In a future commit, we will want to check whether or not a bitmap has
any bits set in any of its words. The best way to do this (prior to the
existence of this patch) is to call `bitmap_popcount()` and check
whether the result is non-zero.
But this is semi-wasteful, since we do not need to know the exact number
of bits set, only whether or not there is at least one of them.
Implement a new helper function to check just that.
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
alloc_nr, ALLOC_GROW, and ALLOC_GROW_BY are commonly used macros for
dynamic array allocation. Moving these macros to git-compat-util.h with
the other alloc macros focuses alloc.[ch] to allocation for Git objects
and additionally allows us to remove inclusions to alloc.h from files
that solely used the above macros.
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This allows us to replace includes of cache.h with includes of the much
smaller alloc.h in many places. It does mean that we also need to add
includes of alloc.h in a number of C files.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce and apply coccinelle rule to discourage an explicit
comparison between a pointer and NULL, and applies the clean-up to
the maintenance track.
* ep/maint-equals-null-cocci:
tree-wide: apply equals-null.cocci
tree-wide: apply equals-null.cocci
contrib/coccinnelle: add equals-null.cocci
This function hasn't been used since 449fa5ee06 (pack-bitmap-write:
ignore BITMAP_FLAG_REUSE, 2020-12-08), which was a cleanup commit
intending to get rid of the code around the reusing of bitmaps.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add and apply a semantic patch for converting code that open-codes
CALLOC_ARRAY to use it instead. It shortens the code and infers the
element size automatically.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The bitmap_is_subset() function checks if the 'self' bitmap contains any
bitmaps that are not on in the 'other' bitmap. Up until this patch, it
had a declaration, but no implementation or callers. A subsequent patch
will want this function, so implement it here.
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There's no easy way to make a copy of a bitmap. Obviously a caller can
iterate over the bits and set them one by one in a new bitmap, but we
can go much faster by copying whole words with memcpy().
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We have a function to bitwise-OR an ewah into an uncompressed bitmap,
but not to OR two uncompressed bitmaps. Let's add it.
Interestingly, we have a public header declaration going back to
e1273106f6 (ewah: compressed bitmap implementation, 2013-11-14), but the
function was never implemented. That was all OK since there were no
users of 'bitmap_or()', but a first caller will be added in a couple of
patches.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If you ask to set a bit in the Nth word and we haven't yet allocated
that many slots in our array, we'll increase the bitmap size to 2*N.
This means we might frequently end up with bitmaps that are twice the
necessary size (as soon as you ask for the biggest bit, we'll size up to
twice that).
But if we just allocate as many words as were asked for, we may not grow
fast enough. The worst case there is setting bit 0, then 1, etc. Each
time we grow we'd just extend by one more word, giving us linear
reallocations (and quadratic memory copies).
A middle ground is relying on alloc_nr(), which causes us to grow by a
factor of roughly 3/2 instead of 2. That's less aggressive than
doubling, and it may help avoid fragmenting memory. (If we start with N,
then grow twice, our total is N*(3/2)^2 = 9N/4. After growing twice,
that array of size 9N/4 can fit into the space vacated by the original
array and first growth, N+3N/2 = 10N/4 > 9N/4, leading to less
fragmentation in memory).
Our worst case is still 3/2N wasted bits (you set bit N-1, then setting
bit N causes us to grow by 3/2), but our average should be much better.
This isn't usually that big a deal, but it will matter as we shift the
reachability bitmap generation code to store more bitmaps in memory.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We auto-grow bitmaps when somebody asks to set a bit whose position is
outside of our currently allocated range. Other operations besides
single bit-setting might need to do this, too, so let's pull it into its
own function.
Note that we change the semantics a little: you now ask for the number
of words you'd like to have, not the id of the block you'd like to write
to.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The object reachability bitmap machinery and the partial cloning
machinery were not prepared to work well together, because some
object-filtering criteria that partial clones use inherently rely
on object traversal, but the bitmap machinery is an optimization
to bypass that object traversal. There however are some cases
where they can work together, and they were taught about them.
