Re: [PATCH v2] commit.c: use the generic "sha1_pos" function for lookup
From: Junio C Hamano <hidden>
Date: 2016-06-15 23:00:01
"Dmitry S. Dolzhenko" [off-list ref] writes:
Refactor binary search in "commit_graft_pos" function: use generic "sha1_pos" function. Signed-off-by: Dmitry S. Dolzhenko <redacted> ---
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.
quoted hunk
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)