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re: https://github.com/Unidata/netcdf-c/issues/1584 Support has been added for multiple filters per variable. This affects a number of components in netcdf. The new APIs are documented in NUG/filters.md. The primary changes are: * A set of new functions are provided (see __include/netcdf_filter.h__). - Obtain a list of the filters associated with a variable - Obtain the parameters for a specific filter. * The existing __nc_inq_var_filter__ function now returns info about the first defined filter. * The utilities (ncgen, ncdump, and nccopy) now support an extended format for specifying a sequence of filters. The general form is __<filter>|<filter>..._. * The ncdump **_Filter** attribute now dumps a list of all the filters associated with a variable using the above new format. * Filter specifications can now use a filter name instead of number for filters known to the netcdf library, which in turn is taken from the HDF5 filter registration page. * New errors are defined: NC_EFILTER and NC_ENOFILTER. The latter is returned if an attempt is made to access an unknown filter. * Internally, the dispatch table has been extended to add a function to handle all of the filter functions. * New, filter-related, tests were added to nc_test4. * A new plugin was added to the plugins directory to help with testing. Notes: 1. The shuffle and fletcher32 filters are not part of the multifilter system. Misc. changes: 1. A debug module was added to libhdf5 to help catch error locations.
155 lines
3.8 KiB
C
155 lines
3.8 KiB
C
/* This is part of the netCDF package.
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Copyright 2018 University Corporation for Atmospheric Research/Unidata
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See COPYRIGHT file for conditions of use.
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*/
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/*
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* Example illustrates the use of SZIP compression in netCDF5
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* Taken from HDF5 example.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "nc_tests.h"
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#include "err_macros.h"
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#include "netcdf.h"
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#undef PLAIN
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#define USECLOSE
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/* Szip Constants. */
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#define HDF5_FILTER_SZIP 4
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#define H5_SZIP_MAX_PIXELS_PER_BLOCK_IN 32
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#define H5_SZIP_MAX_PIXELS_PER_BLOCK_OUT 64
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/* Option Mask Flags (Refere to HDF5 szip documentation) */
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#define H5_SZIP_ALLOW_K13_OPTION_MASK 1 /*Allows k split = 13 compression mode. (Default)*/
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#define H5_SZIP_CHIP_OPTION_MASK 2 /*Compresses exactly as in hardware*/
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#define H5_SZIP_EC_OPTION_MASK 4 /*Selects entropy coding method. (Default)*/
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#define H5_SZIP_NN_OPTION_MASK 32 /*Selects nearest neighbor coding method*/
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#define NX 500
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#define NY 600
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#define CH_NX 100
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#define CH_NY 25
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static void initialize(void);
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static int compare(void);
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static float buf[NX][NY];
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static float buf_r[NX][NY];
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int
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main(void)
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{
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int ncid, varid, dimids[2];
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size_t dims[2], chunk_size[2];
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unsigned int szip_params[2]; /* [0]=options_mask [1]=pixels_per_block */
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int options_mask_in, pixels_per_block_in;
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int errcnt = 0;
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/* Create a new file using read/write access. */
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if(nc_create("testszip.nc", NC_CLOBBER|NC_NETCDF4, &ncid)) ERR;
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/* Create dims */
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dims[0] = NX;
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dims[1] = NY;
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if(nc_def_dim(ncid, "x", dims[0], &dimids[0])) ERR;
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if(nc_def_dim(ncid, "y", dims[1], &dimids[1])) ERR;
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/* Create a dimensioned variable */
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if(nc_def_var(ncid, "datasetF32", NC_FLOAT, 2, dimids, &varid)) ERR;
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/* no fill */
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if(nc_def_var_fill(ncid, varid, 1, NULL)) ERR;
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/* Define chunking for the variable:
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* the raw data is to be partitioned into 100x100 element chunks.
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*/
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chunk_size[0] = CH_NX;
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chunk_size[1] = CH_NY;
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if(nc_def_var_chunking(ncid, varid, NC_CHUNKED, chunk_size)) ERR;
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#ifndef PLAIN
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/*
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* Set parameters for SZIP compression; check the description of
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* the H5Pset_szip function in the HDF5 Reference Manual for more
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* information.
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*/
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szip_params[0] = H5_SZIP_NN_OPTION_MASK;
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szip_params[1] = H5_SZIP_MAX_PIXELS_PER_BLOCK_IN;
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if(nc_def_var_filter(ncid, varid, HDF5_FILTER_SZIP, 2, szip_params)) ERR;
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if(nc_inq_var_szip(ncid, varid, &options_mask_in, &pixels_per_block_in)) ERR;
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if(!(options_mask_in & H5_SZIP_NN_OPTION_MASK)) ERR;
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#endif
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if(nc_enddef(ncid)) ERR;
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initialize();
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/* Write the array to the file */
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if(nc_put_var_float(ncid, varid, &buf[0][0])) ERR;
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#ifdef USECLOSE
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/* Close and re-open the file */
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if(nc_close(ncid)) ERR;
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if(nc_open("testszip.nc", NC_NETCDF4, &ncid)) ERR;
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if(nc_inq_varid(ncid, "datasetF32", &varid)) ERR;
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#endif
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/*
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* Read the array. This is similar to writing data,
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* except the data flows in the opposite direction.
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* Note: Decompression should be automatic.
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*/
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memset(buf_r,0,sizeof(buf_r));
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if(nc_get_var_float(ncid, varid, &buf_r[0][0])) ERR;
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/* Do comparison */
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errcnt = compare();
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if(nc_close(ncid)) ERR;
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if(errcnt) ERR;
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SUMMARIZE_ERR;
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FINAL_RESULTS;
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return (errcnt==0?0:1);
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}
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static int
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compare()
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{
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int i,j;
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int errs = 0;
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/* Do comparison */
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for (i=0; i < NX; i++) {
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for (j=0; j < NY; j++) {
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if(buf[i][j] != buf_r[i][j]) {
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errs++;
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printf("mismatch: [%d][%d]: write = %f read=%f\n",
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i,j,buf[i][j],buf_r[i][j]);
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}
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}
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}
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return errs;
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}
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static void
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initialize(void)
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{
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int i, j;
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/* Initialize data buffer with some bogus data. */
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for(i=0; i < NX; i++) {
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for(j=0; j < NY; j++) {
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buf[i][j] = (float)(i + j);
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}
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}
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}
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