[PATCH 10/17] provide helpers to access the commit buffer
- From
Jeff King <peff@peff.net>
- Date
- Jun 10, 2014, 21:40 UTC
- Message-ID
- <20140610214039.GJ19147@sigill.intra.peff.net>
- In-Reply-To
- <20140610213509.GA26979@sigill.intra.peff.net>
Many sites look at commit->buffer to get more detailed information than what is in the parsed commit struct. However, we sometimes drop commit->buffer to save memory, in which case the caller would need to read the object afresh. Some callers do this (leading to duplicated code), and others do not (which opens the possibility of a segfault if somebody else frees the buffer).
Let's provide a pair of helpers, "get" and "unuse", that let callers easily get the buffer. They will use the cached buffer when possible, and otherwise load from disk using read_sha1_file.
Note that we also need to add a "get_cached" variant which returns NULL when we do not have a cached buffer. At first glance this seems to defeat the purpose of "get", which is to always provide a return value. However, some log code paths actually use the NULL-ness of commit->buffer as a boolean flag to decide whether to try printing the commit. At least for now, we want to continue supporting that use.
Signed-off-by: Jeff King <peff@peff.net> --- Typofix in commit message since v1.
commit.c | 28 ++++++++++++++++++++++++++++ commit.h | 21 +++++++++++++++++++++ 2 files changed, 49 insertions(+)
diff --git a/commit.c b/commit.c index fc8b4e2..b6b0e0d 100644 --- a/commit.c +++ b/commit.c @@ -250,6 +250,34 @@ void set_commit_buffer(struct commit *commit, void *buffer) commit->buffer = buffer; } +const void *get_cached_commit_buffer(const struct commit *commit) +{ + return commit->buffer; +} + +const void *get_commit_buffer(const struct commit *commit) +{ + const void *ret = get_cached_commit_buffer(commit); + if (!ret) { + enum object_type type; + unsigned long size; + ret = read_sha1_file(commit->object.sha1, &type, &size); + if (!ret) + die("cannot read commit object %s", + sha1_to_hex(commit->object.sha1)); + if (type != OBJ_COMMIT) + die("expected commit for %s, got %s", + sha1_to_hex(commit->object.sha1), typename(type)); + } + return ret; +} + +void unuse_commit_buffer(const struct commit *commit, const void *buffer) +{ + if (commit->buffer != buffer) + free((void *)buffer); +} + void free_commit_buffer(struct commit *commit) { free(commit->buffer); diff --git a/commit.h b/commit.h index cc89128..259c0ae 100644 --- a/commit.h +++ b/commit.h @@ -58,6 +58,27 @@ void parse_commit_or_die(struct commit *item); void set_commit_buffer(struct commit *, void *buffer); /* + * Get any cached object buffer associated with the commit. Returns NULL + * if none. The resulting memory should not be freed. + */ +const void *get_cached_commit_buffer(const struct commit *); + +/* + * Get the commit's object contents, either from cache or by reading the object + * from disk. The resulting memory should not be modified, and must be given + * to unuse_commit_buffer when the caller is done. + */ +const void *get_commit_buffer(const struct commit *); + +/* + * Tell the commit subsytem that we are done with a particular commit buffer. + * The commit and buffer should be the input and return value, respectively, + * from an earlier call to get_commit_buffer. The buffer may or may not be + * freed by this call; callers should not access the memory afterwards. + */ +void unuse_commit_buffer(const struct commit *, const void *buffer); + +/* * Free any cached object buffer associated with the commit. */ void free_commit_buffer(struct commit *);
-- 2.0.0.729.g520999f