From 780e6e735be189097dad4b223d8edeb18cce1928 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Fri, 22 Sep 2006 21:25:04 -0400 Subject: [PATCH] make pack data reuse compatible with both delta types This is the missing part to git-pack-objects allowing it to reuse delta data to/from any of the two delta types. It can reuse delta from any type, and it outputs base offsets when --allow-delta-base-offset is provided and the base is also included in the pack. Otherwise it outputs base sha1 references just like it always did. Signed-off-by: Nicolas Pitre Signed-off-by: Junio C Hamano --- builtin-pack-objects.c | 204 ++++++++++++++++++++++++++--------------- pack.h | 3 - sha1_file.c | 19 ---- 3 files changed, 130 insertions(+), 96 deletions(-) diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c index 221264916d..6db97b685f 100644 --- a/builtin-pack-objects.c +++ b/builtin-pack-objects.c @@ -29,6 +29,7 @@ struct object_entry { enum object_type type; enum object_type in_pack_type; /* could be delta */ unsigned long delta_size; /* delta data size (uncompressed) */ +#define in_pack_header_size delta_size /* only when reusing pack data */ struct object_entry *delta; /* delta base object */ struct packed_git *in_pack; /* already in pack */ unsigned int in_pack_offset; @@ -86,17 +87,25 @@ static int object_ix_hashsz; * Pack index for existing packs give us easy access to the offsets into * corresponding pack file where each object's data starts, but the entries * do not store the size of the compressed representation (uncompressed - * size is easily available by examining the pack entry header). We build - * a hashtable of existing packs (pack_revindex), and keep reverse index - * here -- pack index file is sorted by object name mapping to offset; this - * pack_revindex[].revindex array is an ordered list of offsets, so if you - * know the offset of an object, next offset is where its packed - * representation ends. + * size is easily available by examining the pack entry header). It is + * also rather expensive to find the sha1 for an object given its offset. + * + * We build a hashtable of existing packs (pack_revindex), and keep reverse + * index here -- pack index file is sorted by object name mapping to offset; + * this pack_revindex[].revindex array is a list of offset/index_nr pairs + * ordered by offset, so if you know the offset of an object, next offset + * is where its packed representation ends and the index_nr can be used to + * get the object sha1 from the main index. */ +struct revindex_entry { + unsigned int offset; + unsigned int nr; +}; struct pack_revindex { struct packed_git *p; - unsigned long *revindex; -} *pack_revindex = NULL; + struct revindex_entry *revindex; +}; +static struct pack_revindex *pack_revindex; static int pack_revindex_hashsz; /* @@ -143,14 +152,9 @@ static void prepare_pack_ix(void) static int cmp_offset(const void *a_, const void *b_) { - unsigned long a = *(unsigned long *) a_; - unsigned long b = *(unsigned long *) b_; - if (a < b) - return -1; - else if (a == b) - return 0; - else - return 1; + const struct revindex_entry *a = a_; + const struct revindex_entry *b = b_; + return (a->offset < b->offset) ? -1 : (a->offset > b->offset) ? 1 : 0; } /* @@ -163,25 +167,27 @@ static void prepare_pack_revindex(struct pack_revindex *rix) int i; void *index = p->index_base + 256; - rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1)); + 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)); - rix->revindex[i] = ntohl(hl); + rix->revindex[i].offset = ntohl(hl); + rix->revindex[i].nr = i; } /* This knows the pack format -- the 20-byte trailer * follows immediately after the last object data. */ - rix->revindex[num_ent] = p->pack_size - 20; - qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset); + rix->revindex[num_ent].offset = p->pack_size - 20; + rix->revindex[num_ent].nr = -1; + qsort(rix->revindex, num_ent, sizeof(*rix->revindex), cmp_offset); } -static unsigned long find_packed_object_size(struct packed_git *p, - unsigned long ofs) +static struct revindex_entry * find_packed_object(struct packed_git *p, + unsigned int ofs) { int num; int lo, hi; struct pack_revindex *rix; - unsigned long *revindex; + struct revindex_entry *revindex; num = pack_revindex_ix(p); if (num < 0) die("internal error: pack revindex uninitialized"); @@ -193,10 +199,10 @@ static unsigned long find_packed_object_size(struct packed_git *p, hi = num_packed_objects(p) + 1; do { int mi = (lo + hi) / 2; - if (revindex[mi] == ofs) { - return revindex[mi+1] - ofs; + if (revindex[mi].offset == ofs) { + return revindex + mi; } - else if (ofs < revindex[mi]) + else if (ofs < revindex[mi].offset) hi = mi; else lo = mi + 1; @@ -204,6 +210,20 @@ static unsigned long find_packed_object_size(struct packed_git *p, die("internal error: pack revindex corrupt"); } +static unsigned long find_packed_object_size(struct packed_git *p, + unsigned long ofs) +{ + struct revindex_entry *entry = find_packed_object(p, ofs); + return entry[1].offset - ofs; +} + +static unsigned char *find_packed_object_name(struct packed_git *p, + unsigned long ofs) +{ + struct revindex_entry *entry = find_packed_object(p, ofs); + return (unsigned char *)(p->index_base + 256) + 24 * entry->nr + 4; +} + static void *delta_against(void *buf, unsigned long size, struct object_entry *entry) { unsigned long othersize, delta_size; @@ -249,6 +269,10 @@ static int encode_header(enum object_type type, unsigned long size, unsigned cha return n; } +/* + * we are going to reuse the existing object data as is. make + * sure it is not corrupt. + */ static int check_inflate(unsigned char *data, unsigned long len, unsigned long expect) { z_stream stream; @@ -280,32 +304,6 @@ static int check_inflate(unsigned char *data, unsigned long len, unsigned long e return st; } -/* - * we are going to reuse the existing pack entry data. make - * sure it is not corrupt. - */ -static int revalidate_pack_entry(struct object_entry *entry, unsigned char *data, unsigned long len) -{ - enum object_type type; - unsigned long size, used; - - if (pack_to_stdout) - return 0; - - /* the caller has already called use_packed_git() for us, - * so it is safe to access the pack data from mmapped location. - * make sure the entry inflates correctly. - */ - used = unpack_object_header_gently(data, len, &type, &size); - if (!used) - return -1; - if (type == OBJ_REF_DELTA) - used += 20; /* skip base object name */ - data += used; - len -= used; - return check_inflate(data, len, entry->size); -} - static int revalidate_loose_object(struct object_entry *entry, unsigned char *map, unsigned long mapsize) @@ -339,7 +337,7 @@ static unsigned long write_object(struct sha1file *f, obj_type = entry->type; if (! entry->in_pack) to_reuse = 0; /* can't reuse what we don't have */ - else if (obj_type == OBJ_REF_DELTA) + else if (obj_type == OBJ_REF_DELTA || obj_type == OBJ_OFS_DELTA) to_reuse = 1; /* check_object() decided it for us */ else if (obj_type != entry->in_pack_type) to_reuse = 0; /* pack has delta which is unusable */ @@ -415,18 +413,38 @@ static unsigned long write_object(struct sha1file *f, } else { struct packed_git *p = entry->in_pack; - use_packed_git(p); - datalen = find_packed_object_size(p, entry->in_pack_offset); - buf = (char *) p->pack_base + entry->in_pack_offset; + if (entry->delta) { + obj_type = (allow_ofs_delta && entry->delta->offset) ? + OBJ_OFS_DELTA : OBJ_REF_DELTA; + reused_delta++; + } + hdrlen = encode_header(obj_type, entry->size, header); + sha1write(f, header, hdrlen); + if (obj_type == OBJ_OFS_DELTA) { + 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) { + sha1write(f, entry->delta->sha1, 20); + hdrlen += 20; + } - if (revalidate_pack_entry(entry, buf, datalen)) + use_packed_git(p); + buf = (char *) p->pack_base + + entry->in_pack_offset + + entry->in_pack_header_size; + datalen = find_packed_object_size(p, entry->in_pack_offset) + - entry->in_pack_header_size; +//fprintf(stderr, "reusing %d at %d header %d size %d\n", obj_type, entry->in_pack_offset, entry->in_pack_header_size, datalen); + if (!pack_to_stdout && check_inflate(buf, datalen, entry->size)) die("corrupt