[409] | 1 | /** \file |
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| 2 | File create and open functions |
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| 3 | |
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| 4 | These functions end up calling functions in one of the dispatch layers |
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| 5 | (netCDF-4, dap server, etc). |
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| 6 | |
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| 7 | Copyright 2010 University Corporation for Atmospheric |
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| 8 | Research/Unidata. See COPYRIGHT file for more info. |
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| 9 | */ |
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| 10 | |
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| 11 | #include "config.h" |
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| 12 | #include <stdlib.h> |
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| 13 | #ifdef HAVE_SYS_RESOURCE_H |
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| 14 | #include <sys/resource.h> |
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| 15 | #endif |
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| 16 | #ifdef HAVE_SYS_TYPES_H |
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| 17 | #include <sys/types.h> |
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| 18 | #endif |
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| 19 | #ifdef HAVE_SYS_STAT_H |
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| 20 | #include <sys/stat.h> |
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| 21 | #endif |
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| 22 | #ifdef HAVE_FCNTL_H |
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| 23 | #include <fcntl.h> |
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| 24 | #endif |
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| 25 | #include "ncdispatch.h" |
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| 26 | |
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| 27 | static int nc_initialized = 0; |
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| 28 | |
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| 29 | /** \defgroup datasets NetCDF Files |
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| 30 | |
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| 31 | NetCDF opens datasets as files or remote access URLs. |
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| 32 | |
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| 33 | A netCDF dataset that has not yet been opened can only be referred to |
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| 34 | by its dataset name. Once a netCDF dataset is opened, it is referred |
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| 35 | to by a netCDF ID, which is a small non-negative integer returned when |
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| 36 | you create or open the dataset. A netCDF ID is much like a file |
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| 37 | descriptor in C or a logical unit number in FORTRAN. In any single |
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| 38 | program, the netCDF IDs of distinct open netCDF datasets are |
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| 39 | distinct. A single netCDF dataset may be opened multiple times and |
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| 40 | will then have multiple distinct netCDF IDs; however at most one of |
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| 41 | the open instances of a single netCDF dataset should permit |
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| 42 | writing. When an open netCDF dataset is closed, the ID is no longer |
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| 43 | associated with a netCDF dataset. |
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| 44 | |
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| 45 | Functions that deal with the netCDF library include: |
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| 46 | - Get version of library. |
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| 47 | - Get error message corresponding to a returned error code. |
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| 48 | |
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| 49 | The operations supported on a netCDF dataset as a single object are: |
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| 50 | - Create, given dataset name and whether to overwrite or not. |
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| 51 | - Open for access, given dataset name and read or write intent. |
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| 52 | - Put into define mode, to add dimensions, variables, or attributes. |
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| 53 | - Take out of define mode, checking consistency of additions. |
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| 54 | - Close, writing to disk if required. |
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| 55 | - Inquire about the number of dimensions, number of variables, |
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| 56 | number of global attributes, and ID of the unlimited dimension, if |
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| 57 | any. |
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| 58 | - Synchronize to disk to make sure it is current. |
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| 59 | - Set and unset nofill mode for optimized sequential writes. |
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| 60 | - After a summary of conventions used in describing the netCDF |
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| 61 | interfaces, the rest of this chapter presents a detailed description |
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| 62 | of the interfaces for these operations. |
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| 63 | */ |
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| 64 | /**@{*/ |
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| 65 | |
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| 66 | size_t* NC_coord_zero; |
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| 67 | size_t* NC_coord_one; |
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| 68 | |
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| 69 | static void |
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| 70 | nc_local_initialize(void) |
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| 71 | { |
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| 72 | int i; |
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| 73 | NC_coord_zero = (size_t*)malloc(sizeof(size_t)*NC_MAX_VAR_DIMS); |
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| 74 | if(NC_coord_zero == NULL) abort(); |
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| 75 | NC_coord_one = (size_t*)malloc(sizeof(size_t)*NC_MAX_VAR_DIMS); |
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| 76 | if(NC_coord_one == NULL) abort(); |
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| 77 | for(i=0;i<NC_MAX_VAR_DIMS;i++) { |
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| 78 | NC_coord_one[i] = 1; |
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| 79 | NC_coord_zero[i] = 0; |
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| 80 | } |
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| 81 | } |
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| 82 | |
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| 83 | static int |
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| 84 | NC_check_file_type(const char *path, int use_parallel, void *mpi_info, |
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| 85 | int *cdf, int *hdf) |
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| 86 | { |
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| 87 | char magic[MAGIC_NUMBER_LEN]; |
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| 88 | |
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| 89 | *hdf = 0; *cdf = 0; |
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| 90 | |
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| 91 | /* Get the 4-byte magic from the beginning of the file. Don't use posix |
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| 92 | * for parallel, use the MPI functions instead. */ |
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| 93 | #ifdef USE_PARALLEL_MPIO |
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| 94 | if (use_parallel) |
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| 95 | { |
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| 96 | MPI_File fh; |
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| 97 | MPI_Status status; |
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| 98 | int retval; |
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| 99 | MPI_Comm comm = 0; |
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| 100 | MPI_Info info = 0; |
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| 101 | |
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| 102 | if(mpi_info != NULL) { |
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| 103 | comm = ((NC_MPI_INFO*)mpi_info)->comm; |
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| 104 | info = ((NC_MPI_INFO*)mpi_info)->info; |
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| 105 | } |
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| 106 | if((retval = MPI_File_open(comm, (char *)path, MPI_MODE_RDONLY,info, |
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| 107 | &fh)) != MPI_SUCCESS) |
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| 108 | return NC_EPARINIT; |
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| 109 | if((retval = MPI_File_read(fh, magic, MAGIC_NUMBER_LEN, MPI_CHAR, |
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| 110 | &status)) != MPI_SUCCESS) |
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| 111 | return NC_EPARINIT; |
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| 112 | if((retval = MPI_File_close(&fh)) != MPI_SUCCESS) |
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| 113 | return NC_EPARINIT; |
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| 114 | } else |
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| 115 | #endif /* USE_PARALLEL */ |
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| 116 | { |
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| 117 | FILE *fp; |
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| 118 | int i; |
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| 119 | |
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| 120 | if(path == NULL || strlen(path)==0) |
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| 121 | return NC_EINVAL; |
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| 122 | |
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| 123 | if (!(fp = fopen(path, "r"))) |
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| 124 | return errno; |
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| 125 | i = fread(magic, MAGIC_NUMBER_LEN, 1, fp); |
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| 126 | fclose(fp); |
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| 127 | if(i != 1) |
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| 128 | return errno; |
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| 129 | } |
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| 130 | |
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| 131 | /* Ignore the first byte for HDF */ |
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| 132 | if(magic[1] == 'H' && magic[2] == 'D' && magic[3] == 'F') |
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| 133 | *hdf = 5; |
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| 134 | else if(magic[0] == '\016' && magic[1] == '\003' |
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| 135 | && magic[2] == '\023' && magic[3] == '\001') |
