Function deconstruct_array

src/backend/utils/adt/arrayfuncs.c:3590–3649

* deconstruct_array --- simple method for extracting data from an array * * array: array object to examine (must not be NULL) * elmtype, elmlen, elmbyval, elmalign: info for the datatype of the items * elemsp: return value, set to point to palloc'd array of Datum values * nullsp: return value, set to point to palloc'd array of isnull markers * nelemsp: return value, set to number of extract

 * cycle by hard-wiring the type info as well.
 */
void
deconstruct_array(ArrayType *array,
				  Oid elmtype,
				  int elmlen, bool elmbyval, char elmalign,
				  Datum **elemsp, bool **nullsp, int *nelemsp)
{
	Datum	   *elems;
	bool	   *nulls;
	int			nelems;
	char	   *p;
	bits8	   *bitmap;
	int			bitmask;
	int			i;

	Assert(ARR_ELEMTYPE(array) == elmtype);

	nelems = ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array));
	*elemsp = elems = (Datum *) palloc(nelems * sizeof(Datum));
	if (nullsp)
		*nullsp = nulls = (bool *) palloc0(nelems * sizeof(bool));
	else
		nulls = NULL;
	*nelemsp = nelems;

	p = ARR_DATA_PTR(array);
	bitmap = ARR_NULLBITMAP(array);
	bitmask = 1;

	for (i = 0; i < nelems; i++)
	{
		/* Get source element, checking for NULL */
		if (bitmap && (*bitmap & bitmask) == 0)
		{
			elems[i] = (Datum) 0;
			if (nulls)
				nulls[i] = true;
			else
				ereport(ERROR,
						(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
						 errmsg("null array element not allowed in this context")));
		}
		else
		{
			elems[i] = fetch_att(p, elmbyval, elmlen);
			p = att_addlength_pointer(p, elmlen, p);
			p = (char *) att_align_nominal(p, elmalign);
		}

		/* advance bitmap pointer if any */
		if (bitmap)
		{
			bitmask <<= 1;
			if (bitmask == 0x100 /* (1<<8) */)
			{
				bitmap++;
				bitmask = 1;
			}
		}