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teach git-unpack-objects about deltas with offset to base
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For delta resolution to be possible, a list of sha1/offset tuple must
be constructed in memory in order to load the appropriate base object.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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Nicolas Pitre authored and Junio C Hamano committed Sep 27, 2006
1 parent eb32d23 commit 209c554
Showing 1 changed file with 106 additions and 32 deletions.
138 changes: 106 additions & 32 deletions builtin-unpack-objects.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ static const char unpack_usage[] = "git-unpack-objects [-n] [-q] [-r] < pack-fil

/* We always read in 4kB chunks. */
static unsigned char buffer[4096];
static unsigned long offset, len;
static unsigned long offset, len, consumed_bytes;
static SHA_CTX ctx;

/*
Expand Down Expand Up @@ -51,6 +51,7 @@ static void use(int bytes)
die("used more bytes than were available");
len -= bytes;
offset += bytes;
consumed_bytes += bytes;
}

static void *get_data(unsigned long size)
Expand Down Expand Up @@ -89,35 +90,49 @@ static void *get_data(unsigned long size)

struct delta_info {
unsigned char base_sha1[20];
unsigned long base_offset;
unsigned long size;
void *delta;
unsigned nr;
struct delta_info *next;
};

static struct delta_info *delta_list;

static void add_delta_to_list(unsigned char *base_sha1, void *delta, unsigned long size)
static void add_delta_to_list(unsigned nr, unsigned const char *base_sha1,
unsigned long base_offset,
void *delta, unsigned long size)
{
struct delta_info *info = xmalloc(sizeof(*info));

hashcpy(info->base_sha1, base_sha1);
info->base_offset = base_offset;
info->size = size;
info->delta = delta;
info->nr = nr;
info->next = delta_list;
delta_list = info;
}

static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size);
struct obj_info {
unsigned long offset;
unsigned char sha1[20];
};

static struct obj_info *obj_list;

static void write_object(void *buf, unsigned long size, const char *type)
static void added_object(unsigned nr, const char *type, void *data,
unsigned long size);

static void write_object(unsigned nr, void *buf, unsigned long size,
const char *type)
{
unsigned char sha1[20];
if (write_sha1_file(buf, size, type, sha1) < 0)
if (write_sha1_file(buf, size, type, obj_list[nr].sha1) < 0)
die("failed to write object");
added_object(sha1, type, buf, size);
added_object(nr, type, buf, size);
}

static void resolve_delta(const char *type,
static void resolve_delta(unsigned nr, const char *type,
void *base, unsigned long base_size,
void *delta, unsigned long delta_size)
{
Expand All @@ -130,28 +145,32 @@ static void resolve_delta(const char *type,
if (!result)
die("failed to apply delta");
free(delta);
write_object(result, result_size, type);
write_object(nr, result, result_size, type);
free(result);
}

static void added_object(unsigned char *sha1, const char *type, void *data, unsigned long size)
static void added_object(unsigned nr, const char *type, void *data,
unsigned long size)
{
struct delta_info **p = &delta_list;
struct delta_info *info;

while ((info = *p) != NULL) {
if (!hashcmp(info->base_sha1, sha1)) {
if (!hashcmp(info->base_sha1, obj_list[nr].sha1) ||
info->base_offset == obj_list[nr].offset) {
*p = info->next;
p = &delta_list;
resolve_delta(type, data, size, info->delta, info->size);
resolve_delta(info->nr, type, data, size,
info->delta, info->size);
free(info);
continue;
}
p = &info->next;
}
}

static void unpack_non_delta_entry(enum object_type kind, unsigned long size)
static void unpack_non_delta_entry(enum object_type kind, unsigned long size,
unsigned nr)
{
void *buf = get_data(size);
const char *type;
Expand All @@ -164,30 +183,80 @@ static void unpack_non_delta_entry(enum object_type kind, unsigned long size)
default: die("bad type %d", kind);
}
if (!dry_run && buf)
write_object(buf, size, type);
write_object(nr, buf, size, type);
free(buf);
}

static void unpack_delta_entry(unsigned long delta_size)
static void unpack_delta_entry(enum object_type kind, unsigned long delta_size,
unsigned nr)
{
void *delta_data, *base;
unsigned long base_size;
char type[20];
unsigned char base_sha1[20];