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| 136 | *hdf = 4; |
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| 137 | else if(magic[0] == 'C' && magic[1] == 'D' && magic[2] == 'F') |
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| 138 | { |
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| 139 | if(magic[3] == '\001') |
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| 140 | *cdf = 1; /* netcdf classic version 1 */ |
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| 141 | else if(magic[3] == '\002') |
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| 142 | *cdf = 2; /* netcdf classic version 2 */ |
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| 143 | } |
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| 144 | |
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| 145 | return NC_NOERR; |
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| 146 | } |
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| 147 | |
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| 148 | /** \ingroup datasets |
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| 149 | Create a new netCDF file. |
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| 150 | |
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| 151 | This function creates a new netCDF dataset, returning a netCDF ID that |
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| 152 | can subsequently be used to refer to the netCDF dataset in other |
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| 153 | netCDF function calls. The new netCDF dataset opened for write access |
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| 154 | and placed in define mode, ready for you to add dimensions, variables, |
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| 155 | and attributes. |
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| 156 | |
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| 157 | \param path The file name of the new netCDF dataset. |
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| 158 | |
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| 159 | \param cmode The creation mode flag. The following flags are |
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| 160 | available: NC_NOCLOBBER (do not overwrite existing file), NC_SHARE |
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| 161 | (limit write caching - netcdf classic files onlt), NC_64BIT_OFFSET |
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| 162 | (create 64-bit offset file), NC_NETCDF4 (create netCDF-4/HDF5 file), |
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| 163 | NC_CLASSIC_MODEL (enforce netCDF classic mode on netCDF-4/HDF5 |
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| 164 | files), NC_DISKLESS (store data only in memory), NC_MMAP (use MMAP |
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| 165 | for NC_DISKLESS), and NC_WRITE. |
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| 166 | See discussion below. |
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| 167 | |
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| 168 | \param ncidp Pointer to location where returned netCDF ID is to be |
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| 169 | stored. |
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| 170 | |
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| 171 | <h2>The cmode Flag</h2> |
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| 172 | |
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| 173 | The cmode flag is used to control the type of file created, and some |
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| 174 | aspects of how it may be used. |
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| 175 | |
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| 176 | Setting NC_NOCLOBBER means you do not want to clobber (overwrite) an |
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| 177 | existing dataset; an error (NC_EEXIST) is returned if the specified |
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| 178 | dataset already exists. |
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| 179 | |
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| 180 | The NC_SHARE flag is appropriate when one process may be writing the |
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| 181 | dataset and one or more other processes reading the dataset |
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| 182 | concurrently; it means that dataset accesses are not buffered and |
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| 183 | caching is limited. Since the buffering scheme is optimized for |
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| 184 | sequential access, programs that do not access data sequentially may |
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| 185 | see some performance improvement by setting the NC_SHARE flag. This |
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| 186 | flag is ignored for netCDF-4 files. |
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| 187 | |
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| 188 | Setting NC_64BIT_OFFSET causes netCDF to create a 64-bit offset format |
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| 189 | file, instead of a netCDF classic format file. The 64-bit offset |
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| 190 | format imposes far fewer restrictions on very large (i.e. over 2 GB) |
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| 191 | data files. See Large File Support. |
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| 192 | |
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| 193 | A zero value (defined for convenience as NC_CLOBBER) specifies the |
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| 194 | default behavior: overwrite any existing dataset with the same file |
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| 195 | name and buffer and cache accesses for efficiency. The dataset will be |
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| 196 | in netCDF classic format. See NetCDF Classic Format Limitations. |
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| 197 | |
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| 198 | Setting NC_NETCDF4 causes netCDF to create a HDF5/NetCDF-4 file. |
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| 199 | |
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| 200 | Setting NC_CLASSIC_MODEL causes netCDF to enforce the classic data |
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| 201 | model in this file. (This only has effect for netCDF-4/HDF5 files, as |
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| 202 | classic and 64-bit offset files always use the classic model.) When |
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| 203 | used with NC_NETCDF4, this flag ensures that the resulting |
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| 204 | netCDF-4/HDF5 file may never contain any new constructs from the |
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| 205 | enhanced data model. That is, it cannot contain groups, user defined |
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| 206 | types, multiple unlimited dimensions, or new atomic types. The |
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| 207 | advantage of this restriction is that such files are guaranteed to |
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| 208 | work with existing netCDF software. |
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| 209 | |
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| 210 | Setting NC_DISKLESS causes netCDF to create the file only in memory. |
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| 211 | This allows for the use of files that have no long term purpose. Note that |
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| 212 | with one exception, the in-memory file is destroyed upon calling |
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| 213 | nc_close. If, however, the flag combination (NC_DISKLESS|NC_WRITE) |
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| 214 | is used, then at close, the contents of the memory file will be |
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| 215 | made persistent in the file path that was specified in the nc_create |
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| 216 | call. If NC_DISKLESS is going to be used for creating a large classic file, |
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| 217 | it behooves one to use either nc__create or nc_create_mp and specify |
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| 218 | an appropriately large value of the initialsz parameter to avoid |
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| 219 | to many extensions to the in-memory space for the file. |
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| 220 | This flag applies to files in classic format and to file in extended |
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| 221 | format (netcdf-4). |
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| 222 | |
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| 223 | Normally, NC_DISKLESS allocates space in the heap for |
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| 224 | storing the in-memory file. If, however, the ./configure |
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| 225 | flags --enable-mmap is used, and the additional mode flag |
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| 226 | NC_MMAP is specified, then the file will be created using |
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| 227 | the operating system MMAP facility. |
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| 228 | This flag only applies to files in classic format. Extended |
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| 229 | format (netcdf-4) files will ignore the NC_MMAP flag. |
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| 230 | |
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| 231 | Using NC_MMAP for nc_create is |
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| 232 | only included for completeness vis-a-vis nc_open. The |
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| 233 | ability to use MMAP is of limited use for nc_create because |
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| 234 | nc_create is going to create the file in memory anyway. |
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| 235 | Closing a MMAP'd file will be slightly faster, but not significantly. |
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| 236 | |
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| 237 | Note that nc_create(path,cmode,ncidp) is equivalent to the invocation of |
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| 238 | nc__create(path,cmode,NC_SIZEHINT_DEFAULT,NULL,ncidp). |
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| 239 | |
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| 240 | \returns ::NC_NOERR No error. |
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| 241 | |
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| 242 | \returns ::NC_ENOMEM System out of memory. |
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| 243 | |
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| 244 | \returns ::NC_EHDFERR HDF5 error (netCDF-4 files only). |
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| 245 | |
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| 246 | \returns ::NC_EFILEMETA Error writing netCDF-4 file-level metadata in |
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| 247 | HDF5 file. (netCDF-4 files only). |
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| 248 | |
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| 249 | \returns ::NC_EDISKLESS if there was an error in creating the |
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| 250 | in-memory file. |
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| 251 | |
