git/unpack-objects.c

288 lines
6.1 KiB
C
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#include "cache.h"
#include "object.h"
#include "delta.h"
#include "pack.h"
static int dry_run;
static const char unpack_usage[] = "git-unpack-objects < pack-file";
/* We always read in 4kB chunks. */
static unsigned char buffer[4096];
static unsigned long offset, len, eof;
static SHA_CTX ctx;
/*
* Make sure at least "min" bytes are available in the buffer, and
* return the pointer to the buffer.
*/
static void * fill(int min)
{
if (min <= len)
return buffer + offset;
if (eof)
die("unable to fill input");
if (min > sizeof(buffer))
die("cannot fill %d bytes", min);
if (offset) {
SHA1_Update(&ctx, buffer, offset);
memcpy(buffer, buffer + offset, len);
offset = 0;
}
do {
int ret = read(0, buffer + len, sizeof(buffer) - len);
if (ret <= 0) {
if (!ret)
die("early EOF");
if (errno == EAGAIN || errno == EINTR)
continue;
die("read error on input: %s", strerror(errno));
}
len += ret;
} while (len < min);
return buffer;
}
static void use(int bytes)
{
if (bytes > len)
die("used more bytes than were available");
len -= bytes;
offset += bytes;
}
static void *get_data(unsigned long size)
{
z_stream stream;
void *buf = xmalloc(size);
if (!size)
return buf;
memset(&stream, 0, sizeof(stream));
stream.next_out = buf;
stream.avail_out = size;
stream.next_in = fill(1);
stream.avail_in = len;
inflateInit(&stream);
for (;;) {
int ret = inflate(&stream, 0);
use(len - stream.avail_in);
if (stream.total_out == size && ret == Z_STREAM_END)
break;
if (ret != Z_OK)
die("inflate returned %d\n", ret);
stream.next_in = fill(1);
stream.avail_in = len;
}
return buf;
}
struct delta_info {
unsigned char base_sha1[20];
unsigned long size;
void *delta;
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)
{
struct delta_info *info = xmalloc(sizeof(*info));
memcpy(info->base_sha1, base_sha1, 20);
info->size = size;
info->delta = delta;
info->next = delta_list;
delta_list = info;
}
static void added_object(unsigned char *sha1, char *type, void *data, unsigned long size);
static int resolve_delta(char *type,
void *base, unsigned long base_size,
void *delta, unsigned long delta_size)
{
void *result;
unsigned long result_size;
unsigned char sha1[20];
result = patch_delta(base, base_size,
delta, delta_size,
&result_size);
if (!result)
die("failed to apply delta");
free(delta);
if (write_sha1_file(result, result_size, type, sha1) < 0)
die("failed to write object");
added_object(sha1, type, result, result_size);
free(result);
return 0;
}
static void added_object(unsigned char *sha1, char *type, void *data, unsigned long size)
{
struct delta_info **p = &delta_list;
struct delta_info *info;
while ((info = *p) != NULL) {
if (!memcmp(info->base_sha1, sha1, 20)) {
*p = info->next;
p = &delta_list;
resolve_delta(type, data, size, info->delta, info->size);
free(info);
continue;
}
p = &info->next;
}
}
static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
{
void *buf = get_data(size);
unsigned char sha1[20];
char *type;
switch (kind) {
case OBJ_COMMIT: type = "commit"; break;
case OBJ_TREE: type = "tree"; break;
case OBJ_BLOB: type = "blob"; break;
case OBJ_TAG: type = "tag"; break;
default: die("bad type %d", kind);
}
if (write_sha1_file(buf, size, type, sha1) < 0)
die("failed to write object");
added_object(sha1, type, buf, size);
free(buf);
return 0;
}
static int unpack_delta_entry(unsigned long delta_size)
{
void *delta_data, *base;
unsigned long base_size;
char type[20];
unsigned char base_sha1[20];
memcpy(base_sha1, fill(20), 20);
use(20);
delta_data = get_data(delta_size);
if (!has_sha1_file(base_sha1)) {
add_delta_to_list(base_sha1, delta_data, delta_size);
return 0;
}
base = read_sha1_file(base_sha1, type, &base_size);
if (!base)
die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
return resolve_delta(type, base, base_size, delta_data, delta_size);
}
static void unpack_one(void)
{
unsigned shift;
unsigned char *pack, c;
unsigned long size;
enum object_type type;
pack = fill(1);
c = *pack;
use(1);
type = (c >> 4) & 7;
size = (c & 15);
shift = 4;
while (c & 0x80) {
pack = fill(1);
c = *pack++;
use(1);
size += (c & 0x7f) << shift;
shift += 7;
}
switch (type) {
case OBJ_COMMIT:
case OBJ_TREE:
case OBJ_BLOB:
case OBJ_TAG:
unpack_non_delta_entry(type, size);
return;
case OBJ_DELTA:
unpack_delta_entry(size);
return;
default:
die("bad object type %d", type);
}
}
/*
* We unpack from the end, older files first. Now, usually
* there are deltas etc, so we'll not actually write the
* objects in that order, but we might as well try..
*/
static void unpack_all(void)
{
int i;
struct pack_header *hdr = fill(sizeof(struct pack_header));
unsigned version = ntohl(hdr->hdr_version);
unsigned nr_objects = ntohl(hdr->hdr_entries);
if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
die("bad pack file");
if (version != PACK_VERSION)
die("unable to handle pack file version %d", version);
fprintf(stderr, "Unpacking %d objects\n", nr_objects);
use(sizeof(struct pack_header));
for (i = 0; i < nr_objects; i++)
unpack_one();
if (delta_list)
die("unresolved deltas left after unpacking");
}
int main(int argc, char **argv)
{
int i;
unsigned char sha1[20];
for (i = 1 ; i < argc; i++) {
const char *arg = argv[i];
if (*arg == '-') {
if (!strcmp(arg, "-n")) {
dry_run = 1;
continue;
}
usage(unpack_usage);
}
/* We don't take any non-flag arguments now.. Maybe some day */
usage(unpack_usage);
}
SHA1_Init(&ctx);
unpack_all();
SHA1_Update(&ctx, buffer, offset);
SHA1_Final(sha1, &ctx);
if (memcmp(fill(20), sha1, 20))
die("final sha1 did not match");
use(20);
/* Write the last part of the buffer to stdout */
while (len) {
int ret = write(1, buffer + offset, len);
if (!ret)
break;
if (ret < 0) {
if (errno == EAGAIN || errno == EINTR)
continue;
break;
}
len -= ret;
offset += ret;
}
/* All done */
return 0;
}