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From: "Eric W. Biederman" <ebiederm@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org,
	"brian m. carlson" <sandals@crustytoothpaste.net>,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH 01/30] object-file-convert: Stubs for converting from one object format to another
Date: Wed, 27 Sep 2023 14:55:08 -0500	[thread overview]
Message-ID: <20230927195537.1682-1-ebiederm@gmail.com> (raw)
In-Reply-To: <87jzsbjt0a.fsf@gmail.froward.int.ebiederm.org>

From: "Eric W. Biederman" <ebiederm@xmission.com>

Two basic functions are provided:
- convert_object_file Takes an object file it's type and hash algorithm
  and converts it into the equivalent object file that would
  have been generated with hash algorithm "to".

  For blob objects there is no converstion to be done and it is an
  error to use this function on them.

  For commit, tree, and tag objects embedded oids are replaced by the
  oids of the objects they refer to with those objects and their
  object ids reencoded in with the hash algorithm "to".  Signatures
  are rearranged so that they remain valid after the object has
  been reencoded.

- repo_oid_to_algop which takes an oid that refers to an object file
  and returns the oid of the equavalent object file generated
  with the target hash algorithm.

The pair of files object-file-convert.c and object-file-convert.h are
introduced to hold as much of this logic as possible to keep this
conversion logic cleanly separated from everything else and in the
hopes that someday the code will be clean enough git can support
compiling out support for sha1 and the various conversion functions.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 Makefile              |  1 +
 object-file-convert.c | 57 +++++++++++++++++++++++++++++++++++++++++++
 object-file-convert.h | 24 ++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 object-file-convert.c
 create mode 100644 object-file-convert.h

diff --git a/Makefile b/Makefile
index 577630936535..f7e824f25cda 100644
--- a/Makefile
+++ b/Makefile
@@ -1073,6 +1073,7 @@ LIB_OBJS += notes-cache.o
 LIB_OBJS += notes-merge.o
 LIB_OBJS += notes-utils.o
 LIB_OBJS += notes.o
+LIB_OBJS += object-file-convert.o
 LIB_OBJS += object-file.o
 LIB_OBJS += object-name.o
 LIB_OBJS += object.o
diff --git a/object-file-convert.c b/object-file-convert.c
new file mode 100644
index 000000000000..ba3e18f6af44
--- /dev/null
+++ b/object-file-convert.c
@@ -0,0 +1,57 @@
+#include "git-compat-util.h"
+#include "gettext.h"
+#include "strbuf.h"
+#include "repository.h"
+#include "hash-ll.h"
+#include "object.h"
+#include "object-file-convert.h"
+
+int repo_oid_to_algop(struct repository *repo, const struct object_id *src,
+		      const struct git_hash_algo *to, struct object_id *dest)
+{
+	/*
+	 * If the source alogirthm is not set, then we're using the
+	 * default hash algorithm for that object.
+	 */
+	const struct git_hash_algo *from =
+		src->algo ? &hash_algos[src->algo] : repo->hash_algo;
+
+	if (from == to) {
+		if (src != dest)
+			oidcpy(dest, src);
+		return 0;
+	}
+	return -1;
+}
+
+int convert_object_file(struct strbuf *outbuf,
+			const struct git_hash_algo *from,
+			const struct git_hash_algo *to,
+			const void *buf, size_t len,
+			enum object_type type,
+			int gentle)
+{
+	int ret;
+
+	/* Don't call this function when no conversion is necessary */
+	if ((from == to) || (type == OBJ_BLOB))
+		die("Refusing noop object file conversion");
+
+	switch (type) {
+	case OBJ_COMMIT:
+	case OBJ_TREE:
+	case OBJ_TAG:
+	default:
+		/* Not implemented yet, so fail. */
+		ret = -1;
+		break;
+	}
+	if (!ret)
+		return 0;
+	if (gentle) {
+		strbuf_release(outbuf);
+		return ret;
+	}
+	die(_("Failed to convert object from %s to %s"),
+		from->name, to->name);
+}
diff --git a/object-file-convert.h b/object-file-convert.h
new file mode 100644
index 000000000000..a4f802aa8eea
--- /dev/null
+++ b/object-file-convert.h
@@ -0,0 +1,24 @@
+#ifndef OBJECT_CONVERT_H
+#define OBJECT_CONVERT_H
+
+struct repository;
+struct object_id;
+struct git_hash_algo;
+struct strbuf;
+#include "object.h"
+
+int repo_oid_to_algop(struct repository *repo, const struct object_id *src,
+		      const struct git_hash_algo *to, struct object_id *dest);
+
+/*
+ * Convert an object file from one hash algorithm to another algorithm.
+ * Return -1 on failure, 0 on success.
+ */
+int convert_object_file(struct strbuf *outbuf,
+			const struct git_hash_algo *from,
+			const struct git_hash_algo *to,
+			const void *buf, size_t len,
+			enum object_type type,
+			int gentle);
+
+#endif /* OBJECT_CONVERT_H */
-- 
2.41.0


  reply	other threads:[~2023-09-27 19:55 UTC|newest]

