Hello,

This is a first step to make handle sha256 object ids in pack files.
It is also the messiest and the one I'm less sure about.

The `sorted_ids' field is an "array" of 20-bytes SHA1 digests
currently, but in sha256 repos it is made of 40-bytes SHA256 digests.

I'm trying to make it "opaque" and providing a macro for lower-level
code to access it and retiring the struct got_packidx_object_id that
is now completely unused.  I'm still not completely sold on the way
I've handled it, but it's the best idea I could come up with.

I'm also introducing some helpers: got_hash_digest_length and
got_hash_digest_string_length that I'm starting to use but will come
in handy way more in the future.

As always, all these GOT_HASH_SHA1 will be "bubbled up" soon and stop
being hardcoded.

diff refs/heads/main refs/heads/w
commit - 3fa763e5f0869e218fa64750c375a84b706c6f92
commit + 429d1d8c1a59c44d846147442d4e6385d2536d61
blob - 1405a67ac335af59f8e1c2f04ac566ecd07436e7
blob + 5c5eda14f6f68eb22642b1b51f17e933a403026c
--- lib/got_lib_hash.h
+++ lib/got_lib_hash.h
@@ -28,6 +28,32 @@ struct got_hash {
 int got_parse_object_id(struct got_object_id *, const char *,
     enum got_hash_algorithm);
 
+static inline int
+got_hash_digest_length(enum got_hash_algorithm algo)
+{
+	switch (algo) {
+	case GOT_HASH_SHA1:
+		return SHA1_DIGEST_LENGTH;
+	case GOT_HASH_SHA256:
+		return SHA256_DIGEST_LENGTH;
+	default:
+		return 0;
+	}
+}
+
+static inline int
+got_hash_digest_string_length(enum got_hash_algorithm algo)
+{
+	switch (algo) {
+	case GOT_HASH_SHA1:
+		return SHA1_DIGEST_STRING_LENGTH;
+	case GOT_HASH_SHA256:
+		return SHA256_DIGEST_STRING_LENGTH;
+	default:
+		return 0;
+	}
+}
+
 struct got_hash {
 	SHA1_CTX		 sha1_ctx;
 	SHA2_CTX		 sha256_ctx;
blob - 188c28e9e67bdc37146176e911d6226b223c40d2
blob + e1279d24139787a085f780a37632bf4b34e151be
--- lib/got_lib_pack.h
+++ lib/got_lib_pack.h
@@ -67,10 +67,6 @@ struct got_packidx_object_id {
 	u_int8_t	packidx_sha1[SHA1_DIGEST_LENGTH];
 } __attribute__((__packed__));
 
-struct got_packidx_object_id {
-	u_int8_t sha1[SHA1_DIGEST_LENGTH];
-} __attribute__((__packed__));
-
 /* Ignore pack index version 1 which is no longer written by Git. */
 #define GOT_PACKIDX_VERSION 2
 
@@ -90,8 +86,11 @@ struct got_packidx_v2_hdr {
 	uint32_t	*fanout_table;	/* values are big endian */
 #define GOT_PACKIDX_V2_FANOUT_TABLE_ITEMS (0xff + 1)
 
-	/* Sorted SHA1 checksums for each object in the pack file. */
-	struct got_packidx_object_id *sorted_ids;
+	/*
+	 * Sorted hash digest for each object in the pack file.
+	 * Exact size depends on the repository object format.
+	 */
+	void *sorted_ids;
 
 	/* CRC32 of the packed representation of each object. */
 	uint32_t	*crc32;
@@ -129,6 +128,9 @@ struct got_packfile_hdr {
 	struct got_pack_large_offset_index *sorted_large_offsets;
 };
 
+#define GOT_PACKIDX_GET_OBJECT(packidx, n) \
+    ((packidx)->hdr.sorted_ids + (n) * got_hash_digest_length(GOT_HASH_SHA1))
+
 struct got_packfile_hdr {
 	uint32_t	signature;
 #define GOT_PACKFILE_SIGNATURE	0x5041434b	/* 'P' 'A' 'C' 'K' */
blob - af03219f49ee499a7c4d1a39e802bc0773762f06
blob + 65be0482c78ef9765651a657fb61215530a56b4e
--- lib/pack.c
+++ lib/pack.c
@@ -182,14 +182,13 @@ got_packidx_init_hdr(struct got_packidx *p, int verify
 	remain -= len_fanout;
 
 	nobj = be32toh(h->fanout_table[0xff]);
-	len_ids = nobj * sizeof(*h->sorted_ids);
+	len_ids = nobj * got_hash_digest_length(algo);
 	if (len_ids <= nobj || len_ids > remain) {
 		err = got_error(GOT_ERR_BAD_PACKIDX);
 		goto done;
 	}
 	if (p->map)
-		h->sorted_ids =
-		    (struct got_packidx_object_id *)((uint8_t*)(p->map + offset));
+		h->sorted_ids = p->map + offset;
 	else {
 		h->sorted_ids = malloc(len_ids);
 		if (h->sorted_ids == NULL) {
@@ -498,12 +497,13 @@ got_packidx_get_object_idx(struct got_packidx *packidx
 		left = be32toh(packidx->hdr.fanout_table[id0 - 1]);
 
