Johannes Schindelin <Johannes.Schindelin@xxxxxx> writes:
> Certain codepaths (notably "git log --pretty=format...") use
> prefixcmp() extensively, with very short prefixes. In those cases,
> calling strlen() is a wasteful operation, so avoid it.
>
> Initial patch by Marco Costalba.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
> ---
>
> On Sat, 29 Dec 2007, Marco Costalba wrote:
>
> > In case the prefix string is a single char avoid a costly call
> > to strlen() + strncmp()
>
> Could you test this patch, please?
>
> Not only does it avoid the strlen() call also for longer prefixes;
> it also avoids a C++ comment.
>
> git-compat-util.h | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/git-compat-util.h b/git-compat-util.h
> index 79eb10e..7059cbd 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -398,7 +398,11 @@ static inline int sane_case(int x, int high)
>
> static inline int prefixcmp(const char *str, const char *prefix)
> {
> - return strncmp(str, prefix, strlen(prefix));
> + for (; ; str++, prefix++)
> + if (!*prefix)
> + return 0;
> + else if (*str != *prefix)
> + return (unsigned char)*prefix - (unsigned char)*str;
> }
Losing the unnecessary check for !str || !prefix is a good
change.
While I think, for the readability's sake, Marco's original
without the unnecessary check would be the way to go, a profile
from your totally inlined version would also be interesting, as
it may or may not beat the underlying strncmp(), which could be
highly optimized.
-
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