Thread overview: 104+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-27 19:49 [PATCH 00/30] Initial support for multiple hash functions Eric W. Biederman
2023-09-27 19:55 ` Eric W. Biederman [this message]
2023-09-27 20:42   ` [PATCH 01/30] object-file-convert: Stubs for converting from one object format to another Eric Sunshine
2023-10-02  1:22     ` Eric W. Biederman
2023-10-02  2:27       ` Eric Sunshine
2023-09-27 19:55 ` [PATCH 02/30] oid-array: Teach oid-array to handle multiple kinds of oids Eric W. Biederman
2023-09-27 23:20   ` Eric Sunshine
2023-09-27 19:55 ` [PATCH 03/30] object-names: Support input of oids in any supported hash Eric W. Biederman
2023-09-27 23:29   ` Eric Sunshine
2023-10-02  1:54     ` Eric W. Biederman
2023-09-27 19:55 ` [PATCH 04/30] repository: add a compatibility hash algorithm Eric W. Biederman
2023-09-27 19:55 ` [PATCH 05/30] loose: add a mapping between SHA-1 and SHA-256 for loose objects Eric W. Biederman
2023-09-28  7:14   ` Eric Sunshine
2023-10-02  2:11     ` Eric W. Biederman
2023-10-02  2:36       ` Eric Sunshine
2023-09-27 19:55 ` [PATCH 06/30] loose: Compatibilty short name support Eric W. Biederman
2023-09-27 19:55 ` [PATCH 07/30] object-file: Update the loose object map when writing loose objects Eric W. Biederman
2023-09-27 19:55 ` [PATCH 08/30] object-file: Add a compat_oid_in parameter to write_object_file_flags Eric W. Biederman
2023-09-27 19:55 ` [PATCH 09/30] commit: write commits for both hashes Eric W. Biederman
2023-09-27 19:55 ` [PATCH 10/30] commit: Convert mergetag before computing the signature of a commit Eric W. Biederman
2023-09-27 19:55 ` [PATCH 11/30] commit: Export add_header_signature to support handling signatures on tags Eric W. Biederman
2023-09-27 19:55 ` [PATCH 12/30] tag: sign both hashes Eric W. Biederman
2023-09-27 19:55 ` [PATCH 13/30] cache: add a function to read an OID of a specific algorithm Eric W. Biederman
2023-09-27 19:55 ` [PATCH 14/30] object: Factor out parse_mode out of fast-import and tree-walk into in object.h Eric W. Biederman
2023-09-27 19:55 ` [PATCH 15/30] object-file-convert: add a function to convert trees between algorithms Eric W. Biederman
2023-09-27 19:55 ` [PATCH 16/30] object-file-convert: convert tag objects when writing Eric W. Biederman
2023-09-27 19:55 ` [PATCH 17/30] object-file-convert: Don't leak when converting tag objects Eric W. Biederman
2023-09-27 19:55 ` [PATCH 18/30] object-file-convert: convert commit objects when writing Eric W. Biederman
2023-09-27 19:55 ` [PATCH 19/30] object-file-convert: Convert commits that embed signed tags Eric W. Biederman
2023-09-27 19:55 ` [PATCH 20/30] object-file: Update object_info_extended to reencode objects Eric W. Biederman
2023-09-27 19:55 ` [PATCH 21/30] repository: Implement extensions.compatObjectFormat Eric W. Biederman
2023-09-27 21:39   ` Junio C Hamano
2023-09-28 20:18     ` Junio C Hamano
2023-09-29  0:50       ` Eric Biederman
2023-09-29 16:59       ` Eric W. Biederman
2023-09-29 18:48         ` Junio C Hamano
2023-10-02  0:48           ` Eric W. Biederman
2023-10-02  1:31     ` Eric W. Biederman
2023-09-27 19:55 ` [PATCH 22/30] rev-parse: Add an --output-object-format parameter Eric W. Biederman
2023-09-27 19:55 ` [PATCH 23/30] builtin/cat-file: Let the oid determine the output algorithm Eric W. Biederman
2023-09-27 19:55 ` [PATCH 24/30] tree-walk: init_tree_desc take an oid to get the hash algorithm Eric W. Biederman
2023-09-27 19:55 ` [PATCH 25/30] object-file: Handle compat objects in check_object_signature Eric W. Biederman
2023-09-27 19:55 ` [PATCH 26/30] builtin/ls-tree: Let the oid determine the output algorithm Eric W. Biederman
2023-09-27 19:55 ` [PATCH 27/30] test-lib: Compute the compatibility hash so tests may use it Eric W. Biederman
2023-09-27 19:55 ` [PATCH 28/30] t1006: Rename sha1 to oid Eric W. Biederman
2023-09-27 19:55 ` [PATCH 29/30] t1006: Test oid compatibility with cat-file Eric W. Biederman
2023-09-27 19:55 ` [PATCH 30/30] t1016-compatObjectFormat: Add tests to verify the conversion between objects Eric W. Biederman
2023-09-27 21:31 ` [PATCH 00/30] Initial support for multiple hash functions Junio C Hamano
2023-10-02  2:39 ` [PATCH v2 00/30] initial " Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 01/30] object-file-convert: stubs for converting from one object format to another Eric W. Biederman
2024-02-08  8:23     ` Linus Arver