* jk/object-filter-with-bitmap:
rev-list --count: comment on the use of count_right++
pack-objects: support filters with bitmaps
pack-bitmap: implement BLOB_LIMIT filtering
pack-bitmap: implement BLOB_NONE filtering
bitmap: add bitmap_unset() function
rev-list: use bitmap filters for traversal
pack-bitmap: basic noop bitmap filter infrastructure
rev-list: allow commit-only bitmap traversals
t5310: factor out bitmap traversal comparison
rev-list: allow bitmaps when counting objects
rev-list: make --count work with --objects
rev-list: factor out bitmap-optimized routines
pack-bitmap: refuse to do a bitmap traversal with pathspecs
rev-list: fallback to non-bitmap traversal when filtering
pack-bitmap: fix leak of haves/wants object lists
pack-bitmap: factor out type iterator initialization
We've never needed to unset an individual bit in a bitmap until now.
Typically they start with all bits unset and we bitmap_set() them, or we
are applying another bitmap as a mask. But the easiest way to apply an
object filter to a bitmap result will be to unset the individual bits.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In a following commit we will need to allocate a variable
number of bitmap words, instead of always 32, so let's add
bitmap_word_alloc() for this purpose.
Note that we have to adjust the block growth in bitmap_set(),
since a caller could now use an initial size of "0" (we don't
plan to do that, but it doesn't hurt to be defensive).
Helped-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reported-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reported-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The mailing address for the FSF has changed over the years. Rather than
updating the address across all files, refer readers to gnu.org, as the
GNU GPL documentation now suggests for license notices. The mailing
address is retained in the full license files (COPYING and LGPL-2.1).
The old address is still present in t/diff-lib/COPYING. This is
intentional, as the file is used in tests and the contents are not
expected to change.
Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now that we're built around xmalloc and friends, we can use
helpers like REALLOC_ARRAY, ALLOC_GROW, and so on to make
the code shorter and protect against integer overflow.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This code was originally written with the idea that it could
be spun off into its own ewah library, and uses the
overrideable ewah_malloc to do allocations.
We plug in xmalloc as our ewah_malloc, of course. But over
the years the ewah code itself has become more entangled
with git, and the return value of many ewah_malloc sites is
not checked.
Let's just drop the level of indirection and use xmalloc and
friends directly. This saves a few lines, and will let us
adapt these sites to our more advanced malloc helpers.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The ewah/ewok.h header pollutes the global namespace with
"BITS_IN_WORD", without any specific notion that we are
talking about the bits in an eword_t. We can give this the
more specific name "BITS_IN_EWORD".
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
On PowerPC Mac OS X (10.5.8 "Leopard" with Xcode 3.1),
system header /usr/include/ppc/param.h[1] pollutes the
preprocessor namespace with a macro generically named MASK.
This conflicts with the same-named macro in ewah/bitmap.c.
We can avoid this conflict by using a more specific name.
[1]: Included indirectly via:
git-compat-util.h ->
sys/sysctl.h ->
sys/ucred.h ->
sys/param.h ->
machine/param.h ->
ppc/param.h
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
EWAH is a word-aligned compressed variant of a bitset (i.e. a data
structure that acts as a 0-indexed boolean array for many entries).
It uses a 64-bit run-length encoding (RLE) compression scheme,
trading some compression for better processing speed.
The goal of this word-aligned implementation is not to achieve
the best compression, but rather to improve query processing time.
As it stands right now, this EWAH implementation will always be more
efficient storage-wise than its uncompressed alternative.
EWAH arrays will be used as the on-disk format to store reachability
bitmaps for all objects in a repository while keeping reasonable sizes,
in the same way that JGit does.
This EWAH implementation is a mostly straightforward port of the
original `javaewah` library that JGit currently uses. The library is
self-contained and has been embedded whole (4 files) inside the `ewah`
folder to ease redistribution.
The library is re-licensed under the GPLv2 with the permission of Daniel
Lemire, the original author. The source code for the C version can
be found on GitHub:
https://github.com/vmg/libewok
The original Java implementation can also be found on GitHub:
https://github.com/lemire/javaewah
[jc: stripped debug-only code per Peff's $gmane/239768]
Signed-off-by: Vicent Marti <tanoku@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Helped-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