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| 252 | \note When creating a netCDF-4 file HDF5 error reporting is turned |
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| 253 | off, if it is on. This doesn't stop the HDF5 error stack from |
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| 254 | recording the errors, it simply stops their display to the user |
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| 255 | through stderr. |
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| 256 | |
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| 257 | <h1>Examples</h1> |
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| 258 | |
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| 259 | In this example we create a netCDF dataset named foo.nc; we want the |
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| 260 | dataset to be created in the current directory only if a dataset with |
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| 261 | that name does not already exist: |
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| 262 | |
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| 263 | @code |
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| 264 | #include <netcdf.h> |
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| 265 | ... |
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| 266 | int status = NC_NOERR; |
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| 267 | int ncid; |
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| 268 | ... |
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| 269 | status = nc_create("foo.nc", NC_NOCLOBBER, &ncid); |
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| 270 | if (status != NC_NOERR) handle_error(status); |
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| 271 | @endcode |
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| 272 | |
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| 273 | In this example we create a netCDF dataset named foo_large.nc. It will |
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| 274 | be in the 64-bit offset format. |
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| 275 | |
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| 276 | @code |
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| 277 | #include <netcdf.h> |
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| 278 | ... |
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| 279 | int status = NC_NOERR; |
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| 280 | int ncid; |
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| 281 | ... |
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| 282 | status = nc_create("foo_large.nc", NC_NOCLOBBER|NC_64BIT_OFFSET, &ncid); |
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| 283 | if (status != NC_NOERR) handle_error(status); |
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| 284 | @endcode |
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| 285 | |
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| 286 | In this example we create a netCDF dataset named foo_HDF5.nc. It will |
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| 287 | be in the HDF5 format. |
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| 288 | |
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| 289 | @code |
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| 290 | #include <netcdf.h> |
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| 291 | ... |
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| 292 | int status = NC_NOERR; |
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| 293 | int ncid; |
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| 294 | ... |
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| 295 | status = nc_create("foo_HDF5.nc", NC_NOCLOBBER|NC_NETCDF4, &ncid); |
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| 296 | if (status != NC_NOERR) handle_error(status); |
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| 297 | @endcode |
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| 298 | |
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| 299 | In this example we create a netCDF dataset named |
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| 300 | foo_HDF5_classic.nc. It will be in the HDF5 format, but will not allow |
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| 301 | the use of any netCDF-4 advanced features. That is, it will conform to |
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| 302 | the classic netCDF-3 data model. |
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| 303 | |
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| 304 | @code |
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| 305 | #include <netcdf.h> |
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| 306 | ... |
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| 307 | int status = NC_NOERR; |
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| 308 | int ncid; |
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| 309 | ... |
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| 310 | status = nc_create("foo_HDF5_classic.nc", NC_NOCLOBBER|NC_NETCDF4|NC_CLASSIC_MODEL, &ncid); |
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| 311 | if (status != NC_NOERR) handle_error(status); |
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| 312 | @endcode |
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| 313 | |
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| 314 | In this example we create a in-memory netCDF classic dataset named |
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| 315 | diskless.nc whose content will be lost when nc_close() is called. |
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| 316 | |
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| 317 | @code |
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| 318 | #include <netcdf.h> |
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| 319 | ... |
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| 320 | int status = NC_NOERR; |
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| 321 | int ncid; |
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| 322 | ... |
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| 323 | status = nc_create("diskless.nc", NC_DISKLESS, &ncid); |
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| 324 | if (status != NC_NOERR) handle_error(status); |
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| 325 | @endcode |
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| 326 | |
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| 327 | In this example we create a in-memory netCDF classic dataset named |
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| 328 | diskless.nc and specify that it should be made persistent |
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| 329 | in a file named diskless.nc when nc_close() is called. |
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| 330 | |
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| 331 | @code |
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| 332 | #include <netcdf.h> |
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| 333 | ... |
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| 334 | int status = NC_NOERR; |
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| 335 | int ncid; |
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| 336 | ... |
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| 337 | status = nc_create("diskless.nc", NC_DISKLESS|NC_WRITE, &ncid); |
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| 338 | if (status != NC_NOERR) handle_error(status); |
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| 339 | @endcode |
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| 340 | |
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| 341 | A variant of nc_create(), nc__create() (note the double underscore) allows |
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| 342 | users to specify two tuning parameters for the file that it is |
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| 343 | creating. */ |
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| 344 | int |
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| 345 | nc_create(const char *path, int cmode, int *ncidp) |
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| 346 | { |
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| 347 | return nc__create(path,cmode,NC_SIZEHINT_DEFAULT,NULL,ncidp); |
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| 348 | } |
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| 349 | |
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| 350 | /*! |
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| 351 | Create a netCDF file with some extra parameters controlling classic |
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| 352 | file cacheing. |
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| 353 | |
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| 354 | Like nc_create(), this function creates a netCDF file. |
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| 355 | |
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| 356 | \param path The file name of the new netCDF dataset. |
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| 357 | |
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| 358 | \param cmode The creation mode flag, the same as in nc_create(). |
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| 359 | |
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| 360 | \param initialsz On some systems, and with custom I/O layers, it may |
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| 361 | be advantageous to set the size of the output file at creation |
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| 362 | time. This parameter sets the initial size of the file at creation |
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| 363 | time. This only applies to classic and 64-bit offset files. |
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| 364 | The special value NC_SIZEHINT_DEFAULT (which is the value 0), |
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| 365 | lets the netcdf library choose a suitable initial size. |
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| 366 | |
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| 367 | \param chunksizehintp A pointer to the chunk size hint, |
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| 368 | which controls a space versus time tradeoff, memory |
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| 369 | allocated in the netcdf library versus number of system |
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| 370 | calls. Because of internal requirements, the value may not |
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| 371 | be set to exactly the value requested. The actual value |
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| 372 | chosen is returned by reference. Using a NULL pointer or |
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| 373 | having the pointer point to the value NC_SIZEHINT_DEFAULT |
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| 374 | causes the library to choose a default. How the system |
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| 375 | chooses the default depends on the system. On many systems, |
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| 376 | the "preferred I/O block size" is available from the stat() |
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| 377 | system call, struct stat member st_blksize. If this is |
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| 378 | available it is used. Lacking that, twice the system |
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| 379 | pagesize is used. Lacking a call to discover the system |
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| 380 | pagesize, we just set default bufrsize to 8192. The bufrsize |
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| 381 | is a property of a given open netcdf descriptor ncid, it is |
