Method BLB_get_segment

src/jrd/blb.cpp:663–867

USHORT blb::BLB_get_segment(thread_db* tdbb, void* segment, USHORT buffer_length)
{
/**************************************
 *
 *      b l b : : g e t _ s e g m e n t
 *
 **************************************
 *
 * Functional description
 *      Get next segment or fragment from a blob.  Return the number
 *      of bytes returned.
 *
 **************************************/
	SET_TDBB(tdbb);
	Database* dbb = tdbb->getDatabase();

	if (blb_flags & BLB_temporary)
		ERR_post(Arg::Gds(isc_cannot_read_new_blob));

	JRD_reschedule(tdbb);

	// If we reached end of file, we're still there

	if (blb_flags & BLB_eof)
		return 0;

	if (blb_filter)
	{
		blb_fragment_size = 0;
		USHORT tmp_len = 0;
		const ISC_STATUS status =
			BLF_get_segment(tdbb, &blb_filter, &tmp_len, buffer_length, segment);

		switch (status)
		{
			case isc_segstr_eof:
				blb_flags |= BLB_eof;
				break;
			case isc_segment:
				blb_fragment_size = 1;
				break;
			default:
				fb_assert(status == 0);
		}

		return tmp_len;
	}

	// If there is a seek pending, handle it here

	USHORT seek = 0;

	if (blb_flags & BLB_seek)
	{
		if (blb_seek >= blb_length)
		{
			blb_flags |= BLB_eof;
			return 0;