/* Copyright 2010-2018 University Corporation for Atmospheric

   Research/Unidata. See COPYRIGHT file for more info. */

/**

 * @file

 * Functions for defining and inquiring about variables. @note The

 * order of functions in this file affects the doxygen documentation.

 */

#include "config.h"

#include "netcdf.h"

#include "netcdf_filter.h"

#include "ncdispatch.h"

#include "nc4internal.h"

#include "netcdf_f.h"

#include "nc4internal.h"

/**

   @defgroup variables Variables

   Variables hold multi-dimensional arrays of data.

   Variables for a netCDF dataset are defined when the dataset is

   created, while the netCDF dataset is in define mode. Other

   variables may be added later by reentering define mode. A netCDF

   variable has a name, a type, and a shape, which are specified when

   it is defined. A variable may also have values, which are

   established later in data mode.

   Ordinarily, the name, type, and shape are fixed when the variable

   is first defined. The name may be changed, but the type and shape

   of a variable cannot be changed. However, a variable defined in

   terms of the unlimited dimension can grow without bound in that

   dimension.

   A netCDF variable in an open netCDF dataset is referred to by a

   small integer called a variable ID.

   Variable IDs reflect the order in which variables were defined

   within a netCDF dataset. Variable IDs are 0, 1, 2,..., in the order

   in which the variables were defined. A function is available for

   getting the variable ID from the variable name and vice-versa.

   @ref attributes may be associated with a variable to specify such

   properties as units.

   Operations supported on variables are:

   - Create a variable, given its name, data type, and shape.

   - Get a variable ID from its name.

   - Get a variable's name, data type, shape, and number of attributes

   from its ID.

   - Put a data value into a variable, given variable ID, indices, and value.

   - Put an array of values into a variable, given variable ID, corner

   indices, edge lengths, and a block of values.

   - Put a subsampled or mapped array-section of values into a variable,

   given variable ID, corner indices, edge lengths, stride vector,

   index mapping vector, and a block of values.

   - Get a data value from a variable, given variable ID and indices.

   - Get an array of values from a variable, given variable ID, corner

   indices, and edge lengths.

   - Get a subsampled or mapped array-section of values from a variable,

   given variable ID, corner indices, edge lengths, stride vector, and

   index mapping vector.

   - Rename a variable.

   @section language_types Data Types

   NetCDF supported six atomic data types through version 3.6.0 (char,

   byte, short, int, float, and double). Starting with version 4.0, many

   new atomic and user defined data types are supported (unsigned int

   types, strings, compound types, variable length arrays, enums,

   opaque).

   The additional data types are only supported in netCDF-4/HDF5

   files. To create netCDF-4/HDF5 files, use the ::NC_NETCDF4 flag in

   nc_create().

   @section classic_types NetCDF-3 Classic and 64-Bit Offset Data Types

   NetCDF-3 classic and 64-bit offset files support 6 atomic data types,

   and none of the user defined datatype introduced in NetCDF-4.

   The following table gives the netCDF-3 external data types and the

   corresponding type constants for defining variables in the C

   interface:

   <table>

   <tr><td>Type</td><td>C define</td><td>Bits</td></tr>

   <tr><td>byte</td><td>::NC_BYTE</td><td>8</td></tr>

   <tr><td>char</td><td>::NC_CHAR</td><td>8</td></tr>

   <tr><td>short</td><td>::NC_SHORT</td><td>16</td></tr>

   <tr><td>int</td><td>::NC_INT</td><td>32</td></tr>

   <tr><td>float</td><td>::NC_FLOAT</td><td>32</td></tr>

   <tr><td>double</td><td>::NC_DOUBLE</td><td>64</td></tr>

   </table>

   The first column gives the netCDF external data type, which is the

   same as the CDL data type. The next column gives the corresponding C

   pre-processor macro for use in netCDF functions (the pre-processor

   macros are defined in the netCDF C header-file netcdf.h). The last

   column gives the number of bits used in the external representation of

   values of the corresponding type.

   @section netcdf_4_atomic NetCDF-4 Atomic Data Types

   NetCDF-4 files support all of the atomic data types from netCDF-3,

   plus additional unsigned integer types, 64-bit integer types, and a

   string type.

   <table>

   <tr><td>Type</td><td>C define</td><td>Bits

   <tr><td>byte</td><td>::NC_BYTE</td><td>8</td></tr>

   <tr><td>unsigned byte </td><td>::NC_UBYTE^</td><td> 8</td></tr>

   <tr><td>char </td><td>::NC_CHAR </td><td>8</td></tr>

   <tr><td>short </td><td>::NC_SHORT </td><td>16</td></tr>

   <tr><td>unsigned short </td><td>::NC_USHORT^ </td><td>16</td></tr>

   <tr><td>int </td><td>::NC_INT </td><td>32</td></tr>

   <tr><td>unsigned int </td><td>::NC_UINT^ </td><td>32</td></tr>

   <tr><td>unsigned long long </td><td>::NC_UINT64^ </td><td>64</td></tr>

   <tr><td>long long </td><td>::NC_INT64^ </td><td>64</td></tr>

   <tr><td>float </td><td>::NC_FLOAT </td><td>32</td></tr>

   <tr><td>double </td><td>::NC_DOUBLE </td><td>64</td></tr>

   <tr><td>char ** </td><td>::NC_STRING^ </td><td>string length + 1</td></tr>

   </table>

   ^This type was introduced in netCDF-4, and is not supported in netCDF

   classic or 64-bit offset format files, or in netCDF-4 files if they

   are created with the ::NC_CLASSIC_MODEL flags.

