Re: [PATCH] Show binary file size change in diff --stat

From: Andy Parkins <andyparkins@gmail.com>
Date: Apr 4, 2007, 14:40 UTC
Message-ID: <200704041540.59977.andyparkins@gmail.com>
In-Reply-To: <4613A974.60808@dawes.za.net>

On Wednesday 2007 April 04 14:34, Rogan Dawes wrote:

> Well, how about my comments in <45E67978.9030805@dawes.za.net>,
> suggesting that the edit difference (number of steps required to
> transform one to the other) would be a better indication?

Perhaps.  There is certainly a difference between:

 somefile.bin  | 1000 -> 1000 bytes

and

 somefile.bin  | 500 bytes removed, 500 bytes added

> I think it is better because it is consistent with what we currently do
> for text files: show the number of lines added/deleted.

The thing is, "lines" is an understandable unit for a text file, so it's useful to show. I'm not sure the same is true of "bytes" for a binary file. Those bytes could represent anything; the true unit of a binary file is dependent on its type.

> For binary files, it would be consistent to show the number of bytes
> added/deleted. I have not investigated the output format for the
> libxdiff binary patch format, but hopefully it would not be too
> difficult to calculate the deletions and additions.

I'm inclined to agree with Johannes, while it's certainly something that /could/ be shown - is it more useful? There is no guarantee that a small change in the underlying content is represented by a small change in the binary diff.

As an example: compress a file, change a byte, compress it again, perform a binary diff; what is that diff telling you about the change? (My answer is: not much).

Andy

-- 
Dr Andy Parkins, M Eng (hons), MIET
andyparkins@gmail.com