/* * this is just a glorified buffer xor. targbuf points to a buffer * that is one full stripe unit in size. srcbuf points to a buffer * that may be less than 1 SU, but never more. When the access * described by pda is one SU in size (which by implication means it's * SU-aligned), all that happens is (targbuf) <- (srcbuf ^ targbuf). * When the access is less than one SU in size the XOR occurs on only * the portion of targbuf identified in the pda. */