hashcpy(base_sha1, fill(20));
use(20);
if (kind == OBJ_REF_DELTA) {
hashcpy(base_sha1, fill(20));
use(20);
delta_data = get_data(delta_size);
if (dry_run || !delta_data) {
free(delta_data);
return;
}
if (!has_sha1_file(base_sha1)) {
hashcpy(obj_list[nr].sha1, null_sha1);
add_delta_to_list(nr, base_sha1, 0, delta_data, delta_size);
return;
}
} else {
unsigned base_found = 0;
unsigned char *pack, c;
unsigned long base_offset;
unsigned lo, mid, hi;

delta_data = get_data(delta_size);
if (dry_run || !delta_data) {
free(delta_data);
return;
}
pack = fill(1);
c = *pack;
use(1);
base_offset = c & 127;
while (c & 128) {
base_offset += 1;
if (!base_offset || base_offset & ~(~0UL >> 7))
die("offset value overflow for delta base object");
pack = fill(1);
c = *pack;
use(1);
base_offset = (base_offset << 7) + (c & 127);
}
base_offset = obj_list[nr].offset - base_offset;

if (!has_sha1_file(base_sha1)) {
add_delta_to_list(base_sha1, delta_data, delta_size);
return;
delta_data = get_data(delta_size);
if (dry_run || !delta_data) {
free(delta_data);
return;
}
lo = 0;
hi = nr;
while (lo < hi) {
mid = (lo + hi)/2;
if (base_offset < obj_list[mid].offset) {
hi = mid;
} else if (base_offset > obj_list[mid].offset) {
lo = mid + 1;
} else {
hashcpy(base_sha1, obj_list[mid].sha1);
base_found = !is_null_sha1(base_sha1);
break;
}
}
if (!base_found) {
/* The delta base object is itself a delta that
has not been resolved yet. */
hashcpy(obj_list[nr].sha1, null_sha1);
add_delta_to_list(nr, null_sha1, base_offset, delta_data, delta_size);
return;
}
}

base = read_sha1_file(base_sha1, type, &base_size);
if (!base) {
error("failed to read delta-pack base object %s",
Expand All @@ -197,7 +266,7 @@ static void unpack_delta_entry(unsigned long delta_size)
has_errors = 1;
return;
}
resolve_delta(type, base, base_size, delta_data, delta_size);
resolve_delta(nr, type, base, base_size, delta_data, delta_size);
free(base);
}

Expand All @@ -208,6 +277,8 @@ static void unpack_one(unsigned nr, unsigned total)
unsigned long size;
enum object_type type;

obj_list[nr].offset = consumed_bytes;

pack = fill(1);
c = *pack;
use(1);
Expand All @@ -216,7 +287,7 @@ static void unpack_one(unsigned nr, unsigned total)
shift = 4;
while (c & 0x80) {
pack = fill(1);
c = *pack++;
c = *pack;
use(1);
size += (c & 0x7f) << shift;
shift += 7;
Expand All @@ -225,24 +296,26 @@ static void unpack_one(unsigned nr, unsigned total)
static unsigned long last_sec;
static unsigned last_percent;
struct timeval now;
unsigned percentage = (nr * 100) / total;
unsigned percentage = ((nr+1) * 100) / total;

gettimeofday(&now, NULL);
if (percentage != last_percent || now.tv_sec != last_sec) {
last_sec = now.tv_sec;
last_percent = percentage;
fprintf(stderr, "%4u%% (%u/%u) done\r", percentage, nr, total);
fprintf(stderr, "%4u%% (%u/%u) done\r",
percentage, (nr+1), total);
}
}
switch (type) {
case OBJ_COMMIT:
case OBJ_TREE:
case OBJ_BLOB:
case OBJ_TAG:
unpack_non_delta_entry(type, size);
unpack_non_delta_entry(type, size, nr);
return;
case OBJ_REF_DELTA:
unpack_delta_entry(size);
case OBJ_OFS_DELTA:
unpack_delta_entry(type, size, nr);
return;
default:
error("bad object type %d", type);
Expand All @@ -265,9 +338,10 @@ static void unpack_all(void)
die("unknown pack file version %d", ntohl(hdr->hdr_version));
fprintf(stderr, "Unpacking %d objects\n", nr_objects);

obj_list = xmalloc(nr_objects * sizeof(*obj_list));
use(sizeof(struct pack_header));
for (i = 0; i < nr_objects; i++)
unpack_one(i+1, nr_objects);
unpack_one(i, nr_objects);
if (delta_list)
die("unresolved deltas left after unpacking");
}
Expand Down

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