many cleanups to sha1_file.c

Those cleanups are mainly to set the table for the support of deltas
with base objects referenced by offsets instead of sha1.  This means
that many pack lookup functions are converted to take a pack/offset
tuple instead of a sha1.

This eliminates many struct pack_entry usages since this structure
carried redundent information in many cases, and it increased stack
footprint needlessly for a couple recursively called functions that used
to declare a local copy of it for every recursion loop.

In the process, packed_object_info_detail() has been reorganized as well
so to look much saner and more amenable to deltas with offset support.

Finally the appropriate adjustments have been made to functions that
depend on the above changes.  But there is no functionality changes yet
simply some code refactoring at this point.

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

1 files changed, 87 insertions, 98 deletions

diff --git a/sha1_file.c b/sha1_file.c
index 0f9c2b621..27b1ebb72 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -884,33 +884,32 @@ void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned l
 }
 
 /* forward declaration for a mutually recursive function */
-static int packed_object_info(struct pack_entry *entry,
+static int packed_object_info(struct packed_git *p, unsigned long offset,
 			      char *type, unsigned long *sizep);
 
-static int packed_delta_info(unsigned char *base_sha1,
-			     unsigned long delta_size,
-			     unsigned long left,
+static int packed_delta_info(struct packed_git *p,
+			     unsigned long offset,
 			     char *type,
-			     unsigned long *sizep,
-			     struct packed_git *p)
+			     unsigned long *sizep)
 {
-	struct pack_entry base_ent;
+	unsigned long base_offset;
+	unsigned char *base_sha1 = (unsigned char *) p->pack_base + offset;
 
-	if (left < 20)
+	if (p->pack_size < offset + 20)
 		die("truncated pack file");
-
 	/* The base entry _must_ be in the same pack */
-	if (!find_pack_entry_one(base_sha1, &base_ent, p))
+	base_offset = find_pack_entry_one(base_sha1, p);
+	if (!base_offset)
 		die("failed to find delta-pack base object %s",
 		    sha1_to_hex(base_sha1));
+	offset += 20;
 
 	/* We choose to only get the type of the base object and
 	 * ignore potentially corrupt pack file that expects the delta
 	 * based on a base with a wrong size.  This saves tons of
 	 * inflate() calls.
 	 */
-
-	if (packed_object_info(&base_ent, type, NULL))
+	if (packed_object_info(p, base_offset, type, NULL))
 		die("cannot get info for delta-pack base");
 
 	if (sizep) {
@@ -922,8 +921,8 @@ static int packed_delta_info(unsigned char *base_sha1,
 
 		memset(&stream, 0, sizeof(stream));
 
-		data = stream.next_in = base_sha1 + 20;
-		stream.avail_in = left - 20;
+		stream.next_in = (unsigned char *) p->pack_base + offset;
+		stream.avail_in = p->pack_size - offset;
 		stream.next_out = delta_head;
 		stream.avail_out = sizeof(delta_head);
 
@@ -985,75 +984,60 @@ int check_reuse_pack_delta(struct packed_git *p, unsigned long offset,
 	return status;
 }
 
-void packed_object_info_detail(struct pack_entry *e,
+void packed_object_info_detail(struct packed_git *p,
+			       unsigned long offset,
 			       char *type,
 			       unsigned long *size,
 			       unsigned long *store_size,
 			       unsigned int *delta_chain_length,
 			       unsigned char *base_sha1)
 {
-	struct packed_git *p = e->p;
-	unsigned long offset;
-	unsigned char *pack;
+	unsigned long val;
+	unsigned char *next_sha1;
 	enum object_type kind;
 
