bdiff: don't check border condition in loop This is pretty much a copy of d500ddae7494, just to a different loop. The condition `p == plast` (`plast == a + len - 1`) was only true on the final iteration of the loop. So it was wasteful to check for it on every iteration. We decrease the iteration count by 1 and add an explicit check for `p == plast` after the loop. Again, we see modest wins. From the mozilla-unified repository: $ perfbdiff -m 3041e4d59df2 ! wall 0.035502 comb 0.040000 user 0.040000 sys 0.000000 (best of 100) ! wall 0.030480 comb 0.030000 user 0.030000 sys 0.000000 (best of 100) $ perfbdiff 0e9928989e9c --alldata --count 100 ! wall 4.097394 comb 4.100000 user 4.100000 sys 0.000000 (best of 3) ! wall 3.597798 comb 3.600000 user 3.600000 sys 0.000000 (best of 3) The 2nd example throws a total of ~3.3GB of data at bdiff. This change increases the throughput from ~811 MB/s to ~924 MB/s.

     1

#!/usr/bin/env python

     2

     3

from __future__ import absolute_import, print_function

     4

     5

import errno

     6

import os

     7

import sys

     8

     9

for f in sys.argv[1:]:

    10

    try:

    11

        print(f, '->', os.readlink(f))

    12

    except OSError as err:

    13

        if err.errno != errno.EINVAL:

    14

            raise

    15

        print(f, '->', f, 'not a symlink')

    16

    17

sys.exit(0)