[PATCH] annotate: optimize line counting

[Augie Fackler]

On Mon, May 23, 2016 at 11:23:46AM -0500, Matt Mackall wrote:
> # HG changeset patch
> # User Matt Mackall <mpm at selenic.com>
> # Date 1463607452 18000
> #      Wed May 18 16:37:32 2016 -0500
> # Node ID 218a9c673a2cc278b1d53ba28eb0ec46b64d5b4e
> # Parent  8c8442523eefac2d53e3f10ff1ebf37f4d3c63c3
> annotate: optimize line counting

Queued, thanks.

>
> We used len(text.splitlines()) to count lines.

Did I just hear circus music in the distance? *sigh*

> This allocates, copies, and
> deallocates an object for every line in a file. Instead, we use
> count("\n") to count newlines and adjust based on whether there's a
> trailing newline.
>
> This improves the speed of annotating localrepo.py from 4.2 to 4.0
> seconds.
>
> diff -r 8c8442523eef -r 218a9c673a2c mercurial/context.py
> --- a/mercurial/context.py	Tue May 17 11:28:46 2016 -0500
> +++ b/mercurial/context.py	Wed May 18 16:37:32 2016 -0500
> @@ -930,16 +930,20 @@
>          this returns fixed value(False is used) as linenumber,
>          if "linenumber" parameter is "False".'''
>
> +        def lines(text):
> +            if text.endswith("\n"):
> +                return text.count("\n")
> +            return text.count("\n") + 1
> +
>          if linenumber is None:
>              def decorate(text, rev):
> -                return ([rev] * len(text.splitlines()), text)
> +                return ([rev] * lines(text), text)
>          elif linenumber:
>              def decorate(text, rev):
> -                size = len(text.splitlines())
> -                return ([(rev, i) for i in xrange(1, size + 1)], text)
> +                return ([(rev, i) for i in xrange(1, lines(text) + 1)], text)
>          else:
>              def decorate(text, rev):
> -                return ([(rev, False)] * len(text.splitlines()), text)
> +                return ([(rev, False)] * lines(text), text)
>
>          def pair(parent, child):
>              blocks = mdiff.allblocks(parent[1], child[1], opts=diffopts,
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