*/

/** @{ */

/**

   @name Defining Variables

   Use these functions to define variables.

*/

/*! @{ */

/**

   Define a new variable.

   This function adds a new variable to an open netCDF dataset or group.

   It returns (as an argument) a variable ID, given the netCDF ID,

   the variable name, the variable type, the number of dimensions, and a

   list of the dimension IDs.

   @param ncid NetCDF or group ID, from a previous call to nc_open(),

   nc_create(), nc_def_grp(), or associated inquiry functions such as

   nc_inq_ncid().

   @param name Variable @ref object_name.

   @param xtype (Data

   type)[https://docs.unidata.ucar.edu/nug/current/md_types.html#data_type]

   of the variable.

   @param ndims Number of dimensions for the variable. For example, 2

   specifies a matrix, 1 specifies a vector, and 0 means the variable is

   a scalar with no dimensions. Must not be negative or greater than the

   predefined constant ::NC_MAX_VAR_DIMS. In netCDF-4/HDF5 files, may not

   exceed the HDF5 maximum number of dimensions (32).

   @param dimidsp Vector of ndims dimension IDs corresponding to the

   variable dimensions. For classic model netCDF files, if the ID of the

   unlimited dimension is included, it must be first. This argument is

   ignored if ndims is 0. For expanded model netCDF4/HDF5 files, there

   may be any number of unlimited dimensions, and they may be used in any

   element of the dimids array.

   @param varidp Pointer to location for the returned variable ID.

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ncid.

   @return ::NC_ENOTINDEFINE Not in define mode.

   @return ::NC_ESTRICTNC3 Attempting netcdf-4 operation on strict nc3 netcdf-4 file.

   @return ::NC_EMAXVARS NC_MAX_VARS exceeded [Not enforced after 4.5.0]

   @return ::NC_EBADTYPE Bad type.

   @return ::NC_EINVAL Invalid input.

   @return ::NC_ENAMEINUSE Name already in use.

   @return ::NC_EPERM Attempt to create object in read-only file.

   @section nc_def_var_example Example

   Here is an example using nc_def_var to create a variable named rh of

   type double with three dimensions, time, lat, and lon in a new netCDF

   dataset named foo.nc:

   @code

   #include <netcdf.h>

   ...

   int  status;

   int  ncid;

   int  lat_dim, lon_dim, time_dim;

   int  rh_id;

   int  rh_dimids[3];

   ...

   status = nc_create("foo.nc", NC_NOCLOBBER, &ncid);

   if (status != NC_NOERR) handle_error(status);

   ...

   status = nc_def_dim(ncid, "lat", 5L, &lat_dim);

   if (status != NC_NOERR) handle_error(status);

   status = nc_def_dim(ncid, "lon", 10L, &lon_dim);

   if (status != NC_NOERR) handle_error(status);

   status = nc_def_dim(ncid, "time", NC_UNLIMITED, &time_dim);

   if (status != NC_NOERR) handle_error(status);

   ...

   rh_dimids[0] = time_dim;

   rh_dimids[1] = lat_dim;

   rh_dimids[2] = lon_dim;

   status = nc_def_var (ncid, "rh", NC_DOUBLE, 3, rh_dimids, &rh_id);

   if (status != NC_NOERR) handle_error(status);

   @endcode

   @author Glenn Davis, Ed Hartnett, Dennis Heimbigner

*/

int

nc_def_var(int ncid, const char *name, nc_type xtype,

           int ndims,  const int *dimidsp, int *varidp)

{

    NC* ncp;

    int stat = NC_NOERR;

    if ((stat = NC_check_id(ncid, &ncp)))

        return stat;

    TRACE(nc_def_var);

    return ncp->dispatch->def_var(ncid, name, xtype, ndims,

                                  dimidsp, varidp);

}

/**

   Set the fill value for a variable.

   @note For netCDF classic, 64-bit offset, and CDF5 formats, it is

   allowed (but not good practice) to set the fill value after data

   have been written to the variable. In this case, unless the

   variable has been completely specified (without gaps in the data),

   any existing filled values will not be recognized as fill values by

   applications reading the data. Best practice is to set the fill

   value after the variable has been defined, but before any data have

   been written to that variable. In NetCDF-4 files, this is enforced

   by the HDF5 library. For netCDF-4 files, an error is returned if

   the user attempts to set the fill value after writing data to the

   variable.

   @param ncid NetCDF ID, from a previous call to nc_open() or

   nc_create().

   @param varid Variable ID.

   @param no_fill Set to ::NC_NOFILL to turn off fill mode for this

   variable. Set to ::NC_FILL (the default) to turn on fill mode for

   the variable.

   @param fill_value the fill value to be used for this variable. Must

   be the same type as the variable. This must point to enough free

   memory to hold one element of the data type of the variable. (For

   example, an ::NC_INT will require 4 bytes for it's fill value,

   which is also an ::NC_INT.)

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ID.

   @return ::NC_ENOTINDEFINE Not in define mode.  This is returned for

   netCDF classic, 64-bit offset, or 64-bit data files, or for

   netCDF-4 files, when they were created with ::NC_CLASSIC_MODEL flag by

   nc_creae().

