[PATCH] clean up pack index handling a bit

Especially with the new index format to come, it is more appropriate
to encapsulate more into check_packed_git_idx() and assume less of the
index format in struct packed_git.

To that effect, the index_base is renamed to index_data with void * type
so it is not used directly but other pointers initialized with it. This
allows for a couple pointer cast removal, as well as providing a better
generic name to grep for when adding support for new index versions or
formats.

And index_data is declared const too while at it.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-pack-objects.c

@@ -166,11 +166,12 @@ static void prepare_pack_revindex(struct pack_revindex *rix)
 	struct packed_git *p = rix->p;
 	int num_ent = num_packed_objects(p);
 	int i;
-	void *index = p->index_base + 256;
+	const char *index = p->index_data;
 
+	index += 4 * 256;
 	rix->revindex = xmalloc(sizeof(*rix->revindex) * (num_ent + 1));
 	for (i = 0; i < num_ent; i++) {
-		unsigned int hl = *((unsigned int *)((char *) index + 24*i));
+		uint32_t hl = *((uint32_t *)(index + 24 * i));
 		rix->revindex[i].offset = ntohl(hl);
 		rix->revindex[i].nr = i;
 	}
@@ -217,11 +218,11 @@ static off_t find_packed_object_size(struct packed_git *p, off_t ofs)
 	return entry[1].offset - ofs;
 }
 
-static unsigned char *find_packed_object_name(struct packed_git *p,
-					      off_t ofs)
+static const unsigned char *find_packed_object_name(struct packed_git *p,
+						    off_t ofs)
 {
 	struct revindex_entry *entry = find_packed_object(p, ofs);
-	return (unsigned char *)(p->index_base + 256) + 24 * entry->nr + 4;
+	return ((unsigned char *)p->index_data) + 4 * 256 + 24 * entry->nr + 4;
 }
 
 static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
@@ -996,7 +997,8 @@ static void check_object(struct object_entry *entry)
 		 * delta.
 		 */
 		if (!no_reuse_delta) {
-			unsigned char c, *base_name;
+			unsigned char c;
+			const unsigned char *base_name;
 			off_t ofs;
 			unsigned long used_0;
 			/* there is at least 20 bytes left in the pack */

cache.h

@@ -371,10 +371,11 @@ struct pack_window {
 extern struct packed_git {
 	struct packed_git *next;
 	struct pack_window *windows;
-	uint32_t *index_base;
-	time_t mtime;
+	const void *index_data;
 	off_t index_size;
 	off_t pack_size;
+	time_t mtime;
+	int index_version;
 	int pack_fd;
 	int pack_local;
 	unsigned char sha1[20];
@@ -412,7 +413,7 @@ extern int server_supports(const char *feature);
 
 extern struct packed_git *parse_pack_index(unsigned char *sha1);
 extern struct packed_git *parse_pack_index_file(const unsigned char *sha1,
-						char *idx_path);
+						const char *idx_path);
 
 extern void prepare_packed_git(void);
 extern void reprepare_packed_git(void);
@@ -424,7 +425,7 @@ extern struct packed_git *find_sha1_pack(const unsigned char *sha1,
 extern void pack_report(void);
 extern unsigned char* use_pack(struct packed_git *, struct pack_window **, off_t, unsigned int *);
 extern void unuse_pack(struct pack_window **);
-extern struct packed_git *add_packed_git(char *, int, int);
+extern struct packed_git *add_packed_git(const char *, int, int);
 extern uint32_t num_packed_objects(const struct packed_git *p);
 extern int nth_packed_object_sha1(const struct packed_git *, uint32_t, unsigned char*);
 extern off_t find_pack_entry_one(const unsigned char *, struct packed_git *);

pack-check.c

@@ -5,7 +5,7 @@ static int verify_packfile(struct packed_git *p,
 		struct pack_window **w_curs)
 {
 	off_t index_size = p->index_size;
-	void *index_base = p->index_base;
+	const unsigned char *index_base = p->index_data;
 	SHA_CTX ctx;
 	unsigned char sha1[20];
 	off_t offset = 0, pack_sig = p->pack_size - 20;
@@ -31,7 +31,7 @@ static int verify_packfile(struct packed_git *p,
 	if (hashcmp(sha1, use_pack(p, w_curs, pack_sig, NULL)))
 		return error("Packfile %s SHA1 mismatch with itself",
 			     p->pack_name);
-	if (hashcmp(sha1, (unsigned char *)index_base + index_size - 40))
+	if (hashcmp(sha1, index_base + index_size - 40))
 		return error("Packfile %s SHA1 mismatch with idx",
 			     p->pack_name);
 	unuse_pack(w_curs);
@@ -127,7 +127,7 @@ static void show_pack_info(struct packed_git *p)
 int verify_pack(struct packed_git *p, int verbose)
 {
 	off_t index_size = p->index_size;
-	void *index_base = p->index_base;
+	const unsigned char *index_base = p->index_data;
 	SHA_CTX ctx;
 	unsigned char sha1[20];
 	int ret;
@@ -137,7 +137,7 @@ int verify_pack(struct packed_git *p, int verbose)
 	SHA1_Init(&ctx);
 	SHA1_Update(&ctx, index_base, (unsigned int)(index_size - 20));
 	SHA1_Final(sha1, &ctx);
-	if (hashcmp(sha1, (unsigned char *)index_base + index_size - 20))
+	if (hashcmp(sha1, index_base + index_size - 20))
 		ret = error("Packfile index for %s SHA1 mismatch",
 			    p->pack_name);
 

pack-redundant.c

@@ -17,7 +17,7 @@ static int load_all_packs, verbose, alt_odb;
 
 struct llist_item {
 	struct llist_item *next;
-	unsigned char *sha1;
+	const unsigned char *sha1;
 };
 static struct llist {
 	struct llist_item *front;
@@ -104,9 +104,9 @@ static struct llist * llist_copy(struct llist *list)
 	return ret;
 }
 