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| 382 | not a persistent property of the netcdf dataset. This only |
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| 383 | applies to classic and 64-bit offset files. |
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| 384 | |
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| 385 | \param ncidp Pointer to location where returned netCDF ID is to be |
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| 386 | stored. |
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| 387 | |
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| 388 | \note This function uses the same return codes as the nc_create() |
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| 389 | function. |
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| 390 | |
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| 391 | <h1>Examples</h1> |
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| 392 | |
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| 393 | In this example we create a netCDF dataset named foo_large.nc; we want |
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| 394 | the dataset to be created in the current directory only if a dataset |
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| 395 | with that name does not already exist. We also specify that bufrsize |
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| 396 | and initial size for the file. |
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| 397 | |
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| 398 | \code |
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| 399 | #include <netcdf.h> |
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| 400 | ... |
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| 401 | int status = NC_NOERR; |
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| 402 | int ncid; |
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| 403 | int intialsz = 2048; |
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| 404 | int *bufrsize; |
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| 405 | ... |
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| 406 | *bufrsize = 1024; |
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| 407 | status = nc__create("foo.nc", NC_NOCLOBBER, initialsz, bufrsize, &ncid); |
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| 408 | if (status != NC_NOERR) handle_error(status); |
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| 409 | \endcode |
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| 410 | */ |
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| 411 | int |
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| 412 | nc__create(const char *path, int cmode, size_t initialsz, |
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| 413 | size_t *chunksizehintp, int *ncidp) |
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| 414 | { |
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| 415 | return NC_create(path, cmode, initialsz, 0, |
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| 416 | chunksizehintp, 0, NULL, ncidp); |
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| 417 | |
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| 418 | } |
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| 419 | /** |
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| 420 | \internal |
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| 421 | |
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| 422 | \deprecated This function was used in the old days with the Cray at |
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| 423 | NCAR. The Cray is long gone, and this call is supported only for |
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| 424 | backward compatibility. |
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| 425 | |
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| 426 | */ |
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| 427 | int |
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| 428 | nc__create_mp(const char *path, int cmode, size_t initialsz, |
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| 429 | int basepe, size_t *chunksizehintp, int *ncidp) |
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| 430 | { |
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| 431 | return NC_create(path, cmode, initialsz, basepe, |
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| 432 | chunksizehintp, 0, NULL, ncidp); |
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| 433 | } |
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| 434 | |
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| 435 | /** |
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| 436 | Open an existing netCDF file. |
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| 437 | |
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| 438 | This function opens an existing netCDF dataset for access. It |
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| 439 | determines the underlying file format automatically. Use the same call |
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| 440 | to open a netCDF classic, 64-bit offset, or netCDF-4 file. |
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| 441 | |
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| 442 | \param path File name for netCDF dataset to be opened. When DAP |
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| 443 | support is enabled, then the path may be an OPeNDAP URL rather than a |
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| 444 | file path. |
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| 445 | |
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| 446 | \param mode The mode flag may include NC_WRITE (for read/write |
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| 447 | access) and NC_SHARE (see below) and NC_DISKLESS (see below). |
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| 448 | |
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| 449 | \param ncidp Pointer to location where returned netCDF ID is to be |
---|
| 450 | stored. |
---|
| 451 | |
---|
| 452 | <h2>Open Mode</h2> |
---|
| 453 | |
---|
| 454 | A zero value (or NC_NOWRITE) specifies the default behavior: open the |
---|
| 455 | dataset with read-only access, buffering and caching accesses for |
---|
| 456 | efficiency. |
---|
| 457 | |
---|
| 458 | Otherwise, the open mode is NC_WRITE, NC_SHARE, or |
---|
| 459 | NC_WRITE|NC_SHARE. Setting the NC_WRITE flag opens the dataset with |
---|
| 460 | read-write access. ("Writing" means any kind of change to the dataset, |
---|
| 461 | including appending or changing data, adding or renaming dimensions, |
---|
| 462 | variables, and attributes, or deleting attributes.) |
---|
| 463 | |
---|
| 464 | The NC_SHARE flag is only used for netCDF classic and 64-bit offset |
---|
| 465 | files. It is appropriate when one process may be writing the dataset |
---|
| 466 | and one or more other processes reading the dataset concurrently; it |
---|
| 467 | means that dataset accesses are not buffered and caching is |
---|
| 468 | limited. Since the buffering scheme is optimized for sequential |
---|
| 469 | access, programs that do not access data sequentially may see some |
---|
| 470 | performance improvement by setting the NC_SHARE flag. |
---|
| 471 | |
---|
| 472 | This procedure may also be invoked with the NC_DISKLESS flag |
---|
| 473 | set in the mode argument if the file to be opened is a |
---|
| 474 | classic format file. For nc_open(), this flag applies only |
---|
| 475 | to files in classic format. If the file is of type |
---|
| 476 | NC_NETCDF4, then the NC_DISKLESS flag will be ignored. |
---|
| 477 | |
---|
| 478 | If NC_DISKLESS is specified, then the whole file is read completely into |
---|
| 479 | memory. In effect this creates an in-memory cache of the file. |
---|
| 480 | If the mode flag also specifies NC_WRITE, then the in-memory cache |
---|
| 481 | will be re-written to the disk file when nc_close() is called. |
---|
| 482 | For some kinds of manipulations, having the in-memory cache can |
---|
| 483 | speed up file processing. But in simple cases, non-cached |
---|
| 484 | processing may actually be faster than using cached processing. |
---|
| 485 | You will need to experiment to determine if the in-memory caching |
---|
| 486 | is worthwhile for your application. |
---|
| 487 | |
---|
| 488 | Normally, NC_DISKLESS allocates space in the heap for |
---|
| 489 | storing the in-memory file. If, however, the ./configure |
---|
| 490 | flags --enable-mmap is used, and the additional mode flag |
---|
| 491 | NC_MMAP is specified, then the file will be opened using |
---|
| 492 | the operating system MMAP facility. |
---|
| 493 | This flag only applies to files in classic format. Extended |
---|
| 494 | format (netcdf-4) files will ignore the NC_MMAP flag. |
---|
| 495 | |
---|
| 496 | In most cases, using MMAP provides no advantage |
---|
| 497 | for just NC_DISKLESS. The one case where using MMAP is an |
---|
| 498 | advantage is when a file is to be opened and only a small portion |
---|
| 499 | of its data is to be read and/or written. |
---|
| 500 | In this scenario, MMAP will cause only the accessed data to be |
---|
| 501 | retrieved from disk. Without MMAP, NC_DISKLESS will read the whole |
---|
| 502 | file into memory on nc_open. Thus, MMAP will provide some performance |
---|
| 503 | improvement in this case. |
---|
| 504 | |
---|
| 505 | It is not necessary to pass any information about the format of the |
---|
| 506 | file being opened. The file type will be detected automatically by the |
---|
| 507 | netCDF library. |
---|
| 508 | |
---|
| 509 | If a the path is a DAP URL, then the open mode is read-only. |
---|
| 510 | Setting NC_WRITE will be ignored. |
---|
| 511 | |
---|
| 512 | \note When opening a netCDF-4 file HDF5 error reporting is turned off, |
---|
| 513 | if it is on. This doesn't stop the HDF5 error stack from recording the |
---|
| 514 | errors, it simply stops their display to the user through stderr. |
---|
| 515 | |
---|
| 516 | nc_open()returns the value NC_NOERR if no errors occurred. Otherwise, |
---|
| 517 | the returned status indicates an error. Possible causes of errors |
---|
| 518 | include: |
---|
| 519 | |
---|
| 520 | Note that nc_open(path,cmode,ncidp) is equivalent to the invocation of |
---|
| 521 | nc__open(path,cmode,NC_SIZEHINT_DEFAULT,NULL,ncidp). |
---|
| 522 | |
---|
| 523 | \returns ::NC_NOERR No error. |
---|
| 524 | |
---|
| 525 | \returns ::NC_ENOMEM Out of memory. |
---|
| 526 | |
---|
| 527 | \returns ::NC_EHDFERR HDF5 error. (NetCDF-4 files only.) |
---|
| 528 | |
---|
| 529 | \returns ::NC_EDIMMETA Error in netCDF-4 dimension metadata. (NetCDF-4 files only.) |
---|
| 530 | |
---|
| 531 | <h1>Examples</h1> |
---|
| 532 | |
---|
| 533 | Here is an example using nc_open()to open an existing netCDF dataset |
---|
| 534 | named foo.nc for read-only, non-shared access: |
---|
| 535 | |
---|
| 536 | @code |
---|
| 537 | #include <netcdf.h> |
---|
| 538 | ... |
---|
| 539 | int status = NC_NOERR; |
---|
| 540 | int ncid; |
---|
| 541 | ... |
---|
| 542 | status = nc_open("foo.nc", 0, &ncid); |
---|
| 543 | if (status != NC_NOERR) handle_error(status); |
---|
| 544 | @endcode |
---|
| 545 | */ |
---|
| 546 | int |
---|
| 547 | nc_open(const char *path, int mode, int *ncidp) |
---|
| 548 | { |
---|
| 549 | return NC_open(path, mode, 0, NULL, 0, NULL, ncidp); |
---|
| 550 | } |
---|
| 551 | |
---|
| 552 | /** |
---|
| 553 | Open a netCDF file with extra performance parameters for the classic |
---|
| 554 | library. |
---|
| 555 | |
---|
| 556 | \param path File name for netCDF dataset to be opened. When DAP |
---|
| 557 | support is enabled, then the path may be an OPeNDAP URL rather than a |
---|
| 558 | file path. |
---|
| 559 | |
---|
| 560 | \param mode The mode flag may include NC_WRITE (for read/write |
---|
| 561 | access) and NC_SHARE as in nc_open(). |
---|
| 562 | |
---|
| 563 | \param chunksizehintp A size hint for the classic library. Only |
---|
| 564 | applies to classic and 64-bit offset files. See below for more |
---|