   @return ::NC_EPERM Attempt to create object in read-only file.

   @return ::NC_ELATEDEF (NetCDF-4 only). Returned when user attempts

   to set fill value after data are written.

   @return ::NC_EGLOBAL Attempt to set fill value on NC_GLOBAL.

   Warning: Using a vlen type as the fill value may lead to a memory

   leak.

   @section nc_def_var_fill_example Example

   In this example from libsrc4/tst_vars.c, a variable is defined, and

   the fill mode turned off. Then nc_inq_fill() is used to check that

   the setting is correct. Then some data are written to the

   variable. Since the data that are written do not cover the full

   extent of the variable, the missing values will just be random. If

   fill value mode was turned on, the missing values would get the

   fill value.

   @code

   #define DIM7_LEN 2

   #define DIM7_NAME "dim_7_from_Indiana"

   #define VAR7_NAME "var_7_from_Idaho"

   #define NDIMS 1

   int dimids[NDIMS];

   size_t index[NDIMS];

   int varid;

   int no_fill;

   unsigned short ushort_data = 42, ushort_data_in, fill_value_in;

   if (nc_create(FILE_NAME, NC_NETCDF4, &ncid)) ERR;

   if (nc_def_dim(ncid, DIM7_NAME, DIM7_LEN, &dimids[0])) ERR;

   if (nc_def_var(ncid, VAR7_NAME, NC_USHORT, NDIMS, dimids,

   &varid)) ERR;

   if (nc_def_var_fill(ncid, varid, 1, NULL)) ERR;

   if (nc_inq_var_fill(ncid, varid, &no_fill, &fill_value_in)) ERR;

   if (!no_fill) ERR;

   index[0] = 1;

   if (nc_put_var1_ushort(ncid, varid, index, &ushort_data)) ERR;

   index[0] = 0;

   if (nc_get_var1_ushort(ncid, varid, index, &ushort_data_in)) ERR;

   if (nc_close(ncid)) ERR;

   @endcode

   @author Glenn Davis, Ed Hartnett, Dennis Heimbigner

*/

int

nc_def_var_fill(int ncid, int varid, int no_fill, const void *fill_value)

{

    NC* ncp;

    int stat = NC_check_id(ncid,&ncp);

    if(stat != NC_NOERR) return stat;

    /* Using NC_GLOBAL is illegal, as this API has no provision for

     * specifying the type of the fillvalue, it must of necessity be

     * using the type of the variable to interpret the bytes of the

     * fill_value argument. */

    if (varid == NC_GLOBAL) return NC_EGLOBAL;

    return ncp->dispatch->def_var_fill(ncid,varid,no_fill,fill_value);

}

/**

   Set the zlib compression and shuffle settings for a variable in an

   netCDF/HDF5 file.

   This function must be called after nc_def_var and before nc_enddef

   or any functions which writes data to the file.

   Deflation and shuffle are only available for HDF5 files. Attempting

   to set them on non-HDF5 files will return ::NC_ENOTNC4.

   Deflation and shuffle require chunked data. If this function is

   called on a variable with contiguous data, then the data is changed

   to chunked data, with default chunksizes. Use nc_def_var_chunking()

   to tune performance with user-defined chunksizes.

   If this function is called on a scalar variable, ::NC_EINVAL is

   returned. Only chunked variables may use filters.

   Zlib compression cannot be used with szip compression. If this

   function is called on a variable which already has szip compression

   turned on, ::NC_EINVAL is returned.

   @note Parallel I/O reads work with compressed data. Parallel I/O

   writes work with compressed data in netcdf-c-4.7.4 and later

   releases, using hdf5-1.10.3 and later releases. Using the zlib,

   shuffle (or any other) filter requires that collective access be

   used with the variable. Turning on deflate and/or shuffle for a

   variable in a file opened for parallel I/O will automatically

   switch the access for that variable to collective access.

   @note The HDF5 manual has this to say about shuffle:

      The shuffle filter de-interlaces a block of data by reordering

      the bytes. All the bytes from one consistent byte position of

      each data element are placed together in one block; all bytes

      from a second consistent byte position of each data element are

      placed together a second block; etc. For example, given three

      data elements of a 4-byte datatype stored as 012301230123,

      shuffling will re-order data as 000111222333. This can be a

      valuable step in an effective compression algorithm because the

      bytes in each byte position are often closely related to each

      other and putting them together can increase the compression

      ratio.

      As implied above, the primary value of the shuffle filter lies

      in its coordinated use with a compression filter; it does not

      provide data compression when used alone. When the shuffle

      filter is applied to a dataset immediately prior to the use of a

      compression filter, the compression ratio achieved is often

      superior to that achieved by the use of a compression filter

      without the shuffle filter.

  @note The shuffle and deflate flags are ambiguous.

  In most cases, if the shuffle or deflate flag is zero, then it is interpreted

  to mean that shuffle or deflate should not be set. However, if the variable

  already has shuffle or deflate turned on, then it is unclear if a flag

  value of zero means leave the state as it is, or if it means

  that it should be turned off. Since currently no other filters can be

  disabled, it is assumed here that a zero value means to leave the

  state as it is.

   @param ncid NetCDF or group ID, from a previous call to nc_open(),

   nc_create(), nc_def_grp(), or associated inquiry functions such as

   nc_inq_ncid().

