Improve reuse of sha1_file library within fast-import.

Now that the sha1_file.c library routines use the sliding mmap
routines to perform efficient access to portions of a packfile
I can remove that code from fast-import.c and just invoke it.
One benefit is we now have reloading support for any packfile which
uses OBJ_OFS_DELTA.  Another is we have significantly less code
to maintain.

This code reuse change *requires* that fast-import generate only
an OBJ_OFS_DELTA format packfile, as there is absolutely no index
available to perform OBJ_REF_DELTA lookup in while unpacking
an object.  This is probably reasonable to require as the delta
offsets result in smaller packfiles and are faster to unpack,
as no index searching is required.  Its also only a temporary
requirement as users could always repack without offsets before
making the import available to older versions of Git.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 31 insertions, 144 deletions

diff --git a/fast-import.c b/fast-import.c
index 492a859..f0f51a6 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -136,9 +136,9 @@ struct last_object
 {
 	void *data;
 	unsigned long len;
+	unsigned long offset;
 	unsigned int depth;
-	int no_free;
-	unsigned char sha1[20];
+	unsigned no_free:1;
 };
 
 struct mem_pool
@@ -235,13 +235,10 @@ static unsigned int atom_cnt;
 static struct atom_str **atom_table;
 
 /* The .pack file being generated */
+static struct packed_git *pack_data;
 static int pack_fd;
 static unsigned long pack_size;
 static unsigned char pack_sha1[20];
-static unsigned char* pack_base;
-static unsigned long pack_moff;
-static unsigned long pack_mlen = 128*1024*1024;
-static unsigned long page_size;
 
 /* Table of objects we've written. */
 static unsigned int object_entry_alloc = 5000;
@@ -667,14 +664,23 @@ static int store_object(
 	deflateInit(&s, zlib_compression_level);
 
 	if (delta) {
+		unsigned long ofs = e->offset - last->offset;
+		unsigned pos = sizeof(hdr) - 1;
+
 		delta_count_by_type[type]++;
 		last->depth++;
 		s.next_in = delta;
 		s.avail_in = deltalen;
-		hdrlen = encode_header(OBJ_REF_DELTA, deltalen, hdr);
+
+		hdrlen = encode_header(OBJ_OFS_DELTA, deltalen, hdr);
 		write_or_die(pack_fd, hdr, hdrlen);
-		write_or_die(pack_fd, last->sha1, sizeof(sha1));
-		pack_size += hdrlen + sizeof(sha1);
+		pack_size += hdrlen;
+
+		hdr[pos] = ofs & 127;
+		while (ofs >>= 7)
+			hdr[--pos] = 128 | (--ofs & 127);
+		write_or_die(pack_fd, hdr + pos, sizeof(hdr) - pos);
+		pack_size += sizeof(hdr) - pos;
 	} else {
 		if (last)
 			last->depth = 0;
@@ -701,139 +707,17 @@ static int store_object(
 		if (last->data && !last->no_free)
 			free(last->data);
 		last->data = dat;
+		last->offset = e->offset;
 		last->len = datlen;
-		hashcpy(last->sha1, sha1);
 	}
 	return 0;
 }
 
-static unsigned char* map_pack(unsigned long offset, unsigned int *left)
-{
-	if (offset >= pack_size)
-		die("object offset outside of pack file");
-	if (!pack_base
-			|| offset < pack_moff
-			|| (offset + 20) >= (pack_moff + pack_mlen)) {
-		if (pack_base)
-			munmap(pack_base, pack_mlen);
-		pack_moff = (offset / page_size) * page_size;
-		pack_base = mmap(NULL,pack_mlen,PROT_READ,MAP_SHARED,
-			pack_fd,pack_moff);
-		if (pack_base == MAP_FAILED)
-			die("Failed to map generated pack: %s", strerror(errno));
-		remap_count++;
-	}
-	offset -= pack_moff;
-	if (left)
-		*left = pack_mlen - offset;
-	return pack_base + offset;
-}
-
-static unsigned long unpack_object_header(unsigned long offset,
-	enum object_type *type,
-	unsigned long *sizep)
-{
-	unsigned shift;
-	unsigned char c;
-	unsigned long size;
-
-	c = *map_pack(offset++, NULL);
-	*type = (c >> 4) & 7;
-	size = c & 15;
-	shift = 4;
-	while (c & 0x80) {
-		c = *map_pack(offset++, NULL);
-		size += (c & 0x7f) << shift;
-		shift += 7;
-	}
-	*sizep = size;
-	return offset;
-}
-
-static void *unpack_non_delta_entry(unsigned long o, unsigned long sz)
-{
-	z_stream stream;
-	unsigned char *result;
-
-	result = xmalloc(sz + 1);
-	result[sz] = 0;
-
-	memset(&stream, 0, sizeof(stream));
-	stream.next_in = map_pack(o, &stream.avail_in);
-	stream.next_out = result;
-	stream.avail_out = sz;
-
-	inflateInit(&stream);
-	for (;;) {
-		int st = inflate(&stream, Z_FINISH);
-		if (st == Z_STREAM_END)
-			break;
-		if (st == Z_OK || st == Z_BUF_ERROR) {
-			o = stream.next_in - pack_base + pack_moff;
-			stream.next_in = map_pack(o, &stream.avail_in);
-			continue;
-		}
-		die("Error %i from zlib during inflate.", st);
-	}
-	inflateEnd(&stream);
-	if (stream.total_out != sz)
-		die("Error after inflate: sizes mismatch");
-	return result;
-}
-
-static void *gfi_unpack_entry(unsigned long offset,
-	unsigned long *sizep,
-	unsigned int *delta_depth);
-
-static void *unpack_delta_entry(unsigned long offset,
-	unsigned long delta_size,
-	unsigned long *sizep,
-	unsigned int *delta_depth)
-{
-	struct object_entry *base_oe;
-	unsigned char *base_sha1;
-	void *delta_data, *base, *result;
-	unsigned long base_size, result_size;
-
-	base_sha1 = map_pack(offset, NULL);
-	base_oe = find_object(base_sha1);
-	if (!base_oe)
-		die("I'm broken; I can't find a base I know must be here.");
-	base = gfi_unpack_entry(base_oe->offset, &base_size, delta_depth);
-	delta_data = unpack_non_delta_entry(offset + 20, delta_size);
-	result = patch_delta(base, base_size,
-			     delta_data, delta_size,
-			     &result_size);
-	if (!result)
-		die("failed to apply delta");
-	free(delta_data);
-	free(base);
-	*sizep = result_size;
-	(*delta_depth)++;
-	return result;
-}
-
-static void *gfi_unpack_entry(unsigned long offset,
-	unsigned long *sizep,
-	unsigned int *delta_depth)
+static void *gfi_unpack_entry(unsigned long ofs, unsigned long *sizep)
 {
-	unsigned long size;
-	enum object_type kind;
-
-	offset = unpack_object_header(offset, &kind, &size);
-	switch (kind) {
-	case OBJ_REF_DELTA:
-		return unpack_delta_entry(offset, size, sizep, delta_depth);
-	case OBJ_COMMIT:
-	case OBJ_TREE:
-	case OBJ_BLOB:
-	case OBJ_TAG:
-		*sizep = size;
-		*delta_depth = 0;
-		return unpack_non_delta_entry(offset, size);
-	default:
-		die("I created an object I can't read!");
-	}
+	char type[20];
+	pack_data->pack_size = pack_size + 20;
+	return unpack_entry(pack_data, ofs, type, sizep);
 }
 
