create a netCDF-4/HDF5 file.*/
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if ((retval = nc_create(FILE_NAME, NC_NETCDF4|NC_CLOBBER, &ncid)))
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ERR(retval);
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/* Define the dimensions in the root group. Dimensions are visible
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* in all subgroups. */
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if ((retval = nc_def_dim(ncid, "x", NX, &x_dimid)))
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ERR(retval);
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if ((retval = nc_def_dim(ncid, "y", NY, &y_dimid)))
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ERR(retval);
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/* The dimids passes the IDs of the dimensions of the variable. */
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dimids[0] = x_dimid;
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dimids[1] = y_dimid;
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/* Define two groups, "grp1" and "grp2." */
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if ((retval = nc_def_grp(ncid, "grp1", &grp1id)))
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ERR (retval);
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if ((retval = nc_def_grp(ncid, "grp2", &grp2id)))
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ERR (retval);
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/* Define an unsigned 64bit integer variable in grp1, using dimensions
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* in the root group. */
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if ((retval = nc_def_var(grp1id, "data", NC_UINT64, NDIMS,
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dimids, &varid1)))
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ERR(retval);
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/* Write unsigned long long data to the file. For netCDF-4 files,
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* nc_enddef will be called automatically. */
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if ((retval = nc_put_var_ulonglong(grp1id, varid1, &data_out[0][0])))
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ERR(retval);
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/* Create a compound type. This will cause nc_reddef to be called. */
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if (nc_def_compound(grp2id, sizeof(struct s1), "sample_compound_type",
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&typeid))
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ERR(retval);
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if (nc_insert_compound(grp2id, typeid, "i1",
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offsetof(struct s1, i1), NC_INT))
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ERR(retval);
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if (nc_insert_compound(grp2id, typeid, "i2",
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offsetof(struct s1, i2), NC_INT))
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ERR(retval);
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/* Define a compound type variable in grp2, using dimensions
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* in the root group. */
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if ((retval = nc_def_var(grp2id, "data", typeid, NDIMS,
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dimids, &varid2)))
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ERR(retval);
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/* Write the array of struct to the file. This will cause nc_endef
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* to be called. */
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if ((retval = nc_put_var(grp2id, varid2, &compound_data[0][0])))
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ERR(retval);
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/* Close the file. */
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if ((retval = nc_close(ncid)))
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ERR(retval);
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printf("*** SUCCESS writing example file simple_nc4.nc!\n");
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return 0;
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}
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