On Tue, 2011-08-02 at 16:23 +0200, Bert Huijben wrote: > > > -----Original Message----- > > From: Julian Foad [mailto:julian.f...@wandisco.com] > > Sent: dinsdag 2 augustus 2011 15:59 > > To: Subversion Development > > Subject: RFC: Improving the 'diff callbacks' > > > > I'm looking at rationalizing the way the client handles diffs, which is > > currently mostly through the "svn_wc_diff_callbacks4_t" interface, with > > some use made of svn_delta_editor_t. I'll loosely abbreviate symbol > > names below, for example "diff_callbacks_t" to refer to the former. > > > > In libsvn_client, currently: > > > > Diff what? Producer Interface Consumer > > > > Normal diff: > > repo-repo svn_ra_do_diff3 + |> diff_callbacks_t |> diff_callbacks > > get_diff_editor | | in diff.c; > > repo-wc svn_ra + svn_wc | | prints diff to > > wc-wc svn_wc_diff6 | | stdout > > > > Summarizing diff: > > repo-repo svn_ra_do_diff3 |> delta_editor_t |> repos_diff_ > > | | summarize.c; > > | | calls sum-cb > > repo-wc not implemented > > wc-wc not implemented > > > > What's going on here? Why is the summarizing diff output subsystem not > > simply an alternative consumer to the normal diff? If it used the same > > interface, we should be able to plug it straight in. > > > > First I wondered why the delta_editor_t isn't a suitable interface for > > diffs, and why the WC defines its own 'callback' type for this. One > > reason is because we want a symmetric diff, one that provides the full > > content of both what's added and what's deleted. Although the > > summarizing diff doesn't need to know about file content or property > > deletions, it does want to know about file and directory deletions, so > > that would seem to be a good thing. So why aren't we using the > > diff_callbacks_t here? > > Maybe because the diff callbacks transfer the full texts of both > before and after a change to provide them to the callback?
It appears that the diff_callbacks_t can already avoid that: the 'file_opened' callback says: /* This function is called before @a file_changed to allow callbacks to * skip the most expensive processing of retrieving the file data. */ - Julian > The summarize function might have been designed to reduce that overhead?