 static const char *get_mode(const char *str, unsigned int *modep)
@@ -867,7 +751,8 @@ static void load_tree(struct tree_entry *root)
 	if (myoe) {
 		if (myoe->type != OBJ_TREE)
 			die("Not a tree: %s", sha1_to_hex(sha1));
-		buf = gfi_unpack_entry(myoe->offset, &size, &t->delta_depth);
+		t->delta_depth = 0;
+		buf = gfi_unpack_entry(myoe->offset, &size);
 	} else {
 		char type[20];
 		buf = read_sha1_file(sha1, type, &size);
@@ -956,6 +841,7 @@ static void store_tree(struct tree_entry *root)
 	unsigned int i, j, del;
 	unsigned long new_len;
 	struct last_object lo;
+	struct object_entry *le;
 
 	if (!is_null_sha1(root->versions[1].sha1))
 		return;
@@ -965,17 +851,16 @@ static void store_tree(struct tree_entry *root)
 			store_tree(t->entries[i]);
 	}
 
-	if (!S_ISDIR(root->versions[0].mode)
-			|| is_null_sha1(root->versions[0].sha1)
-			|| !find_object(root->versions[0].sha1)) {
+	le = find_object(root->versions[0].sha1);
+	if (!S_ISDIR(root->versions[0].mode) || !le) {
 		lo.data = NULL;
 		lo.depth = 0;
 	} else {
 		mktree(t, 0, &lo.len, &old_tree);
 		lo.data = old_tree.buffer;
+		lo.offset = le->offset;
 		lo.depth = t->delta_depth;
 		lo.no_free = 1;
-		hashcpy(lo.sha1, root->versions[0].sha1);
 	}
 
 	mktree(t, 1, &new_len, &new_tree);
@@ -1471,12 +1356,11 @@ static void cmd_from(struct branch *b)
 		unsigned long idnum = strtoul(from + 1, NULL, 10);
 		struct object_entry *oe = find_mark(idnum);
 		unsigned long size;
-		unsigned int depth;
 		char *buf;
 		if (oe->type != OBJ_COMMIT)
 			die("Mark :%lu not a commit", idnum);
 		hashcpy(b->sha1, oe->sha1);
-		buf = gfi_unpack_entry(oe->offset, &size, &depth);
+		buf = gfi_unpack_entry(oe->offset, &size);
 		if (!buf || size < 46)
 			die("Not a valid commit: %s", from);
 		if (memcmp("tree ", buf, 5)
@@ -1818,7 +1702,6 @@ int main(int argc, const char **argv)
 
 	setup_ident();
 	git_config(git_default_config);
-	page_size = getpagesize();
 
 	for (i = 1; i < argc; i++) {
 		const char *a = argv[i];
@@ -1854,6 +1737,10 @@ int main(int argc, const char **argv)
 	if (pack_fd < 0)
 		die("Can't create %s: %s", pack_name, strerror(errno));
 
+	pack_data = xcalloc(1, sizeof(*pack_data) + strlen(pack_name) + 2);
+	strcpy(pack_data->pack_name, pack_name);
+	pack_data->pack_fd = pack_fd;
+
 	init_pack_header();
 	alloc_objects(est_obj_cnt);
 	strbuf_init(&command_buf);