Method move

src/jrd/blb.cpp:1003–1305

This function can't take from_desc as const because it may call store_array, which in turn calls blb::create2 that writes in the blob id. Although the compiler allows to modify from_desc->dsc_address' contents when from_desc is constant, this is misleading so I didn't make the source descriptor constant.

// compiler allows to modify from_desc->dsc_address' contents when from_desc is
// constant, this is misleading so I didn't make the source descriptor constant.
void blb::move(thread_db* tdbb, dsc* from_desc, dsc* to_desc,
			   jrd_rel* relation, Record* record, USHORT fieldId, bool bulk)
{
/**************************************
 *
 *      b l b : : m o v e
 *
 **************************************
 *
 * Functional description
 *      Perform an assignment to a blob field or a blob descriptor.
 *      When assigning to a field, unless the blob is null,
 *      this requires that either a temporary blob be materialized or that
 *      a permanent blob be copied.  Note: it is illegal to have a blob
 *      field in a message.
 *
 **************************************/
	SET_TDBB(tdbb);

	if (to_desc->dsc_dtype == dtype_array)
	{
		// only array->array conversions are allowed
		if (from_desc->dsc_dtype != dtype_array && from_desc->dsc_dtype != dtype_quad)
		{
			ERR_post(Arg::Gds(isc_array_convert_error));
		}
	}
	else if (DTYPE_IS_BLOB_OR_QUAD(to_desc->dsc_dtype))
	{
		if (!DTYPE_IS_BLOB_OR_QUAD(from_desc->dsc_dtype))
		{
			// anything that can be copied into a string can be copied into a blob
			move_from_string(tdbb, from_desc, to_desc, relation, record, fieldId);
			return;
		}
	}
	else if (DTYPE_IS_BLOB_OR_QUAD(from_desc->dsc_dtype))
	{
		move_to_string(tdbb, from_desc, to_desc);
		return;
	}
	else
		fb_assert(false);

	// If the target node is a field, we need more work to do.

	// We should not materialize the blob if the destination field
	// stream (nod_union, for example) doesn't have a relation.
	const bool simpleMove = (relation == NULL);

	// Use local copy of source blob id to not change contents of from_desc in
	// a case when it points to materialized temporary blob (see below for
	// assignment to *source).
	bid srcBlobID = *(bid*)from_desc->dsc_address;
	bid* source = &srcBlobID;
	bid* destination = (bid*) to_desc->dsc_address;

	// If nothing changed, do nothing.  If it isn't broken, don't fix it.