Make our overflow checking look more like gcc and clang's, so that
we can substitute it out with the compiler instrinsics on platforms
that support it. This means dropping the ability to pass `NULL` as
an out parameter.
As a result, the macros also get updated to reflect this as well.
This is a contract that we made in the library and that we need to uphold. The
contents of a blob can never be NULL because several parts of the library (including
the filter and attributes code) expect `git_blob_rawcontent` to always return a
valid pointer.
git hardocodes these as objects which exist regardless of whether they
are in the odb and uses them in the shell interface as a way of
expressing the lack of a blob or tree for one side of e.g. a diff.
In the library we use each language's natural way of declaring a lack of
value which makes a workaround like this unnecessary. Since git uses it,
it does however mean each shell application would need to perform this
check themselves.
This makes it common work across a range of applications and an issue
with compatibility with git, which fits right into what the library aims
to provide.
Thus we introduce the hard-coded empty blob and tree in the odb
frontend. These hard-coded objects are checked for before going to the
backends, but after the cache check, which means the second time they're
used, they will be treated as normal cached objects instead of creating
new ones.
The git_odb_exists_prefix API was not dealing correctly when a
later backend returned GIT_ENOTFOUND even if an earlier backend
had found the object.
Additionally, the unit tests were not properly exercising the API
and had a couple mistakes in checking the results.
Lastly, since the backends are not expected to behavior correctly
unless all bytes of the short id are zero except for the prefix,
this makes the ODB prefix APIs explicitly clear out the extra
bytes so the user doesn't have to be as careful.
When given an ODB from which to read objects, the indexer will attempt
to inject the missing bases at the end of the pack and update the
header and trailer to reflect the new contents.
This makes the git_buf struct that was used internally into an
externally available structure and eliminates the git_buffer.
As part of that, some of the special cases that arose with the
externally used git_buffer were blended into the git_buf, such as
being careful about git_buf objects that may have a NULL ptr and
allowing for bufs with a valid ptr and size but zero asize as a
way of referring to externally owned data.
This moves the git_filter_list into the public API so that users
can create, apply, and dispose of filter lists. This allows more
granular application of filters to user data outside of libgit2
internals.
This also converts all the internal usage of filters to the public
APIs along with a few small tweaks to make it easier to use the
public git_buffer stuff alongside the internal git_buf.
This creates include/sys/filter.h with a basic definition of a
git_filter and then converts the internal code to use it. There
are related internal objects (git_filter_list) that we will want
to publish at some point, but this is a first step.
Now that #1785 is merged, git_odb_stream_finalize_write() calculates the object id before invoking the odb backend.
This commit gives a chance to the backend to check if it already knows this object.
Previously, `git_object_read()`, `git_object_read_prefix()` and
`git_object_exists()` were implementing an auto refresh logic. When the
expected object couldn't be found in any backend, a call to
`git_odb_refresh()` was triggered and the lookup was once again performed
against all backends.
This commit removes this auto-refresh logic from the odb layer and pushes
it down into the pack-backend (as it's the only one currently exposing
a `refresh()` endpoint).
If none of the backends support direct writes and we must stream the
whole file, we already know what the object's id should be; so use the
stream's functions directly, bypassing the frontend's hashing and
overwriting of our existing id.
The frontend is in charge of calculating the id of the objects. Thus
the backends should treat it as a read-only value. The positioning in
the function signature made it seem as though it was an output
parameter.
Make the id const and move it from the front to behind the subject
(backend or stream).
Hash the data as it's coming into the stream and tell the backend what
its name is when finalizing the write. This makes it consistent with
the way a plain git_odb_write() performs the write.
This is in preparation for moving the hashing to the frontend, which
requires us to handle the incoming data before passing it to the
backend's stream.
By zeroing out the memory when we free larger objects (i.e. those
that serve as collections of other data, such as repos, odb, refdb),
I'm hoping that it will be easier for libgit2 bindings to find
errors in their object management code.
There are some cases, particularly where no loaded ODB backends
support a particular operation, where we would return an error
code without having set an error. This catches those cases and
reports that no ODB backends support the operation in question.
This adds create and free callback to the git_objects_table so
that more of the creation and destruction of objects can be table
driven instead of using switch statements. This also makes the
semantics of certain object creation functions consistent so that
we can make better use of function pointers. This also fixes a
theoretical error case where an object allocation fails and we
end up storing NULL into the cache.