   @param varid Variable ID

   @param shuffle True to turn on the shuffle filter. The shuffle

   filter can assist with the compression of data by changing the byte

   order in the data stream. It makes no sense to use the shuffle

   filter without setting a deflate level.

   @param deflate True to turn on deflation for this variable.

   @param deflate_level A number between 0 (no compression) and 9

   (maximum compression).

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ncid.

   @return ::NC_ENOTVAR Invalid variable ID.

   @return ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is

   not netCDF-4/HDF5.

   @return ::NC_ESTRICTNC3 Attempting netcdf-4 operation on strict nc3

   netcdf-4 file.

   @return ::NC_ELATEDEF Too late to change settings for this variable.

   @return ::NC_ENOTINDEFINE Not in define mode.

   @return ::NC_EPERM File is read only.

   @return ::NC_ESTRICTNC3 Attempting to create netCDF-4 type var in

   classic model file

   @return ::NC_EHDFERR Error returned by HDF5 layer.

   @return ::NC_EINVAL Invalid input. Deflate can't be set unless

   variable storage is NC_CHUNK.

   @section nc_def_var_deflate_example Example

   Here is an example from /examples/C/simple_xy_nc4_wr.c using

   nc_def_var_deflate to create a variable and then turn on the shuffle

   filter and compression.

   @code

   #include <netcdf.h>

   #define NDIMS 2

   #define NX 6

   #define NY 12

   int ncid, x_dimid, y_dimid, varid;

   int dimids[NDIMS];

   int shuffle, deflate, deflate_level;

   int data_out[NX][NY];

   int x, y, retval;

   shuffle = NC_SHUFFLE;

   deflate = 1;

   deflate_level = 1;

   ...

   if ((retval = nc_create(FILE_NAME, NC_NETCDF4, &ncid)))

   ERR(retval);

   if ((retval = nc_def_dim(ncid, "x", NX, &x_dimid)))

   ERR(retval);

   if ((retval = nc_def_dim(ncid, "y", NY, &y_dimid)))

   ERR(retval);

   dimids[0] = x_dimid;

   dimids[1] = y_dimid;

   if ((retval = nc_def_var(ncid, "data", NC_INT, NDIMS,

   dimids, &varid)))

   ERR(retval);

   ...

   if ((retval = nc_def_var_deflate(ncid, varid, shuffle, deflate,

   deflate_level)))

   ERR(retval);

   ...

   @endcode

   @author Ed Hartnett, Dennis Heimbigner

*/

int

nc_def_var_deflate(int ncid, int varid, int shuffle, int deflate, int deflate_level)

{

    NC* ncp;

    int stat = NC_check_id(ncid,&ncp);

    if(stat != NC_NOERR) return stat;

    return ncp->dispatch->def_var_deflate(ncid,varid,shuffle,deflate,deflate_level);

}

/**

   Turn on quantization for a variable.

   The data are quantized by setting unneeded bits to zeros or ones

   so that they may compress well. BitGroom sets bits alternately to 1/0, 

   while BitRound and Granular BitRound (GBR) round (more) bits to zeros

   Quantization is lossy (data are irretrievably altered), and it 

   improves the compression ratio provided by a subsequent lossless 

   compression filter. Quantization alone will not reduce the data size.

   Lossless compression like zlib must also be used (see nc_def_var_deflate()).

   Producers of large datasets may find that using quantize with

   compression will result in significant improvent in the final data

   size.

   A notable feature of all the quantization algorithms is data remain 

   in IEEE754 format afterwards. Therefore quantization algorithms do

   nothing when data are read.

   Quantization is only available for variables of type NC_FLOAT or

   NC_DOUBLE. Attempts to set quantization for other variable

   types return an error (NC_EINVAL). 

   Variables that use quantize will have added an attribute with name

   NC_QUANTIZE_[ALGORITHM_NAME]_ATT_NAME, which will contain the 

   number of significant digits. Users should not delete or change this

   attribute. This is the only record that quantize has been applied

   to the data.

   Quantization is not applied to values equal to the value of the

   _FillValue attribute, if any. If the _FillValue attribute is not

   set, then quantization is not applied to values matching the

   default fill value.

   Quantization may be applied to scalar variables.

   When type conversion takes place during a write, then it occurs

   before quantization is applied. For example, if nc_put_var_double()

   is called on a variable of type NC_FLOAT, which has quantize

   turned on, then the data are first converted from double to float,

   then quantization is applied to the float values.

   As with the deflate settings, quantize settings may only be

   modified before the first call to nc_enddef(). Once nc_enddef() is

   called for the file, quantize settings for any variable in the file

   may not be changed.

   Use of quantization is fully backwards compatible with existing

   versions and packages that can read compressed netCDF data. A

   variable which has been quantized is readable to older versions of

   the netCDF libraries, and to netCDF-Java.

   For more information about quantization and the BitGroom filter,

   see @ref quantize.

   @note Users new to quantization should start with Granular Bit

   Round, which results in the best compression. The Bit Groom

   algorithm is not as effective when compressing, but is faster than

   Granular Bit Round. The Bit Round algorithm accepts a number of

   bits to maintain, rather than a number of decimal digits, and is

   provided for users who are already performing some bit-based

   quantization, and wish to turn this task over to the netCDF

   library.

   @param ncid File ID.

   @param varid Variable ID. ::NC_GLOBAL may not be used.

