midx: use `strset` for retained MIDX files

Both `clear_midx_files_ext()` and `clear_incremental_midx_files_ext()`
build a list of filenames to keep while pruning stale MIDX files. Today
they hand-roll an array instead of using a `strset`, thus requiring us
to pass an additional length parameter, and makes lookups linear.

Replace the bare array with a `strset` which can be passed around as a
single parameter. Though it improves lookup performance, the difference
is likely immeasurable given how small the keep_hashes array typically
is.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/midx.c b/midx.c
index 81d6ab11e6eb0ef0da4ecab0ee87a52ec71eced1..f75e3c9fa6dcfea1e2fe0b6ef00b38fb153c9efd 100644 (file)
--- a/midx.c
+++ b/midx.c
@@ -758,8 +758,7 @@ int midx_checksum_valid(struct multi_pack_index *m)
 }
 
 struct clear_midx_data {
-       char **keep;
-       uint32_t keep_nr;
+       struct strset keep;
        const char *ext;
 };
 
@@ -767,15 +766,12 @@ static void clear_midx_file_ext(const char *full_path, size_t full_path_len UNUS
                                const char *file_name, void *_data)
 {
        struct clear_midx_data *data = _data;
-       uint32_t i;
 
        if (!(starts_with(file_name, "multi-pack-index-") &&
              ends_with(file_name, data->ext)))
                return;
-       for (i = 0; i < data->keep_nr; i++) {
-               if (!strcmp(data->keep[i], file_name))
-                       return;
-       }
+       if (strset_contains(&data->keep, file_name))
+               return;
        if (unlink(full_path))
                die_errno(_("failed to remove %s"), full_path);
 }
@@ -783,48 +779,49 @@ static void clear_midx_file_ext(const char *full_path, size_t full_path_len UNUS
 void clear_midx_files_ext(struct odb_source *source, const char *ext,
                          const char *keep_hash)
 {
-       struct clear_midx_data data;
-       memset(&data, 0, sizeof(struct clear_midx_data));
+       struct clear_midx_data data = {
+               .keep = STRSET_INIT,
+               .ext = ext,
+       };
 
        if (keep_hash) {
-               ALLOC_ARRAY(data.keep, 1);
+               struct strbuf buf = STRBUF_INIT;
+               strbuf_addf(&buf, "multi-pack-index-%s.%s", keep_hash, ext);
+
+               strset_add(&data.keep, buf.buf);
 
-               data.keep[0] = xstrfmt("multi-pack-index-%s.%s", keep_hash, ext);
-               data.keep_nr = 1;
+               strbuf_release(&buf);
        }
-       data.ext = ext;
 
-       for_each_file_in_pack_dir(source->path,
-                                 clear_midx_file_ext,
-                                 &data);
+       for_each_file_in_pack_dir(source->path, clear_midx_file_ext, &data);
 
-       if (keep_hash)
-               free(data.keep[0]);
-       free(data.keep);
+       strset_clear(&data.keep);
 }
 
 void clear_incremental_midx_files_ext(struct odb_source *source, const char *ext,
                                      char **keep_hashes,
                                      uint32_t hashes_nr)
 {
-       struct clear_midx_data data;
+       struct clear_midx_data data = {
+               .keep = STRSET_INIT,
+               .ext = ext,
+       };
+       struct strbuf buf = STRBUF_INIT;
        uint32_t i;
 
-       memset(&data, 0, sizeof(struct clear_midx_data));
+       for (i = 0; i < hashes_nr; i++) {
+               strbuf_reset(&buf);
+               strbuf_addf(&buf, "multi-pack-index-%s.%s", keep_hashes[i],
+                           ext);
 
-       ALLOC_ARRAY(data.keep, hashes_nr);
-       for (i = 0; i < hashes_nr; i++)
-               data.keep[i] = xstrfmt("multi-pack-index-%s.%s", keep_hashes[i],
-                                      ext);
-       data.keep_nr = hashes_nr;
-       data.ext = ext;
+               strset_add(&data.keep, buf.buf);
+       }
 
        for_each_file_in_pack_subdir(source->path, "multi-pack-index.d",
                                     clear_midx_file_ext, &data);
 
-       for (i = 0; i < hashes_nr; i++)
-               free(data.keep[i]);
-       free(data.keep);
+       strbuf_release(&buf);
+       strset_clear(&data.keep);
 }
 
 void clear_midx_file(struct repository *r)