From 5e9d802a33ef2912a04984d431defe9809c809e1 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 1 Oct 2023 21:40:05 -0500 Subject: [PATCH] object-file-convert: stubs for converting from one object format to another 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 conversation 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 equivalent 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" Signed-off-by: Junio C Hamano --- 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 5776309365..f7e824f25c 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 0000000000..4777aba836 --- /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 algorithm 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)) + BUG("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 0000000000..a4f802aa8e --- /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 */