Write directly to the ODB when possible#724
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CreatingABlob From TooShortAStreamThrows?
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Rebased. Ok to merge? |
LibGit2Sharp/ObjectDatabase.cs
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there's a word missing here. Either "prior to being stored" or "before storing it" or something work work.
ObjectDatabase.CreateBlob() accepts a number of bytes to read. It currently however treats this as a max, rather than a hard size, which seems ripe for introducing bugs. Assert that we should throw when asked to read too much from a Stream.
When given a size and no path, we know that we do not need to buffer the content or apply any filters, so we can create an write-stream into the object database and put in our content directly, avoiding the temporary file and callbacks altogether.
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While trying to get rid of the uglyness that is
git_blob_create_fromchunks(), I realised we can do it bit by bit, so here's the first bit.If we're given no path (and thus cannot do any filtering) and a size, we know that we can stream the data directly into the database, so let's do that with a
git_odb_stream.This brought up the fact that we expect a short read to succeed, which is only possible because
fromchunkswaits for an EOF signal from us, which we can simply pass along fromStream.Read(). Trying to keep this behaviour would make it impossible to optimise anything, and it also seems like a great place to introduce subtle bugs, so I've changed the tests to reflect that we need to read that amount of bytes.This however is still the behaviour for the case when we have a path, since that needs filtering and thus must still rely on
fromchunks. This however means that the place where we would raise the exception is beyond a C wall, so that probably wouldn't work without storing the exception somewhere.