 	while (left <= right) {
-		struct got_packidx_object_id *oid;
+		void *oid;
 		int i, cmp;
 
 		i = ((left + right) / 2);
-		oid = &packidx->hdr.sorted_ids[i];
-		cmp = memcmp(id->sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
+		cmp = memcmp(id->sha1, oid,
+		    got_hash_digest_length(GOT_HASH_SHA1));
 		if (cmp == 0)
 			return i;
 		else if (cmp > 0)
@@ -653,13 +653,15 @@ got_packidx_get_object_id(struct got_object_id *id,
     struct got_packidx *packidx, int idx)
 {
 	uint32_t totobj = be32toh(packidx->hdr.fanout_table[0xff]);
-	struct got_packidx_object_id *oid;
+	void *oid;
+	size_t idlen;
 
 	if (idx < 0 || idx >= totobj)
 		return got_error(GOT_ERR_NO_OBJ);
 
-	oid = &packidx->hdr.sorted_ids[idx];
-	memcpy(id->sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
+	oid = GOT_PACKIDX_GET_OBJECT(packidx, idx);
+	memcpy(id->sha1, oid, idlen);
 	return NULL;
 }
 
@@ -672,7 +674,7 @@ got_packidx_match_id_str_prefix(struct got_object_id_q
 	uint32_t totobj = be32toh(packidx->hdr.fanout_table[0xff]);
 	char hex[3];
 	size_t prefix_len = strlen(id_str_prefix);
-	struct got_packidx_object_id *oid;
+	uint8_t *oid;
 	uint32_t i = 0;
 
 	STAILQ_INIT(matched_ids);
@@ -688,18 +690,18 @@ got_packidx_match_id_str_prefix(struct got_object_id_q
 
 	if (id0 > 0)
 		i = be32toh(packidx->hdr.fanout_table[id0 - 1]);
-	oid = &packidx->hdr.sorted_ids[i];
-	while (i < totobj && oid->sha1[0] == id0) {
+	oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
+	while (i < totobj && oid[0] == id0) {
 		char id_str[SHA1_DIGEST_STRING_LENGTH];
 		struct got_object_qid *qid;
 		int cmp;
 
-		if (!got_sha1_digest_to_str(oid->sha1, id_str, sizeof(id_str)))
+		if (!got_sha1_digest_to_str(oid, id_str, sizeof(id_str)))
 		        return got_error(GOT_ERR_NO_SPACE);
 
 		cmp = strncmp(id_str, id_str_prefix, prefix_len);
 		if (cmp < 0) {
-			oid = &packidx->hdr.sorted_ids[++i];
+			oid = GOT_PACKIDX_GET_OBJECT(packidx, ++i);
 			continue;
 		} else if (cmp > 0)
 			break;
@@ -707,10 +709,11 @@ got_packidx_match_id_str_prefix(struct got_object_id_q
 		err = got_object_qid_alloc_partial(&qid);
 		if (err)
 			break;
-		memcpy(qid->id.sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+		memcpy(qid->id.sha1, oid,
+		    got_hash_digest_length(GOT_HASH_SHA1));
 		STAILQ_INSERT_TAIL(matched_ids, qid, entry);
 
-		oid = &packidx->hdr.sorted_ids[++i];
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, ++i);
 	}
 
 	if (err)
blob - 25889d5c1fc15e6c52fd8f251cc2c9c692d0cbcf
blob + a6918ffc21e8236686568168477e68ee4b901965
--- lib/pack_index.c
+++ lib/pack_index.c
@@ -474,17 +474,16 @@ find_object_idx(struct got_packidx *packidx, uint8_t *
 	uint32_t nindexed = be32toh(packidx->hdr.fanout_table[0xff]);
 	int left = 0, right = nindexed - 1;
 	int cmp = 0, i = 0;
+	void *oid;
 
 	if (id0 > 0)
 		left = be32toh(packidx->hdr.fanout_table[id0 - 1]);
 
 	while (left <= right) {
-		struct got_packidx_object_id *oid;
-
 		i = ((left + right) / 2);
-		oid = &packidx->hdr.sorted_ids[i];
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
 
-		cmp = memcmp(sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+		cmp = memcmp(sha1, oid, got_hash_digest_length(GOT_HASH_SHA1));
 		if (cmp == 0)
 			return -1; /* object already indexed */
 		else if (cmp > 0)
@@ -506,8 +505,10 @@ print_packidx(struct got_packidx *packidx)
 	fprintf(stderr, "object IDs:\n");
 	for (i = 0; i < nindexed; i++) {
 		char hex[SHA1_DIGEST_STRING_LENGTH];
-		got_sha1_digest_to_str(packidx->hdr.sorted_ids[i].sha1,
-		    hex, sizeof(hex));
+		void *oid;
+
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
+		got_sha1_digest_to_str(oid, hex, sizeof(hex));
 		fprintf(stderr, "%s\n", hex);
 	}
 	fprintf(stderr, "\n");
@@ -535,10 +536,11 @@ add_indexed_object(struct got_packidx *packidx, uint32
 add_indexed_object(struct got_packidx *packidx, uint32_t idx,
     struct got_indexed_object *obj)
 {
+	void *oid;
 	int i;
 
