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midx.c: write MIDX filenames to strbuf

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To ask for the name of a MIDX and its corresponding .rev file, callers
invoke get_midx_filename() and get_midx_rev_filename(), respectively.
These both invoke xstrfmt(), allocating a chunk of memory which must be
freed later on.

This makes callers in pack-bitmap.c somewhat awkward. Specifically,
midx_bitmap_filename(), which is implemented like:

    return xstrfmt("%s-%s.bitmap",
                   get_midx_filename(midx->object_dir),
                   hash_to_hex(get_midx_checksum(midx)));

this leaks the second argument to xstrfmt(), which itself was allocated
with xstrfmt(). This caller could assign both the result of
get_midx_filename() and the outer xstrfmt() to a temporary variable,
remembering to free() the former before returning. But that involves a
wasteful copy.

Instead, get_midx_filename() and get_midx_rev_filename() take a strbuf
as an output parameter. This way midx_bitmap_filename() can manipulate
and pass around a temporary buffer which it detaches back to its caller.

That allows us to implement the function without copying or open-coding
get_midx_filename() in a way that doesn't leak.

Update the other callers of get_midx_filename() and
get_midx_rev_filename() accordingly.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2021-10-26 17:01:21 -04:00
committed by Junio C Hamano
parent ee4a1d63d7
commit 60980aed78
4 changed files with 49 additions and 37 deletions
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8
pack-revindex.c
View File

@@ -296,14 +296,14 @@ int load_pack_revindex(struct packed_git *p)
int load_midx_revindex(struct multi_pack_index *m)
{
char *revindex_name;
struct strbuf revindex_name = STRBUF_INIT;
int ret;
if (m->revindex_data)
return 0;
revindex_name = get_midx_rev_filename(m);
get_midx_rev_filename(&revindex_name, m);
ret = load_revindex_from_disk(revindex_name,
ret = load_revindex_from_disk(revindex_name.buf,
m->num_objects,
&m->revindex_map,
&m->revindex_len);
@@ -313,7 +313,7 @@ int load_midx_revindex(struct multi_pack_index *m)
m->revindex_data = (const uint32_t *)((const char *)m->revindex_map + RIDX_HEADER_SIZE);
cleanup:
free(revindex_name);
strbuf_release(&revindex_name);
return ret;
}