Jeff King <peff@xxxxxxxx> 于2021年4月8日周四 上午3:28写道： > > On Sat, Apr 03, 2021 at 10:27:39PM +0800, ZheNing Hu wrote: > > > > - figure out which data will be needed for each item based on the > > > parsed format, and then do the minimum amount of work to get that > > > data (using "oid_object_info_extended()" helps here, because it > > > likewise tries to do as little work as possible to satisfy the > > > request, but there are many elements that it doesn't know about) > > > > > > > I have indeed noticed that `oid_object_info_extended()` > > can get information about the object which we actually want. > > In `cat-file.c`, It has been used in `batch_object_write()`, and > > `expanding_atom()` specify what data we need. > > In `ref-filter.c`, It has been used in `get_object()`. > > I am not sure what you mean about "many elements that it > > doesn't know about", For the time being, `cat-file` can get 5 > > kind of objects info it need. > > I think there are things one might want to format that > oid_object_info_extended() does not know about. For example, if you are > asking about %(authorname), it can't provide that. But we want to do as > little work as possible to satisfy the request. So for example, with the > format "%(objectsize)", we'd prefer _not_ to load the contents of each > object, and just ask oid_object_info_extended() for the size. But if we > are asked for "%(authorname)", we know we'll have to read and parse the > object contents. > OK, I understand it now, `%(authorname)` needs to grub info in object content so that content must be parsed, If we need to let cat-file learn `%(authorname)`, It takes extra work to extract from the object. > So this notion of "figure out the least amount of work" will have to be > part of the format code (and ref-filter and the pretty.c formatters do > make an attempt at this; I'm saying that a universal formatter will want > to keep this behavior). > You're right. %(tree) %(parent) ... reliant on commit object info, %(tagger) %(taggername) ... reliant on tag object info.But If it is some %(objectsize) or %(objectname) content, we do not need to parse the content of the objects. Future work we should also keep avoid parsing of non-dependent info. > > Maybe you think that `cat-file` can learn some features in > > `ref-filter` to extend the function of `cat-file --batch`? > > E.g. %(objectname:short)? I think I may have a better > > understanding of the topic of this mini-project now. > > We may not want to port the logic of cat-file,but to learn some > > design in `ref-filter`, right? > > Yes, I think the goal is for all of the commands that allow format > specifiers to support the same set (at least where it makes sense; > obviously you cannot ask for %(refname) in cat-file). > The future new API may need to deny such access. > And IMHO the best way to do that is to write a new universal formatting > API that takes the best parts from all of the existing ones. It _could_ > also be done by choosing ref-filter as the best implementation, slowly > teaching it formats the other commands know (which is what Olga had > started with), and then cleaning up any performance deficiencies. But I > think that last part would actually be easier when starting from scratch > (e.g., I think it would help to actually produce an abstract syntax tree > of the parsed format, and then walk that tree to fill in the values). > > -Peff It is the unified "%an" and "%author" you said last time. I think maybe Olga and Hariom might have done similar things: Calling `ref-filter` results in slower speed. And you said we may can refactor to abstract syntax tree, this is a good idea, and this may be a big project, In particular, pre-knowledge of compilation principles is required, and we may also need to deal with each different atom carefully. Thanks. -- ZheNing Hu