   @param quantize_mode Quantization mode. May be ::NC_NOQUANTIZE or

   ::NC_QUANTIZE_BITGROOM or ::NC_QUANTIZE_GRANULARBR or

   ::NC_QUANTIZE_BITROUND.

   @param nsd Number of significant digits (either decimal or binary). 

   May be any integer from 1 to ::NC_QUANTIZE_MAX_FLOAT_NSD (for variables 

   of type ::NC_FLOAT) or ::NC_QUANTIZE_MAX_DOUBLE_NSD (for variables 

   of type ::NC_DOUBLE) for mode ::NC_QUANTIZE_BITGROOM and mode

   ::NC_QUANTIZE_GRANULARBR. May be any integer from 1 to 

   ::NC_QUANTIZE_MAX_FLOAT_NSB (for variables of type ::NC_FLOAT) or 

   ::NC_QUANTIZE_MAX_DOUBLE_NSB (for variables of type ::NC_DOUBLE) 

   for mode ::NC_QUANTIZE_BITROUND. Ignored if quantize_mode = NC_NOQUANTIZE.

   @return ::NC_NOERR No error.

   @return ::NC_EGLOBAL Can't use ::NC_GLOBAL with this function.

   @return ::NC_EBADID Bad ncid.

   @return ::NC_ENOTVAR Invalid variable ID.

   @return ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is

   not netCDF-4/HDF5.

   @return ::NC_ESTRICTNC3 Attempting netcdf-4 operation on strict nc3

   netcdf-4 file.

   @return ::NC_ELATEDEF Too late to change settings for this variable.

   @return ::NC_EINVAL Invalid input.

   @author Charlie Zender, Ed Hartnett

 */

int

nc_def_var_quantize(int ncid, int varid, int quantize_mode, int nsd)

{

    NC* ncp;

    int stat = NC_check_id(ncid,&ncp);

    if(stat != NC_NOERR) return stat;

    /* Using NC_GLOBAL is illegal. */

    if (varid == NC_GLOBAL) return NC_EGLOBAL;

    return ncp->dispatch->def_var_quantize(ncid,varid,quantize_mode,nsd);

}

/**

   Set checksum for a var.

   This function must be called after nc_def_var and before nc_enddef

   or any functions which writes data to the file.

   Checksums require chunked data. If this function is called on a

   variable with contiguous data, then the data is changed to chunked

   data, with default chunksizes. Use nc_def_var_chunking() to tune

   performance with user-defined chunksizes.

   @note Parallel I/O reads work with fletcher32 encoded

   data. Parallel I/O writes work with fletcher32 in netcdf-c-4.7.4

   and later releases, using hdf5-1.10.2 and later releases. Using the

   fletcher32 (or any) filter requires that collective access be used

   with the variable. Turning on fletcher32 for a variable in a file

   opened for parallel I/O will automatically switch the access for

   that variable to collective access.

   @param ncid NetCDF or group ID, from a previous call to nc_open(),

   nc_create(), nc_def_grp(), or associated inquiry functions such as

   nc_inq_ncid().

   @param varid Variable ID

   @param fletcher32 True to turn on Fletcher32 checksums for this

   variable.

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ncid.

   @return ::NC_ENOTVAR Invalid variable ID.

   @return ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is

   not netCDF-4/HDF5.

   @return ::NC_ESTRICTNC3 Attempting netcdf-4 operation on strict nc3

   netcdf-4 file.

   @return ::NC_ELATEDEF Too late to change settings for this variable.

   @return ::NC_EINVAL Invalid input

   @author Ed Hartnett, Dennis Heimbigner

*/

int

nc_def_var_fletcher32(int ncid, int varid, int fletcher32)

{

    NC* ncp;

    int stat = NC_check_id(ncid,&ncp);

    if(stat != NC_NOERR) return stat;

    return ncp->dispatch->def_var_fletcher32(ncid,varid,fletcher32);

}

/**

   Define storage and, if chunked storage is used, chunking parameters

   for a variable

   The storage may be set to NC_CONTIGUOUS, NC_COMPACT, or NC_CHUNKED.

   Contiguous storage means the variable is stored as one block of

   data in the file. This is the default storage.

   Compact storage means the variable is stored in the header record

   of the file. This can have large performance benefits on HPC system

   running many processors. Compact storage is only available for

   variables whose data are 64 KB or less. Attempting to turn on

   compact storage for a variable that is too large will result in the

   ::NC_EVARSIZE error.

   Chunked storage means the data are stored as chunks, of

   user-configurable size. Chunked storage is required for variable

   with one or more unlimted dimensions, or variable which use

   compression, or any other filter.

   The total size of a chunk must be less than 4 GiB. That is, the

   product of all chunksizes and the size of the data (or the size of

   nc_vlen_t for VLEN types) must be less than 4 GiB.

   This function may only be called after the variable is defined, but

   before nc_enddef is called. Once the chunking parameters are set for a

   variable, they cannot be changed.

   @note Scalar variables may have a storage of NC_CONTIGUOUS or

   NC_COMPACT. Attempts to set chunking on a scalare variable will

   cause ::NC_EINVAL to be returned. Only non-scalar variables can

   have chunking.

   @param ncid NetCDF ID, from a previous call to nc_open() or

   nc_create().

   @param varid Variable ID.

