git/index-pack.c

469 строки
12 KiB
C

#include "cache.h"
#include "delta.h"
#include "pack.h"
#include "csum-file.h"
static const char index_pack_usage[] =
"git-index-pack [-o index-file] pack-file";
struct object_entry
{
unsigned long offset;
enum object_type type;
enum object_type real_type;
unsigned char sha1[20];
};
struct delta_entry
{
struct object_entry *obj;
unsigned char base_sha1[20];
};
static const char *pack_name;
static unsigned char *pack_base;
static unsigned long pack_size;
static struct object_entry *objects;
static struct delta_entry *deltas;
static int nr_objects;
static int nr_deltas;
static void open_pack_file(void)
{
int fd;
struct stat st;
fd = open(pack_name, O_RDONLY);
if (fd < 0)
die("cannot open packfile '%s': %s", pack_name,
strerror(errno));
if (fstat(fd, &st)) {
int err = errno;
close(fd);
die("cannot fstat packfile '%s': %s", pack_name,
strerror(err));
}
pack_size = st.st_size;
pack_base = mmap(NULL, pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (pack_base == MAP_FAILED) {
int err = errno;
close(fd);
die("cannot mmap packfile '%s': %s", pack_name,
strerror(err));
}
close(fd);
}
static void parse_pack_header(void)
{
const struct pack_header *hdr;
unsigned char sha1[20];
SHA_CTX ctx;
/* Ensure there are enough bytes for the header and final SHA1 */
if (pack_size < sizeof(struct pack_header) + 20)
die("packfile '%s' is too small", pack_name);
/* Header consistency check */
hdr = (void *)pack_base;
if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
die("packfile '%s' signature mismatch", pack_name);
if (!pack_version_ok(hdr->hdr_version))
die("packfile '%s' version %d unsupported",
pack_name, ntohl(hdr->hdr_version));
nr_objects = ntohl(hdr->hdr_entries);
/* Check packfile integrity */
SHA1_Init(&ctx);
SHA1_Update(&ctx, pack_base, pack_size - 20);
SHA1_Final(sha1, &ctx);
if (memcmp(sha1, pack_base + pack_size - 20, 20))
die("packfile '%s' SHA1 mismatch", pack_name);
}
static void bad_object(unsigned long offset, const char *format,
...) NORETURN __attribute__((format (printf, 2, 3)));
static void bad_object(unsigned long offset, const char *format, ...)
{
va_list params;
char buf[1024];
va_start(params, format);
vsnprintf(buf, sizeof(buf), format, params);
va_end(params);
die("packfile '%s': bad object at offset %lu: %s",
pack_name, offset, buf);
}
static void *unpack_entry_data(unsigned long offset,
unsigned long *current_pos, unsigned long size)
{
unsigned long pack_limit = pack_size - 20;
unsigned long pos = *current_pos;
z_stream stream;
void *buf = xmalloc(size);
memset(&stream, 0, sizeof(stream));
stream.next_out = buf;
stream.avail_out = size;
stream.next_in = pack_base + pos;
stream.avail_in = pack_limit - pos;
inflateInit(&stream);
for (;;) {
int ret = inflate(&stream, 0);
if (ret == Z_STREAM_END)
break;
if (ret != Z_OK)
bad_object(offset, "inflate returned %d", ret);
}
inflateEnd(&stream);
if (stream.total_out != size)
bad_object(offset, "size mismatch (expected %lu, got %lu)",
size, stream.total_out);
*current_pos = pack_limit - stream.avail_in;
return buf;
}
static void *unpack_raw_entry(unsigned long offset,
enum object_type *obj_type,
unsigned long *obj_size,
unsigned char *delta_base,
unsigned long *next_obj_offset)
{
unsigned long pack_limit = pack_size - 20;
unsigned long pos = offset;
unsigned char c;
unsigned long size;
unsigned shift;
enum object_type type;
void *data;
c = pack_base[pos++];
type = (c >> 4) & 7;
size = (c & 15);
shift = 4;
while (c & 0x80) {
if (pos >= pack_limit)
bad_object(offset, "object extends past end of pack");
c = pack_base[pos++];
size += (c & 0x7fUL) << shift;
shift += 7;
}
switch (type) {
case OBJ_DELTA:
if (pos + 20 >= pack_limit)
bad_object(offset, "object extends past end of pack");
memcpy(delta_base, pack_base + pos, 20);
pos += 20;
/* fallthru */
