To implement SHA1 compatibility on SHA256 repositories the loose
object map needs to be updated whenver a loose object is written.
Updating the loose object map this way allows git to support
the old hash algorithm in constant time.
The functions write_loose_object, and stream_loose_object are
the only two functions that write to the loose object store.
Update stream_loose_object to compute the compatibiilty hash, update
the loose object, and then call repo_add_loose_object_map to update
the loose object map.
Update write_object_file_flags to convert the object into
it's compatibility encoding, hash the compatibility encoding,
write the object, and then update the loose object map.
Update force_object_loose to lookup the hash of the compatibility
encoding, write the loose object, and then update the loose object
map.
Update write_object_file_litterally to refuse to write any objects
when a compatibility encoding is enabled. The problem is that
write_object_file_literally is frequently used to write ill-formed
objects. Especially when the type of those objects is changed there
is by definition no possibile way to convert them, as no converstion
has been defined.
Since a compatibilty encoding can not be found and a compatibility
mapping can not be written the cleanest behavior is to simply
disallow write_object_file_literraly from writing files.
Except that the loose objects are updated before the loose object map
I have not done any analysis to see how robust this scheme is in the
event of failure.
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
object-file.c | 94 +++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 76 insertions(+), 18 deletions(-)
diff --git a/object-file.c b/object-file.c
index 7f24f19b8a68..6a14b8875343 100644
--- a/object-file.c
+++ b/object-file.c
@@ -44,6 +44,7 @@
#include "setup.h"
#include "submodule.h"
#include "fsck.h"
+#include "loose.h"
/* The maximum size for an object header. */
#define MAX_HEADER_LEN 32
@@ -2035,9 +2036,12 @@ static int start_loose_object_common(struct strbuf *tmp_file,
const char *filename, unsigned flags,
git_zstream *stream,
unsigned char *buf, size_t buflen,
- git_hash_ctx *c,
+ git_hash_ctx *c, git_hash_ctx *compat_c,
char *hdr, int hdrlen)
{
+ struct repository *repo = the_repository;
+ const struct git_hash_algo *algo = repo->hash_algo;
+ const struct git_hash_algo *compat = repo->compat_hash_algo;
int fd;
fd = create_tmpfile(tmp_file, filename);
@@ -2057,14 +2061,18 @@ static int start_loose_object_common(struct strbuf *tmp_file,
git_deflate_init(stream, zlib_compression_level);
stream->next_out = buf;
stream->avail_out = buflen;
- the_hash_algo->init_fn(c);
+ algo->init_fn(c);
+ if (compat && compat_c)
+ compat->init_fn(compat_c);
/* Start to feed header to zlib stream */
stream->next_in = (unsigned char *)hdr;
stream->avail_in = hdrlen;
while (git_deflate(stream, 0) == Z_OK)
; /* nothing */
- the_hash_algo->update_fn(c, hdr, hdrlen);
+ algo->update_fn(c, hdr, hdrlen);
+ if (compat && compat_c)
+ compat->update_fn(compat_c, hdr, hdrlen);
return fd;
}
@@ -2073,16 +2081,21 @@ static int start_loose_object_common(struct strbuf *tmp_file,
* Common steps for the inner git_deflate() loop for writing loose
* objects. Returns what git_deflate() returns.
*/
-static int write_loose_object_common(git_hash_ctx *c,
+static int write_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c,
git_zstream *stream, const int flush,
unsigned char *in0, const int fd,
unsigned char *compressed,
const size_t compressed_len)
{
+ struct repository *repo = the_repository;
+ const struct git_hash_algo *algo = repo->hash_algo;
+ const struct git_hash_algo *compat = repo->compat_hash_algo;
int ret;
ret = git_deflate(stream, flush ? Z_FINISH : 0);
- the_hash_algo->update_fn(c, in0, stream->next_in - in0);
+ algo->update_fn(c, in0, stream->next_in - in0);
+ if (compat && compat_c)
+ compat->update_fn(compat_c, in0, stream->next_in - in0);
if (write_in_full(fd, compressed, stream->next_out - compressed) < 0)
die_errno(_("unable to write loose object file"));
stream->next_out = compressed;
@@ -2097,15 +2110,21 @@ static int write_loose_object_common(git_hash_ctx *c,
* - End the compression of zlib stream.
* - Get the calculated oid to "oid".
