Bring back the use of the delta base cache for unpacking objects. When
generating the delta chain, we stop when we find a delta base in the
pack's cache and use that as the starting point.
We currently make use of recursive function calls to unpack an object,
resolving the deltas as we come back down the chain. This means that we
have unbounded stack growth as we look up objects in a pack.
This is now done in two steps: first we figure out what the dependency
chain is by looking up the delta bases until we reach a non-delta
object, pushing the information we need onto a stack and then we pop
from that stack and apply the deltas until there are no more left.
This version of the code does not make use of the delta base cache so it
is slower than what's in the mainline. A later commit will reintroduce
it.
Rename git_packfile_check to git_packfile_alloc since it is now
being used more in that capacity. Fix the various places that use
it. Consolidate some repeated code in odb_pack.c related to the
allocation of a new pack_backend.
This builds on the earlier thread safety work to make it so that
setting the odb, index, refdb, or config for a repository is done
in a threadsafe manner with minimized locking time. This is done
by adding a lock to the repository object and using it to guard
the assignment of the above listed pointers. The lock is only
held to assign the pointer value.
This also contains some minor fixes to the other work with pack
files to reduce the time that locks are being held to and fix an
apparently memory leak.
When I was writing threading tests for the new cache, the main
error I kept running into was a pack file having it's content
unmapped underneath the running thread. This adds a lock around
the routines that map and unmap the pack data so that threads can
effectively reload the data when they need it.
This also required reworking the error handling paths in a couple
places in the code which I tried to make consistent.
These offsets are needed for REF_DELTA objects, which encode which
object they use as a base, but not where it lies in the packfile, so
we need a list.
These objects are mostly from older packfiles, before OFS_DELTA was
widely spread. The time spent in indexing these packfiles is greatly
reduced, though remains above what git is able to do.
The indexer needs to call the packfile's free function so it takes care of
freeing the caches.
We still need to close the mwf descriptor manually so we can rename the
packfile into its final name on Windows.
Many delta bases are re-used. Cache them to avoid inflating the same
data repeatedly.
This version doesn't limit the amount of entries to store, so it can
end up using a considerable amound of memory.
To paraphrase @peff:
You can get both size and type from a packed object reasonably cheaply.
If you have:
* An object that is not a delta; both type and size are available in the
packfile header.
* An object that is a delta. The packfile type will be OBJ_*_DELTA, and
you have to resolve back to the base to find the real type. That means
potentially a lot of packfile index lookups, but each one is
relatively cheap. For the size, you inflate the first few bytes of the
delta, whose header will tell you the resulting size of applying the
delta to the base.
For simplicity, we just decompress the whole delta for now.
This migrates odb.c, odb_loose.c, odb_pack.c and pack.c to
the new style of error handling. Also got the unix and win32
versions of map.c. There are some minor changes to other
files but no others were completely converted.
This also contains an update to filebuf so that a zeroed out
filebuf will not think that the fd (== 0) is actually open
(and inadvertently call close() on fd 0 if cleaned up).
Lastly, this was built and tested on win32 and contains a
bunch of fixes for the win32 build which was pretty broken.
The following files now have 0444 permissions:
- loose objects
- pack indexes
- pack files
- packs downloaded by fetch
- packs downloaded by the HTTP transport
And the following files now have 0666 permissions:
- config files
- repository indexes
- reflogs
- refs
This brings libgit2 more in line with Git.
Note that git_filebuf_commit() and git_filebuf_commit_at() have both
gained a new mode parameter.
The latter change fixes an important issue where filebufs created with
GIT_FILEBUF_TEMPORARY received 0600 permissions (due to mkstemp(3)
usage). Now we chmod() the file before renaming it into place.
Tests have been added to confirm that new commit, tag, and tree
objects are created with the right permissions. I don't have access to
Windows, so for now I've guarded the tests with "#ifndef GIT_WIN32".
There were quite a few places were spaces were being used instead of
tabs. Try to catch them all. This should hopefully not break anything.
Except for `git blame`. Oh well.
1. The license header is technically not valid if it doesn't have a
copyright signature.
2. The COPYING file has been updated with the different licenses used in
the project.
3. The full GPLv2 header in each file annoys me.
When indexing a file with ref deltas, a temporary cache for the
offsets has to be built, as we don't have an index file yet. If the
user takes the responsiblity for filling the cache, the packing code
will look there first when it finds a ref delta.
Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
The callers immediately throw away the offset, so we don't need any
logical changes in any of them. This will be useful for the indexer,
as it does need to know where the compressed data ends.
Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>
