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Now that all code paths correctly set the hash algorithm member of
struct object_id, write an object's hex representation using the hash
algorithm member embedded in it.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There are numerous places in the codebase where we assume we can
initialize data by zeroing all its bytes. However, when we do that with
a struct object_id, it leaves the structure with a zero value for the
algorithm, which is invalid.
We could forbid this pattern and require that all struct object_id
instances be initialized using oidclr, but this seems burdensome and
it's unnatural to most C programmers. Instead, if the algorithm is
zero, assume we wanted to use the default hash algorithm instead.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Now that struct object_id has an algorithm field, we should populate it.
This will allow us to handle object IDs in any supported algorithm and
distinguish between them. Ensure that the field is written whenever we
write an object ID by storing it explicitly every time we write an
object. Set values for the empty blob and tree values as well.
In addition, use the algorithm field to compare object IDs. Note that
because we zero-initialize struct object_id in many places throughout
the codebase, we default to the default algorithm in cases where the
algorithm field is zero rather than explicitly initialize all of those
locations.
This leads to a branch on every comparison, but the alternative is to
compare the entire buffer each time and padding the buffer for SHA-1.
That alternative ranges up to 3.9% worse than this approach on the perf
t0001, t1450, and t1451.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There are some places where we need to parse a hex object ID in any
algorithm without knowing beforehand which algorithm is in use. An
example is when parsing fast-import marks.
Add a get_oid_hex_any to parse an object ID and return the algorithm it
belongs to, and additionally add parse_oid_hex_any which is the
equivalent change for parse_oid_hex. If the object is not parseable, we
return GIT_HASH_UNKNOWN.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Introduce variants of get_oid_hex and parse_oid_hex that parse an
arbitrary hash algorithm, implementing internal functions to avoid
duplication. These functions can be used in the transport code to parse
refs properly.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There's only a single caller left of sha1_to_hex(), since everybody
that has an object name in "unsigned char[]" now uses hash_to_hex()
instead.
This case is in the sha1dc wrapper, where we print a hex sha1 when
we find a collision. This one will always be sha1, regardless of the
current hash algorithm, so we can't use hash_to_hex() here. In
practice we'd probably not be running sha1 at all if it isn't the
current algorithm, but it's possible we might still occasionally
need to compute a sha1 in a post-sha256 world.
Since sha1_to_hex() is just a wrapper for hash_to_hex_algop(), let's
call that ourselves. There's value in getting rid of the sha1-specific
wrapper to de-clutter the global namespace, and to make sure nobody uses
it (and as with sha1_to_hex_r() in the previous patch, we'll drop the
coccinelle transformations, too).
The sha1_to_hex() function is mentioned in a comment; we can easily
swap that out for oid_to_hex() to give a better example. Also
update the comment that was left stale when we added "struct
object_id *" as a way to name an object and added functions to
convert it to hex.
The function is also mentioned in some test vectors in t4100, but
that's not runnable code, so there's no point in trying to clean it
up.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There are no callers left; everybody uses oid_to_hex_r() or
hash_to_hex_algop_r(). This used to actually be the underlying
implementation for oid_to_hex_r(), but that's no longer the case since
47edb64997 (hex: introduce functions to print arbitrary hashes,
2018-11-14).
Let's get rid of it to de-clutter and to make sure nobody uses it.
Likewise we can drop the coccinelle rules that mention it, since the
compiler will make it quite clear that the code does not work.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Currently, we have functions that turn an arbitrary SHA-1 value or an
object ID into hex format, either using a static buffer or with a
user-provided buffer. Add variants of these functions that can handle
an arbitrary hash algorithm, specified by constant. Update the
documentation as well.
While we're at it, remove the "extern" declaration from this family of
functions, since it's not needed and our style now recommends against
it.
We use the variant taking the algorithm structure pointer as the
internal variant, since taking an algorithm pointer is the easiest way
to handle all of the variants in use.
Note that we maintain these functions because there are hashes which
must change based on the hash algorithm in use but are not object IDs
(such as pack checksums).
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Instead of using the GIT_SHA1_* constants, switch to using the_hash_algo
to convert object IDs to and from hex format.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Make the function for converting pairs of hexadecimal digits to binary
available to other call sites.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Since we will likely be introducing a new hash function at some point,
and that hash function might be longer than 40 hex characters, use the
constant GIT_MAX_HEXSZ, which is designed to be suitable for
allocations, instead of GIT_SHA1_HEXSZ. This will ease the transition
down the line by distinguishing between places where we need to allocate
memory suitable for the largest hash from those where we need to handle
the current hash.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Introduce a function, parse_oid_hex, which parses a hexadecimal object
ID and if successful, sets a pointer to just beyond the last character.
This allows for simpler, more robust parsing without needing to
hard-code integer values throughout the codebase.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Overflow is defined for unsigned integers, but not for signed ones.
We could make the ring-buffer index in sha1_to_hex() and
get_pathname() unsigned to be on the safe side to resolve this, but
let's make it explicit that we are wrapping around at whatever the
number of elements the ring-buffer has. The compiler is smart enough
to turn modulus into bitmask for these codepaths that use
ring-buffers of a size that is a power of 2.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Code cleanup.
* rs/hex2chr:
introduce hex2chr() for converting two hexadecimal digits to a character
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Add and use a helper function that decodes the char value of two
hexadecimal digits. It returns a negative number on error, avoids
running over the end of the given string and doesn't shift negative
values.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This function works just like sha1_to_hex_r, except that it takes a
pointer to struct object_id instead of a pointer to unsigned char.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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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>
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There are several utility functions (hashcmp and friends) that are used
for comparing object IDs (SHA-1 values). Using these functions, which
take pointers to unsigned char, with struct object_id requires tiresome
access to the sha1 member, which bloats code and violates the desired
encapsulation. Provide wrappers around these functions for struct
object_id for neater, more maintainable code. Use the new constants to
avoid the hard-coded 20s and 40s throughout the original functions.
These functions simply call the underlying pointer-to-unsigned-char
versions to ensure that any performance improvements will be passed
through to the new functions.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Code clean-up.
* sb/hex-object-name-is-at-most-41-bytes-long:
hex.c: reduce memory footprint of sha1_to_hex static buffers
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41 bytes is the exact number of bytes needed for having the returned
hex string represented. 50 seems to be an arbitrary number, such
that there are no benefits from alignment to certain address boundaries.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Previously, get_sha1_hex() would read one character past the end of a
null-terminated string whose strlen was an even number less than 40.
Although the function correctly returned -1 in these cases, the extra
memory access might have been to uninitialized (or even, conceivably,
unallocated) memory.
Add a check to avoid reading past the end of a string.
This problem was discovered by Thomas Rast <trast@student.ethz.ch>
using valgrind.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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As the documentation says, this is primarily for debugging, and
in the longer term we should rename it to test-show-index or something.
In the meantime, just avoid xmalloc (which slurps in the rest of git), and
separating out the trivial hex functions into "hex.o".
This results in
[torvalds@nehalem git]$ size git-show-index
text data bss dec hex filename
222818 2276 112688 337782 52776 git-show-index (before)
5696 624 1264 7584 1da0 git-show-index (after)
which is a whole lot better.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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brian m. carlson
Jeff King
René Scharfe
Junio C Hamano
Stefan Beller
Michael Haggerty
Linus Torvalds