From: Karthik Nayak <karthik.188@gmail.com>
Date: Thu, 05 Mar 2026 13:07:15 GMT
Subject: Re: [PATCH 11/17] odb/source: make `for_each_object()` function pluggable
Message-ID: <CAOLa=ZS9ODS1EdZMDW7aRjp+9yk1E0mW15wabPNzTmBxOtwOgQ@mail.gmail.com>
In-Reply-To: <20260223-b4-pks-odb-source-pluggable-v1-11-253bac1db598@pks.im>

[snip]

> diff --git a/odb/source.h b/odb/source.h
> index edb425fdef..35aa78e140 100644
> --- a/odb/source.h
> +++ b/odb/source.h
> @@ -53,6 +53,18 @@ struct object_id;
>  struct object_info;
>  struct odb_read_stream;
>
> +/*
> + * A callback function that can be used to iterate through objects. If given,
> + * the optional `oi` parameter will be populated the same as if you would call
> + * `odb_read_object_info()`.
> + *
> + * Returning a non-zero error code will cause iteration to abort. The error
> + * code will be propagated.
> + */
> +typedef int (*odb_for_each_object_cb)(const struct object_id *oid,
> +				      struct object_info *oi,
> +				      void *cb_data);
> +
>  /*
>   * The source is the part of the object database that stores the actual
>   * objects. It thus encapsulates the logic to read and write the specific
> @@ -151,6 +163,27 @@ struct odb_source {
>  	int (*read_object_stream)(struct odb_read_stream **out,
>  				  struct odb_source *source,
>  				  const struct object_id *oid);
> +
> +	/*
> +	 * This callback is expected to iterate over all objects stored in this

This isn't a callback though, this is a function which calls the
callback, right?

> +	 * source and invoke the callback function for each of them. It is
> +	 * valid to yield the same object multiple time. A non-zero exit code
> +	 * from the object callback shall abort iteration.
> +	 *
> +	 * The optional `oi` structure shall be populated similar to how an individual
> +	 * call to `odb_source_read_object_info()` would have behaved. If the caller
> +	 * passes a `NULL` pointer then the object itself shall not be read.
> +	 *

Nit: here and below, we talk about the `oi` structure, but that's in the
callback function, maybe we should clarify that.

> +	 * The callback is expected to return a negative error code in case the
> +	 * iteration has failed to read all objects, 0 otherwise. When the
> +	 * callback function returns a non-zero error code then that error code
> +	 * should be returned.
> +	 */
> +	int (*for_each_object)(struct odb_source *source,
> +			       const struct object_info *request,
> +			       odb_for_each_object_cb cb,
> +			       void *cb_data,
> +			       unsigned flags);
>  };
>
>  /*
> @@ -233,4 +266,30 @@ static inline int odb_source_read_object_stream(struct odb_read_stream **out,
>  	return source->read_object_stream(out, source, oid);
>  }
>
> +/*
> + * Iterate through all objects contained in the given source and invoke the
> + * callback function for each of them. Returning a non-zero code from the
> + * callback function aborts iteration. There is no guarantee that objects
> + * are only iterated over once.
> + *
> + * The optional `oi` structure shall be populated similar to how an individual
> + * call to `odb_source_read_object_info()` would have behaved. If the caller
> + * passes a `NULL` pointer then the object itself shall not be read.
> + *
> + * The flags is a bitfield of `ODB_FOR_EACH_OBJECT_*` flags. Not all flags may
> + * apply to a specific backend, so whether or not they are honored is defined
> + * by the implementation.
> + *
> + * Returns 0 when all objects have been iterated over, a negative error code in
> + * case iteration has failed, or a non-zero value returned from the callback.
> + */
> +static inline int odb_source_for_each_object(struct odb_source *source,
> +					     const struct object_info *request,
> +					     odb_for_each_object_cb cb,
> +					     void *cb_data,
> +					     unsigned flags)
> +{
> +	return source->for_each_object(source, request, cb, cb_data, flags);
> +}
> +
>  #endif
>
> --
> 2.53.0.536.g309c995771.dirty