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Re: %-escapes in file URL
From: |
YAMAMOTO Mitsuharu |
Subject: |
Re: %-escapes in file URL |
Date: |
Fri, 19 May 2006 08:09:39 +0000 (UTC) |
User-agent: |
Loom/3.14 (http://gmane.org/) |
Richard Stallman <rms <at> gnu.org> writes:
>
> In dnd-handle-one-url, %-escapes in the given file URL is decoded
> immediately. But I think that should be done when extracting the file
> name from it (i.e., in dnd-get-local-file-name) in order to cope with
> applications outside Emacs via browse-url.
>
> Could you explain the connection, please?
>
(I'm resending this from Gmane, because my emails seem to be rejected by
mx10.gnu.org with "Unrouteable address" these days.)
Sure. RFC 2396 says:
2.4.2. When to Escape and Unescape
A URI is always in an "escaped" form, since escaping or unescaping a
completed URI might change its semantics. Normally, the only time
escape encodings can safely be made is when the URI is being created
from its component parts; each component may have its own set of
characters that are reserved, so only the mechanism responsible for
generating or interpreting that component can determine whether or
not escaping a character will change its semantics. Likewise, a URI
must be separated into its components before the escaped characters
within those components can be safely decoded.
So, URLs coming from other applications (e.g, via drag-and-drop)
should be assumed to be in escaped forms. Likewise, URLs going to
other applications (e.g., via browse-url) should be in escaped forms.
Some functions in browse-url such as `browse-url-netscape' does
%-escaping, but that is not re-escaping but just increasing the kind
of characters that should be escaped (notably `,' and `)').
A simple and natural policy is to always keep URLs in escaped forms,
whether or not they are used inside Emacs only. So, my proposal is as
follows:
* Always treat URLs as those in escaped form. Don't re-escape or
unescape them as long as they are URLs (i.e, have a prefix such as
"file://"). Increasing the kind of escaped characters is not
re-escaping.
* When creating a URL from a file name, encode the file name with
the file name coding system and then %-escape it.
* When creating a file name from a URL, %-unescape the URL and then
decode it with the file name coding system.
YAMAMOTO Mitsuharu
address@hidden