Gentoo Archives: gentoo-portage-dev

From: Paul de Vrieze <pauldv@g.o>
To: gentoo-portage-dev@l.g.o
Subject: Re: [gentoo-portage-dev] PATCH: initial EAPI awareness
Date: Fri, 02 Sep 2005 08:45:28
In Reply to: Re: [gentoo-portage-dev] PATCH: initial EAPI awareness by Zac Medico
1 On Friday 02 September 2005 07:27, Zac Medico wrote:
2 > Paul de Vrieze wrote:
3 > > On Wednesday 31 August 2005 14:57, Brian Harring wrote:
4 > >> Re: tagging EAPI at the top of a file, infra would probably shoot me
5 > >> for doing such- till a live, fully compatible and *roughly*
6 > >> equivalent parser is available, portage would have to do a bit of
7 > >> grepping, jacking up the regen times.
8 > >
9 > > If in cache EAPI can be gotten from the cache. If not, I don't think
10 > > it matters where in the file EAPI occurs from the standpoint of
11 > > getting it's value. The only thing would be that in the future a fast
12 > > EAPI parser could be made that would just look at EAPI and get its
13 > > version. I could easilly write you such a parser.
14 >
15 > It is impossible write a parser for an unconstrained and unknown format
16 > that may exist in the future. If we put a constraint on the format, in
17 > order to parse the EAPI, then we contradict our original goal (to
18 > unconstrain the format).
20 It would be possible to make these restrictions small. A workable
21 restriction could be to put the EAPI statement in the front of the file
22 only preceded by whitespace and comments. After the line with the EAPI
23 statement anything could happen. Even a completely binary format could be
24 used. But indeed no constraints is impossible, so putting the format
25 statement in the start of the file is the best solution. Besides the fact
26 that it makes detecting the format that much faster, and allows bailing
27 out before parsing the whole file if an unsupported api is detected.
29 > A better approach IMO would be to store the EAPI in a separate file
30 > such as metadata.xml. This would allow *absolute* flexibility in the
31 > "ebuild" format. Portage would be able to select an appropriate parser
32 > with no need to examine the "ebuild" itself.
34 Please don't. Parsing xml is a lot harder than recognizing lines. A simple
35 EAPI parser would probably use canned (library) line reading functions
36 and then look if the line starts with "EAPI=". If so it reads the EAPI,
37 else it checks the next line. No need to understand anything else of the
38 file format.
40 Paul
42 --
43 Paul de Vrieze
44 Gentoo Developer
45 Mail: pauldv@g.o
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