Function array_get_element

src/backend/utils/adt/arrayfuncs.c:1833–1929

* array_get_element : * This routine takes an array datum and a subscript array and returns * the referenced item as a Datum. Note that for a pass-by-reference * datatype, the returned Datum is a pointer into the array object. * * This handles both ordinary varlena arrays and fixed-length arrays. * * Inputs: * arraydatum: the array object (mustn't be NULL) * nSubscripts: number of

 *	*isNull is set to indicate whether the element is NULL.
 */
Datum
array_get_element(Datum arraydatum,
				  int nSubscripts,
				  int *indx,
				  int arraytyplen,
				  int elmlen,
				  bool elmbyval,
				  char elmalign,
				  bool *isNull)
{
	int			i,
				ndim,
			   *dim,
			   *lb,
				offset,
				fixedDim[1],
				fixedLb[1];
	char	   *arraydataptr,
			   *retptr;
	bits8	   *arraynullsptr;

	if (arraytyplen > 0)
	{
		/*
		 * fixed-length arrays -- these are assumed to be 1-d, 0-based
		 */
		ndim = 1;
		fixedDim[0] = arraytyplen / elmlen;
		fixedLb[0] = 0;
		dim = fixedDim;
		lb = fixedLb;
		arraydataptr = (char *) DatumGetPointer(arraydatum);
		arraynullsptr = NULL;
	}
	else if (VARATT_IS_EXTERNAL_EXPANDED(DatumGetPointer(arraydatum)))
	{
		/* expanded array: let's do this in a separate function */
		return array_get_element_expanded(arraydatum,
										  nSubscripts,
										  indx,
										  arraytyplen,
										  elmlen,
										  elmbyval,
										  elmalign,
										  isNull);
	}
	else
	{
		/* detoast array if necessary, producing normal varlena input */
		ArrayType  *array = DatumGetArrayTypeP(arraydatum);

		ndim = ARR_NDIM(array);
		dim = ARR_DIMS(array);
		lb = ARR_LBOUND(array);
		arraydataptr = ARR_DATA_PTR(array);
		arraynullsptr = ARR_NULLBITMAP(array);
	}