   @param storage If ::NC_CONTIGUOUS or ::NC_COMPACT, then contiguous

   or compact storage is used for this variable. Variables with one or

   more unlimited dimensions cannot use contiguous or compact

   storage. If contiguous or compact storage is turned on, the

   chunksizes parameter is ignored. If ::NC_CHUNKED, then chunked

   storage is used for this variable. Chunk sizes may be specified

   with the chunksizes parameter or default sizes will be used if that

   parameter is NULL.

   @param chunksizesp A pointer to an array list of chunk sizes. The

   array must have one chunksize for each dimension of the variable. If

   ::NC_CONTIGUOUS storage is set, then the chunksizes parameter is

   ignored. Ignored if NULL.

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ID.

   @return ::NC_ENOTNC4 Not a netCDF-4 file.

   @return ::NC_ELATEDEF This variable has already been the subject of

   a nc_enddef call.  In netCDF-4 files nc_enddef will be called

   automatically for any data read or write. Once nc_enddef has been

   called after the nc_def_var call for a variable, it is impossible

   to set the chunking for that variable.

   @return ::NC_ENOTINDEFINE Not in define mode.  This is returned for

   netCDF classic or 64-bit offset files, or for netCDF-4 files, when

   they wwere created with ::NC_CLASSIC_MODEL flag by nc_create().

   @return ::NC_EPERM Attempt to create object in read-only file.

   @return ::NC_EBADCHUNK Returns if the chunk size specified for a

   variable is larger than the length of the dimensions associated with

   variable.

   @return ::NC_EVARSIZE Compact storage attempted for variable bigger

   than 64 KB.

   @return ::NC_EINVAL Attempt to set contiguous or compact storage

   for var with one or more unlimited dimensions, or chunking for a

   scalar var.

   @section nc_def_var_chunking_example Example

   In this example from libsrc4/tst_vars2.c, chunksizes are set with

   nc_var_def_chunking, and checked with nc_var_inq_chunking.

   @code

   printf("**** testing chunking...");

   {

   #define NDIMS5 1

   #define DIM5_NAME "D5"

   #define VAR_NAME5 "V5"

   #define DIM5_LEN 1000

   int dimids[NDIMS5], dimids_in[NDIMS5];

   int varid;

   int ndims, nvars, natts, unlimdimid;

   nc_type xtype_in;

   char name_in[NC_MAX_NAME + 1];

   int data[DIM5_LEN], data_in[DIM5_LEN];

   size_t chunksize[NDIMS5] = {5};

   size_t chunksize_in[NDIMS5];

   int storage_in;

   int i, d;

   for (i = 0; i < DIM5_LEN; i++)

   data[i] = i;

   if (nc_create(FILE_NAME, NC_NETCDF4, &ncid)) ERR;

   if (nc_def_dim(ncid, DIM5_NAME, DIM5_LEN, &dimids[0])) ERR;

   if (nc_def_var(ncid, VAR_NAME5, NC_INT, NDIMS5, dimids, &varid)) ERR;

   if (nc_def_var_chunking(ncid, varid, NC_CHUNKED, chunksize)) ERR;

   if (nc_put_var_int(ncid, varid, data)) ERR;

   if (nc_inq_var_chunking(ncid, varid, &storage_in, chunksize_in)) ERR;

   for (d = 0; d < NDIMS5; d++)

   if (chunksize[d] != chunksize_in[d]) ERR;

   if (storage_in != NC_CHUNKED) ERR;

   @endcode

   @author Ed Hartnett, Dennis Heimbigner

*/

int

nc_def_var_chunking(int ncid, int varid, int storage, const size_t *chunksizesp)

{

    NC* ncp;

    int stat = NC_check_id(ncid, &ncp);

    if(stat != NC_NOERR) return stat;

    return ncp->dispatch->def_var_chunking(ncid, varid, storage,

                                           chunksizesp);

}

/**

   Define endianness of a variable.

   With this function the endianness (i.e. order of bits in integers) can

   be changed on a per-variable basis. By default, the endianness is the

   same as the default endianness of the platform. But with

   nc_def_var_endianness the endianness can be explicitly set for a

   variable.

   Warning: this function is only defined if the type of the variable

   is an atomic integer or float type.

   This function may only be called after the variable is defined, but

   before nc_enddef is called.

   @param ncid NetCDF ID, from a previous call to nc_open() or

   nc_create().

   @param varid Variable ID.

   @param endian ::NC_ENDIAN_NATIVE to select the native endianness of

   the platform (the default), ::NC_ENDIAN_LITTLE to use

   little-endian, ::NC_ENDIAN_BIG to use big-endian.

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ID.

   @return ::NC_ENOTNC4 Not a netCDF-4 file.

   @return ::NC_ELATEDEF This variable has already been the subject of a

   nc_enddef call. In netCDF-4 files nc_enddef will be called

   automatically for any data read or write. Once nc_enddef has been

   called after the nc_def_var call for a variable, it is impossible to

   set the chunking for that variable.

   @return ::NC_ENOTINDEFINE Not in define mode. This is returned for

   netCDF classic or 64-bit offset files, or for netCDF-4 files, when

   they wwere created with ::NC_CLASSIC_MODEL flag by nc_create().

   @return ::NC_EPERM Attempt to create object in read-only file.

   @section nc_def_var_endian_example Example

   In this example from libsrc4/tst_vars2.c, a variable is created, and

   the endianness set to ::NC_ENDIAN_BIG.

