From be6b19145f64f62790049c06320c35011f7312a7 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Thu, 21 Sep 2006 00:09:44 -0400 Subject: [PATCH] make git-pack-objects able to create deltas with offset to base This is enabled with --delta-base-offset only, and doesn't work with pack data reuse yet. The idea is to allow for the fetch protocol to use an extension flag to notify the remote end that --delta-base-offset can be used with git-pack-objects. Eventually git-repack will always provide this flag. With this, all delta base objects are now pushed before deltas that depend on them. This is a requirements for OBJ_OFS_DELTA. This is not a requirement for OBJ_REF_DELTA but always doing so makes the code simpler. Signed-off-by: Nicolas Pitre Signed-off-by: Junio C Hamano --- builtin-pack-objects.c | 47 +++++++++++++++++++++++++++++++++-------------- 1 file changed, 33 insertions(+), 14 deletions(-) diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c index c62734a2a6..221264916d 100644 --- a/builtin-pack-objects.c +++ b/builtin-pack-objects.c @@ -60,6 +60,8 @@ static int non_empty; static int no_reuse_delta; static int local; static int incremental; +static int allow_ofs_delta; + static struct object_entry **sorted_by_sha, **sorted_by_type; static struct object_entry *objects; static int nr_objects, nr_alloc, nr_result; @@ -334,9 +336,6 @@ static unsigned long write_object(struct sha1file *f, enum object_type obj_type; int to_reuse = 0; - if (entry->preferred_base) - return 0; - obj_type = entry->type; if (! entry->in_pack) to_reuse = 0; /* can't reuse what we don't have */ @@ -380,18 +379,35 @@ static unsigned long write_object(struct sha1file *f, if (entry->delta) { buf = delta_against(buf, size, entry); size = entry->delta_size; - obj_type = OBJ_REF_DELTA; + obj_type = (allow_ofs_delta && entry->delta->offset) ? + OBJ_OFS_DELTA : OBJ_REF_DELTA; } /* * The object header is a byte of 'type' followed by zero or - * more bytes of length. For deltas, the 20 bytes of delta - * sha1 follows that. + * more bytes of length. */ hdrlen = encode_header(obj_type, size, header); sha1write(f, header, hdrlen); - if (entry->delta) { - sha1write(f, entry->delta, 20); + if (obj_type == OBJ_OFS_DELTA) { + /* + * Deltas with relative base contain an additional + * encoding of the relative offset for the delta + * base from this object's position in the pack. + */ + unsigned long ofs = entry->offset - entry->delta->offset; + unsigned pos = sizeof(header) - 1; + header[pos] = ofs & 127; + while (ofs >>= 7) + header[--pos] = 128 | (--ofs & 127); + sha1write(f, header + pos, sizeof(header) - pos); + hdrlen += sizeof(header) - pos; + } else if (obj_type == OBJ_REF_DELTA) { + /* + * Deltas with a base reference contain + * an additional 20 bytes for the base sha1. + */ + sha1write(f, entry->delta->sha1, 20); hdrlen += 20; } datalen = sha1write_compressed(f, buf, size); @@ -413,7 +429,7 @@ static unsigned long write_object(struct sha1file *f, reused_delta++; reused++; } - if (obj_type == OBJ_REF_DELTA) + if (entry->delta) written_delta++; written++; return hdrlen + datalen; @@ -423,17 +439,16 @@ static unsigned long write_one(struct sha1file *f, struct object_entry *e, unsigned long offset) { - if (e->offset) + if (e->offset || e->preferred_base) /* offset starts from header size and cannot be zero * if it is written already. */ return offset; - e->offset = offset; - offset += write_object(f, e); - /* if we are deltified, write out its base object. */ + /* if we are deltified, write out its base object first. */ if (e->delta) offset = write_one(f, e->delta, offset); - return offset; + e->offset = offset; + return offset + write_object(f, e); } static void write_pack_file(void) @@ -1484,6 +1499,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) no_reuse_delta = 1; continue; } + if (!strcmp("--delta-base-offset", arg)) { + allow_ofs_delta = no_reuse_delta = 1; + continue; + } if (!strcmp("--stdout", arg)) { pack_to_stdout = 1; continue; -- 2.11.4.GIT