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[PATCH v2 1/4] midx: access pack names through `nth_midxed_pack_name()`

From
Taylor Blau <me@ttaylorr.com>
Date
May 28, 2025, 22:59 UTC
Message-ID
<d3508d3cfbddb512dbca4c2177731fffb5827084.1748473122.git.me@ttaylorr.com>
In-Reply-To
<cover.1748473122.git.me@ttaylorr.com>

Accessing a MIDX's 'pack_names' array is somewhat error-prone when dealing with incremental MIDX chains, where the (global) pack_int_id for some pack may differ from the containing layer's index for that pack.

Introduce `nth_midxed_pack_name()` in an effort to reduce a common source of errors by discouraging external callers from accessing a layer's `pack_names` array directly.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 midx.c                    | 7 +++++++
 midx.h                    | 2 ++
 pack-bitmap.c             | 4 ++--
 t/helper/test-read-midx.c | 7 ++++---
 4 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/midx.c b/midx.c
index cd6e766ce2..6705e77881 100644
--- a/midx.c
+++ b/midx.c
@@ -506,6 +506,13 @@ struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
 	return m->packs[local_pack_int_id];
 }
 
+const char *nth_midxed_pack_name(struct multi_pack_index *m,
+				 uint32_t pack_int_id)
+{
+	uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id);
+	return m->pack_names[local_pack_int_id];
+}
+
 #define MIDX_CHUNK_BITMAPPED_PACKS_WIDTH (2 * sizeof(uint32_t))
 
 int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
diff --git a/midx.h b/midx.h
index 9d1374cbd5..0fb490f4d4 100644
--- a/midx.h
+++ b/midx.h
@@ -107,6 +107,8 @@ struct multi_pack_index *load_multi_pack_index(struct repository *r,
 int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
 struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
 				   uint32_t pack_int_id);
+const char *nth_midxed_pack_name(struct multi_pack_index *m,
+				 uint32_t pack_int_id);
 int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
 		       struct bitmapped_pack *bp, uint32_t pack_int_id);
 int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
diff --git a/pack-bitmap.c b/pack-bitmap.c
index b9f1d86604..8ddc150778 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -490,7 +490,7 @@ static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
 	for (i = 0; i < bitmap_git->midx->num_packs + bitmap_git->midx->num_packs_in_base; i++) {
 		if (prepare_midx_pack(bitmap_repo(bitmap_git), bitmap_git->midx, i)) {
 			warning(_("could not open pack %s"),
-				bitmap_git->midx->pack_names[i]);
+				nth_midxed_pack_name(bitmap_git->midx, i));
 			goto cleanup;
 		}
 	}
@@ -2469,7 +2469,7 @@ void reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
 			struct bitmapped_pack pack;
 			if (nth_bitmapped_pack(r, bitmap_git->midx, &pack, i) < 0) {
 				warning(_("unable to load pack: '%s', disabling pack-reuse"),
-					bitmap_git->midx->pack_names[i]);
+					nth_midxed_pack_name(bitmap_git->midx, i));
 				free(packs);
 				return;
 			}
diff --git a/t/helper/test-read-midx.c b/t/helper/test-read-midx.c
index ac81390899..fbed0f6919 100644
--- a/t/helper/test-read-midx.c
+++ b/t/helper/test-read-midx.c
@@ -53,8 +53,9 @@ static int read_midx_file(const char *object_dir, const char *checksum,
 	printf("\nnum_objects: %d\n", m->num_objects);
 
 	printf("packs:\n");
-	for (i = 0; i < m->num_packs; i++)
-		printf("%s\n", m->pack_names[i]);
+	for (i = m->num_packs_in_base; i < m->num_packs + m->num_packs_in_base;
+	     i++)
+		printf("%s\n", nth_midxed_pack_name(m, i));
 
 	printf("object-dir: %s\n", m->object_dir);
 
@@ -108,7 +109,7 @@ static int read_midx_preferred_pack(const char *object_dir)
 		return 1;
 	}
 
