netcdf-c/include/nc.h
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

90 lines
2.6 KiB
C

/*
* Copyright 1996, University Corporation for Atmospheric Research
* See netcdf/COPYRIGHT file for copying and redistribution conditions.
*/
#ifndef _NC_H_
#define _NC_H_
#include "config.h"
#include "netcdf.h"
/* There's an external ncid (ext_ncid) and an internal ncid
* (int_ncid). The ext_ncid is the ncid returned to the user. If
* the user has opened or created a netcdf-4 file, then the
* ext_ncid is the same as the int_ncid. If he has opened or
* created a netcdf-3 file ext_ncid (which the user sees) is
* different from the int_ncid, which is the ncid returned by the
* netcdf-3 layer, which insists on inventing its own ncids,
* regardless of what is already in use due to previously opened
* netcdf-4 files. The ext_ncid contains the ncid for the root
* group (i.e. group zero). */
/* Common Shared Structure for all Dispatched Objects */
typedef struct NC {
int ext_ncid;
int int_ncid;
struct NC_Dispatch* dispatch;
void* dispatchdata; /*per-'file' data; points to e.g. NC3_INFO data*/
char* path;
int mode; /* as provided to nc_open/nc_create */
int model; /* as determined by libdispatch/dfile.c */
#ifdef USE_REFCOUNT
int refcount; /* To enable multiple name-based opens */
#endif
} NC;
/*
* Counted string for names and such
*/
typedef struct {
/* all xdr'd */
size_t nchars;
char *cp;
} NC_string;
/* Define functions that are used across multiple dispatchers */
/* Begin defined in string.c */
extern void
free_NC_string(NC_string *ncstrp);
extern int
NC_check_name(const char *name);
extern NC_string *
new_NC_string(size_t slen, const char *str);
extern int
set_NC_string(NC_string *ncstrp, const char *str);
/* End defined in string.c */
extern int
NC_check_id(int ncid, NC **ncpp);
/* Create a pseudo file descriptor that does not
overlap real file descriptors */
extern int nc__pseudofd(void);
/* This function gets a current default create flag */
extern int nc_get_default_format(void);
extern int NC_check_file_type(const char *path, int flags, void *parameters, int* model, int* version);
extern int add_to_NCList(NC*);
extern void del_from_NCList(NC*);/* does not free object */
extern NC* find_in_NCList(int ext_ncid);
extern NC* find_in_NCList_by_name(const char*);
extern void free_NCList(void);/* reclaim whole list */
extern int count_NCList(void); /* return # of entries in NClist */
extern int iterate_NCList(int i,NC**); /* Walk from 0 ...; ERANGE return => stop */
/* Defined in nc.c */
extern void free_NC(NC*);
extern int new_NC(struct NC_Dispatch*, const char*, int, int, NC**);
/* Defined in nc.c */
extern int ncdebug;
#endif /* _NC_H_ */