forked from Unidata/netcdf-c
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nclistmgr.c
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/
nclistmgr.c
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/*********************************************************************
Copyright 2018, UCAR/Unidata See netcdf/COPYRIGHT file for
copying and redistribution conditions.
*********************************************************************/
/**
* @file
*
* Functions to manage the list of NC structs. There is one NC struct
* for each open file.
*
* @author Dennis Heimbigner
*/
#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "ncdispatch.h"
/** This shift is applied to the ext_ncid in order to get the index in
* the array of NC. */
#define ID_SHIFT (16)
/** This is the length of the NC list - the number of files that can
* be open at one time. We use 2^16 = 65536 entries in the array, but
* slot 0 is not used, so only 65535 files may be open at one
* time. */
#define NCFILELISTLENGTH 0x10000
/** This is the pointer to the array of NC, one for each open file. */
static NC** nc_filelist = NULL;
/** The number of files currently open. */
static int numfiles = 0;
/**
* How many files are currently open?
*
* @return number of open files.
* @author Dennis Heimbigner
*/
int
count_NCList(void)
{
return numfiles;
}
/**
* Free an empty NCList. @note If list is not empty, or has not been
* allocated, function will silently exit.
*
* @author Dennis Heimbigner
*/
void
free_NCList(void)
{
if(numfiles > 0) return; /* not empty */
if(nc_filelist != NULL) free(nc_filelist);
nc_filelist = NULL;
}
/**
* Add an already-allocated NC to the list. It will be assigned an
* ncid in this function.
*
* If this is the first file to be opened, the nc_filelist will be
* allocated and set to all 0.
*
* The ncid is assigned by finding the first open index in the
* nc_filelist array (skipping index 0). The ncid is this index
* left-shifted ID_SHIFT bits (16). This puts the file ID in the first
* two bytes of the 4-byte integer, and leaves the last two bytes for
* group IDs for netCDF-4 files.
*
* @param ncp Pointer to already-allocated and initialized NC struct.
*
* @return ::NC_NOERR No error.
* @return ::NC_ENOMEM Out of memory.
* @author Dennis Heimbigner
*/
int
add_to_NCList(NC* ncp)
{
int i;
int new_id;
if(nc_filelist == NULL) {
if (!(nc_filelist = calloc(1, sizeof(NC*)*NCFILELISTLENGTH)))
return NC_ENOMEM;
numfiles = 0;
}
new_id = 0; /* id's begin at 1 */
for(i=1; i < NCFILELISTLENGTH; i++) {
if(nc_filelist[i] == NULL) {new_id = i; break;}
}
if(new_id == 0) return NC_ENOMEM; /* no more slots */
nc_filelist[new_id] = ncp;
numfiles++;
ncp->ext_ncid = (new_id << ID_SHIFT);
return NC_NOERR;
}
/**
* Move an NC in the nc_filelist. This is required by PIO.
*
* @param ncp Pointer to already-allocated and initialized NC struct.
* @param new_id New index in the nc_filelist for this file.
*
* @return ::NC_NOERR No error.
* @return ::NC_EINVAL Invalid input.
* @author Ed Hartnett
*/
int
move_in_NCList(NC *ncp, int new_id)
{
/* If no files in list, error. */
if (!nc_filelist)
return NC_EINVAL;
/* If new slot is already taken, error. */
if (nc_filelist[new_id])
return NC_EINVAL;
/* Move the file. */
nc_filelist[ncp->ext_ncid >> ID_SHIFT] = NULL;
nc_filelist[new_id] = ncp;
ncp->ext_ncid = (new_id << ID_SHIFT);
return NC_NOERR;
}
/**
* Delete an NC struct from the list. This happens when the file is
* closed. Relies on all memory in the NC being deallocated after this
* function with freeNC().
*
* @note If the file list is empty, or this NC can't be found in the
* list, this function will silently exit.
*
* @param ncp Pointer to NC to be removed from list.
*
* @author Dennis Heimbigner
*/
void
del_from_NCList(NC* ncp)
{
unsigned int ncid = ((unsigned int)ncp->ext_ncid) >> ID_SHIFT;
if(numfiles == 0 || ncid == 0 || nc_filelist == NULL) return;
if(nc_filelist[ncid] != ncp) return;
nc_filelist[ncid] = NULL;
numfiles--;
/* If all files have been closed, release the filelist memory. */
if (numfiles == 0)
free_NCList();
}
/**
* Find an NC in the list, given an ext_ncid. The NC list is indexed
* with the first two bytes of ext_ncid. (The last two bytes specify
* the group for netCDF4 files, or are zeros for classic files.)
*
* @param ext_ncid The ncid of the file to find.
*
* @return pointer to NC or NULL if not found.
* @author Dennis Heimbigner, Ed Hartnett
*/
NC *
find_in_NCList(int ext_ncid)
{
NC* f = NULL;
/* Discard the first two bytes of ext_ncid to get ncid. */
unsigned int ncid = ((unsigned int)ext_ncid) >> ID_SHIFT;
/* If we have a filelist, there will be an entry, possibly NULL,
* for this ncid. */
if (nc_filelist)
{
assert(numfiles);
f = nc_filelist[ncid];
}
/* For classic files, ext_ncid must be a multiple of
* (1<<ID_SHIFT). That is, the group part of the ext_ncid (the
* last two bytes) must be zero. If not, then return NULL, which
* will eventually lead to an NC_EBADID error being returned to
* user. */
if (f != NULL && f->dispatch != NULL
&& f->dispatch->model == NC_FORMATX_NC3 && (ext_ncid % (1<<ID_SHIFT)))
return NULL;
return f;
}
/**
* Find an NC in the list using the file name.
*
* @param path Name of the file.
*
* @return pointer to NC or NULL if not found.
* @author Dennis Heimbigner
*/
NC*
find_in_NCList_by_name(const char* path)
{
int i;
NC* f = NULL;
if(nc_filelist == NULL)
return NULL;
for(i=1; i < NCFILELISTLENGTH; i++) {
if(nc_filelist[i] != NULL) {
if(strcmp(nc_filelist[i]->path,path)==0) {
f = nc_filelist[i];
break;
}
}
}
return f;
}
/**
* Find an NC in list based on its index. The index is ((unsigned
* int)ext_ncid) >> ID_SHIFT. This is the two high bytes of the
* ext_ncid. (The other two bytes are used for the group ID for
* netCDF-4 files.)
*
* @param index The index in the NC list.
* @param ncp Pointer that gets pointer to the next NC. Ignored if
* NULL.
*
* @return ::NC_NOERR No error.
* @return ::NC_ERANGE Index out of range.
* @author Dennis Heimbigner
*/
int
iterate_NCList(int index, NC** ncp)
{
/* Walk from 0 ...; 0 return => stop */
if(index < 0 || index >= NCFILELISTLENGTH)
return NC_ERANGE;
if(ncp) *ncp = nc_filelist[index];
return NC_NOERR;
}