*/
-static int end_loose_object_common(git_hash_ctx *c, git_zstream *stream,
- struct object_id *oid)
+static int end_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c,
+ git_zstream *stream, struct object_id *oid,
+ struct object_id *compat_oid)
{
+ struct repository *repo = the_repository;
+ const struct git_hash_algo *algo = repo->hash_algo;
+ const struct git_hash_algo *compat = repo->compat_hash_algo;
int ret;
ret = git_deflate_end_gently(stream);
if (ret != Z_OK)
return ret;
- the_hash_algo->final_oid_fn(oid, c);
+ algo->final_oid_fn(oid, c);
+ if (compat && compat_c)
+ compat->final_oid_fn(compat_oid, compat_c);
return Z_OK;
}
@@ -2129,7 +2148,7 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
fd = start_loose_object_common(&tmp_file, filename.buf, flags,
&stream, compressed, sizeof(compressed),
- &c, hdr, hdrlen);
+ &c, NULL, hdr, hdrlen);
if (fd < 0)
return -1;
@@ -2139,14 +2158,14 @@ static int write_loose_object(const struct object_id *oid, char *hdr,
do {
unsigned char *in0 = stream.next_in;
- ret = write_loose_object_common(&c, &stream, 1, in0, fd,
+ ret = write_loose_object_common(&c, NULL, &stream, 1, in0, fd,
compressed, sizeof(compressed));
} while (ret == Z_OK);
if (ret != Z_STREAM_END)
die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid),
ret);
- ret = end_loose_object_common(&c, &stream, ¶no_oid);
+ ret = end_loose_object_common(&c, NULL, &stream, ¶no_oid, NULL);
if (ret != Z_OK)
die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid),
ret);
@@ -2191,10 +2210,12 @@ static int freshen_packed_object(const struct object_id *oid)
int stream_loose_object(struct input_stream *in_stream, size_t len,
struct object_id *oid)
{
+ const struct git_hash_algo *compat = the_repository->compat_hash_algo;
+ struct object_id compat_oid;
int fd, ret, err = 0, flush = 0;
unsigned char compressed[4096];
git_zstream stream;
- git_hash_ctx c;
+ git_hash_ctx c, compat_c;
struct strbuf tmp_file = STRBUF_INIT;
struct strbuf filename = STRBUF_INIT;
int dirlen;
@@ -2218,7 +2239,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len,
*/
fd = start_loose_object_common(&tmp_file, filename.buf, 0,
&stream, compressed, sizeof(compressed),
- &c, hdr, hdrlen);
+ &c, &compat_c, hdr, hdrlen);
if (fd < 0) {
err = -1;
goto cleanup;
@@ -2236,7 +2257,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len,
if (in_stream->is_finished)
flush = 1;
}
- ret = write_loose_object_common(&c, &stream, flush, in0, fd,
+ ret = write_loose_object_common(&c, &compat_c, &stream, flush, in0, fd,
compressed, sizeof(compressed));
/*
* Unlike write_loose_object(), we do not have the entire
@@ -2259,7 +2280,7 @@ int stream_loose_object(struct input_stream *in_stream, size_t len,
*/
if (ret != Z_STREAM_END)
die(_("unable to stream deflate new object (%d)"), ret);
- ret = end_loose_object_common(&c, &stream, oid);
+ ret = end_loose_object_common(&c, &compat_c, &stream, oid, &compat_oid);
if (ret != Z_OK)
die(_("deflateEnd on stream object failed (%d)"), ret);
close_loose_object(fd, tmp_file.buf);
@@ -2286,6 +2307,8 @@ int stream_loose_object(struct input_stream *in_stream, size_t len,
}
err = finalize_object_file(tmp_file.buf, filename.buf);
+ if (!err && compat)
+ err = repo_add_loose_object_map(the_repository, oid, &compat_oid);
cleanup:
strbuf_release(&tmp_file);
strbuf_release(&filename);
@@ -2296,17 +2319,38 @@ int write_object_file_flags(const void *buf, unsigned long len,
enum object_type type, struct object_id *oid,
unsigned flags)
{
+ struct repository *repo = the_repository;
+ const struct git_hash_algo *algo = repo->hash_algo;
+ const struct git_hash_algo *compat = repo->compat_hash_algo;
+ struct object_id compat_oid;
char hdr[MAX_HEADER_LEN];
int hdrlen = sizeof(hdr);
+ /* Generate compat_oid */
+ if (compat) {
+ if (type == OBJ_BLOB)
+ hash_object_file(compat, buf, len, type, &compat_oid);
+ else {
+ struct strbuf converted = STRBUF_INIT;
+ convert_object_file(&converted, algo, compat,
+ buf, len, type, 0);
+ hash_object_file(compat, converted.buf, converted.len,
+ type, &compat_oid);
+ strbuf_release(&converted);
+ }
+ }
+
/* Normally if we have it in the pack then we do not bother writing
* it out into .git/objects/??/?{38} file.
*/
- write_object_file_prepare(the_hash_algo, buf, len, type, oid, hdr,
- &hdrlen);
+ write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
if (freshen_packed_object(oid) || freshen_loose_object(oid))
return 0;
- return write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags);
+ if (write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags))
+ return -1;
+ if (compat)
+ return repo_add_loose_object_map(repo, oid, &compat_oid);
+ return 0;
}
int write_object_file_literally(const void *buf, unsigned long len,
@@ -2324,6 +2368,10 @@ int write_object_file_literally(const void *buf, unsigned long len,
if (!(flags & HASH_WRITE_OBJECT))
goto cleanup;
+ else if (the_repository->compat_hash_algo) {
+ status = -1;
+ goto cleanup;
+ }
if (freshen_packed_object(oid) || freshen_loose_object(oid))
goto cleanup;
status = write_loose_object(oid, header, hdrlen, buf, len, 0, 0);
@@ -2335,9 +2383,12 @@ int write_object_file_literally(const void *buf, unsigned long len,
int force_object_loose(const struct object_id *oid, time_t mtime)
{
+ struct repository *repo = the_repository;
+ const struct git_hash_algo *compat = repo->compat_hash_algo;
void *buf;
unsigned long len;
struct object_info oi = OBJECT_INFO_INIT;
+ struct object_id compat_oid;
enum object_type type;
char hdr[MAX_HEADER_LEN];
int hdrlen;
@@ -2350,8 +2401,15 @@ int force_object_loose(const struct object_id *oid, time_t mtime)
oi.contentp = &buf;
if (oid_object_info_extended(the_repository, oid, &oi, 0))
return error(_("cannot read object for %s"), oid_to_hex(oid));
+ if (compat) {
+ if (repo_oid_to_algop(repo, oid, compat, &compat_oid))
+ return error(_("cannot map object %s to %s"),
+ oid_to_hex(oid), compat->name);
+ }
hdrlen = format_object_header(hdr, sizeof(hdr), type, len);
ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime, 0);
+ if (!ret && compat)
+ ret = repo_add_loose_object_map(the_repository, oid, &compat_oid);
free(buf);
return ret;
--
2.41.0
