This is needed for upcoming work on sha256 pack file handling.  We can't
assume that the sorted_id field in pack files is made by
SHA1_DIGEST_LENGTH objects.  This is probably not the prettiest but
works in practice, is it acceptable?

diff 03a62f6dd737910257cd4602766adca863cc8811 39ed7bd6df2cf61cb90dc543a311aa09ecb9a74f
commit - 03a62f6dd737910257cd4602766adca863cc8811
commit + 39ed7bd6df2cf61cb90dc543a311aa09ecb9a74f
blob - 88c77f6eb9da4d589aefd2ed3e9539327d379e53
blob + 3142e9056bb96d9e90120d4a1b1a6bf9e09e937a
--- lib/got_lib_hash.h
+++ lib/got_lib_hash.h
@@ -36,6 +36,32 @@ char *got_object_id_hex(struct got_object_id *, char *
 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 - 08acf40b3e797365f5cc41914e99e091f0f09fe7
blob + e813447f99bea12da2a2e63fe9373bd05dd76ea0
--- lib/got_lib_pack.h
+++ lib/got_lib_pack.h
@@ -67,10 +67,6 @@ struct got_packidx_trailer {
 	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;
blob - 84302f45b8db014cc23483d23a273c03f7fa077c
blob + f0abad5b3a94221383e81ecf1f6f34f1f238ecd9
--- lib/pack.c
+++ lib/pack.c
@@ -183,14 +183,13 @@ 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) {
@@ -493,17 +492,19 @@ got_packidx_get_object_idx(struct got_packidx *packidx
 	u_int8_t id0 = id->sha1[0];
 	uint32_t totobj = be32toh(packidx->hdr.fanout_table[0xff]);
 	int left = 0, right = totobj - 1;
+	size_t idlen;
 
 	if (id0 > 0)
 		left = be32toh(packidx->hdr.fanout_table[id0 - 1]);
 
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
 	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 = packidx->hdr.sorted_ids + i * idlen;
+		cmp = memcmp(id->sha1, oid, idlen);
 		if (cmp == 0)
 			return i;
 		else if (cmp > 0)
@@ -653,13 +654,15 @@ 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 = packidx->hdr.sorted_ids + idx * idlen;
+	memcpy(id->sha1, oid, idlen);
 	return NULL;
 }
 
@@ -671,8 +674,8 @@ got_packidx_match_id_str_prefix(struct got_object_id_q
 	u_int8_t id0;
 	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;
+	size_t idlen, prefix_len = strlen(id_str_prefix);
+	uint8_t *oid;
 	uint32_t i = 0;
 
 	if (prefix_len < 2)
@@ -686,29 +689,33 @@ 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) {
+
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
+	oid = packidx->hdr.sorted_ids + i * idlen;
+	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];
+			++i;
+			oid = packidx->hdr.sorted_ids + i * idlen;
 			continue;
 		} else if (cmp > 0)
 			break;
 
 		err = got_object_qid_alloc_partial(&qid);
 		if (err)
-			return err;
-		memcpy(qid->id.sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+			break;
+		memcpy(qid->id.sha1, oid, idlen);
 		STAILQ_INSERT_TAIL(matched_ids, qid, entry);
 
-		oid = &packidx->hdr.sorted_ids[++i];
+		++i;
+		oid = packidx->hdr.sorted_ids + i * idlen;
 	}
 
 	return NULL;
blob - 8aa0ad08ca44ef4b71ccf60df2cf2b962c13da78
blob + fff06d1a475eab84eaf7f63c0f72f688a91ce15c
--- lib/pack_index.c
+++ lib/pack_index.c
@@ -442,17 +442,18 @@ 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;
+	size_t idlen;
 
 	if (id0 > 0)
 		left = be32toh(packidx->hdr.fanout_table[id0 - 1]);
 
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
 	while (left <= right) {
-		struct got_packidx_object_id *oid;
-
 		i = ((left + right) / 2);
-		oid = &packidx->hdr.sorted_ids[i];
+		oid = packidx->hdr.sorted_ids + i * idlen;
 