-	printf("%s\n", midx->pack_names[preferred_pack]);
+	printf("%s\n", nth_midxed_pack_name(midx, preferred_pack));
 	close_midx(midx);
 	return 0;
 }
-- 
2.49.0.640.ga4de40e6a8
Previous: Taylor BlauNext: Junio C Hamano
Message 36 of 53 in “packfile: avoid access(3p) calls for missing packs”
  1. packfile: avoid access(3p) calls for missing packsPatrick Steinhardt, May 16, 2025
  2. Junio C HamanoMay 16, 2025
  3. Jeff KingMay 19, 2025
  4. Junio C HamanoMay 19, 2025
  5. Patrick SteinhardtMay 20, 2025
  6. Jeff KingMay 22, 2025
  7. Taylor BlauMay 23, 2025
  8. Jeff KingMay 23, 2025
  9. 0/2 packfile: avoid access(3p) calls for missing packsPatrick Steinhardt, May 20, 2025
  10. 1/2 packfile: explain ordering of how we look up auxiliary pack filesPatrick Steinhardt, May 20, 2025
  11. Taylor BlauMay 23, 2025
  12. 2/2 midx: stop repeatedly looking up nonexistent packfilesPatrick Steinhardt, May 20, 2025
  13. Jeff KingMay 22, 2025
  14. Junio C HamanoMay 22, 2025
  15. Jeff KingMay 22, 2025
  16. Junio C HamanoMay 22, 2025
  17. Taylor BlauMay 23, 2025
  18. Jeff KingMay 23, 2025
  19. Taylor BlauMay 23, 2025
  20. 0/5 midx: improve prepare_midx_pack() ergonomicsTaylor Blau, May 25, 2025
  21. 1/5 pack-bitmap.c: fix broken warning() when missing MIDX'd packTaylor Blau, May 25, 2025
  22. Patrick SteinhardtMay 26, 2025
  23. Taylor BlauMay 28, 2025
  24. 2/5 midx-write.c: guard against incremental MIDXs in want_included_pack()Taylor Blau, May 25, 2025
  25. Patrick SteinhardtMay 26, 2025
  26. Taylor BlauMay 28, 2025
  27. 3/5 midx-write.c: simplify fill_packs_from_midx()Taylor Blau, May 25, 2025
  28. Patrick SteinhardtMay 26, 2025
  29. Taylor BlauMay 28, 2025
  30. 4/5 midx-write.c: extract inner loop from fill_packs_from_midx()Taylor Blau, May 25, 2025
  31. 5/5 midx: return a `packed_git` pointer from `prepare_midx_pack()`Taylor Blau, May 25, 2025
  32. Patrick SteinhardtMay 26, 2025
  33. Taylor BlauMay 28, 2025
  34. Patrick SteinhardtMay 28, 2025
  35. 0/4 midx: improve prepare_midx_pack() ergonomicsTaylor Blau, May 28, 2025
  36. 1/4 midx: access pack names through `nth_midxed_pack_name()`Taylor Blau, May 28, 2025
  37. Junio C HamanoMay 29, 2025
  38. Taylor BlauJun 3, 2025
  39. Junio C HamanoMay 29, 2025
  40. Taylor BlauJun 3, 2025
  41. 2/4 midx-write.c: guard against incremental MIDXs in want_included_pack()Taylor Blau, May 28, 2025
  42. 3/4 midx-write.c: extract inner loop from fill_packs_from_midx()Taylor Blau, May 28, 2025
  43. 4/4 midx: return a `packed_git` pointer from `prepare_midx_pack()`Taylor Blau, May 28, 2025
  44. Jeff KingMay 30, 2025
  45. Taylor BlauJun 3, 2025
  46. Junio C HamanoAug 28, 2025
  47. Taylor BlauMay 23, 2025
  48. Jeff KingMay 23, 2025
  49. Junio C HamanoMay 21, 2025
  50. 0/2 packfile: avoid access(3p) calls for missing packsPatrick Steinhardt, May 28, 2025
  51. 2/2 midx: stop repeatedly looking up nonexistent packfilesPatrick Steinhardt, May 28, 2025
  52. 1/2 packfile: explain ordering of how we look up auxiliary pack filesPatrick Steinhardt, May 28, 2025
  53. Jeff KingMay 30, 2025

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