Re: [Bug-wget] [PATCH 20/25] New option --metalink-index to process Metalink application/metalink4+xml

[Tim Ruehsen]

On Thursday, September 15, 2016 7:56:45 PM CEST Matthew White wrote:
> On Thu, 15 Sep 2016 16:48:01 +0200
> 
> Tim Ruehsen <address@hidden> wrote:
> > On Thursday, September 15, 2016 4:16:44 PM CEST Matthew White wrote:
> > > On Thu, 15 Sep 2016 09:11:31 +0200
> > > 
> > > Giuseppe Scrivano <address@hidden> wrote:
> > > > Hi Matthew,
> > > > 
> > > > Matthew White <address@hidden> writes:
> > > > >> > Function amended to modify *name in place.
> > > > >> > 
> > > > >> > Followed Tim's suggestions for Patch 09/25 about different
> > > > >> > environments compatibility, the function now uses
> > > > >> > last_component()
> > > > >> > to detect the basename:
> > > > >> > http://lists.gnu.org/archive/html/bug-wget/2016-09/msg00083.html
> > > > >> > 
> > > > >> > NOTES: if *name is NULL and ref is like 'dir/C:D:file', the
> > > > >> > result
> > > > >> > will be 'C:D:file'; is it advisable to remove the drive letters
> > > > >> > 'C:D:' and return only 'file'?
> > > > >> > 
> > > > >> > /*
> > > > >> > 
> > > > >> >   Replace/remove the basename of a file name.
> > > > >> >   
> > > > >> >   The file name is permanently modified.
> > > > >> >   
> > > > >> >   Always set NAME to a string, even an empty one.
> > > > >> >   
> > > > >> >   Use REF's basename as replacement.  If REF is NULL or if it
> > > > >> >   doesn't
> > > > >> >   provide a valid basename candidate, then remove NAME's
> > > > >> >   basename.
> > > > >> > 
> > > > >> > */
> > > > >> > void
> > > > >> > replace_metalink_basename (char **name, char *ref)
> > > > >> > {
> > > > >> 
> > > > >> is it something we could do using only dirname and basename?  What
> > > > >> you
> > > > >> need here is "dirname(name) + basename(ref)"?
> > > > > 
> > > > > You asked to avoid superfluous memory allocations, right?
> > > > 
> > > > yes, and that is still my idea.  I was just wondering if the cost of
> > > > these extra memory allocations was worth.  Is it enough to use
> > > > last_component() to get it working on Windows?
> > > 
> > > Extra memory allocations shouldn't be a concern any longer, they are
> > > removed in the amended function definition previously posted:
> > > http://lists.gnu.org/archive/html/bug-wget/2016-09/msg00094.html
> > > 
> > > About base_name() and last_component() multi-environment compatibility:
> > > * lib/basename.c (base_name): Call last_component() to find the
> > > basename,
> > > allocate the basename (prefix with './' if required) *
> > > lib/basename-lgpl.c
> > > (last_component): Use the macros FILE_SYSTEM_PREFIX_LEN and ISSLASH to
> > > isolate the basename * lib/dosname.h: Define the macros
> > > FILE_SYSTEM_PREFIX_LEN and ISSLASH to work on different system
> > > environments
> > > 
> > > Forgive this copy and paste, but my question about
> > > replace_metalink_basename() is "if *name is NULL and ref is like
> > > 'dir/C:D:file', the result will be 'C:D:file'; is it advisable to remove
> > > the drive letters 'C:D:' and return only 'file'?".
> > 
> > Yes, if you use the result as file name to any file/system calls.
> 
> Function amended to remove prefix drive letters (aka FILE_SYSTEM_PREFIX_LEN)
> from the resulting file name, when the file name is a bare basename.
> 
> Use the dirname from *name and the basename from ref to compute the
> resulting file name.
> 
>   *name          +  ref           -> result
>   -----------------------------------------
>   NULL           + "foo/C:D:file" -> "file"             [bare basename]
>   "foobar"       + "foo/C:D:file" -> "file"             [bare basename]
>   "dir/old"      + "foo/C:D:file" -> "dir/C:D:file"
>   "C:D:file/old" + "foo/E:F:new"  -> "C:D:file/E:F:new" [is this ok?]

Just make sure that no file name beginning with letter+colon is used for system 
calls on Windows (e.g. open("C:D:file/E:F:new", ...) is not a good idea). 
Either you strip the 'C:D:', or percent escape ':' on Windows. Wget has 
functions to percent escape special characters in file names, depending on the 
OS it is built on.

Regards, Tim

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