diff options
author | Jeff King <peff@peff.net> | 2015-09-25 00:05:45 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2015-09-25 20:18:18 +0300 |
commit | af49c6d0918bf04aad89bd885a4eef5767a33d0e (patch) | |
tree | 5037171be3cd4be197a9fafdbbcec9b305b96f99 /cache.h | |
parent | 399ad553ce87fca77a9bc5a0e734a361a9e8a5a3 (diff) |
add reentrant variants of sha1_to_hex and find_unique_abbrev
The sha1_to_hex and find_unique_abbrev functions always
write into reusable static buffers. There are a few problems
with this:
- future calls overwrite our result. This is especially
annoying with find_unique_abbrev, which does not have a
ring of buffers, so you cannot even printf() a result
that has two abbreviated sha1s.
- if you want to put the result into another buffer, we
often strcpy, which looks suspicious when auditing for
overflows.
This patch introduces sha1_to_hex_r and find_unique_abbrev_r,
which write into a user-provided buffer. Of course this is
just punting on the overflow-auditing, as the buffer
obviously needs to be GIT_SHA1_HEXSZ + 1 bytes. But it is
much easier to audit, since that is a well-known size.
We retain the non-reentrant forms, which just become thin
wrappers around the reentrant ones. This patch also adds a
strbuf variant of find_unique_abbrev, which will be handy in
later patches.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'cache.h')
-rw-r--r-- | cache.h | 31 |
1 files changed, 30 insertions, 1 deletions
@@ -785,7 +785,24 @@ extern char *sha1_pack_name(const unsigned char *sha1); */ extern char *sha1_pack_index_name(const unsigned char *sha1); -extern const char *find_unique_abbrev(const unsigned char *sha1, int); +/* + * Return an abbreviated sha1 unique within this repository's object database. + * The result will be at least `len` characters long, and will be NUL + * terminated. + * + * The non-`_r` version returns a static buffer which will be overwritten by + * subsequent calls. + * + * The `_r` variant writes to a buffer supplied by the caller, which must be at + * least `GIT_SHA1_HEXSZ + 1` bytes. The return value is the number of bytes + * written (excluding the NUL terminator). + * + * Note that while this version avoids the static buffer, it is not fully + * reentrant, as it calls into other non-reentrant git code. + */ +extern const char *find_unique_abbrev(const unsigned char *sha1, int len); +extern int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len); + extern const unsigned char null_sha1[GIT_SHA1_RAWSZ]; static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2) @@ -1067,6 +1084,18 @@ extern int for_each_abbrev(const char *prefix, each_abbrev_fn, void *); extern int get_sha1_hex(const char *hex, unsigned char *sha1); extern int get_oid_hex(const char *hex, struct object_id *sha1); +/* + * Convert a binary sha1 to its hex equivalent. The `_r` variant is reentrant, + * and writes the NUL-terminated output to the buffer `out`, which must be at + * least `GIT_SHA1_HEXSZ + 1` bytes, and returns a pointer to out for + * convenience. + * + * The non-`_r` variant returns a static buffer, but uses a ring of 4 + * buffers, making it safe to make multiple calls for a single statement, like: + * + * printf("%s -> %s", sha1_to_hex(one), sha1_to_hex(two)); + */ +extern char *sha1_to_hex_r(char *out, const unsigned char *sha1); extern char *sha1_to_hex(const unsigned char *sha1); /* static buffer result! */ extern char *oid_to_hex(const struct object_id *oid); /* same static buffer as sha1_to_hex */ |