case OBJ_COMMIT:
case OBJ_TREE:
case OBJ_BLOB:
case OBJ_TAG:
data = unpack_entry_data(offset, &pos, size);
break;
default:
bad_object(offset, "bad object type %d", type);
}
*obj_type = type;
*obj_size = size;
*next_obj_offset = pos;
return data;
}
static int find_delta(const unsigned char *base_sha1)
{
int first = 0, last = nr_deltas;
while (first < last) {
int next = (first + last) / 2;
struct delta_entry *delta = &deltas[next];
int cmp;
cmp = memcmp(base_sha1, delta->base_sha1, 20);
if (!cmp)
return next;
if (cmp < 0) {
last = next;
continue;
}
first = next+1;
}
return -first-1;
}
static int find_deltas_based_on_sha1(const unsigned char *base_sha1,
int *first_index, int *last_index)
{
int first = find_delta(base_sha1);
int last = first;
int end = nr_deltas - 1;
if (first < 0)
return -1;
while (first > 0 && !memcmp(deltas[first-1].base_sha1, base_sha1, 20))
--first;
while (last < end && !memcmp(deltas[last+1].base_sha1, base_sha1, 20))
++last;
*first_index = first;
*last_index = last;
return 0;
}
static void sha1_object(const void *data, unsigned long size,
enum object_type type, unsigned char *sha1)
{
SHA_CTX ctx;
char header[50];
int header_size;
const char *type_str;
switch (type) {
case OBJ_COMMIT: type_str = "commit"; break;
case OBJ_TREE: type_str = "tree"; break;
case OBJ_BLOB: type_str = "blob"; break;
case OBJ_TAG: type_str = "tag"; break;
default:
die("bad type %d", type);
}
header_size = sprintf(header, "%s %lu", type_str, size) + 1;
SHA1_Init(&ctx);
SHA1_Update(&ctx, header, header_size);
SHA1_Update(&ctx, data, size);
SHA1_Final(sha1, &ctx);
}
static void resolve_delta(struct delta_entry *delta, void *base_data,
unsigned long base_size, enum object_type type)
{
struct object_entry *obj = delta->obj;
void *delta_data;
unsigned long delta_size;
void *result;
unsigned long result_size;
enum object_type delta_type;
unsigned char base_sha1[20];
unsigned long next_obj_offset;
int j, first, last;
obj->real_type = type;
delta_data = unpack_raw_entry(obj->offset, &delta_type,
&delta_size, base_sha1,
&next_obj_offset);
result = patch_delta(base_data, base_size, delta_data, delta_size,
&result_size);
free(delta_data);
if (!result)
bad_object(obj->offset, "failed to apply delta");
sha1_object(result, result_size, type, obj->sha1);
if (!find_deltas_based_on_sha1(obj->sha1, &first, &last)) {
for (j = first; j <= last; j++)
resolve_delta(&deltas[j], result, result_size, type);
}
free(result);
}
static int compare_delta_entry(const void *a, const void *b)
{
const struct delta_entry *delta_a = a;
const struct delta_entry *delta_b = b;
return memcmp(delta_a->base_sha1, delta_b->base_sha1, 20);
}
static void parse_pack_objects(void)
{
int i;
unsigned long offset = sizeof(struct pack_header);
unsigned char base_sha1[20];
void *data;
unsigned long data_size;
/*
* First pass:
* - find locations of all objects;
* - calculate SHA1 of all non-delta objects;
* - remember base SHA1 for all deltas.
*/
for (i = 0; i < nr_objects; i++) {
struct object_entry *obj = &objects[i];
obj->offset = offset;
data = unpack_raw_entry(offset, &obj->type, &data_size,
base_sha1, &offset);
obj->real_type = obj->type;
if (obj->type == OBJ_DELTA) {
struct delta_entry *delta = &deltas[nr_deltas++];
delta->obj = obj;
memcpy(delta->base_sha1, base_sha1, 20);
} else
sha1_object(data, data_size, obj->type, obj->sha1);
free(data);
}
if (offset != pack_size - 20)
die("packfile '%s' has junk at the end", pack_name);
/* Sort deltas by base SHA1 for fast searching */
qsort(deltas, nr_deltas, sizeof(struct delta_entry),
compare_delta_entry);
/*
* Second pass:
* - for all non-delta objects, look if it is used as a base for
* deltas;
* - if used as a base, uncompress the object and apply all deltas,
* recursively checking if the resulting object is used as a base
* for some more deltas.