| 565 | information. |
---|
| 566 | |
---|
| 567 | \param ncidp Pointer to location where returned netCDF ID is to be |
---|
| 568 | stored. |
---|
| 569 | |
---|
| 570 | <h1>The chunksizehintp Parameter</h1> |
---|
| 571 | |
---|
| 572 | The argument referenced by bufrsizehintp controls a space versus time |
---|
| 573 | tradeoff, memory allocated in the netcdf library versus number of |
---|
| 574 | system calls. |
---|
| 575 | |
---|
| 576 | Because of internal requirements, the value may not be set to exactly |
---|
| 577 | the value requested. The actual value chosen is returned by reference. |
---|
| 578 | |
---|
| 579 | Using a NULL pointer or having the pointer point to the value |
---|
| 580 | NC_SIZEHINT_DEFAULT causes the library to choose a default. |
---|
| 581 | How the system chooses the default depends on the system. On |
---|
| 582 | many systems, the "preferred I/O block size" is available from the |
---|
| 583 | stat() system call, struct stat member st_blksize. If this is |
---|
| 584 | available it is used. Lacking that, twice the system pagesize is used. |
---|
| 585 | |
---|
| 586 | Lacking a call to discover the system pagesize, we just set default |
---|
| 587 | bufrsize to 8192. |
---|
| 588 | |
---|
| 589 | The bufrsize is a property of a given open netcdf descriptor ncid, it |
---|
| 590 | is not a persistent property of the netcdf dataset. |
---|
| 591 | |
---|
| 592 | |
---|
| 593 | \returns ::NC_NOERR No error. |
---|
| 594 | |
---|
| 595 | \returns ::NC_ENOMEM Out of memory. |
---|
| 596 | |
---|
| 597 | \returns ::NC_EHDFERR HDF5 error. (NetCDF-4 files only.) |
---|
| 598 | |
---|
| 599 | \returns ::NC_EDIMMETA Error in netCDF-4 dimension metadata. (NetCDF-4 |
---|
| 600 | files only.) |
---|
| 601 | |
---|
| 602 | */ |
---|
| 603 | int |
---|
| 604 | nc__open(const char *path, int mode, |
---|
| 605 | size_t *chunksizehintp, int *ncidp) |
---|
| 606 | { |
---|
| 607 | return NC_open(path, mode, 0, chunksizehintp, 0, |
---|
| 608 | NULL, ncidp); |
---|
| 609 | } |
---|
| 610 | |
---|
| 611 | /** |
---|
| 612 | \internal |
---|
| 613 | |
---|
| 614 | \deprecated This function was used in the old days with the Cray at |
---|
| 615 | NCAR. The Cray is long gone, and this call is supported only for |
---|
| 616 | backward compatibility. |
---|
| 617 | |
---|
| 618 | */ |
---|
| 619 | int |
---|
| 620 | nc__open_mp(const char *path, int mode, int basepe, |
---|
| 621 | size_t *chunksizehintp, int *ncidp) |
---|
| 622 | { |
---|
| 623 | return NC_open(path, mode, basepe, chunksizehintp, |
---|
| 624 | 0, NULL, ncidp); |
---|
| 625 | } |
---|
| 626 | |
---|
| 627 | /** |
---|
| 628 | Get the file pathname (or the opendap URL) which was used to |
---|
| 629 | open/create the ncid's file. |
---|
| 630 | |
---|
| 631 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 632 | nc_create(). |
---|
| 633 | |
---|
| 634 | \param pathlen Pointer where length of path will be returned. Ignored |
---|
| 635 | if NULL. |
---|
| 636 | |
---|
| 637 | \param path Pointer where path name will be copied. Space must already |
---|
| 638 | be allocated. Ignored if NULL. |
---|
| 639 | |
---|
| 640 | \returns ::NC_NOERR No error. |
---|
| 641 | |
---|
| 642 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 643 | */ |
---|
| 644 | int |
---|
| 645 | nc_inq_path(int ncid, size_t *pathlen, char *path) |
---|
| 646 | { |
---|
| 647 | NC* ncp; |
---|
| 648 | int stat = NC_NOERR; |
---|
| 649 | if ((stat = NC_check_id(ncid, &ncp))) |
---|
| 650 | return stat; |
---|
| 651 | if(ncp->path == NULL) { |
---|
| 652 | if(pathlen) *pathlen = 0; |
---|
| 653 | if(path) path[0] = '\0'; |
---|
| 654 | } else { |
---|
| 655 | if (pathlen) *pathlen = strlen(ncp->path); |
---|
| 656 | if (path) strcpy(path, ncp->path); |
---|
| 657 | } |
---|
| 658 | return stat; |
---|
| 659 | } |
---|
| 660 | |
---|
| 661 | /** |
---|
| 662 | Put open netcdf dataset into define mode |
---|
| 663 | |
---|
| 664 | The function nc_redef puts an open netCDF dataset into define mode, so |
---|
| 665 | dimensions, variables, and attributes can be added or renamed and |
---|
| 666 | attributes can be deleted. |
---|
| 667 | |
---|
| 668 | For netCDF-4 files (i.e. files created with NC_NETCDF4 in the cmode in |
---|
| 669 | their call to nc_create()), it is not necessary to call nc_redef() |
---|
| 670 | unless the file was also created with NC_STRICT_NC3. For straight-up |
---|
| 671 | netCDF-4 files, nc_redef() is called automatically, as needed. |
---|
| 672 | |
---|
| 673 | For all netCDF-4 files, the root ncid must be used. This is the ncid |
---|
| 674 | returned by nc_open() and nc_create(), and points to the root of the |
---|
| 675 | hierarchy tree for netCDF-4 files. |
---|
| 676 | |
---|
| 677 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 678 | nc_create(). |
---|
| 679 | |
---|
| 680 | \returns ::NC_NOERR No error. |
---|
| 681 | |
---|
| 682 | \returns ::NC_EBADID Bad ncid. |
---|
| 683 | |
---|
| 684 | \returns ::NC_EBADGRPID The ncid must refer to the root group of the |
---|
| 685 | file, that is, the group returned by nc_open() or nc_create(). |
---|
| 686 | |
---|
| 687 | \returns ::NC_EINDEFINE Already in define mode. |
---|
| 688 | |
---|
| 689 | \returns ::NC_EPERM File is read-only. |
---|
| 690 | |
---|
| 691 | <h1>Example</h1> |
---|
| 692 | |
---|
| 693 | Here is an example using nc_redef to open an existing netCDF dataset |
---|
| 694 | named foo.nc and put it into define mode: |
---|
| 695 | |
---|
| 696 | \code |
---|
| 697 | #include <netcdf.h> |
---|
| 698 | ... |
---|
| 699 | int status = NC_NOERR; |
---|
| 700 | int ncid; |
---|
| 701 | ... |
---|
| 702 | status = nc_open("foo.nc", NC_WRITE, &ncid); |
---|
| 703 | if (status != NC_NOERR) handle_error(status); |
---|
| 704 | ... |
---|
| 705 | status = nc_redef(ncid); |
---|
| 706 | if (status != NC_NOERR) handle_error(status); |
---|
| 707 | \endcode |
---|
| 708 | */ |
---|
| 709 | int |
---|
| 710 | nc_redef(int ncid) |
---|
| 711 | { |
---|
| 712 | NC* ncp; |
---|
| 713 | int stat = NC_check_id(ncid, &ncp); |
---|
| 714 | if(stat != NC_NOERR) return stat; |
---|
| 715 | return ncp->dispatch->redef(ncid); |
---|
| 716 | } |
---|
| 717 | |
---|
| 718 | /** |
---|
| 719 | Leave define mode |
---|
| 720 | |
---|
| 721 | The function nc_enddef() takes an open netCDF dataset out of define |
---|
| 722 | mode. The changes made to the netCDF dataset while it was in define |
---|
| 723 | mode are checked and committed to disk if no problems |
---|
| 724 | occurred. Non-record variables may be initialized to a "fill value" as |
---|
| 725 | well with nc_set_fill(). The netCDF dataset is then placed in data |
---|
| 726 | mode, so variable data can be read or written. |
---|
| 727 | |
---|
| 728 | It's not necessary to call nc_enddef() for netCDF-4 files. With netCDF-4 |
---|
| 729 | files, nc_enddef() is called when needed by the netcdf-4 library. User |
---|
| 730 | calls to nc_enddef() for netCDF-4 files still flush the metadata to |
---|
| 731 | disk. |
---|
| 732 | |
---|
| 733 | This call may involve copying data under some circumstances. For a |
---|
| 734 | more extensive discussion see File Structure and Performance. |
---|
| 735 | |
---|
| 736 | For netCDF-4/HDF5 format files there are some variable settings (the |
---|
| 737 | compression, endianness, fletcher32 error correction, and fill value) |
---|
| 738 | which must be set (if they are going to be set at all) between the |
---|
| 739 | nc_def_var() and the next nc_enddef(). Once the nc_enddef() is called, |
---|
| 740 | these settings can no longer be changed for a variable. |
---|
| 741 | |
---|
| 742 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 743 | nc_create(). |
---|
| 744 | |
---|
| 745 | If you use a group id (in a netCDF-4/HDF5 file), the enddef |
---|
| 746 | will apply to the entire file. That means the enddef will not just end |
---|
| 747 | define mode in one group, but in the entire file. |
---|
| 748 | |
---|
| 749 | \returns ::NC_NOERR no error |
---|
| 750 | |
---|
| 751 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 752 | |
---|
| 753 | <h1>Example</h1> |
---|
| 754 | |
---|
| 755 | Here is an example using nc_enddef() to finish the definitions of a new |
---|
| 756 | netCDF dataset named foo.nc and put it into data mode: |
---|
| 757 | |
---|
| 758 | \code |
---|
| 759 | #include <netcdf.h> |
---|
| 760 | ... |
---|
| 761 | int status = NC_NOERR; |
---|
| 762 | int ncid; |
---|
| 763 | ... |
---|
| 764 | status = nc_create("foo.nc", NC_NOCLOBBER, &ncid); |
---|
| 765 | if (status != NC_NOERR) handle_error(status); |
---|
| 766 | |
---|
| 767 | ... create dimensions, variables, attributes |
---|
| 768 | |
---|
| 769 | status = nc_enddef(ncid); |
---|
| 770 | if (status != NC_NOERR) handle_error(status); |
---|
| 771 | \endcode |
---|
| 772 | */ |
---|
| 773 | int |
---|
| 774 | nc_enddef(int ncid) |
---|
| 775 | { |
---|
| 776 | int status = NC_NOERR; |
---|
| 777 | NC *ncp; |
---|
| 778 | status = NC_check_id(ncid, &ncp); |
---|
| 779 | if(status != NC_NOERR) return status; |
---|
| 780 | return ncp->dispatch->_enddef(ncid,0,1,0,1); |
---|
| 781 | } |
---|
| 782 | |
---|
| 783 | /** |
---|
| 784 | Leave define mode with performance tuning |
---|
| 785 | |
---|
| 786 | The function nc__enddef takes an open netCDF dataset out of define |
---|
| 787 | mode. The changes made to the netCDF dataset while it was in define |
---|
| 788 | mode are checked and committed to disk if no problems |
---|
| 789 | occurred. Non-record variables may be initialized to a "fill value" as |
---|
| 790 | well with nc_set_fill(). The netCDF dataset is then placed in data mode, |
---|
| 791 | so variable data can be read or written. |
---|
| 792 | |
---|
| 793 | This call may involve copying data under some circumstances. For a |
---|
| 794 | more extensive discussion see File Structure and Performance. |
---|
| 795 | |
---|
| 796 | \warning This function exposes internals of the netcdf version 1 file |
---|
| 797 | format. Users should use nc_enddef() in most circumstances. This |
---|
| 798 | function may not be available on future netcdf implementations. |
---|
| 799 | |
---|
| 800 | The classic netcdf file format has three sections, the "header" |
---|
| 801 | section, the data section for fixed size variables, and the data |
---|
| 802 | section for variables which have an unlimited dimension (record |
---|
| 803 | variables). |
---|
| 804 | |
---|
| 805 | The header begins at the beginning of the file. The index (offset) of |
---|
| 806 | the beginning of the other two sections is contained in the |
---|
| 807 | header. Typically, there is no space between the sections. This causes |
---|
| 808 | copying overhead to accrue if one wishes to change the size of the |
---|
| 809 | sections, as may happen when changing names of things, text attribute |
---|
| 810 | values, adding attributes or adding variables. Also, for buffered i/o, |
---|
| 811 | there may be advantages to aligning sections in certain ways. |
---|
| 812 | |
---|
| 813 | The minfree parameters allow one to control costs of future calls to |
---|
| 814 | nc_redef, nc_enddef() by requesting that minfree bytes be available at |
---|
| 815 | the end of the section. |
---|
| 816 | |
---|
| 817 | The align parameters allow one to set the alignment of the beginning |
---|
| 818 | of the corresponding sections. The beginning of the section is rounded |
---|
| 819 | up to an index which is a multiple of the align parameter. The flag |
---|
| 820 | value ALIGN_CHUNK tells the library to use the bufrsize (see above) as |
---|
| 821 | the align parameter. It has nothing to do with the chunking |
---|
| 822 | (multidimensional tiling) features of netCDF-4. |
---|
| 823 | |
---|
| 824 | The file format requires mod 4 alignment, so the align parameters are |
---|
| 825 | silently rounded up to multiples of 4. The usual call, |
---|
| 826 | |
---|
| 827 | \code |
---|
| 828 | nc_enddef(ncid); |
---|
| 829 | \endcode |
---|
| 830 | |
---|
| 831 | is equivalent to |
---|
| 832 | |
---|
| 833 | \code |
---|
| 834 | nc__enddef(ncid, 0, 4, 0, 4); |
---|
| 835 | \endcode |
---|
| 836 | |
---|