-static inline struct llist_item * llist_insert(struct llist *list,
-					       struct llist_item *after,
-					       unsigned char *sha1)
+static inline struct llist_item *llist_insert(struct llist *list,
+					      struct llist_item *after,
+					       const unsigned char *sha1)
 {
 	struct llist_item *new = llist_item_get();
 	new->sha1 = sha1;
@@ -128,12 +128,14 @@ static inline struct llist_item * llist_insert(struct llist *list,
 	return new;
 }
 
-static inline struct llist_item *llist_insert_back(struct llist *list, unsigned char *sha1)
+static inline struct llist_item *llist_insert_back(struct llist *list,
+						   const unsigned char *sha1)
 {
 	return llist_insert(list, list->back, sha1);
 }
 
-static inline struct llist_item *llist_insert_sorted_unique(struct llist *list, unsigned char *sha1, struct llist_item *hint)
+static inline struct llist_item *llist_insert_sorted_unique(struct llist *list,
+			const unsigned char *sha1, struct llist_item *hint)
 {
 	struct llist_item *prev = NULL, *l;
 
@@ -246,12 +248,12 @@ static struct pack_list * pack_list_difference(const struct pack_list *A,
 static void cmp_two_packs(struct pack_list *p1, struct pack_list *p2)
 {
 	int p1_off, p2_off;
-	unsigned char *p1_base, *p2_base;
+	const unsigned char *p1_base, *p2_base;
 	struct llist_item *p1_hint = NULL, *p2_hint = NULL;
 
 	p1_off = p2_off = 256 * 4 + 4;
-	p1_base = (unsigned char *) p1->pack->index_base;
-	p2_base = (unsigned char *) p2->pack->index_base;
+	p1_base = p1->pack->index_data;
+	p2_base = p2->pack->index_data;
 
 	while (p1_off <= p1->pack->index_size - 3 * 20 &&
 	       p2_off <= p2->pack->index_size - 3 * 20)
@@ -351,11 +353,11 @@ static size_t sizeof_union(struct packed_git *p1, struct packed_git *p2)
 {
 	size_t ret = 0;
 	int p1_off, p2_off;
-	unsigned char *p1_base, *p2_base;
+	const unsigned char *p1_base, *p2_base;
 
 	p1_off = p2_off = 256 * 4 + 4;
-	p1_base = (unsigned char *)p1->index_base;
-	p2_base = (unsigned char *)p2->index_base;
+	p1_base = p1->index_data;
+	p2_base = p2->index_data;
 
 	while (p1_off <= p1->index_size - 3 * 20 &&
 	       p2_off <= p2->index_size - 3 * 20)
@@ -534,7 +536,7 @@ static struct pack_list * add_pack(struct packed_git *p)
 {
 	struct pack_list l;
 	size_t off;
-	unsigned char *base;
+	const unsigned char *base;
 
 	if (!p->pack_local && !(alt_odb || verbose))
 		return NULL;
@@ -543,7 +545,7 @@ static struct pack_list * add_pack(struct packed_git *p)
 	llist_init(&l.all_objects);
 
 	off = 256 * 4 + 4;
-	base = (unsigned char *)p->index_base;
+	base = p->index_data;
 	while (off <= p->index_size - 3 * 20) {
 		llist_insert_back(l.all_objects, base + off);
 		off += 24;

pack.h

@@ -16,24 +16,15 @@ struct pack_header {
 };
 
 /*
- * Packed object index header
- *
- * struct pack_idx_header {
- * 	uint32_t idx_signature;
- *	uint32_t idx_version;
- * };
- *
- * Note: this header isn't active yet.  In future versions of git
- * we may change the index file format.  At that time we would start
- * the first four bytes of the new index format with this signature,
- * as all older git binaries would find this value illegal and abort
- * reading the file.
+ * The first four bytes of index formats later than version 1 should
+ * start with this signature, as all older git binaries would find this
+ * value illegal and abort reading the file.
  *
  * This is the case because the number of objects in a packfile
  * cannot exceed 1,431,660,000 as every object would need at least
- * 3 bytes of data and the overall packfile cannot exceed 4 GiB due
- * to the 32 bit offsets used by the index.  Clearly the signature
- * exceeds this maximum.
+ * 3 bytes of data and the overall packfile cannot exceed 4 GiB with
+ * version 1 of the index file due to the offsets limited to 32 bits.
+ * Clearly the signature exceeds this maximum.
  *
  * Very old git binaries will also compare the first 4 bytes to the
  * next 4 bytes in the index and abort with a "non-monotonic index"
@@ -43,6 +34,15 @@ struct pack_header {
  */
 #define PACK_IDX_SIGNATURE 0xff744f63	/* "\377tOc" */
 
+/*
+ * Packed object index header
+ */
+struct pack_idx_header {
+	uint32_t idx_signature;
+	uint32_t idx_version;
+};
+
+
 extern int verify_pack(struct packed_git *, int);
 
 #define PH_ERROR_EOF		(-1)