-		cmp = memcmp(sha1, oid->sha1, SHA1_DIGEST_LENGTH);
+		cmp = memcmp(sha1, oid, idlen);
 		if (cmp == 0)
 			return -1; /* object already indexed */
 		else if (cmp > 0)
@@ -474,8 +475,11 @@ 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 = packidx->hdr.sorted_ids +
+		    i * got_hash_digest_length(GOT_HASH_SHA1);
+		got_sha1_digest_to_str(oid, hex, sizeof(hex));
 		fprintf(stderr, "%s\n", hex);
 	}
 	fprintf(stderr, "\n");
@@ -503,10 +507,13 @@ static void
 add_indexed_object(struct got_packidx *packidx, uint32_t idx,
     struct got_indexed_object *obj)
 {
+	void *oid;
 	int i;
+	size_t idlen;
 
-	memcpy(packidx->hdr.sorted_ids[idx].sha1, obj->id.sha1,
-	    SHA1_DIGEST_LENGTH);
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
+	oid = packidx->hdr.sorted_ids + idx * idlen;
+	memcpy(oid, obj->id.sha1, idlen);
 	packidx->hdr.crc32[idx] = htobe32(obj->crc);
 	if (obj->off < GOT_PACKIDX_OFFSET_VAL_IS_LARGE_IDX)
 		packidx->hdr.offsets[idx] = htobe32(obj->off);
@@ -561,15 +568,17 @@ 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));
 
@@ -671,7 +680,7 @@ 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;
@@ -914,7 +923,7 @@ 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 - 271a0e86825dde1ffd9062349f1b0ff19c086697
blob + 0d7fadbd1906889c21ed98e3cd2febdfb48d6aff
--- lib/repository.c
+++ lib/repository.c
@@ -1231,7 +1231,7 @@ add_packidx_bloom_filter(struct got_repository *repo,
 {
 	int i, nobjects = be32toh(packidx->hdr.fanout_table[0xff]);
 	struct got_packidx_bloom_filter *bf;
-	size_t len;
+	size_t len, idlen;
 
 	/*
 	 * Don't use bloom filters for very large pack index files.
@@ -1266,12 +1266,14 @@ add_packidx_bloom_filter(struct got_repository *repo,
 	}
 	bf->path_len = len;
 
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
+
 	/* 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 = packidx->hdr.sorted_ids + i * idlen;
+		bloom_add(bf->bloom, oid, idlen);
 	}
 
 	RB_INSERT(got_packidx_bloom_filter_tree,
blob - b0168b3397ef9e155f6ca23c6057126006b3f1f6
blob + a5cc628fec534d7d4aad89002bea4e0202645c0c
--- lib/repository_admin.c
+++ lib/repository_admin.c
@@ -532,6 +532,7 @@ got_repo_list_pack(FILE *packfile, struct got_object_i
 	struct got_packidx *packidx = NULL;
 	struct got_pack *pack = NULL;
 	uint32_t nobj, i;
+	size_t idlen;
 
 	err = got_object_id_str(&id_str, pack_hash);
 	if (err)
@@ -556,9 +557,10 @@ got_repo_list_pack(FILE *packfile, struct got_object_i
 	if (err)
 		goto done;
 
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
 	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 +572,9 @@ 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 = packidx->hdr.sorted_ids + i * idlen;
+		memset(&id, 0, sizeof(id));
+		memcpy(id.sha1, oid, idlen);
 
 		offset = got_packidx_get_object_offset(packidx, i);
 		if (offset == -1) {
@@ -1269,9 +1272,9 @@ pack_is_redundant(int *redundant, struct got_repositor
 {
 	const struct got_error *err;
 	struct got_packidx *packidx;
-	struct got_packidx_object_id *pid;
 	struct got_object_id id;
-	size_t i, nobjects;
+	void *pid;
+	size_t i, nobjects, idlen;
 
 	*redundant = 1;
 
@@ -1280,11 +1283,12 @@ pack_is_redundant(int *redundant, struct got_repositor
 		return err;
 
 	nobjects = be32toh(packidx->hdr.fanout_table[0xff]);
+	idlen = got_hash_digest_length(GOT_HASH_SHA1);
 	for (i = 0; i < nobjects; ++i) {
-		pid = &packidx->hdr.sorted_ids[i];
+		pid = packidx->hdr.sorted_ids + i * idlen;
 
 		memset(&id, 0, sizeof(id));
-		memcpy(&id.sha1, pid->sha1, sizeof(id.sha1));
+		memcpy(&id.sha1, pid, idlen);
 
 		if (got_object_idset_contains(idset, &id))
 			continue;