2024-02-15 11:21     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 02/30] oid-array: teach oid-array to handle multiple kinds of oids Eric W. Biederman
2024-02-13  8:16     ` Linus Arver
2024-02-15  6:22       ` Eric W. Biederman
2024-02-16  0:16         ` Linus Arver
2024-02-16  4:48           ` Eric W. Biederman
2024-02-17  1:59             ` Linus Arver
2024-02-13  8:31     ` Kristoffer Haugsbakk
2024-02-15  6:24       ` Eric W. Biederman
2024-02-15 11:21     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 03/30] object-names: support input of oids in any supported hash Eric W. Biederman
2024-02-13  9:33     ` Linus Arver
2024-02-15 11:21     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 04/30] repository: add a compatibility hash algorithm Eric W. Biederman
2024-02-13 10:02     ` Linus Arver
2024-02-15 11:22     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 05/30] loose: add a mapping between SHA-1 and SHA-256 for loose objects Eric W. Biederman
2024-02-14  7:20     ` Linus Arver
2024-02-15  5:33       ` Eric W. Biederman
2024-02-15 11:22     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 06/30] loose: compatibilty short name support Eric W. Biederman
2024-02-15 11:22     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 07/30] object-file: update the loose object map when writing loose objects Eric W. Biederman
2024-02-15 11:22     ` Patrick Steinhardt
2023-10-02  2:40   ` [PATCH v2 08/30] object-file: add a compat_oid_in parameter to write_object_file_flags Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 09/30] commit: write commits for both hashes Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 10/30] commit: convert mergetag before computing the signature of a commit Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 11/30] commit: export add_header_signature to support handling signatures on tags Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 12/30] tag: sign both hashes Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 13/30] cache: add a function to read an OID of a specific algorithm Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 14/30] object: factor out parse_mode out of fast-import and tree-walk into in object.h Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 15/30] object-file-convert: add a function to convert trees between algorithms Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 16/30] object-file-convert: convert tag objects when writing Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 17/30] object-file-convert: don't leak when converting tag objects Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 18/30] object-file-convert: convert commit objects when writing Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 19/30] object-file-convert: convert commits that embed signed tags Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 20/30] object-file: update object_info_extended to reencode objects Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 21/30] repository: implement extensions.compatObjectFormat Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 22/30] rev-parse: add an --output-object-format parameter Eric W. Biederman
2024-02-08 16:25     ` Jean-Noël Avila
2023-10-02  2:40   ` [PATCH v2 23/30] builtin/cat-file: let the oid determine the output algorithm Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 24/30] tree-walk: init_tree_desc take an oid to get the hash algorithm Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 25/30] object-file: handle compat objects in check_object_signature Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 26/30] builtin/ls-tree: let the oid determine the output algorithm Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 27/30] test-lib: compute the compatibility hash so tests may use it Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 28/30] t1006: rename sha1 to oid Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 29/30] t1006: test oid compatibility with cat-file Eric W. Biederman
2023-10-02  2:40   ` [PATCH v2 30/30] t1016-compatObjectFormat: add tests to verify the conversion between objects Eric W. Biederman
2024-02-07 22:18   ` [PATCH v2 00/30] initial support for multiple hash functions Junio C Hamano
2024-02-08  0:24     ` Linus Arver
2024-02-08  6:11       ` Patrick Steinhardt
2024-02-14  7:36       ` Linus Arver
2024-02-15 11:27   ` Patrick Steinhardt

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