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list-objects: convert name_path to a strbuf

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The "struct name_path" data is examined in only two places:
we generate it in process_tree(), and we convert it to a
single string in path_name(). Everyone else just passes it
through to those functions.

We can further note that process_tree() already keeps a
single strbuf with the leading tree path, for use with
tree_entry_interesting().

Instead of building a separate name_path linked list, let's
just use the one we already build in "base". This reduces
the amount of code (especially tricky code in path_name()
which did not check for integer overflows caused by deep
or large pathnames).

It is also more efficient in some instances.  Any time we
were using tree_entry_interesting, we were building up the
strbuf anyway, so this is an immediate and obvious win
there. In cases where we were not, we trade off storing
"pathname/" in a strbuf on the heap for each level of the
path, instead of two pointers and an int on the stack (with
one pointer into the tree object). On a 64-bit system, the
latter is 20 bytes; so if path components are less than that
on average, this has lower peak memory usage.  In practice
it probably doesn't matter either way; we are already
holding in memory all of the tree objects leading up to each
pathname, and for normal-depth pathnames, we are only
talking about hundreds of bytes.

This patch leaves "struct name_path" as a thin wrapper
around the strbuf, to avoid disrupting callbacks. We should
fix them, but leaving it out makes this diff easier to view.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2016-02-11 17:26:18 -05:00
committed by Junio C Hamano
parent 8eee9f9277
commit f3badaed51
3 changed files with 15 additions and 36 deletions
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22
list-objects.c
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@ -62,7 +62,6 @@ static void process_gitlink(struct rev_info *revs,
static void process_tree(struct rev_info *revs,
struct tree *tree,
show_object_fn show,
struct name_path *path,
struct strbuf *base,
const char *name,
void *cb_data)
@ -86,17 +85,14 @@ static void process_tree(struct rev_info *revs,
return;
die("bad tree object %s", sha1_to_hex(obj->sha1));
}
obj->flags |= SEEN;
show(obj, path, name, cb_data);
me.up = path;
me.elem = name;
me.elem_len = strlen(name);
if (!match) {
strbuf_addstr(base, name);
if (base->len)
strbuf_addch(base, '/');
}
obj->flags |= SEEN;
me.base = base;
show(obj, &me, name, cb_data);
strbuf_addstr(base, name);
if (base->len)
strbuf_addch(base, '/');
init_tree_desc(&desc, tree->buffer, tree->size);
@ -113,7 +109,7 @@ static void process_tree(struct rev_info *revs,
if (S_ISDIR(entry.mode))
process_tree(revs,
lookup_tree(entry.sha1),
show, &me, base, entry.path,
show, base, entry.path,
cb_data);
else if (S_ISGITLINK(entry.mode))
process_gitlink(revs, entry.sha1,
@ -220,7 +216,7 @@ void traverse_commit_list(struct rev_info *revs,
path = "";
if (obj->type == OBJ_TREE) {
process_tree(revs, (struct tree *)obj, show_object,
NULL, &base, path, data);
&base, path, data);
continue;
}
if (obj->type == OBJ_BLOB) {