Function slice_callback

src/jrd/blb.cpp:2784–2891

static void slice_callback(array_slice* arg, ULONG /*count*/, DSC* descriptors)
{
/**************************************
 *
 *      s l i c e _ c a l l b a c k
 *
 **************************************
 *
 * Functional description
 *      Perform slice assignment.
 *
 **************************************/
	thread_db* tdbb = JRD_get_thread_data();

	dsc* array_desc = descriptors;
	dsc* slice_desc = &arg->slice_desc;
	BLOB_PTR* const next = slice_desc->dsc_address + arg->slice_element_length;

	if (next > arg->slice_end)
		ERR_post(Arg::Gds(isc_out_of_bounds));

	if (array_desc->dsc_address < arg->slice_base)
		ERR_error(198);			// msg 198 array subscript computation error

	if (arg->slice_direction == array_slice::slc_writing_array)
	{
		// Storing INTO array
		// FROM slice_desc TO array_desc

		// If storing beyond the high-water mark, ensure elements
		// from the high-water mark to current position are zeroed

		// Since we are only initializing, it makes sense to throw away
		// the constness of arg->slice_high_water.
		const SLONG l = array_desc->dsc_address - arg->slice_high_water;
		if (l > 0)
			memset(const_cast<BLOB_PTR*>(arg->slice_high_water), 0, l);

		// The individual elements of a varying string array may not be aligned
		// correctly.  If they aren't, some RISC machines may break.  In those
		// cases, calculate the actual length and then move the length and text manually.

		if (array_desc->dsc_dtype == dtype_varying &&
			array_desc->dsc_address !=
				FB_ALIGN(array_desc->dsc_address, (MIN(sizeof(USHORT), FB_ALIGNMENT))))
		{
			// Note: cannot remove this JRD_get_thread_data without api change
			// to slice callback routines
			/*thread_db* tdbb = */ JRD_get_thread_data();

			DynamicVaryStr<1024> tmp_buffer;
			const USHORT tmp_len = array_desc->dsc_length;
			const char* p;
			const USHORT len = MOV_make_string(tdbb, slice_desc, INTL_TEXT_TYPE(*array_desc), &p,
											   tmp_buffer.getBuffer(tmp_len), tmp_len);
			memcpy(array_desc->dsc_address, &len, sizeof(USHORT));
			memcpy(array_desc->dsc_address + sizeof(USHORT), p, (int) len);
		}