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add object_as_type helper for casting objects

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When we call lookup_commit, lookup_tree, etc, the logic goes
something like:

  1. Look for an existing object struct. If we don't have
     one, allocate and return a new one.

  2. Double check that any object we have is the expected
     type (and complain and return NULL otherwise).

  3. Convert an object with type OBJ_NONE (from a prior
     call to lookup_unknown_object) to the expected type.

We can encapsulate steps 2 and 3 in a helper function which
checks whether we have the expected object type, converts
OBJ_NONE as appropriate, and returns the object.

Not only does this shorten the code, but it also provides
one central location for converting OBJ_NONE objects into
objects of other types. Future patches will use that to
enforce type-specific invariants.

Since this is a refactoring, we would want it to behave
exactly as the current code. It takes a little reasoning to
see that this is the case:

  - for lookup_{commit,tree,etc} functions, we are just
    pulling steps 2 and 3 into a function that does the same
    thing.

  - for the call in peel_object, we currently only do step 3
    (but we want to consolidate it with the others, as
    mentioned above). However, step 2 is a noop here, as the
    surrounding conditional makes sure we have OBJ_NONE
    (which we want to keep to avoid an extraneous call to
    sha1_object_info).

  - for the call in lookup_commit_reference_gently, we are
    currently doing step 2 but not step 3. However, step 3
    is a noop here. The object we got will have just come
    from deref_tag, which must have figured out the type for
    each object in order to know when to stop peeling.
    Therefore the type will never be OBJ_NONE.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2014-07-13 02:42:03 -04:00
committed by Junio C Hamano
parent 5af01caa08
commit 8ff226a9d5
7 changed files with 25 additions and 43 deletions
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19
commit.c
View File

@ -18,19 +18,6 @@ int save_commit_buffer = 1;
const char *commit_type = "commit";
static struct commit *check_commit(struct object *obj,
const unsigned char *sha1,
int quiet)
{
if (obj->type != OBJ_COMMIT) {
if (!quiet)
error("Object %s is a %s, not a commit",
sha1_to_hex(sha1), typename(obj->type));
return NULL;
}
return (struct commit *) obj;
}
struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
int quiet)
{
@ -38,7 +25,7 @@ struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
if (!obj)
return NULL;
return check_commit(obj, sha1, quiet);
return object_as_type(obj, OBJ_COMMIT, quiet);
}
struct commit *lookup_commit_reference(const unsigned char *sha1)
@ -63,9 +50,7 @@ struct commit *lookup_commit(const unsigned char *sha1)
struct object *obj = lookup_object(sha1);
if (!obj)
return create_object(sha1, alloc_commit_node());
if (!obj->type)
obj->type = OBJ_COMMIT;
return check_commit(obj, sha1, 0);
return object_as_type(obj, OBJ_COMMIT, 0);
}
struct commit *lookup_commit_reference_by_name(const char *name)