# [PATCH v2] commit.c: use the generic "sha1_pos" function for lookup 2 messages from 2014-02-26 to 2014-02-27. Participants: Dmitry S. Dolzhenko, Junio C Hamano. Thread: https://gitlist.dev/t/35963 ## Dmitry S. Dolzhenko, 2014-02-26 18:49 Subject: [PATCH v2] commit.c: use the generic "sha1_pos" function for lookup Message-ID: <530E3732.3060708@yandex.ru> URL: https://gitlist.dev/e/530E3732.3060708%40yandex.ru ``` Refactor binary search in "commit_graft_pos" function: use generic "sha1_pos" function. Signed-off-by: Dmitry S. Dolzhenko --- commit.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-) diff --git a/commit.c b/commit.c index 6bf4fe0..6ceee6a 100644 --- a/commit.c +++ b/commit.c @@ -10,6 +10,7 @@ #include "mergesort.h" #include "commit-slab.h" #include "prio-queue.h" +#include "sha1-lookup.h" static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **); @@ -114,23 +115,16 @@ static unsigned long parse_commit_date(const char *buf, const char *tail) static struct commit_graft **commit_graft; static int commit_graft_alloc, commit_graft_nr; +static const unsigned char *commit_graft_sha1_access(size_t index, void *table) +{ + struct commit_graft **commit_graft_table = table; + return commit_graft_table[index]->sha1; +} + static int commit_graft_pos(const unsigned char *sha1) { - int lo, hi; - lo = 0; - hi = commit_graft_nr; - while (lo < hi) { - int mi = (lo + hi) / 2; - struct commit_graft *graft = commit_graft[mi]; - int cmp = hashcmp(sha1, graft->sha1); - if (!cmp) - return mi; - if (cmp < 0) - hi = mi; - else - lo = mi + 1; - } - return -lo - 1; + return sha1_pos(sha1, commit_graft, commit_graft_nr, + commit_graft_sha1_access); } int register_commit_graft(struct commit_graft *graft, int ignore_dups) -- 1.8.3.2 ``` ## Junio C Hamano, 2014-02-27 19:06 Subject: Re: [PATCH v2] commit.c: use the generic "sha1_pos" function for lookup Message-ID: URL: https://gitlist.dev/e/xmqqppm8z86l.fsf%40gitster.dls.corp.google.com In-Reply-To: <530E3732.3060708@yandex.ru> ``` "Dmitry S. Dolzhenko" writes: > Refactor binary search in "commit_graft_pos" function: use > generic "sha1_pos" function. > > Signed-off-by: Dmitry S. Dolzhenko > --- Looks trivially correct; thanks. Looking at this patch makes me wonder why we have sha1_pos() and sha1_entry_pos() helper functions, though. It feels as if the former could be written in terms of the latter, but there may be some performance and correctness downsides if we did so: - rewriting sha1_entry_pos() in terms of sha1_pos() would add the cost of callback to obtain the keys; - sha1_entry_pos() picks the middle location conservatively to avoid overshooting penalty, which sha1_pos() does not do; - sha1_entry_pos() has been updated recently to tolerate duplicates. > commit.c | 24 +++++++++--------------- > 1 file changed, 9 insertions(+), 15 deletions(-) > > diff --git a/commit.c b/commit.c > index 6bf4fe0..6ceee6a 100644 > --- a/commit.c > +++ b/commit.c > @@ -10,6 +10,7 @@ > #include "mergesort.h" > #include "commit-slab.h" > #include "prio-queue.h" > +#include "sha1-lookup.h" > > static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **); > > @@ -114,23 +115,16 @@ static unsigned long parse_commit_date(const char *buf, const char *tail) > static struct commit_graft **commit_graft; > static int commit_graft_alloc, commit_graft_nr; > > +static const unsigned char *commit_graft_sha1_access(size_t index, void *table) > +{ > + struct commit_graft **commit_graft_table = table; > + return commit_graft_table[index]->sha1; > +} > + > static int commit_graft_pos(const unsigned char *sha1) > { > - int lo, hi; > - lo = 0; > - hi = commit_graft_nr; > - while (lo < hi) { > - int mi = (lo + hi) / 2; > - struct commit_graft *graft = commit_graft[mi]; > - int cmp = hashcmp(sha1, graft->sha1); > - if (!cmp) > - return mi; > - if (cmp < 0) > - hi = mi; > - else > - lo = mi + 1; > - } > - return -lo - 1; > + return sha1_pos(sha1, commit_graft, commit_graft_nr, > + commit_graft_sha1_access); > } > > int register_commit_graft(struct commit_graft *graft, int ignore_dups) ```