| 837 | The file format does not contain a "record size" value, this is |
---|
| 838 | calculated from the sizes of the record variables. This unfortunate |
---|
| 839 | fact prevents us from providing minfree and alignment control of the |
---|
| 840 | "records" in a netcdf file. If you add a variable which has an |
---|
| 841 | unlimited dimension, the third section will always be copied with the |
---|
| 842 | new variable added. |
---|
| 843 | |
---|
| 844 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 845 | nc_create(). |
---|
| 846 | |
---|
| 847 | \param h_minfree Sets the pad at the end of the "header" section. |
---|
| 848 | |
---|
| 849 | \param v_align Controls the alignment of the beginning of the data |
---|
| 850 | section for fixed size variables. |
---|
| 851 | |
---|
| 852 | \param v_minfree Sets the pad at the end of the data section for fixed |
---|
| 853 | size variables. |
---|
| 854 | |
---|
| 855 | \param r_align Controls the alignment of the beginning of the data |
---|
| 856 | section for variables which have an unlimited dimension (record |
---|
| 857 | variables). |
---|
| 858 | |
---|
| 859 | \returns ::NC_NOERR No error. |
---|
| 860 | |
---|
| 861 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 862 | |
---|
| 863 | */ |
---|
| 864 | int |
---|
| 865 | nc__enddef(int ncid, size_t h_minfree, size_t v_align, size_t v_minfree, |
---|
| 866 | size_t r_align) |
---|
| 867 | { |
---|
| 868 | NC* ncp; |
---|
| 869 | int stat = NC_check_id(ncid, &ncp); |
---|
| 870 | if(stat != NC_NOERR) return stat; |
---|
| 871 | return ncp->dispatch->_enddef(ncid,h_minfree,v_align,v_minfree,r_align); |
---|
| 872 | } |
---|
| 873 | |
---|
| 874 | /** |
---|
| 875 | Synchronize an open netcdf dataset to disk |
---|
| 876 | |
---|
| 877 | The function nc_sync() offers a way to synchronize the disk copy of a |
---|
| 878 | netCDF dataset with in-memory buffers. There are two reasons you might |
---|
| 879 | want to synchronize after writes: |
---|
| 880 | - To minimize data loss in case of abnormal termination, or |
---|
| 881 | - To make data available to other processes for reading immediately |
---|
| 882 | after it is written. But note that a process that already had the |
---|
| 883 | dataset open for reading would not see the number of records |
---|
| 884 | increase when the writing process calls nc_sync(); to accomplish this, |
---|
| 885 | the reading process must call nc_sync. |
---|
| 886 | |
---|
| 887 | This function is backward-compatible with previous versions of the |
---|
| 888 | netCDF library. The intent was to allow sharing of a netCDF dataset |
---|
| 889 | among multiple readers and one writer, by having the writer call |
---|
| 890 | nc_sync() after writing and the readers call nc_sync() before each |
---|
| 891 | read. For a writer, this flushes buffers to disk. For a reader, it |
---|
| 892 | makes sure that the next read will be from disk rather than from |
---|
| 893 | previously cached buffers, so that the reader will see changes made by |
---|
| 894 | the writing process (e.g., the number of records written) without |
---|
| 895 | having to close and reopen the dataset. If you are only accessing a |
---|
| 896 | small amount of data, it can be expensive in computer resources to |
---|
| 897 | always synchronize to disk after every write, since you are giving up |
---|
| 898 | the benefits of buffering. |
---|
| 899 | |
---|
| 900 | An easier way to accomplish sharing (and what is now recommended) is |
---|
| 901 | to have the writer and readers open the dataset with the NC_SHARE |
---|
| 902 | flag, and then it will not be necessary to call nc_sync() at |
---|
| 903 | all. However, the nc_sync() function still provides finer granularity |
---|
| 904 | than the NC_SHARE flag, if only a few netCDF accesses need to be |
---|
| 905 | synchronized among processes. |
---|
| 906 | |
---|
| 907 | It is important to note that changes to the ancillary data, such as |
---|
| 908 | attribute values, are not propagated automatically by use of the |
---|
| 909 | NC_SHARE flag. Use of the nc_sync() function is still required for this |
---|
| 910 | purpose. |
---|
| 911 | |
---|
| 912 | Sharing datasets when the writer enters define mode to change the data |
---|
| 913 | schema requires extra care. In previous releases, after the writer |
---|
| 914 | left define mode, the readers were left looking at an old copy of the |
---|
| 915 | dataset, since the changes were made to a new copy. The only way |
---|
| 916 | readers could see the changes was by closing and reopening the |
---|
| 917 | dataset. Now the changes are made in place, but readers have no |
---|
| 918 | knowledge that their internal tables are now inconsistent with the new |
---|
| 919 | dataset schema. If netCDF datasets are shared across redefinition, |
---|
| 920 | some mechanism external to the netCDF library must be provided that |
---|
| 921 | prevents access by readers during redefinition and causes the readers |
---|
| 922 | to call nc_sync before any subsequent access. |
---|
| 923 | |
---|
| 924 | When calling nc_sync(), the netCDF dataset must be in data mode. A |
---|
| 925 | netCDF dataset in define mode is synchronized to disk only when |
---|
| 926 | nc_enddef() is called. A process that is reading a netCDF dataset that |
---|
| 927 | another process is writing may call nc_sync to get updated with the |
---|
| 928 | changes made to the data by the writing process (e.g., the number of |
---|
| 929 | records written), without having to close and reopen the dataset. |
---|
| 930 | |
---|
| 931 | Data is automatically synchronized to disk when a netCDF dataset is |
---|
| 932 | closed, or whenever you leave define mode. |
---|
| 933 | |
---|
| 934 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 935 | nc_create(). |
---|
| 936 | |
---|
| 937 | \returns ::NC_NOERR No error. |
---|
| 938 | |
---|
| 939 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 940 | */ |
---|
| 941 | int |
---|
| 942 | nc_sync(int ncid) |
---|
| 943 | { |
---|
| 944 | NC* ncp; |
---|
| 945 | int stat = NC_check_id(ncid, &ncp); |
---|
| 946 | if(stat != NC_NOERR) return stat; |
---|
| 947 | return ncp->dispatch->sync(ncid); |
---|
| 948 | } |
---|
| 949 | |
---|
| 950 | /** |
---|
| 951 | \internal |
---|
| 952 | |
---|
| 953 | Users no longer need to call this function, since it is called |
---|
| 954 | automatically by nc_close() in case the dataset is in define mode and |
---|
| 955 | something goes wrong with committing the changes. The function |
---|
| 956 | nc_abort() just closes the netCDF dataset, if not in define mode. If |
---|
| 957 | the dataset is being created and is still in define mode, the dataset |
---|
| 958 | is deleted. If define mode was entered by a call to nc_redef(), the |
---|
| 959 | netCDF dataset is restored to its state before definition mode was |
---|
| 960 | entered and the dataset is closed. |
---|
| 961 | |
---|
| 962 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 963 | nc_create(). |
---|
| 964 | |
---|
| 965 | \returns ::NC_NOERR No error. |
---|
| 966 | |
---|
| 967 | <h1>Example</h1> |
---|
| 968 | |
---|
| 969 | Here is an example using nc_abort to back out of redefinitions of a |
---|
| 970 | dataset named foo.nc: |
---|
| 971 | |
---|
| 972 | \code |
---|
| 973 | #include <netcdf.h> |
---|
| 974 | ... |
---|
| 975 | int ncid, status, latid; |
---|
| 976 | ... |
---|
| 977 | status = nc_open("foo.nc", NC_WRITE, &ncid); |
---|
| 978 | if (status != NC_NOERR) handle_error(status); |
---|
| 979 | ... |
---|
| 980 | status = nc_redef(ncid); |
---|
| 981 | if (status != NC_NOERR) handle_error(status); |
---|
| 982 | ... |
---|
| 983 | status = nc_def_dim(ncid, "lat", 18L, &latid); |
---|
| 984 | if (status != NC_NOERR) { |
---|
| 985 | handle_error(status); |
---|
| 986 | status = nc_abort(ncid); |
---|
| 987 | if (status != NC_NOERR) handle_error(status); |
---|
| 988 | } |
---|
| 989 | \endcode |
---|
| 990 | |
---|
| 991 | */ |
---|
| 992 | int |
---|
| 993 | nc_abort(int ncid) |
---|
| 994 | { |
---|
| 995 | NC* ncp; |
---|
| 996 | int stat = NC_check_id(ncid, &ncp); |
---|
| 997 | if(stat != NC_NOERR) return stat; |
---|
| 998 | if(ncp->path != NULL) free(ncp->path); |
---|
| 999 | ncp->path = NULL; |
---|
| 1000 | return ncp->dispatch->abort(ncid); |
---|
| 1001 | } |
---|
| 1002 | |
---|
| 1003 | /** |
---|
| 1004 | Close an open netCDF dataset |
---|
| 1005 | |
---|
| 1006 | If the dataset in define mode, nc_enddef() will be called before |
---|
| 1007 | closing. (In this case, if nc_enddef() returns an error, nc_abort() will |
---|
| 1008 | automatically be called to restore the dataset to the consistent state |
---|
| 1009 | before define mode was last entered.) After an open netCDF dataset is |
---|
| 1010 | closed, its netCDF ID may be reassigned to the next netCDF dataset |
---|
| 1011 | that is opened or created. |
---|
| 1012 | |
---|
| 1013 | \param ncid NetCDF ID, from a previous call to nc_open() or nc_create(). |
---|
| 1014 | |
---|
| 1015 | \returns ::NC_NOERR No error. |
---|
| 1016 | |
---|
| 1017 | \returns ::NC_EBADID Invalid id passed. |
---|
| 1018 | |
---|
| 1019 | \returns ::NC_EBADGRPID ncid did not contain the root group id of this |
---|
| 1020 | file. (NetCDF-4 only). |
---|
| 1021 | |
---|
| 1022 | <h1>Example</h1> |
---|
| 1023 | |
---|
| 1024 | Here is an example using nc_close to finish the definitions of a new |
---|
| 1025 | netCDF dataset named foo.nc and release its netCDF ID: |
---|
| 1026 | |
---|
| 1027 | \code |
---|
| 1028 | #include <netcdf.h> |
---|
| 1029 | ... |
---|
| 1030 | int status = NC_NOERR; |
---|
| 1031 | int ncid; |
---|
| 1032 | ... |
---|
| 1033 | status = nc_create("foo.nc", NC_NOCLOBBER, &ncid); |
---|
| 1034 | if (status != NC_NOERR) handle_error(status); |
---|
| 1035 | |
---|
| 1036 | ... create dimensions, variables, attributes |
---|
| 1037 | |
---|
| 1038 | status = nc_close(ncid); |
---|
| 1039 | if (status != NC_NOERR) handle_error(status); |
---|
| 1040 | \endcode |
---|
| 1041 | |
---|
| 1042 | */ |
---|
| 1043 | int |
---|
| 1044 | nc_close(int ncid) |
---|
| 1045 | { |
---|
| 1046 | NC* ncp; |
---|
| 1047 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1048 | if(stat != NC_NOERR) return stat; |
---|
| 1049 | return ncp->dispatch->close(ncid); |
---|
| 1050 | } |
---|
| 1051 | |
---|
| 1052 | /** |
---|
| 1053 | Change the fill-value mode to improve write performance. |
---|
| 1054 | |
---|
| 1055 | This function is intended for advanced usage, to optimize writes under |
---|
| 1056 | some circumstances described below. The function nc_set_fill() sets the |
---|
| 1057 | fill mode for a netCDF dataset open for writing and returns the |
---|
| 1058 | current fill mode in a return parameter. The fill mode can be |
---|
| 1059 | specified as either ::NC_FILL or ::NC_NOFILL. The default behavior |
---|
| 1060 | corresponding to ::NC_FILL is that data is pre-filled with fill values, |
---|
| 1061 | that is fill values are written when you create non-record variables |
---|
| 1062 | or when you write a value beyond data that has not yet been |
---|
| 1063 | written. This makes it possible to detect attempts to read data before |
---|
| 1064 | it was written. For more information on the use of fill values see |
---|
| 1065 | Fill Values. For information about how to define your own fill values |
---|
| 1066 | see Attribute Conventions. |
---|
| 1067 | |
---|
| 1068 | The behavior corresponding to ::NC_NOFILL overrides the default behavior |
---|
| 1069 | of prefilling data with fill values. This can be used to enhance |
---|
| 1070 | performance, because it avoids the duplicate writes that occur when |
---|
| 1071 | the netCDF library writes fill values that are later overwritten with |
---|
| 1072 | data. |
---|
| 1073 | |
---|
| 1074 | A value indicating which mode the netCDF dataset was already in is |
---|
| 1075 | returned. You can use this value to temporarily change the fill mode |
---|
| 1076 | of an open netCDF dataset and then restore it to the previous mode. |
---|
| 1077 | |
---|
| 1078 | After you turn on ::NC_NOFILL mode for an open netCDF dataset, you must |
---|
