Function array_get_element_expanded

src/backend/utils/adt/arrayfuncs.c:1934–2011

* Implementation of array_get_element() for an expanded array */

 * Implementation of array_get_element() for an expanded array
 */
static Datum
array_get_element_expanded(Datum arraydatum,
						   int nSubscripts, int *indx,
						   int arraytyplen,
						   int elmlen, bool elmbyval, char elmalign,
						   bool *isNull)
{
	ExpandedArrayHeader *eah;
	int			i,
				ndim,
			   *dim,
			   *lb,
				offset;
	Datum	   *dvalues;
	bool	   *dnulls;

	eah = (ExpandedArrayHeader *) DatumGetEOHP(arraydatum);
	Assert(eah->ea_magic == EA_MAGIC);

	/* sanity-check caller's info against object */
	Assert(arraytyplen == -1);
	Assert(elmlen == eah->typlen);
	Assert(elmbyval == eah->typbyval);
	Assert(elmalign == eah->typalign);

	ndim = eah->ndims;
	dim = eah->dims;
	lb = eah->lbound;

	/*
	 * Return NULL for invalid subscript
	 */
	if (ndim != nSubscripts || ndim <= 0 || ndim > MAXDIM)
	{
		*isNull = true;
		return (Datum) 0;
	}
	for (i = 0; i < ndim; i++)
	{
		if (indx[i] < lb[i] || indx[i] >= (dim[i] + lb[i]))
		{
			*isNull = true;
			return (Datum) 0;
		}
	}

	/*
	 * Calculate the element number
	 */
	offset = ArrayGetOffset(nSubscripts, dim, lb, indx);

	/*
	 * Deconstruct array if we didn't already.  Note that we apply this even
	 * if the input is nominally read-only: it should be safe enough.
	 */
	deconstruct_expanded_array(eah);

	dvalues = eah->dvalues;