delta in pack %s", sha1_to_hex(entry->sha1)); sha1write(f, buf, datalen); unuse_packed_git(p); - hdrlen = 0; /* not really */ - if (obj_type == OBJ_REF_DELTA) - reused_delta++; reused++; } if (entry->delta) @@ -914,26 +932,64 @@ static void check_object(struct object_entry *entry) char type[20]; if (entry->in_pack && !entry->preferred_base) { - unsigned char base[20]; - unsigned long size; - struct object_entry *base_entry; + struct packed_git *p = entry->in_pack; + unsigned long left = p->pack_size - entry->in_pack_offset; + unsigned long size, used; + unsigned char *buf; + struct object_entry *base_entry = NULL; + + use_packed_git(p); + buf = p->pack_base; + buf += entry->in_pack_offset; /* We want in_pack_type even if we do not reuse delta. * There is no point not reusing non-delta representations. */ - check_reuse_pack_delta(entry->in_pack, - entry->in_pack_offset, - base, &size, - &entry->in_pack_type); + used = unpack_object_header_gently(buf, left, + &entry->in_pack_type, &size); + if (!used || left - used <= 20) + die("corrupt pack for %s", sha1_to_hex(entry->sha1)); /* Check if it is delta, and the base is also an object * we are going to pack. If so we will reuse the existing * delta. */ - if (!no_reuse_delta && - entry->in_pack_type == OBJ_REF_DELTA && - (base_entry = locate_object_entry(base)) && - (!base_entry->preferred_base)) { + if (!no_reuse_delta) { + unsigned char c, *base_name; + unsigned long ofs; + /* there is at least 20 bytes left in the pack */ + switch (entry->in_pack_type) { + case OBJ_REF_DELTA: + base_name = buf + used; + used += 20; + break; + case OBJ_OFS_DELTA: + c = buf[used++]; + ofs = c & 127; + while (c & 128) { + ofs += 1; + if (!ofs || ofs & ~(~0UL >> 7)) + die("delta base offset overflow in pack for %s", + sha1_to_hex(entry->sha1)); + c = buf[used++]; + ofs = (ofs << 7) + (c & 127); + } + if (ofs >= entry->in_pack_offset) + die("delta base offset out of bound for %s", + sha1_to_hex(entry->sha1)); + ofs = entry->in_pack_offset - ofs; + base_name = find_packed_object_name(p, ofs); + break; + default: + base_name = NULL; + } + if (base_name) + base_entry = locate_object_entry(base_name); + } + unuse_packed_git(p); + entry->in_pack_header_size = used; + + if (base_entry && !base_entry->preferred_base) { /* Depth value does not matter - find_deltas() * will never consider reused delta as the @@ -942,9 +998,9 @@ static void check_object(struct object_entry *entry) */ /* uncompressed size of the delta data */ - entry->size = entry->delta_size = size; + entry->size = size; entry->delta = base_entry; - entry->type = OBJ_REF_DELTA; + entry->type = entry->in_pack_type; entry->delta_sibling = base_entry->delta_child; base_entry->delta_child = entry; @@ -1500,7 +1556,7 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) continue; } if (!strcmp("--delta-base-offset", arg)) { - allow_ofs_delta = no_reuse_delta = 1; + allow_ofs_delta = 1; continue; } if (!strcmp("--stdout", arg)) { diff --git a/pack.h b/pack.h index 05557da152..4c9bddd4f2 100644 --- a/pack.h +++ b/pack.h @@ -16,7 +16,4 @@ struct pack_header { }; extern int verify_pack(struct packed_git *, int); -extern int check_reuse_pack_delta(struct packed_git *, unsigned long, - unsigned char *, unsigned long *, - enum object_type *); #endif diff --git a/sha1_file.c b/sha1_file.c index fdb4588280..18c2f88112 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -1000,25 +1000,6 @@ static unsigned long unpack_object_header(struct packed_git *p, unsigned long of return offset + used; } -int check_reuse_pack_delta(struct packed_git *p, unsigned long offset, - unsigned char *base, unsigned long *sizep, - enum object_type *kindp) -{ - unsigned long ptr; - int status = -1; - - use_packed_git(p); - ptr = offset; - ptr = unpack_object_header(p, ptr, kindp, sizep); - if (*kindp != OBJ_REF_DELTA) - goto done; - hashcpy(base, (unsigned char *) p->pack_base + ptr); - status = 0; - done: - unuse_packed_git(p); - return status; -} - void packed_object_info_detail(struct packed_git *p, unsigned long offset, char *type, -- GitLab