*/
for (i = 0; i < nr_objects; i++) {
struct object_entry *obj = &objects[i];
int j, first, last;
if (obj->type == OBJ_DELTA)
continue;
if (find_deltas_based_on_sha1(obj->sha1, &first, &last))
continue;
data = unpack_raw_entry(obj->offset, &obj->type, &data_size,
base_sha1, &offset);
for (j = first; j <= last; j++)
resolve_delta(&deltas[j], data, data_size, obj->type);
free(data);
}
/* Check for unresolved deltas */
for (i = 0; i < nr_deltas; i++) {
if (deltas[i].obj->real_type == OBJ_DELTA)
die("packfile '%s' has unresolved deltas", pack_name);
}
}
static int sha1_compare(const void *_a, const void *_b)
{
struct object_entry *a = *(struct object_entry **)_a;
struct object_entry *b = *(struct object_entry **)_b;
return memcmp(a->sha1, b->sha1, 20);
}
static void write_index_file(const char *index_name, unsigned char *sha1)
{
struct sha1file *f;
struct object_entry **sorted_by_sha, **list, **last;
unsigned int array[256];
int i;
SHA_CTX ctx;
if (nr_objects) {
sorted_by_sha =
xcalloc(nr_objects, sizeof(struct object_entry *));
list = sorted_by_sha;
last = sorted_by_sha + nr_objects;
for (i = 0; i < nr_objects; ++i)
sorted_by_sha[i] = &objects[i];
qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
sha1_compare);
}
else
sorted_by_sha = list = last = NULL;
unlink(index_name);
f = sha1create("%s", index_name);
/*
* Write the first-level table (the list is sorted,
* but we use a 256-entry lookup to be able to avoid
* having to do eight extra binary search iterations).
*/
for (i = 0; i < 256; i++) {
struct object_entry **next = list;
while (next < last) {
struct object_entry *obj = *next;
if (obj->sha1[0] != i)
break;
next++;
}
array[i] = htonl(next - sorted_by_sha);
list = next;
}
sha1write(f, array, 256 * sizeof(int));
/* recompute the SHA1 hash of sorted object names.
* currently pack-objects does not do this, but that
* can be fixed.
*/
SHA1_Init(&ctx);
/*
* Write the actual SHA1 entries..
*/
list = sorted_by_sha;
for (i = 0; i < nr_objects; i++) {
struct object_entry *obj = *list++;
unsigned int offset = htonl(obj->offset);
sha1write(f, &offset, 4);
sha1write(f, obj->sha1, 20);
SHA1_Update(&ctx, obj->sha1, 20);
}
sha1write(f, pack_base + pack_size - 20, 20);
sha1close(f, NULL, 1);
free(sorted_by_sha);
SHA1_Final(sha1, &ctx);
}
int main(int argc, char **argv)
{
int i;
char *index_name = NULL;
char *index_name_buf = NULL;
unsigned char sha1[20];
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
if (*arg == '-') {
if (!strcmp(arg, "-o")) {
if (index_name || (i+1) >= argc)
usage(index_pack_usage);
index_name = argv[++i];
} else
usage(index_pack_usage);
continue;
}
if (pack_name)
usage(index_pack_usage);
pack_name = arg;
}
if (!pack_name)
usage(index_pack_usage);
if (!index_name) {
int len = strlen(pack_name);
if (len < 5 || strcmp(pack_name + len - 5, ".pack"))
die("packfile name '%s' does not end with '.pack'",
pack_name);
index_name_buf = xmalloc(len);
memcpy(index_name_buf, pack_name, len - 5);
strcpy(index_name_buf + len - 5, ".idx");
index_name = index_name_buf;
}
open_pack_file();
parse_pack_header();
objects = xcalloc(nr_objects, sizeof(struct object_entry));
deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
parse_pack_objects();
free(deltas);
write_index_file(index_name, sha1);
free(objects);
free(index_name_buf);
printf("%s\n", sha1_to_hex(sha1));
return 0;
}