From: Jeff King <peff@peff•net>
To: Git List <git@vger•kernel.org>
Cc: Junio C Hamano <gitster@pobox•com>, Wink Saville <wink@saville•com>
Subject: [PATCH 08/14] tree-diff: pass whole path string to path_appendnew()
Date: Thu, 9 Jan 2025 03:49:07 -0500 [thread overview]
Message-ID: <20250109084907.GH2748836@coredump.intra.peff.net> (raw)
In-Reply-To: <20250109082723.GA2748497@coredump.intra.peff.net>
When diffing trees, we'll have a strbuf "base" containing the
slash-separted names of our parent trees, and a "path" string
representing an entry name from the current tree. We pass these
separately to path_appendnew(), which combines them to form a single
path string in the combine_diff_path struct.
Instead, let's append the path string to our base strbuf ourselves, pass
in the result, and then roll it back with strbuf_setlen(). This lets us
simplify path_appendnew() a bit, enabling further refactoring.
And while it might seem like this causes extra wasted allocations, it
does not in practice. We reuse the same strbuf for each tree entry, so
we only have to allocate it to match the largest name. Plus, in a
recursive diff we'll end up doing this same operation to extend the base
for the next level of recursion. So we're really just incurring a small
memcpy().
Signed-off-by: Jeff King <peff@peff•net>
---
tree-diff.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/tree-diff.c b/tree-diff.c
index 22fc2d8f8c..d2f8dd14a6 100644
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -129,20 +129,18 @@ static int emit_diff_first_parent_only(struct diff_options *opt, struct combine_
* and append it to paths list tail.
*/
static struct combine_diff_path *path_appendnew(struct combine_diff_path *last,
- int nparent, const struct strbuf *base, const char *path, int pathlen,
+ int nparent, const char *path, size_t len,
unsigned mode, const struct object_id *oid)
{
struct combine_diff_path *p;
- size_t len = st_add(base->len, pathlen);
size_t alloclen = combine_diff_path_size(nparent, len);
p = xmalloc(alloclen);
p->next = NULL;
last->next = p;
p->path = (char *)&(p->parent[nparent]);
- memcpy(p->path, base->buf, base->len);
- memcpy(p->path + base->len, path, pathlen);
+ memcpy(p->path, path, len);
p->path[len] = 0;
p->mode = mode;
oidcpy(&p->oid, oid ? oid : null_oid());
@@ -206,7 +204,10 @@ static struct combine_diff_path *emit_path(struct combine_diff_path *p,
if (emitthis) {
int keep;
struct combine_diff_path *pprev = p;
- p = path_appendnew(p, nparent, base, path, pathlen, mode, oid);
+
+ strbuf_add(base, path, pathlen);
+ p = path_appendnew(p, nparent, base->buf, base->len, mode, oid);
+ strbuf_setlen(base, old_baselen);
for (i = 0; i < nparent; ++i) {
/*
--
2.48.0.rc2.413.gc1c80375a3
next prev parent reply other threads:[~2025-01-09 8:49 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-03 19:28 [BUGREPORT] git diff-tree --cc SEGFAUTs Wink Saville
2025-01-03 20:46 ` Jeff King
2025-01-03 23:34 ` Wink Saville
2025-01-04 0:31 ` Jeff King
2025-01-04 2:55 ` Junio C Hamano
2025-01-04 3:32 ` Jeff King
2025-01-04 18:09 ` Wink Saville
2025-01-05 22:13 ` Wink Saville
2025-01-09 8:27 ` [PATCH 0/14] combine-diff cleanups Jeff King
2025-01-09 8:28 ` [PATCH 01/14] run_diff_files(): delay allocation of combine_diff_path Jeff King
2025-01-09 17:57 ` Junio C Hamano
2025-01-09 8:32 ` [PATCH 02/14] combine-diff: add combine_diff_path_new() Jeff King
2025-01-09 18:05 ` Junio C Hamano
2025-01-13 15:40 ` Patrick Steinhardt
2025-01-14 9:29 ` Jeff King
2025-01-09 8:33 ` [PATCH 03/14] tree-diff: clear parent array in path_appendnew() Jeff King
2025-01-09 18:28 ` Junio C Hamano
2025-01-10 10:54 ` Jeff King
2025-01-09 8:42 ` [PATCH 04/14] combine-diff: use pointer for parent paths Jeff King
2025-01-09 18:49 ` Junio C Hamano
2025-01-09 8:42 ` [PATCH 05/14] diff: add a comment about combine_diff_path.parent.path Jeff King
2025-01-13 15:40 ` Patrick Steinhardt
2025-01-09 8:44 ` [PATCH 06/14] run_diff_files(): de-mystify the size of combine_diff_path struct Jeff King
2025-01-10 16:40 ` Junio C Hamano
2025-01-09 8:46 ` [PATCH 07/14] tree-diff: drop path_appendnew() alloc optimization Jeff King
2025-01-13 15:40 ` Patrick Steinhardt
2025-01-14 10:30 ` Jeff King
2025-01-09 8:49 ` Jeff King [this message]
2025-01-13 15:40 ` [PATCH 08/14] tree-diff: pass whole path string to path_appendnew() Patrick Steinhardt
2025-01-14 9:26 ` Jeff King
2025-01-09 8:49 ` [PATCH 09/14] tree-diff: inline path_appendnew() Jeff King
2025-01-11 0:41 ` Junio C Hamano
2025-01-09 8:50 ` [PATCH 10/14] combine-diff: drop public declaration of combine_diff_path_size() Jeff King
2025-01-09 8:51 ` [PATCH 11/14] tree-diff: drop list-tail argument to diff_tree_paths() Jeff King
2025-01-18 0:33 ` Junio C Hamano
2025-01-09 8:53 ` [PATCH 12/14] tree-diff: use the name "tail" to refer to list tail Jeff King
2025-01-09 8:54 ` [PATCH 13/14] tree-diff: simplify emit_path() list management Jeff King
2025-01-09 8:57 ` [PATCH 14/14] tree-diff: make list tail-passing more explicit Jeff King
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