-	offset = unpack_object_header(p, e->offset, &kind, size);
-	pack = (unsigned char *) p->pack_base + offset;
-	if (kind != OBJ_DELTA)
-		*delta_chain_length = 0;
-	else {
-		unsigned int chain_length = 0;
-		if (p->pack_size <= offset + 20)
-			die("pack file %s records an incomplete delta base",
-			    p->pack_name);
-		hashcpy(base_sha1, pack);
-		do {
-			struct pack_entry base_ent;
-			unsigned long junk;
-
-			find_pack_entry_one(pack, &base_ent, p);
-			offset = unpack_object_header(p, base_ent.offset,
-						      &kind, &junk);
-			pack = (unsigned char *) p->pack_base + offset;
-			chain_length++;
-		} while (kind == OBJ_DELTA);
-		*delta_chain_length = chain_length;
-	}
-	switch (kind) {
-	case OBJ_COMMIT:
-	case OBJ_TREE:
-	case OBJ_BLOB:
-	case OBJ_TAG:
-		strcpy(type, type_names[kind]);
-		break;
-	default:
-		die("corrupted pack file %s containing object of kind %d",
-		    p->pack_name, kind);
+	*delta_chain_length = 0;
+	offset = unpack_object_header(p, offset, &kind, size);
+
+	for (;;) {
+		switch (kind) {
+		default:
+			die("corrupted pack file %s containing object of kind %d",
+			    p->pack_name, kind);
+		case OBJ_COMMIT:
+		case OBJ_TREE:
+		case OBJ_BLOB:
+		case OBJ_TAG:
+			strcpy(type, type_names[kind]);
+			*store_size = 0; /* notyet */
+			return;
+		case OBJ_DELTA:
+			if (p->pack_size <= offset + 20)
+				die("pack file %s records an incomplete delta base",
+				    p->pack_name);
+			next_sha1 = (unsigned char *) p->pack_base + offset;
+			if (*delta_chain_length == 0)
+				hashcpy(base_sha1, next_sha1);
+			offset = find_pack_entry_one(next_sha1, p);
+			break;
+		}
+		offset = unpack_object_header(p, offset, &kind, &val);
+		(*delta_chain_length)++;
 	}
-	*store_size = 0; /* notyet */
 }
 
-static int packed_object_info(struct pack_entry *entry,
+static int packed_object_info(struct packed_git *p, unsigned long offset,
 			      char *type, unsigned long *sizep)
 {
-	struct packed_git *p = entry->p;
-	unsigned long offset, size, left;
-	unsigned char *pack;
+	unsigned long size;
 	enum object_type kind;
-	int retval;
 
-	if (use_packed_git(p))
-		die("cannot map packed file");
+	offset = unpack_object_header(p, offset, &kind, &size);
 
-	offset = unpack_object_header(p, entry->offset, &kind, &size);
-	pack = (unsigned char *) p->pack_base + offset;
-	left = p->pack_size - offset;
+	if (kind == OBJ_DELTA)
+		return packed_delta_info(p, offset, type, sizep);
 
 	switch (kind) {
-	case OBJ_DELTA:
-		retval = packed_delta_info(pack, size, left, type, sizep, p);
-		unuse_packed_git(p);
-		return retval;
 	case OBJ_COMMIT:
 	case OBJ_TREE:
 	case OBJ_BLOB:
@@ -1066,7 +1050,6 @@ static int packed_object_info(struct pack_entry *entry,
 	}
 	if (sizep)
 		*sizep = size;
-	unuse_packed_git(p);
 	return 0;
 }
 
@@ -1103,25 +1086,26 @@ static void *unpack_delta_entry(struct packed_git *p,
 				char *type,
 				unsigned long *sizep)
 {
-	struct pack_entry base_ent;
 	void *delta_data, *result, *base;
-	unsigned long result_size, base_size;
-	unsigned char* base_sha1;
+	unsigned long result_size, base_size, base_offset;
+	unsigned char *base_sha1;
 
-	if ((offset + 20) >= p->pack_size)
+	if (p->pack_size < offset + 20)
 		die("truncated pack file");
-
 	/* The base entry _must_ be in the same pack */
 	base_sha1 = (unsigned char*)p->pack_base + offset;
-	if (!find_pack_entry_one(base_sha1, &base_ent, p))
+	base_offset = find_pack_entry_one(base_sha1, p);
+	if (!base_offset)
 		die("failed to find delta-pack base object %s",
 		    sha1_to_hex(base_sha1));
-	base = unpack_entry_gently(&base_ent, type, &base_size);
+	offset += 20;
+
+	base = unpack_entry_gently(p, base_offset, type, &base_size);
 	if (!base)
-		die("failed to read delta-pack base object %s",
-		    sha1_to_hex(base_sha1));
+		die("failed to read delta base object at %lu from %s",
+		    base_offset, p->pack_name);
 
-	delta_data = unpack_compressed_entry(p, offset + 20, delta_size);
+	delta_data = unpack_compressed_entry(p, offset, delta_size);
 	result = patch_delta(base, base_size,
 			     delta_data, delta_size,
 			     &result_size);
@@ -1141,7 +1125,7 @@ static void *unpack_entry(struct pack_entry *entry,
 
 	if (use_packed_git(p))
 		die("cannot map packed file");
-	retval = unpack_entry_gently(entry, type, sizep);
+	retval = unpack_entry_gently(p, entry->offset, type, sizep);
 	unuse_packed_git(p);
 	if (!retval)
 		die("corrupted pack file %s", p->pack_name);
@@ -1149,14 +1133,13 @@ static void *unpack_entry(struct pack_entry *entry,
 }
 