| 1079 | be certain to write valid data in all the positions that will later be |
---|
| 1080 | read. Note that nofill mode is only a transient property of a netCDF |
---|
| 1081 | dataset open for writing: if you close and reopen the dataset, it will |
---|
| 1082 | revert to the default behavior. You can also revert to the default |
---|
| 1083 | behavior by calling nc_set_fill() again to explicitly set the fill mode |
---|
| 1084 | to ::NC_FILL. |
---|
| 1085 | |
---|
| 1086 | There are three situations where it is advantageous to set nofill |
---|
| 1087 | mode: |
---|
| 1088 | - Creating and initializing a netCDF dataset. In this case, you should |
---|
| 1089 | set nofill mode before calling nc_enddef() and then write completely |
---|
| 1090 | all non-record variables and the initial records of all the record |
---|
| 1091 | variables you want to initialize. |
---|
| 1092 | - Extending an existing record-oriented netCDF dataset. Set nofill |
---|
| 1093 | mode after opening the dataset for writing, then append the |
---|
| 1094 | additional records to the dataset completely, leaving no intervening |
---|
| 1095 | unwritten records. |
---|
| 1096 | - Adding new variables that you are going to initialize to an existing |
---|
| 1097 | netCDF dataset. Set nofill mode before calling nc_enddef() then write |
---|
| 1098 | all the new variables completely. |
---|
| 1099 | |
---|
| 1100 | If the netCDF dataset has an unlimited dimension and the last record |
---|
| 1101 | was written while in nofill mode, then the dataset may be shorter than |
---|
| 1102 | if nofill mode was not set, but this will be completely transparent if |
---|
| 1103 | you access the data only through the netCDF interfaces. |
---|
| 1104 | |
---|
| 1105 | The use of this feature may not be available (or even needed) in |
---|
| 1106 | future releases. Programmers are cautioned against heavy reliance upon |
---|
| 1107 | this feature. |
---|
| 1108 | |
---|
| 1109 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 1110 | nc_create(). |
---|
| 1111 | |
---|
| 1112 | \param fillmode Desired fill mode for the dataset, either ::NC_NOFILL or |
---|
| 1113 | ::NC_FILL. |
---|
| 1114 | |
---|
| 1115 | \param old_modep Pointer to location for returned current fill mode of |
---|
| 1116 | the dataset before this call, either ::NC_NOFILL or ::NC_FILL. |
---|
| 1117 | |
---|
| 1118 | \returns ::NC_NOERR No error. |
---|
| 1119 | |
---|
| 1120 | \returns ::NC_EBADID The specified netCDF ID does not refer to an open |
---|
| 1121 | netCDF dataset. |
---|
| 1122 | |
---|
| 1123 | \returns ::NC_EPERM The specified netCDF ID refers to a dataset open for |
---|
| 1124 | read-only access. |
---|
| 1125 | |
---|
| 1126 | \returns ::NC_EINVAL The fill mode argument is neither ::NC_NOFILL nor |
---|
| 1127 | ::NC_FILL. |
---|
| 1128 | |
---|
| 1129 | <h1>Example</h1> |
---|
| 1130 | |
---|
| 1131 | Here is an example using nc_set_fill() to set nofill mode for subsequent |
---|
| 1132 | writes of a netCDF dataset named foo.nc: |
---|
| 1133 | |
---|
| 1134 | \code |
---|
| 1135 | #include <netcdf.h> |
---|
| 1136 | ... |
---|
| 1137 | int ncid, status, old_fill_mode; |
---|
| 1138 | ... |
---|
| 1139 | status = nc_open("foo.nc", NC_WRITE, &ncid); |
---|
| 1140 | if (status != NC_NOERR) handle_error(status); |
---|
| 1141 | |
---|
| 1142 | ... write data with default prefilling behavior |
---|
| 1143 | |
---|
| 1144 | status = nc_set_fill(ncid, ::NC_NOFILL, &old_fill_mode); |
---|
| 1145 | if (status != NC_NOERR) handle_error(status); |
---|
| 1146 | |
---|
| 1147 | ... write data with no prefilling |
---|
| 1148 | \endcode |
---|
| 1149 | */ |
---|
| 1150 | int |
---|
| 1151 | nc_set_fill(int ncid, int fillmode, int *old_modep) |
---|
| 1152 | { |
---|
| 1153 | NC* ncp; |
---|
| 1154 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1155 | if(stat != NC_NOERR) return stat; |
---|
| 1156 | return ncp->dispatch->set_fill(ncid,fillmode,old_modep); |
---|
| 1157 | } |
---|
| 1158 | |
---|
| 1159 | /** |
---|
| 1160 | \internal |
---|
| 1161 | |
---|
| 1162 | \deprecated This function was used in the old days with the Cray at |
---|
| 1163 | NCAR. The Cray is long gone, and this call is supported only for |
---|
| 1164 | backward compatibility. |
---|
| 1165 | |
---|
| 1166 | \returns ::NC_NOERR No error. |
---|
| 1167 | |
---|
| 1168 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 1169 | */ |
---|
| 1170 | int |
---|
| 1171 | nc_inq_base_pe(int ncid, int *pe) |
---|
| 1172 | { |
---|
| 1173 | NC* ncp; |
---|
| 1174 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1175 | if(stat != NC_NOERR) return stat; |
---|
| 1176 | return ncp->dispatch->inq_base_pe(ncid,pe); |
---|
| 1177 | } |
---|
| 1178 | |
---|
| 1179 | /** |
---|
| 1180 | \internal |
---|
| 1181 | |
---|
| 1182 | \deprecated This function was used in the old days with the Cray at |
---|
| 1183 | NCAR. The Cray is long gone, and this call is supported only for |
---|
| 1184 | backward compatibility. |
---|
| 1185 | |
---|
| 1186 | \returns ::NC_NOERR No error. |
---|
| 1187 | |
---|
| 1188 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 1189 | */ |
---|
| 1190 | int |
---|
| 1191 | nc_set_base_pe(int ncid, int pe) |
---|
| 1192 | { |
---|
| 1193 | NC* ncp; |
---|
| 1194 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1195 | if(stat != NC_NOERR) return stat; |
---|
| 1196 | return ncp->dispatch->set_base_pe(ncid,pe); |
---|
| 1197 | } |
---|
| 1198 | |
---|
| 1199 | /** |
---|
| 1200 | Inquire about the binary format of a netCDF file. |
---|
| 1201 | |
---|
| 1202 | This function returns the (rarely needed) format version. |
---|
| 1203 | |
---|
| 1204 | \param ncid NetCDF ID, from a previous call to nc_open() or |
---|
| 1205 | nc_create(). |
---|
| 1206 | |
---|
| 1207 | \param formatp Pointer to location for returned format version, one of |
---|
| 1208 | NC_FORMAT_CLASSIC, NC_FORMAT_64BIT, NC_FORMAT_NETCDF4, |
---|
| 1209 | NC_FORMAT_NETCDF4_CLASSIC. |
---|
| 1210 | |
---|
| 1211 | \returns ::NC_NOERR No error. |
---|
| 1212 | |
---|
| 1213 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 1214 | |
---|
| 1215 | */ |
---|
| 1216 | int |
---|
| 1217 | nc_inq_format(int ncid, int *formatp) |
---|
| 1218 | { |
---|
| 1219 | NC* ncp; |
---|
| 1220 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1221 | if(stat != NC_NOERR) return stat; |
---|
| 1222 | return ncp->dispatch->inq_format(ncid,formatp); |
---|
| 1223 | } |
---|
| 1224 | |
---|
| 1225 | /** |
---|
| 1226 | Inquire about a file or group. |
---|
| 1227 | |
---|
| 1228 | \param ncid NetCDF or group ID, from a previous call to nc_open(), |
---|
| 1229 | nc_create(), nc_def_grp(), or associated inquiry functions such as |
---|
| 1230 | nc_inq_ncid(). |
---|
| 1231 | |
---|
| 1232 | \param ndimsp Pointer to location for returned number of dimensions |
---|
| 1233 | defined for this netCDF dataset. Ignored if NULL. |
---|
| 1234 | |
---|
| 1235 | \param nvarsp Pointer to location for returned number of variables |
---|
| 1236 | defined for this netCDF dataset. Ignored if NULL. |
---|
| 1237 | |
---|
| 1238 | \param nattsp Pointer to location for returned number of global |
---|
| 1239 | attributes defined for this netCDF dataset. Ignored if NULL. |
---|
| 1240 | |
---|
| 1241 | \param unlimdimidp Pointer to location for returned ID of the |
---|
| 1242 | unlimited dimension, if there is one for this netCDF dataset. If no |
---|
| 1243 | unlimited length dimension has been defined, -1 is returned. Ignored |
---|
| 1244 | if NULL. If there are multiple unlimited dimensions (possible only |
---|
| 1245 | for netCDF-4 files), only a pointer to the first is returned, for |
---|
| 1246 | backward compatibility. If you want them all, use nc_inq_unlimids(). |
---|
| 1247 | |
---|
| 1248 | \returns ::NC_NOERR No error. |
---|
| 1249 | |
---|
| 1250 | \returns ::NC_EBADID Invalid ncid passed. |
---|
| 1251 | |
---|
| 1252 | <h1>Example</h1> |
---|
| 1253 | |
---|
| 1254 | Here is an example using nc_inq to find out about a netCDF dataset |
---|
| 1255 | named foo.nc: |
---|
| 1256 | |
---|
| 1257 | \code |
---|
| 1258 | #include <netcdf.h> |
---|
| 1259 | ... |
---|
| 1260 | int status, ncid, ndims, nvars, ngatts, unlimdimid; |
---|
| 1261 | ... |
---|
| 1262 | status = nc_open("foo.nc", NC_NOWRITE, &ncid); |
---|
| 1263 | if (status != NC_NOERR) handle_error(status); |
---|
| 1264 | ... |
---|
| 1265 | status = nc_inq(ncid, &ndims, &nvars, &ngatts, &unlimdimid); |
---|
| 1266 | if (status != NC_NOERR) handle_error(status); |
---|
| 1267 | \endcode |
---|
| 1268 | */ |
---|
| 1269 | int |
---|
| 1270 | nc_inq(int ncid, int *ndimsp, int *nvarsp, int *nattsp, int *unlimdimidp) |
---|
| 1271 | { |
---|
| 1272 | NC* ncp; |
---|
| 1273 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1274 | if(stat != NC_NOERR) return stat; |
---|
| 1275 | return ncp->dispatch->inq(ncid,ndimsp,nvarsp,nattsp,unlimdimidp); |
---|
| 1276 | } |
---|
| 1277 | |
---|
| 1278 | int |
---|
| 1279 | nc_inq_nvars(int ncid, int *nvarsp) |
---|
| 1280 | { |
---|
| 1281 | NC* ncp; |
---|
| 1282 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1283 | if(stat != NC_NOERR) return stat; |
---|
| 1284 | return ncp->dispatch->inq(ncid, NULL, nvarsp, NULL, NULL); |
---|
| 1285 | } |
---|
| 1286 | |
---|
| 1287 | /** |
---|
| 1288 | Inquire about a type. |
---|
| 1289 | |
---|
| 1290 | Given an ncid and a typeid, get the information about a type. This |
---|
| 1291 | function will work on any type, including atomic and any user defined |
---|
| 1292 | type, whether compound, opaque, enumeration, or variable length array. |
---|
| 1293 | |
---|
| 1294 | For even more information about a user defined type nc_inq_user_type(). |
---|
| 1295 | |
---|
| 1296 | \param ncid The ncid for the group containing the type (ignored for |
---|
| 1297 | atomic types). |
---|
| 1298 | |
---|
| 1299 | \param xtype The typeid for this type, as returned by nc_def_compound, |
---|
| 1300 | nc_def_opaque, nc_def_enum, nc_def_vlen, or nc_inq_var, or as found in |
---|
| 1301 | netcdf.h in the list of atomic types (NC_CHAR, NC_INT, etc.). |
---|
| 1302 | |
---|
| 1303 | \param name If non-NULL, the name of the user defined type will be |
---|
| 1304 | copied here. It will be NC_MAX_NAME bytes or less. For atomic types, |
---|
| 1305 | the type name from CDL will be given. |
---|
| 1306 | |
---|
| 1307 | \param size If non-NULL, the (in-memory) size of the type in bytes |
---|
| 1308 | will be copied here. VLEN type size is the size of nc_vlen_t. String |
---|
| 1309 | size is returned as the size of a character pointer. The size may be |
---|
| 1310 | used to malloc space for the data, no matter what the type. |
---|
| 1311 | |
---|
| 1312 | \returns ::NC_NOERR No error. |
---|
| 1313 | |
---|
| 1314 | \returns ::NC_EBADTYPE Bad typeid. |
---|
| 1315 | |
---|
| 1316 | \returns ::NC_ENOTNC4 Seeking a user-defined type in a netCDF-3 file. |
---|
| 1317 | |
---|
| 1318 | \returns ::NC_ESTRICTNC3 Seeking a user-defined type in a netCDF-4 file |
---|
| 1319 | for which classic model has been turned on. |
---|
| 1320 | |
---|
| 1321 | \returns ::NC_EBADGRPID Bad group ID in ncid. |
---|
| 1322 | |
---|
| 1323 | \returns ::NC_EBADID Type ID not found. |
---|
| 1324 | |
---|
| 1325 | \returns ::NC_EHDFERR An error was reported by the HDF5 layer. |
---|
| 1326 | |
---|
| 1327 | <h1>Example</h1> |
---|
| 1328 | |
---|
| 1329 | This example is from the test program tst_enums.c, and it uses all the |
---|
| 1330 | possible inquiry functions on an enum type. |
---|
| 1331 | |
---|
| 1332 | \code |
---|
| 1333 | if (nc_inq_user_type(ncid, typeids[0], name_in, &base_size_in, &base_nc_type_in, |
---|
| 1334 | &nfields_in, &class_in)) ERR; |
---|
| 1335 | if (strcmp(name_in, TYPE_NAME) || base_size_in != sizeof(int) || |
---|
| 1336 | base_nc_type_in != NC_INT || nfields_in != NUM_MEMBERS || class_in != NC_ENUM) ERR; |
---|
| 1337 | if (nc_inq_type(ncid, typeids[0], name_in, &base_size_in)) ERR; |
---|
| 1338 | if (strcmp(name_in, TYPE_NAME) || base_size_in != sizeof(int)) ERR; |
---|
| 1339 | if (nc_inq_enum(ncid, typeids[0], name_in, &base_nc_type, &base_size_in, &num_members)) ERR; |
---|