   @code

   #define NDIMS4 1

   #define DIM4_NAME "Joe"

   #define VAR_NAME4 "Ed"

   #define DIM4_LEN 10

   {

   int dimids[NDIMS4], dimids_in[NDIMS4];

   int varid;

   int ndims, nvars, natts, unlimdimid;

   nc_type xtype_in;

   char name_in[NC_MAX_NAME + 1];

   int data[DIM4_LEN], data_in[DIM4_LEN];

   int endian_in;

   int i;

   for (i = 0; i < DIM4_LEN; i++)

   data[i] = i;

   if (nc_create(FILE_NAME, NC_NETCDF4, &ncid)) ERR;

   if (nc_def_dim(ncid, DIM4_NAME, DIM4_LEN, &dimids[0])) ERR;

   if (dimids[0] != 0) ERR;

   if (nc_def_var(ncid, VAR_NAME4, NC_INT, NDIMS4, dimids, &varid)) ERR;

   if (nc_def_var_endian(ncid, varid, NC_ENDIAN_BIG)) ERR;

   @endcode

   @author Ed Hartnett

*/

int

nc_def_var_endian(int ncid, int varid, int endian)

{

    NC* ncp;

    int stat = NC_check_id(ncid,&ncp);

    if(stat != NC_NOERR) return stat;

    return ncp->dispatch->def_var_endian(ncid,varid,endian);

}

/**

 * Set szip compression settings on a variable. Szip is an

 * implementation of the extended-Rice lossless compression algorithm;

 * it is reported to provide fast and effective compression. Szip is

 * only available to netCDF if HDF5 was built with szip support.

 *

 * SZIP compression cannot be applied to variables with any

 * user-defined type.

 *

 * If zlib compression has already be turned on for a variable, then

 * this function will return ::NC_EINVAL.

 *

 * To learn the szip settings for a variable, use nc_inq_var_szip().

 *

 * @note The options_mask parameter may be either ::NC_SZIP_EC (entropy

 * coding) or ::NC_SZIP_NN (nearest neighbor):

 * * The entropy coding method is best suited for data that has been

 * processed. The EC method works best for small numbers.

 * * The nearest neighbor coding method preprocesses the data then the

 * applies EC method as above.

 *

 * For more information about HDF5 and szip, see

 * https://support.hdfgroup.org/HDF5/doc/RM/RM_H5P.html#Property-SetSzip

 * and

 * https://support.hdfgroup.org/doc_resource/SZIP/index.html.

 *

 * @param ncid File ID.

 * @param varid Variable ID.

 * @param options_mask The options mask. Can be ::NC_SZIP_EC or

 * ::NC_SZIP_NN.

 * @param pixels_per_block Pixels per block. Must be even and not

 * greater than 32, with typical values being 8, 10, 16, or 32. This

 * parameter affects compression ratio; the more pixel values vary,

 * the smaller this number should be to achieve better performance. If

 * pixels_per_block is bigger than the total number of elements in a

 * dataset chunk, ::NC_EINVAL will be returned.

 *

 * @returns ::NC_NOERR No error.

 * @returns ::NC_EBADID Bad ncid.

 * @returns ::NC_ENOTVAR Invalid variable ID.

 * @returns ::NC_ENOTNC4 Attempting netcdf-4 operation on file that is

 * not netCDF-4/HDF5.

 * @returns ::NC_ELATEDEF Too late to change settings for this variable.

 * @returns ::NC_ENOTINDEFINE Not in define mode.

 * @returns ::NC_EINVAL Invalid input, or zlib filter already applied

 * to this var.

 * @author Ed Hartnett

 */

int

nc_def_var_szip(int ncid, int varid, int options_mask, int pixels_per_block)

{

    int ret;

    /* This will cause H5Pset_szip to be called when the var is

     * created. */

    unsigned int params[2] = {(unsigned int)options_mask, (unsigned int)pixels_per_block};

    if ((ret = nc_def_var_filter(ncid, varid, H5Z_FILTER_SZIP, 2, params)))

        return ret;

    return NC_NOERR;

}

/** @} */

/**

   @name Rename a Variable

   Rename a variable.

*/

/** @{ */

/**

   Rename a variable.

   This function changes the name of a netCDF variable in an open netCDF

   file or group. You cannot rename a variable to have the name of any existing

   variable.

   For classic format, 64-bit offset format, and netCDF-4/HDF5 with

   classic mode, if the new name is longer than the old name, the netCDF

   dataset must be in define mode.

   For netCDF-4/HDF5 files, renaming the variable changes the order of

   the variables in the file. The renamed variable becomes the last

   variable in the file.

   @param ncid NetCDF or group ID, from a previous call to nc_open(),

   nc_create(), nc_def_grp(), or associated inquiry functions such as

   nc_inq_ncid().

   @param varid Variable ID

   @param name New name of the variable.

   @return ::NC_NOERR No error.

   @return ::NC_EBADID Bad ncid.

   @return ::NC_ENOTVAR Invalid variable ID.

   @return ::NC_EBADNAME Bad name.

   @return ::NC_EMAXNAME Name is too long.

   @return ::NC_ENAMEINUSE Name in use.

   @return ::NC_ENOMEM Out of memory.

