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nc_iter.c
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nc_iter.c
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/*********************************************************************
* Copyright 2018, University Corporation for Atmospheric Research
* See netcdf/README file for copying and redistribution conditions.
* "$Id $"
*********************************************************************/
/*
This nciter code was derived from the ncdump/nciter code.
It has diverged slightly over time.
*/
#include "includes.h"
#include "nc_iter.h"
#define CHECK(stat,f) if(stat != NC_NOERR) {check(stat,#f,__FILE__,__LINE__);} else {}
/* forward declarations */
static int nc_blkio_init(size_t bufsize, size_t value_size, int rank,
const size_t *dims, nciter_t *iter);
static int up_start(int ndims, const size_t *dims, int incdim, size_t inc,
size_t* odom);
static int nciter_ndims(Symbol*,int*);
static int nciter_dimlens(Symbol*,size_t*);
static int nciter_vartype(Symbol*,Symbol**);
static int nciter_valuesize(Symbol*,size_t*);
static void
check(int err, const char* fcn, const char* file, const int line)
{
fprintf(stderr,"%s\n",nc_strerror(err));
fprintf(stderr,"Location: function %s; file %s; line %d\n",
fcn,file,line);
fflush(stderr); fflush(stdout);
exit(1);
}
/* Initialize iteration for a variable. Just a wrapper for
* nc_blkio_init() that makes the netCDF calls needed to initialize
* lower-level iterator. */
int
nc_get_iter(Symbol* vsym,
size_t bufsize, /* size in bytes of memory buffer */
nciter_t *iterp /* returned opaque iteration state */)
{
int stat = NC_NOERR;
Symbol* vartype;
size_t value_size; /* size in bytes of each variable element */
int ndims; /* number of dimensions for variable */
size_t dimsizes[NC_MAX_VAR_DIMS] = {0}; /* variable dimension sizes */
long long nvalues = 1;
int dim;
memset((void*)iterp,0,sizeof(nciter_t)); /* make sure it is initialized */
stat = nciter_ndims(vsym, &ndims);
CHECK(stat, nciter_ndims);
stat = nciter_dimlens(vsym,dimsizes);
CHECK(stat, nciter_dimlens);
/* compute total # elements */
nvalues=1;
for(dim = 0; dim < ndims; dim++) {
nvalues *= dimsizes[dim];
}
stat = nciter_vartype(vsym, &vartype);
CHECK(stat, nciter_vartype);
stat = nciter_valuesize(vartype,&value_size);
CHECK(stat, nciter_valuesize);
stat = nc_blkio_init(bufsize, value_size, ndims, dimsizes, iterp);
CHECK(stat, nc_blkio_init);
iterp->to_get = 0;
return stat;
}
/* Iterate on blocks for variables, by updating start and count vector
* for next vara call. Assumes nc_get_iter called first. Returns
* number of variable values to get, 0 if done, negative number if
* error, so use like this:
size_t to_get;
while((to_get = nc_next_iter(&iter, start, count)) > 0) {
... iteration ...
}
if(to_get < 0) { ... handle error ... }
*/
size_t
nc_next_iter(nciter_t *iter, /* returned opaque iteration state */
size_t *start, /* returned start vector for next vara call */
size_t *count /* returned count vector for next vara call */
) {
int i;
if(iter->first) {
for(i = 0; i < iter->right_dim; i++) {
start[i] = 0;
count[i] = 1;
}
start[iter->right_dim] = 0;
count[iter->right_dim] = iter->rows;
for(i = iter->right_dim + 1; i < iter->rank; i++) {
start[i] = 0;
count[i] = iter->dimsizes[i];
}
iter->first = 0;
} else {
iter->more = up_start(iter->rank, iter->dimsizes, iter->right_dim,
iter->inc, start);
/* iterate on pieces of variable */
if(iter->cur < iter->numrows) {
iter->inc = iter->rows;
count[iter->right_dim] = iter->rows;
iter->cur++;
} else {
if(iter->leftover > 0) {
count[iter->right_dim] = iter->leftover;
iter->inc = iter->leftover;
iter->cur = 0;
}
}
}
iter->to_get = 1;
for(i = 0; i < iter->rank; i++) {
iter->to_get *= count[i];
}
return iter->more == 0 ? 0 : iter->to_get ;
}
/* Initialize block iteration for variables, including those that
* won't fit in the copy buffer all at once.
*/
static int
nc_blkio_init(size_t bufsize, /* size in bytes of in-memory copy buffer */
size_t value_size, /* size in bytes of each variable element */
int rank, /* number of dimensions for variable */
const size_t *dims, /* variable dimension sizes */
nciter_t *iter /* returned iteration state, don't mess with it */
) {
int stat = NC_NOERR;
int i;
long long prod;
iter->rank = rank;
iter->first = 1;
iter->more = 1;
for(i = 0; i < rank; i++)
iter->dimsizes[i] = dims[i];
prod = value_size;
iter->right_dim = rank - 1;
for(i = rank; i > 0; i--) {
if(prod*dims[i-1] <= bufsize) {
prod *= dims[i-1];
iter->right_dim--;
} else {
break;
}
}
if (i > 0) { /* variable won't fit in bufsize bytes */
iter->rows = bufsize/prod;
iter->numrows = dims[iter->right_dim] / iter->rows;
iter->leftover = dims[iter->right_dim] - iter->numrows * iter->rows;
iter->cur = 1;
iter->inc = iter->rows;
return stat;
}
/* else, variable will fit in bufsize bytes of memory. */
iter->right_dim = 0;
iter->rows = dims[0];
iter->inc = 0;
return stat;
}
/*
* Updates a vector of size_t, odometer style. Returns 0 if odometer
* overflowed, else 1.
*/
static int
up_start(
int ndims, /* Number of dimensions */
const size_t *dims, /* The "odometer" limits for each dimension */
int incdim, /* the odmometer increment dimension */
size_t inc, /* the odometer increment for that dimension */
size_t* odom /* The "odometer" vector to be updated */
)
{
int id;
int ret = 1;
if(inc == 0) {
return 0;
}
odom[incdim] += inc;
for (id = incdim; id > 0; id--) {
if(odom[id] >= dims[id]) {
odom[id-1]++;
odom[id] -= dims[id];
}
}
if (odom[0] >= dims[0])
ret = 0;
return ret;
}
static int
nciter_ndims(Symbol* sym, int* ndimsp)
{
if(ndimsp) *ndimsp = sym->typ.dimset.ndims;
return NC_NOERR;
}
static int
nciter_dimlens(Symbol* sym, size_t* dimlens)
{
int i;
int ndims = sym->typ.dimset.ndims;
for(i=0;i<ndims;i++) {
Symbol* dim = sym->typ.dimset.dimsyms[i];
dimlens[i] = dim->dim.declsize;
}
return NC_NOERR;
}
static int
nciter_vartype(Symbol* sym, Symbol** tsymp)
{
if(tsymp)
*tsymp = sym->typ.basetype;
return NC_NOERR;
}
/* For ncgen, we want the iterator to return
dimension indices, not offsets, so force size
to be one.
*/
static int
nciter_valuesize(Symbol* tsym, size_t* valuesizep)
{
if(valuesizep)
*valuesizep = 1;
return NC_NOERR;
}