bug in hpecc() ?

[Clifford Spencer]

In 4.2 and ULTRIX hp.c(hpecc) I see the following happening under 
the ECC case:


	npf--;		/* because block in error is previous block */
	*
	mpte = mbp->mba_map[npf+btop(byte)];
	* (correct error here)
	*
	npf++;


Why the fiddling with npf? What if npf is initially zero and byte < 512? 
If the error occurs in the first page of a transfer, isn't npf going to 
go negative and we will reference mba_map[-1] ?  Can someone explain this?  
						
						-cliff


-- 
cliff spencer
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