-	memcpy(packidx->hdr.sorted_ids[idx].sha1, obj->id.sha1,
-	    SHA1_DIGEST_LENGTH);
+	oid = GOT_PACKIDX_GET_OBJECT(packidx, idx);
+	memcpy(oid, obj->id.sha1, got_hash_digest_length(GOT_HASH_SHA1));
 	packidx->hdr.crc32[idx] = htobe32(obj->crc);
 	if (obj->off < GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX)
 		packidx->hdr.offsets[idx] = htobe32(obj->off);
@@ -593,15 +595,17 @@ update_packidx(struct got_packidx *packidx, uint32_t n
     struct got_indexed_object *obj)
 {
 	int idx;
+	size_t idlen;
 	uint32_t nindexed = be32toh(packidx->hdr.fanout_table[0xff]);
 
 	idx = find_object_idx(packidx, obj->id.sha1);
 	if (idx == -1)
 		return; /* object already indexed */
 
-	memmove(&packidx->hdr.sorted_ids[idx + 1],
-	    &packidx->hdr.sorted_ids[idx],
-	    sizeof(struct got_packidx_object_id) * (nindexed - idx));
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
+	memmove(packidx->hdr.sorted_ids + (idx + 1) * idlen,
+	    packidx->hdr.sorted_ids + idx * idlen,
+	    idlen * (nindexed - idx));
 	memmove(&packidx->hdr.offsets[idx + 1], &packidx->hdr.offsets[idx],
 	    sizeof(uint32_t) * (nindexed - idx));
 
@@ -703,7 +707,7 @@ got_pack_index(struct got_pack *pack, int idxfd, FILE 
 		goto done;
 	}
 	packidx.hdr.sorted_ids = calloc(nobj,
-	    sizeof(struct got_packidx_object_id));
+	    got_hash_digest_length(GOT_HASH_SHA1));
 	if (packidx.hdr.sorted_ids == NULL) {
 		err = got_error_from_errno("calloc");
 		goto done;
@@ -946,7 +950,7 @@ got_pack_index(struct got_pack *pack, int idxfd, FILE 
 	if (err)
 		goto done;
 	err = got_pack_hwrite(idxfd, packidx.hdr.sorted_ids,
-	    nobj * SHA1_DIGEST_LENGTH, &ctx);
+	    nobj * got_hash_digest_length(GOT_HASH_SHA1), &ctx);
 	if (err)
 		goto done;
 	err = got_pack_hwrite(idxfd, packidx.hdr.crc32,
blob - 6a757d85bc1ec107e2faa5b5d8a2f03388bef3d7
blob + 49925f8b0ef27e9fbec7746b9864f16867c3a53c
--- lib/repository.c
+++ lib/repository.c
@@ -1156,9 +1156,10 @@ add_packidx_bloom_filter(struct got_repository *repo,
 	/* Minimum size supported by our bloom filter is 1000 entries. */
 	bloom_init(bf->bloom, nobjects < 1000 ? 1000 : nobjects, 0.1);
 	for (i = 0; i < nobjects; i++) {
-		struct got_packidx_object_id *id;
-		id = &packidx->hdr.sorted_ids[i];
-		bloom_add(bf->bloom, id->sha1, sizeof(id->sha1));
+		void *oid;
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
+		bloom_add(bf->bloom, oid,
+		    got_hash_digest_length(GOT_HASH_SHA1));
 	}
 
 	RB_INSERT(got_packidx_bloom_filter_tree,
blob - 48bed8a15e5f885c25ca796741f37fb70f1b87e3
blob + bb16d00bb2cbcef62005ced69f00144a9f994a96
--- lib/repository_admin.c
+++ lib/repository_admin.c
@@ -558,7 +558,7 @@ got_repo_list_pack(FILE *packfile, struct got_object_i
 
 	nobj = be32toh(packidx->hdr.fanout_table[0xff]);
 	for (i = 0; i < nobj; i++) {
-		struct got_packidx_object_id *oid;
+		void *oid;
 		struct got_object_id id, base_id;
 		off_t offset, base_offset = 0;
 		uint8_t type;
@@ -570,8 +570,9 @@ got_repo_list_pack(FILE *packfile, struct got_object_i
 			if (err)
 				break;
 		}
-		oid = &packidx->hdr.sorted_ids[i];
-		memcpy(id.sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+		oid = GOT_PACKIDX_GET_OBJECT(packidx, i);
+		memset(&id, 0, sizeof(id));
+		memcpy(id.sha1, oid, got_hash_digest_length(GOT_HASH_SHA1));
 
 		offset = got_packidx_get_object_offset(packidx, i);
 		if (offset == -1) {