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.
[('string', 'string value'), ('bool1', 'true'), ('bool2', 'false'), ('boolinvalid', 'foo'), ('int1', '42'), ('int2', '-42'), ('intinvalid', 'foo')]
[('list1', 'foo'), ('list2', 'foo bar baz'), ('list3', 'alice, bob'), ('list4', 'foo bar baz alice, bob'), ('list5', 'abc d"ef"g "hij def"'), ('list6', '"hello world", "how are you?"'), ('list7', 'Do"Not"Separate'), ('list8', '"Do"Separate'), ('list9', '"Do\\"NotSeparate"'), ('list10', 'string "with extraneous" quotation mark"'), ('list11', 'x, y'), ('list12', '"x", "y"'), ('list13', '""" key = "x", "y" """'), ('list14', ',,,,'), ('list15', '" just with starting quotation'), ('list16', '"longer quotation" with "no ending quotation'), ('list17', 'this is \\" "not a quotation mark"'), ('list18', 'ding\ndong')]
---
'string value'
'true'
'false'
None
---
values.string is not a boolean ('string value')
True
False
False
False
True
---
42
-42
---
['foo']
['foo', 'bar', 'baz']
['alice', 'bob']
['foo', 'bar', 'baz', 'alice', 'bob']
['foo', 'bar', 'baz', 'alice', 'bob']
['abc', 'd"ef"g', 'hij def']
['hello world', 'how are you?']
['Do"Not"Separate']
['Do', 'Separate']
['Do"NotSeparate']
['string', 'with extraneous', 'quotation', 'mark"']
['x', 'y']
['x', 'y']
['', ' key = ', 'x"', 'y', '', '"']
[]
['"', 'just', 'with', 'starting', 'quotation']
['longer quotation', 'with', '"no', 'ending', 'quotation']
['this', 'is', '"', 'not a quotation mark']
['ding', 'dong']
[]
[]
['foo']
['foo']
['foo', 'bar']
['foo', 'bar']
['foo bar']
['foo', 'bar']
None
True
boolinvalid
intinvalid