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/*-------------------------------------------------------------------------
*
* arrayaccess.h
* Declarations for element-by-element access to Postgres arrays.
*
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/arrayaccess.h
*
*-------------------------------------------------------------------------
*/
#ifndef ARRAYACCESS_H
#define ARRAYACCESS_H
#include "access/tupmacs.h"
#include "utils/array.h"
/*
* Functions for iterating through elements of a flat or expanded array.
* These require a state struct "array_iter iter".
*
* Use "array_iter_setup(&iter, arrayptr);" to prepare to iterate, and
* "datumvar = array_iter_next(&iter, &isnullvar, index, ...);" to fetch
* the next element into datumvar/isnullvar.
* "index" must be the zero-origin element number; we make caller provide
* this since caller is generally counting the elements anyway. Despite
* that, these functions can only fetch elements sequentially.
*/
typedef struct array_iter
{
/* datumptr being NULL or not tells if we have flat or expanded array */
/* Fields used when we have an expanded array */
Datum *datumptr; /* Pointer to Datum array */
bool *isnullptr; /* Pointer to isnull array */
/* Fields used when we have a flat array */
char *dataptr; /* Current spot in the data area */
bits8 *bitmapptr; /* Current byte of the nulls bitmap, or NULL */
int bitmask; /* mask for current bit in nulls bitmap */
} array_iter;
static inline void
array_iter_setup(array_iter *it, AnyArrayType *a)
{
if (VARATT_IS_EXPANDED_HEADER(a))
{
if (a->xpn.dvalues)
{
it->datumptr = a->xpn.dvalues;
it->isnullptr = a->xpn.dnulls;
/* we must fill all fields to prevent compiler warnings */
it->dataptr = NULL;
it->bitmapptr = NULL;
}
else
{
/* Work with flat array embedded in the expanded datum */
it->datumptr = NULL;
it->isnullptr = NULL;
it->dataptr = ARR_DATA_PTR(a->xpn.fvalue);
it->bitmapptr = ARR_NULLBITMAP(a->xpn.fvalue);
}
}
else
{
it->datumptr = NULL;
it->isnullptr = NULL;
it->dataptr = ARR_DATA_PTR((ArrayType *) a);
it->bitmapptr = ARR_NULLBITMAP((ArrayType *) a);
}
it->bitmask = 1;
}
static inline Datum
array_iter_next(array_iter *it, bool *isnull, int i,
int elmlen, bool elmbyval, char elmalign)
{
Datum ret;
if (it->datumptr)
{
ret = it->datumptr[i];
*isnull = it->isnullptr ? it->isnullptr[i] : false;
}
else
{
if (it->bitmapptr && (*(it->bitmapptr) & it->bitmask) == 0)
{
*isnull = true;
ret = (Datum) 0;
}
else
{
*isnull = false;
ret = fetch_att(it->dataptr, elmbyval, elmlen);
it->dataptr = att_addlength_pointer(it->dataptr, elmlen,
it->dataptr);
it->dataptr = (char *) att_align_nominal(it->dataptr, elmalign);
}
it->bitmask <<= 1;
if (it->bitmask == 0x100)
{
if (it->bitmapptr)
it->bitmapptr++;
it->bitmask = 1;
}
}
return ret;
}
#endif /* ARRAYACCESS_H */
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