 /* The caller is responsible for use_packed_git()/unuse_packed_git() pair */
-void *unpack_entry_gently(struct pack_entry *entry,
+void *unpack_entry_gently(struct packed_git *p, unsigned long offset,
 			  char *type, unsigned long *sizep)
 {
-	struct packed_git *p = entry->p;
-	unsigned long offset, size;
+	unsigned long size;
 	enum object_type kind;
 
-	offset = unpack_object_header(p, entry->offset, &kind, &size);
+	offset = unpack_object_header(p, offset, &kind, &size);
 	switch (kind) {
 	case OBJ_DELTA:
 		return unpack_delta_entry(p, offset, size, type, sizep);
@@ -1188,8 +1171,8 @@ int nth_packed_object_sha1(const struct packed_git *p, int n,
 	return 0;
 }
 
-int find_pack_entry_one(const unsigned char *sha1,
-			struct pack_entry *e, struct packed_git *p)
+unsigned long find_pack_entry_one(const unsigned char *sha1,
+				  struct packed_git *p)
 {
 	unsigned int *level1_ofs = p->index_base;
 	int hi = ntohl(level1_ofs[*sha1]);
@@ -1199,12 +1182,8 @@ int find_pack_entry_one(const unsigned char *sha1,
 	do {
 		int mi = (lo + hi) / 2;
 		int cmp = hashcmp((unsigned char *)index + (24 * mi) + 4, sha1);
-		if (!cmp) {
-			e->offset = ntohl(*((unsigned int *) ((char *) index + (24 * mi))));
-			hashcpy(e->sha1, sha1);
-			e->p = p;
-			return 1;
-		}
+		if (!cmp)
+			return ntohl(*((unsigned int *) ((char *) index + (24 * mi))));
 		if (cmp > 0)
 			hi = mi;
 		else
@@ -1216,6 +1195,8 @@ int find_pack_entry_one(const unsigned char *sha1,
 static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e, const char **ignore_packed)
 {
 	struct packed_git *p;
+	unsigned long offset;
+
 	prepare_packed_git();
 
 	for (p = packed_git; p; p = p->next) {
@@ -1227,8 +1208,13 @@ static int find_pack_entry(const unsigned char *sha1, struct pack_entry *e, cons
 			if (*ig)
 				continue;
 		}
-		if (find_pack_entry_one(sha1, e, p))
+		offset = find_pack_entry_one(sha1, p);
+		if (offset) {
+			e->offset = offset;
+			e->p = p;
+			hashcpy(e->sha1, sha1);
 			return 1;
+		}
 	}
 	return 0;
 }
@@ -1237,10 +1223,9 @@ struct packed_git *find_sha1_pack(const unsigned char *sha1,
 				  struct packed_git *packs)
 {
 	struct packed_git *p;
-	struct pack_entry e;
 
 	for (p = packs; p; p = p->next) {
-		if (find_pack_entry_one(sha1, &e, p))
+		if (find_pack_entry_one(sha1, p))
 			return p;
 	}
 	return NULL;
@@ -1259,12 +1244,16 @@ int sha1_object_info(const unsigned char *sha1, char *type, unsigned long *sizep
 	if (!map) {
 		struct pack_entry e;
 
-		if (find_pack_entry(sha1, &e, NULL))
-			return packed_object_info(&e, type, sizep);
-		reprepare_packed_git();
-		if (find_pack_entry(sha1, &e, NULL))
-			return packed_object_info(&e, type, sizep);
-		return error("unable to find %s", sha1_to_hex(sha1));
+		if (!find_pack_entry(sha1, &e, NULL)) {
+			reprepare_packed_git();
+			if (!find_pack_entry(sha1, &e, NULL))
+				return error("unable to find %s", sha1_to_hex(sha1));
+		}
+		if (use_packed_git(e.p))
+			die("cannot map packed file");
+		status = packed_object_info(e.p, e.offset, type, sizep);
+		unuse_packed_git(e.p);
+		return status;
 	}
 	if (unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr)) < 0)
 		status = error("unable to unpack %s header",