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From Stefan Fuhrmann <stefan.fuhrm...@wandisco.com>
Subject Re: r1673875: Provide a central and complete implementation for handling FSFS quirks...
Date Thu, 16 Apr 2015 23:06:57 GMT
On Thu, Apr 16, 2015 at 1:26 PM, Julian Foad <julianfoad@gmail.com> wrote:

> Just a couple of observations on the comments.
>
> +  /* EXPANDED_SIZE is 0. If the MD5 does not match the one for empty
> +   * contents, we know that we need to correct EXPANDED_SIZE. */
> +  empty_md5 = svn_checksum_empty_checksum(svn_checksum_md5, scratch_pool);
> +  if (memcmp(empty_md5->digest, rep->md5_digest, sizeof(rep->md5_digest)))
> +    {
> +      rep->expanded_size = rep->size;
> +      return SVN_NO_ERROR;
> +    }
>
> The comment could be clearer. At every step though this function we
> "know that we need to correct EXPANDED_SIZE", if "correct" can mean
> either "change to a correct value" or "confirm that 0 is the correct
> value".
>
> I suggest:
>
> /* EXPANDED_SIZE is 0. If the MD5 does not match the one for empty
>  * contents, the content is definitely non-empty. It must be a PLAIN rep,
> as
>  * EXPANDED_SIZE is always set correctly in a delta rep. Therefore the
>  * rep SIZE field is also the expanded size. */
>
> +  /* Only two cases are left here.
> +   * (1) A non-empty PLAIN rep with a MD5 collision on EMPTY_MD5.
> +   * (2) An empty DELTA rep. */
> +
> +  /* SVN always stores an empty DELTA rep as an empty sequence of txdelta
> +   * windows, i.e. as "SVN\1".  In that case, SIZE is 4 bytes.  There is
> [...]
> +   * Note that it technically legal to have DELTA reps with a 0 length
> +   * output window.  Their on-disk size would be longer.  [...]
>
> The phrase "empty DELTA rep" is ambiguous. I suggest:
>
> [...] (2) A DELTA rep with zero-length output. [...] SVN always stores
> a DELTA rep with zero-length output as [...]
>

Thanks for the corrections!
Committed as r1674165.

-- Stefan^2.

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