netcdf-c/libdispatch/nc.c
Dennis Heimbigner 9983b9d911 re e-support UBS-599337
re pull request https://github.com/Unidata/netcdf-c/pull/405
re pull request https://github.com/Unidata/netcdf-c/pull/446

Notes:
1. This branch is a cleanup of the magic.dmh branch.
2. magic.dmh was originally merged, but caused problems with parallel IO.
   It was re-issued as pull request https://github.com/Unidata/netcdf-c/pull/446.
3. This branch + pull request replace any previous pull requests and magic.dmh branch.

Given an otherwise valid netCDF file that has a corrupted header,
the netcdf library currently crashes. Instead, it should return
NC_ENOTNC.

Additionally, the NC_check_file_type code does not do the
forward search required by hdf5 files. It currently only looks
at file position 0 instead of 512, 1024, 2048,... Also, it turns
out that the HDF4 magic number is assumed to always be at the
beginning of the file (unlike HDF5).
The change is localized to libdispatch/dfile.c See
https://support.hdfgroup.org/release4/doc/DSpec_html/DS.pdf

Also, it turns out that the code in NC_check_file_type is duplicated
(mostly) in the function libsrc4/nc4file.c#nc_check_for_hdf.

This branch does the following.
1. Make NC_check_file_type return NC_ENOTNC instead of crashing.
2. Remove nc_check_for_hdf and centralize all file format checking
   NC_check_file_type.
3. Add proper forward search for HDF5 files (but not HDF4 files)
   to look for the magic number at offsets of 0, 512, 1024...
4. Add test tst_hdf5_offset.sh. This tests that hdf5 files with
   an offset are properly recognized. It does so by prefixing
   a legal file with some number of zero bytes: 512, 1024, etc.
5. Off-topic: Added -N flag to ncdump to force a specific output dataset name.
2017-10-24 16:25:09 -06:00

109 lines
2.5 KiB
C

/*
* Copyright 1996, University Corporation for Atmospheric Research
* See netcdf/COPYRIGHT file for copying and redistribution conditions.
*/
#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#if defined(LOCKNUMREC) /* && _CRAYMPP */
# include <mpp/shmem.h>
# include <intrinsics.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include "nc.h"
#include "ncdispatch.h"
int ncdebug = 0;
/* This is the default create format for nc_create and nc__create. */
static int default_create_format = NC_FORMAT_CLASSIC;
/* These have to do with version numbers. */
#define MAGIC_NUM_LEN 4
#define VER_CLASSIC 1
#define VER_64BIT_OFFSET 2
#define VER_HDF5 3
int
NC_check_id(int ncid, NC** ncpp)
{
NC* nc = find_in_NCList(ncid);
if(nc == NULL) return NC_EBADID;
if(ncpp) *ncpp = nc;
return NC_NOERR;
}
void
free_NC(NC *ncp)
{
if(ncp == NULL)
return;
if(ncp->path)
free(ncp->path);
/* We assume caller has already cleaned up ncp->dispatchdata */
#if _CRAYMPP && defined(LOCKNUMREC)
shfree(ncp);
#else
free(ncp);
#endif /* _CRAYMPP && LOCKNUMREC */
}
int
new_NC(NC_Dispatch* dispatcher, const char* path, int mode, int model, NC** ncpp)
{
NC *ncp = (NC*)calloc(1,sizeof(NC));
if(ncp == NULL) return NC_ENOMEM;
ncp->dispatch = dispatcher;
ncp->path = nulldup(path);
ncp->mode = mode;
ncp->model = model;
if(ncp->path == NULL) { /* fail */
free_NC(ncp);
return NC_ENOMEM;
}
if(ncpp) {
*ncpp = ncp;
} else {
free_NC(ncp);
}
return NC_NOERR;
}
/* This function sets a default create flag that will be logically
or'd to whatever flags are passed into nc_create for all future
calls to nc_create.
Valid default create flags are NC_64BIT_OFFSET, NC_CLOBBER,
NC_LOCK, NC_SHARE. */
int
nc_set_default_format(int format, int *old_formatp)
{
/* Return existing format if desired. */
if (old_formatp)
*old_formatp = default_create_format;
/* Make sure only valid format is set. */
#ifdef USE_NETCDF4
if (format != NC_FORMAT_CLASSIC && format != NC_FORMAT_64BIT_OFFSET &&
format != NC_FORMAT_NETCDF4 && format != NC_FORMAT_NETCDF4_CLASSIC &&
format != NC_FORMAT_CDF5)
return NC_EINVAL;
#else
if (format != NC_FORMAT_CLASSIC && format != NC_FORMAT_64BIT_OFFSET &&
format != NC_FORMAT_CDF5)
return NC_EINVAL;
#endif
default_create_format = format;
return NC_NOERR;
}
int
nc_get_default_format(void)
{
return default_create_format;
}