   @section nc_rename_var_example Example

   Here is an example using nc_rename_var to rename the variable rh to

   rel_hum in an existing netCDF dataset named foo.nc:

   @code

   #include <netcdf.h>

   ...

   int  status;

   int  ncid;

   int  rh_id;

   ...

   status = nc_open("foo.nc", NC_WRITE, &ncid);

   if (status != NC_NOERR) handle_error(status);

   ...

   status = nc_redef(ncid);

   if (status != NC_NOERR) handle_error(status);

   status = nc_inq_varid (ncid, "rh", &rh_id);

   if (status != NC_NOERR) handle_error(status);

   status = nc_rename_var (ncid, rh_id, "rel_hum");

   if (status != NC_NOERR) handle_error(status);

   status = nc_enddef(ncid);

   if (status != NC_NOERR) handle_error(status);

   @endcode

   @author Glenn Davis, Ed Hartnett, Dennis Heimbigner

*/

int

nc_rename_var(int ncid, int varid, const char *name)

{

    NC* ncp;

    int stat = NC_check_id(ncid, &ncp);

    if(stat != NC_NOERR) return stat;

    TRACE(nc_rename_var);

    return ncp->dispatch->rename_var(ncid, varid, name);

}

/** @} */

/**

   @internal Does a variable have a record dimension?

   @param ncid File ID.

   @param varid Variable ID.

   @param nrecs Pointer that gets number of records.

   @return 0 if not a record var, 1 if it is.

*/

int

NC_is_recvar(int ncid, int varid, size_t* nrecs)

{

    int status = NC_NOERR;

    int unlimid;

    int ndims;

    int dimset[NC_MAX_VAR_DIMS];

    status = nc_inq_unlimdim(ncid,&unlimid);

    if(status != NC_NOERR) return 0; /* no unlimited defined */

    status = nc_inq_varndims(ncid,varid,&ndims);

    if(status != NC_NOERR) return 0; /* no unlimited defined */

    if(ndims == 0) return 0; /* scalar */

    status = nc_inq_vardimid(ncid,varid,dimset);

    if(status != NC_NOERR) return 0; /* no unlimited defined */

    status = nc_inq_dim(ncid,dimset[0],NULL,nrecs);

    if(status != NC_NOERR) return 0;

    return (dimset[0] == unlimid ? 1: 0);

}

/**

   @internal Get the number of record dimensions for a variable and an

   array that identifies which of a variable's dimensions are record

   dimensions. Intended to be used instead of NC_is_recvar(), which

   doesn't work for netCDF-4 variables which have multiple unlimited

   dimensions or an unlimited dimension that is not the first of a

   variable's dimensions.

   @param ncid File ID.

   @param varid Variable ID.

   @param nrecdimsp Pointer that gets number of record dims.

   @param is_recdim Pointer that gets 1 if there is one or more record

   dimensions, 0 if not.

   @return 0 if not a record var, 1 if it is.

   Example use:

   @code

   int nrecdims;

   int is_recdim[NC_MAX_VAR_DIMS];

   ...

   status = NC_inq_recvar(ncid,varid,&nrecdims,is_recdim);

   isrecvar = (nrecdims > 0);

   @endcode

*/

int

NC_inq_recvar(int ncid, int varid, int* nrecdimsp, int *is_recdim)

{

    int status = NC_NOERR;

    int unlimid;

    int nvardims;

    int dimset[NC_MAX_VAR_DIMS];

    int dim;

    int nrecdims = 0;

    status = nc_inq_varndims(ncid,varid,&nvardims);

    if(status != NC_NOERR) return status;

    if(nvardims == 0) return NC_NOERR; /* scalars have no dims */

    for(dim = 0; dim < nvardims; dim++)

        is_recdim[dim] = 0;

    status = nc_inq_unlimdim(ncid, &unlimid);

    if(status != NC_NOERR) return status;

    if(unlimid == -1) return status; /* no unlimited dims for any variables */

#ifdef USE_NETCDF4

    {

        int nunlimdims;

        int *unlimids;

        int recdim;

        status = nc_inq_unlimdims(ncid, &nunlimdims, NULL); /* for group or file, not variable */

        if(status != NC_NOERR) return status;

        if(nunlimdims == 0) return status;

        if (!(unlimids = malloc((size_t)nunlimdims * sizeof(int))))

            return NC_ENOMEM;

        status = nc_inq_unlimdims(ncid, &nunlimdims, unlimids); /* for group or file, not variable */

        if(status != NC_NOERR) {

            free(unlimids);

            return status;

        }

        status = nc_inq_vardimid(ncid, varid, dimset);

        if(status != NC_NOERR) {

            free(unlimids);

            return status;

        }

        for (dim = 0; dim < nvardims; dim++) { /* netCDF-4 rec dims need not be first dim for a rec var */

            for(recdim = 0; recdim < nunlimdims; recdim++) {

                if(dimset[dim] == unlimids[recdim]) {

                    is_recdim[dim] = 1;

                    nrecdims++;

                }

            }

        }

        free(unlimids);

    }

#else

    status = nc_inq_vardimid(ncid, varid, dimset);

    if(status != NC_NOERR) return status;

    if(dimset[0] == unlimid) {

        is_recdim[0] = 1;

        nrecdims++;

    }

#endif /* USE_NETCDF4 */

    if(nrecdimsp) *nrecdimsp = nrecdims;

    return status;

}

/* Ok to use NC pointers because

   all IOSP's will use that structure,

   but not ok to use e.g. NC_Var pointers

   because they may be different structure

   entirely.

*/

/**