Re: [PATCH v2 5/8] odb/streaming: consolidate read and write streams

Karthik Nayak <[email protected]> Tue, 11 Aug 2026 06:12:05 -0400
Newsgroups	org.kernel.vger.git
Message-ID	<CAOLa=ZTi8tL896_F2ONQck0z+H8NYhzcbTorb80NOdiqvnpjNg@mail.gmail.com>
Patrick Steinhardt <[email protected]> writes:

> The `struct odb_read_stream` and `struct odb_write_stream` both provide
> the same functionality: they allow a caller to read object data from an
> arbitrary source. Historically, the only difference was that the read
> stream was used to read data out of the object database, whereas the
> write stream was used to write data into the object database, but the
> interfaces were mostly the same.
>
> Over the preceding commits we have refactored the write stream to have
> almost exactly the same interface as the read stream. With these
> refactorings we can now easily merge those two streams into a single
> interface that's used for both use cases.
>
> While most of the changes are mechanical, there are two sites that need
> special mention:
>
>   - "builtin/unpack-objects.c" creates a write stream from compressed
>     object data.
>
>   - "odb/streaming.c" creates a write stream from a file descriptor.
>
> Adapting these sites to yield the new stream type requires a couple more
> changes. Most importantly, instead of embedding the pointer to the data
> in `struct odb_write_stream`, we now allocate a structure that wraps the
> new `struct odb_stream` base. Other than that though, the changes are
> rather straight forward.
>

So instead of `odb_write_stream.data` which was pointing to the data, we
simply wrap the stream with the data's structure, this allows us to get
the parent struct if we have the `odb_stream`. Alright!

> Some of the structures and functions are now somewhat misnamed. These
> will be fixed in subsequent commits.
>
> Signed-off-by: Patrick Steinhardt <[email protected]>
> ---
>  builtin/unpack-objects.c      | 31 ++++++++++++++++---------------
>  object-file.c                 | 25 ++++++++++++-------------
>  odb.c                         |  2 +-
>  odb.h                         |  4 ++--
>  odb/source-files.c            |  2 +-
>  odb/source-inmemory.c         |  4 ++--
>  odb/source-loose.c            |  6 +++---
>  odb/source-packed.c           |  2 +-
>  odb/source.h                  |  4 ++--
>  odb/streaming.c               | 35 ++++++++++++++++-------------------
>  odb/streaming.h               | 31 +++----------------------------
>  odb/transaction.c             |  2 +-
>  odb/transaction.h             |  4 ++--
>  t/unit-tests/u-odb-inmemory.c |  6 +++---
>  14 files changed, 65 insertions(+), 93 deletions(-)
>
> diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
> index 7439ec53be..05a2d48011 100644
> --- a/builtin/unpack-objects.c
> +++ b/builtin/unpack-objects.c
> @@ -359,20 +359,21 @@ static void unpack_non_delta_entry(enum object_type type, unsigned long size,
>  }
>
>  struct input_zstream_data {
> +	struct odb_stream base;
>  	git_zstream *zstream;
>  	int status;
>  };
>
> -static ssize_t feed_input_zstream(struct odb_write_stream *in_stream,
> -				  unsigned char *buf, size_t buf_len)
> +static ssize_t feed_input_zstream(struct odb_stream *in_stream,
> +				  char *buf, size_t buf_len)
>  {
> -	struct input_zstream_data *data = in_stream->data;
> +	struct input_zstream_data *data = container_of(in_stream, struct input_zstream_data, base);
>  	git_zstream *zstream = data->zstream;
>
>  	if (data->status != Z_OK)
>  		return 0;
>
> -	zstream->next_out = buf;
> +	zstream->next_out = (unsigned char *) buf;

But we do loose information here since we now use 'char *' for both
read/write. But we gain flexibility.

[snip]

The rest looks good.
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