Function DatumGetExpandedArray

src/backend/utils/adt/array_expanded.c:351–366

* DatumGetExpandedArray: get a writable expanded array from an input argument * * Caution: if the input is a read/write pointer, this returns the input * argument; so callers must be sure that their changes are "safe", that is * they cannot leave the array in a corrupt state. */

 * they cannot leave the array in a corrupt state.
 */
ExpandedArrayHeader *
DatumGetExpandedArray(Datum d)
{
	/* If it's a writable expanded array already, just return it */
	if (VARATT_IS_EXTERNAL_EXPANDED_RW(DatumGetPointer(d)))
	{
		ExpandedArrayHeader *eah = (ExpandedArrayHeader *) DatumGetEOHP(d);

		Assert(eah->ea_magic == EA_MAGIC);
		return eah;
	}

	/* Else expand the hard way */
	d = expand_array(d, CurrentMemoryContext, NULL);
	return (ExpandedArrayHeader *) DatumGetEOHP(d);
}

/*
 * As above, when caller has the ability to cache element type info