list-objects: convert name_path to a strbuf

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>

diff --git a/list-objects.c b/list-objects.c
index 41736d2..dc46b9a 100644 (file)
--- a/list-objects.c
+++ b/list-objects.c
@@ -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, '/');
-       }
+       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) {

diff --git a/revision.c b/revision.c
index cf544b6..f8c3034 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -23,26 +23,11 @@ volatile show_early_output_fn_t show_early_output;
 
 char *path_name(const struct name_path *path, const char *name)
 {
-       const struct name_path *p;
-       char *n, *m;
-       int nlen = strlen(name);
-       int len = nlen + 1;
-
-       for (p = path; p; p = p->up) {
-               if (p->elem_len)
-                       len += p->elem_len + 1;
-       }
-       n = xmalloc(len);
-       m = n + len - (nlen + 1);
-       strcpy(m, name);
-       for (p = path; p; p = p->up) {
-               if (p->elem_len) {
-                       m -= p->elem_len + 1;
-                       memcpy(m, p->elem, p->elem_len);
-                       m[p->elem_len] = '/';
-               }
-       }
-       return n;
+       struct strbuf ret = STRBUF_INIT;
+       if (path)
+               strbuf_addbuf(&ret, path->base);
+       strbuf_addstr(&ret, name);
+       return strbuf_detach(&ret, NULL);
 }
 
 void show_object_with_name(FILE *out, struct object *obj,

diff --git a/revision.h b/revision.h
index 0ea8b4e..5e3c47c 100644 (file)
--- a/revision.h
+++ b/revision.h
@@ -257,9 +257,7 @@ extern void mark_parents_uninteresting(struct commit *commit);
 extern void mark_tree_uninteresting(struct tree *tree);
 
 struct name_path {
-       struct name_path *up;
-       int elem_len;
-       const char *elem;
+       struct strbuf *base;
 };
 
 char *path_name(const struct name_path *path, const char *name);