• Nicolai Stange's avatar
    lib/mpi: mpi_read_raw_from_sgl(): sanitize meaning of indices · 85d541a3
    Nicolai Stange authored
    Within the byte reading loop in mpi_read_raw_sgl(), there are two
    housekeeping indices used, z and x.
    At all times, the index z represents the number of output bytes covered
    by the input SGEs for which processing has completed so far. This includes
    any leading zero bytes within the most significant limb.
    The index x changes its meaning after the first outer loop's iteration
    though: while processing the first input SGE, it represents
      "number of leading zero bytes in most significant output limb" +
       "current position within current SGE"
    For the remaining SGEs OTOH, x corresponds just to
      "current position within current SGE"
    After all, it is only the sum of z and x that has any meaning for the
    output buffer and thus, the
      "number of leading zero bytes in most significant output limb"
    part can be moved away from x into z from the beginning, opening up the
    opportunity for cleaner code.
    Before the outer loop iterating over the SGEs, don't initialize z with
    zero, but with the number of leading zero bytes in the most significant
    output limb. For the inner loop iterating over a single SGE's bytes,
    get rid of the buf_shift offset to x' bounds and let x run from zero to
    sg->length - 1.
    Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>