| 1340 | if (strcmp(name_in, TYPE_NAME) || base_nc_type != NC_INT || num_members != NUM_MEMBERS) ERR; |
---|
| 1341 | for (i = 0; i < NUM_MEMBERS; i++) |
---|
| 1342 | { |
---|
| 1343 | if (nc_inq_enum_member(ncid, typeid, i, name_in, &value_in)) ERR; |
---|
| 1344 | if (strcmp(name_in, member_name[i]) || value_in != member_value[i]) ERR; |
---|
| 1345 | if (nc_inq_enum_ident(ncid, typeid, member_value[i], name_in)) ERR; |
---|
| 1346 | if (strcmp(name_in, member_name[i])) ERR; |
---|
| 1347 | } |
---|
| 1348 | |
---|
| 1349 | if (nc_close(ncid)) ERR; |
---|
| 1350 | \endcode |
---|
| 1351 | */ |
---|
| 1352 | int |
---|
| 1353 | nc_inq_type(int ncid, nc_type xtype, char *name, size_t *size) |
---|
| 1354 | { |
---|
| 1355 | NC* ncp; |
---|
| 1356 | /* For compatibility, we need to allow inq about |
---|
| 1357 | atomic types, even if ncid is ill-defined */ |
---|
| 1358 | if(xtype <= ATOMICTYPEMAX) { |
---|
| 1359 | if(xtype <= NC_NAT) return NC_EBADTYPE; |
---|
| 1360 | if(name) strncpy(name,NC_atomictypename(xtype),NC_MAX_NAME); |
---|
| 1361 | if(size) *size = NC_atomictypelen(xtype); |
---|
| 1362 | return NC_NOERR; |
---|
| 1363 | } else { |
---|
| 1364 | int stat = NC_check_id(ncid, &ncp); |
---|
| 1365 | if(stat != NC_NOERR) return NC_EBADTYPE; /* compatibility */ |
---|
| 1366 | return ncp->dispatch->inq_type(ncid,xtype,name,size); |
---|
| 1367 | } |
---|
| 1368 | } |
---|
| 1369 | /**@}*/ |
---|
| 1370 | |
---|
| 1371 | /** |
---|
| 1372 | \internal |
---|
| 1373 | \ingroup dispatch |
---|
| 1374 | |
---|
| 1375 | Create a file, calling the appropriate dispatch create call. |
---|
| 1376 | |
---|
| 1377 | For create, we have the following pieces of information to use to |
---|
| 1378 | determine the dispatch table: |
---|
| 1379 | - table specified by override |
---|
| 1380 | - path |
---|
| 1381 | - cmode |
---|
| 1382 | |
---|
| 1383 | \param path The file name of the new netCDF dataset. |
---|
| 1384 | |
---|
| 1385 | \param cmode The creation mode flag, the same as in nc_create(). |
---|
| 1386 | |
---|
| 1387 | \param initialsz This parameter sets the initial size of the file at creation |
---|
| 1388 | time. This only applies to classic and 64-bit offset files. |
---|
| 1389 | |
---|
| 1390 | \param basepe Deprecated parameter from the Cray days. |
---|
| 1391 | |
---|
| 1392 | \param chunksizehintp A pointer to the chunk size hint. This only |
---|
| 1393 | applies to classic and 64-bit offset files. |
---|
| 1394 | |
---|
| 1395 | \param useparallel Non-zero if parallel I/O is to be used on this |
---|
| 1396 | file. |
---|
| 1397 | |
---|
| 1398 | \param mpi_info Pointer to MPI comm and info. |
---|
| 1399 | |
---|
| 1400 | \param ncidp Pointer to location where returned netCDF ID is to be |
---|
| 1401 | stored. |
---|
| 1402 | |
---|
| 1403 | \returns ::NC_NOERR No error. |
---|
| 1404 | */ |
---|
| 1405 | int |
---|
| 1406 | NC_create(const char *path, int cmode, size_t initialsz, |
---|
| 1407 | int basepe, size_t *chunksizehintp, int useparallel, |
---|
| 1408 | void* mpi_info, int *ncidp) |
---|
| 1409 | { |
---|
| 1410 | int stat = NC_NOERR; |
---|
| 1411 | NC* ncp = NULL; |
---|
| 1412 | NC_Dispatch* dispatcher = NULL; |
---|
| 1413 | /* Need three pieces of information for now */ |
---|
| 1414 | int model = 0; /* one of the NC_DISPATCH_XXX values */ |
---|
| 1415 | int isurl = 0; /* dap or cdmremote or neither */ |
---|
| 1416 | int xcmode = 0; /* for implied cmode flags */ |
---|
| 1417 | extern int default_create_format; |
---|
| 1418 | |
---|
| 1419 | /* Initialize the dispatch table. The function pointers in the |
---|
| 1420 | * dispatch table will depend on how netCDF was built |
---|
| 1421 | * (with/without netCDF-4, DAP, CDMREMOTE). */ |
---|
| 1422 | if(!nc_initialized) |
---|
| 1423 | { |
---|
| 1424 | if ((stat = NC_initialize())) |
---|
| 1425 | return stat; |
---|
| 1426 | /* Do local initialization */ |
---|
| 1427 | nc_local_initialize(); |
---|
| 1428 | nc_initialized = 1; |
---|
| 1429 | } |
---|
| 1430 | |
---|
| 1431 | if((isurl = NC_testurl(path))) |
---|
| 1432 | model = NC_urlmodel(path); |
---|
| 1433 | |
---|
| 1434 | /* Look to the incoming cmode for hints */ |
---|
| 1435 | if(model == 0) { |
---|
| 1436 | if(cmode & NC_NETCDF4 || cmode & NC_PNETCDF) |
---|
| 1437 | model = NC_DISPATCH_NC4; |
---|
| 1438 | } |
---|
| 1439 | |
---|
| 1440 | if(model == 0) { |
---|
| 1441 | /* Check default format */ |
---|
| 1442 | int format = default_create_format; |
---|
| 1443 | switch (format) { |
---|
| 1444 | #ifdef USE_NETCDF4 |
---|
| 1445 | case NC_FORMAT_NETCDF4: |
---|
| 1446 | xcmode |= NC_NETCDF4; |
---|
| 1447 | model = NC_DISPATCH_NC4; |
---|
| 1448 | break; |
---|
| 1449 | case NC_FORMAT_NETCDF4_CLASSIC: |
---|
| 1450 | xcmode |= NC_CLASSIC_MODEL; |
---|
| 1451 | model = NC_DISPATCH_NC4; |
---|
| 1452 | break; |
---|
| 1453 | #endif |
---|
| 1454 | case NC_FORMAT_64BIT: |
---|
| 1455 | xcmode |= NC_64BIT_OFFSET; |
---|
| 1456 | /* fall thru */ |
---|
| 1457 | case NC_FORMAT_CLASSIC: |
---|
| 1458 | default: |
---|
| 1459 | model = NC_DISPATCH_NC3; |
---|
| 1460 | break; |
---|
| 1461 | } |
---|
| 1462 | } |
---|
| 1463 | |
---|
| 1464 | /* Add inferred flags */ |
---|
| 1465 | cmode |= xcmode; |
---|
| 1466 | |
---|
| 1467 | #ifdef USE_NETCDF4 |
---|
| 1468 | if((cmode & NC_MPIIO && cmode & NC_MPIPOSIX)) |
---|
| 1469 | return NC_EINVAL; |
---|
| 1470 | #endif |
---|
| 1471 | |
---|
| 1472 | if (!(dispatcher = NC_get_dispatch_override())) |
---|
| 1473 | { |
---|
| 1474 | |
---|
| 1475 | /* Figure out what dispatcher to use */ |
---|
| 1476 | #ifdef USE_NETCDF4 |
---|
| 1477 | #ifdef USE_CDMREMOTE |
---|
| 1478 | if(model == (NC_DISPATCH_NC4 | NC_DISPATCH_NCR)) |
---|
| 1479 | dispatcher = NCCR_dispatch_table; |
---|
| 1480 | else |
---|
| 1481 | #endif |
---|
| 1482 | if(model == (NC_DISPATCH_NC4)) |
---|
| 1483 | dispatcher = NC4_dispatch_table; |
---|
| 1484 | else |
---|
| 1485 | #endif /*USE_NETCDF4*/ |
---|
| 1486 | #ifdef USE_DAP |
---|
| 1487 | if(model == (NC_DISPATCH_NC3 | NC_DISPATCH_NCD)) |
---|
| 1488 | dispatcher = NCD3_dispatch_table; |
---|
| 1489 | else |
---|
| 1490 | #endif |
---|
| 1491 | if(model == (NC_DISPATCH_NC3)) |
---|
| 1492 | dispatcher = NC3_dispatch_table; |
---|
| 1493 | else |
---|
| 1494 | return NC_ENOTNC; |
---|
| 1495 | } |
---|
| 1496 | |
---|
| 1497 | if ((stat = dispatcher->create(path, cmode, initialsz, basepe, chunksizehintp, |
---|
| 1498 | useparallel, mpi_info, dispatcher, &ncp))) |
---|
| 1499 | return stat; |
---|
| 1500 | |
---|
| 1501 | ncp->dispatch = dispatcher; |
---|
| 1502 | if(ncidp) |
---|
| 1503 | *ncidp = ncp->ext_ncid; |
---|
| 1504 | if (!(ncp->path = nulldup(path))) |
---|
| 1505 | return NC_ENOMEM; |
---|
| 1506 | return NC_NOERR; |
---|
| 1507 | } |
---|
| 1508 | |
---|
| 1509 | /** |
---|
| 1510 | \internal |
---|
| 1511 | \ingroup dispatch |
---|
| 1512 | |
---|
| 1513 | Open a netCDF file (or remote dataset) calling the appropriate |
---|
| 1514 | dispatch function. |
---|
| 1515 | |
---|
| 1516 | For open, we have the following pieces of information to use to determine the dispatch table. |
---|
| 1517 | - table specified by override |
---|
| 1518 | - path |
---|
| 1519 | - cmode |
---|
| 1520 | - the contents of the file (if it exists), basically checking its magic number. |
---|
| 1521 | |
---|
| 1522 | \returns ::NC_NOERR No error. |
---|
| 1523 | */ |
---|
| 1524 | int |
---|
| 1525 | NC_open(const char *path, int cmode, |
---|
| 1526 | int basepe, size_t *chunksizehintp, |
---|
| 1527 | int useparallel, void* mpi_info, |
---|
| 1528 | int *ncidp) |
---|
| 1529 | { |
---|
| 1530 | int stat = NC_NOERR; |
---|
| 1531 | NC* ncp = NULL; |
---|
| 1532 | NC_Dispatch* dispatcher = NULL; |
---|
| 1533 | /* Need two pieces of information for now */ |
---|
| 1534 | int model = 0; |
---|
| 1535 | int isurl = 0; |
---|
| 1536 | int cdfversion = 0; |
---|
| 1537 | int hdfversion = 0; |
---|
| 1538 | extern int default_create_format; |
---|
| 1539 | |
---|
| 1540 | if(!nc_initialized) { |
---|
| 1541 | stat = NC_initialize(); |
---|
| 1542 | if(stat) return stat; |
---|
| 1543 | /* Do local initialization */ |
---|
| 1544 | nc_local_initialize(); |
---|
| 1545 | nc_initialized = 1; |
---|
| 1546 | } |
---|
| 1547 | |
---|
| 1548 | isurl = NC_testurl(path); |
---|
| 1549 | if(isurl) |
---|
| 1550 | model = NC_urlmodel(path); |
---|
| 1551 | |
---|
| 1552 | if(!isurl) { |
---|
| 1553 | /* Look at the file if it exists */ |
---|
| 1554 | stat = NC_check_file_type(path,useparallel,mpi_info,&cdfversion,&hdfversion); |
---|
| 1555 | if(stat == NC_NOERR) { |
---|
| 1556 | if(hdfversion != 0) { |
---|
| 1557 | model = NC_DISPATCH_NC4; |
---|
| 1558 | } else if(cdfversion != 0) { |
---|
| 1559 | model = NC_DISPATCH_NC3; |
---|
| 1560 | } |
---|
| 1561 | } |
---|
| 1562 | /* else ignore the file */ |
---|
| 1563 | } |
---|
| 1564 | |
---|
| 1565 | /* Look to the incoming cmode for hints */ |
---|
| 1566 | if(model == 0) { |
---|
| 1567 | if(cmode & NC_NETCDF4 || cmode & NC_PNETCDF) model |= NC_DISPATCH_NC4; |
---|
| 1568 | } |
---|
| 1569 | |
---|
| 1570 | if(model == 0) model = NC_DISPATCH_NC3; /* final default */ |
---|
| 1571 | |
---|
| 1572 | /* Force flag consistentcy */ |
---|
| 1573 | if(model & NC_DISPATCH_NC4) |
---|
| 1574 | cmode |= NC_NETCDF4; |
---|
| 1575 | else if(model & NC_DISPATCH_NC3) { |
---|
| 1576 | cmode &= ~NC_NETCDF4; /* must be netcdf-3 */ |
---|
| 1577 | if(cdfversion == 2) cmode |= NC_64BIT_OFFSET; |
---|
| 1578 | } |
---|
| 1579 | |
---|
| 1580 | if((cmode & NC_MPIIO && cmode & NC_MPIPOSIX)) |
---|
| 1581 | return NC_EINVAL; |
---|
| 1582 | |
---|
| 1583 | /* override overrides any other table choice */ |
---|
| 1584 | dispatcher = NC_get_dispatch_override(); |
---|
| 1585 | if(dispatcher != NULL) goto havetable; |
---|
| 1586 | |
---|
| 1587 | /* Figure out what dispatcher to use */ |
---|
| 1588 | #if defined(USE_CDMREMOTE) |
---|
| 1589 | if(model == (NC_DISPATCH_NC4 | NC_DISPATCH_NCR)) |
---|
| 1590 | dispatcher = NCCR_dispatch_table; |
---|
| 1591 | else |
---|
| 1592 | #endif |
---|
| 1593 | #if defined(USE_DAP) |
---|
| 1594 | if(model == (NC_DISPATCH_NC3 | NC_DISPATCH_NCD)) |
---|
| 1595 | dispatcher = NCD3_dispatch_table; |
---|
| 1596 | else |
---|
| 1597 | #endif |
---|
| 1598 | #if defined(USE_NETCDF4) |
---|
| 1599 | if(model == (NC_DISPATCH_NC4)) |
---|
| 1600 | dispatcher = NC4_dispatch_table; |
---|
| 1601 | else |
---|
| 1602 | #endif |
---|
| 1603 | if(model == (NC_DISPATCH_NC3)) |
---|
| 1604 | dispatcher = NC3_dispatch_table; |
---|
| 1605 | else |
---|
| 1606 | return NC_ENOTNC; |
---|
| 1607 | |
---|
| 1608 | havetable: |
---|
| 1609 | stat = dispatcher->open(path, cmode, basepe, chunksizehintp, |
---|
| 1610 | useparallel, mpi_info, dispatcher, &ncp); |
---|
| 1611 | if(stat == NC_NOERR) { |
---|
| 1612 | ncp->dispatch = dispatcher; |
---|
| 1613 | if(ncidp) *ncidp = ncp->ext_ncid; |
---|
| 1614 | ncp->path = nulldup(path); |
---|
| 1615 | if(path == NULL) stat = NC_ENOMEM; |
---|
| 1616 | } |
---|
| 1617 | return stat; |
---|
| 1618 | } |
---|
| 1619 | |
---|
| 1620 | /*Provide an internal function for generating pseudo file descriptors |
---|
| 1621 | for systems that are not file based (e.g. dap, memio). |
---|
| 1622 | */ |
---|
| 1623 | |
---|
| 1624 | /* Static counter for pseudo file descriptors (incremented) */ |
---|
| 1625 | static int pseudofd = 0; |
---|
| 1626 | |
---|
| 1627 | /* Create a pseudo file descriptor that does not |
---|
| 1628 | overlap real file descriptors |
---|
| 1629 | */ |
---|
| 1630 | int |
---|
| 1631 | nc__pseudofd(void) |
---|
| 1632 | { |
---|
| 1633 | if(pseudofd == 0) { |
---|
| 1634 | int maxfd = 32767; /* default */ |
---|
| 1635 | #ifdef HAVE_GETRLIMIT |
---|
| 1636 | struct rlimit rl; |
---|
| 1637 | if(getrlimit(RLIMIT_NOFILE,&rl) == 0) { |
---|
| 1638 | if(rl.rlim_max != RLIM_INFINITY) |
---|
| 1639 | maxfd = rl.rlim_max; |
---|
| 1640 | if(rl.rlim_cur != RLIM_INFINITY) |
---|
| 1641 | maxfd = rl.rlim_cur; |
---|
| 1642 | } |
---|
| 1643 | pseudofd = maxfd+1; |
---|
| 1644 | #endif |
---|
| 1645 | } |
---|
| 1646 | |
---|
| 1647 | return pseudofd++; |
---|
| 1648 | } |
---|
| 1649 | |
---|
| 1650 | |
---|