On Wed, Jun 20, 2012 at 5:23 AM, Daniel Stenberg <daniel_at_haxx.se> wrote:
> On Mon, 18 Jun 2012, Tatsuhiro Tsujikawa wrote:
>
>>> $ curl 'http://curl.haxx.se/metalink.cgi?curl=tar.gz'
>>>
>>> This downloads Metalink XML and prints it in stdout and nothing more.
>>> If we instruct curl to save it in the disk, e.g., -O option, it parses
>>> downloaded file as Metalink (if the Content-Type indicates Metalink)
>>> and downloads URIs described there. So the following command line:
>>>
>>> $ curl -O 'http://curl.haxx.se/metalink.cgi?curl=tar.gz'
>>>
>>> will actually download Metalink file and the URI described there.
>>>
>>> Does we need --metalink like switch in this case too?
>
>
> Yes. I think default should be to just get the data, just like it would
> without metalink support.
>
>
>> If the answer is yes, we perhaps make --metalink take no argument and make
>> it a switch to toggle further metalink parsing. So the last example command
>> line will become:
>>
>> $ curl --metalink -O http://.../file.metalink
>>
>> The --metalink is also used to toggle upcoming metalink/http feature.
>
>
> Yes, I think that would make perfect sense.
>
>
>> For reading local metalink file, new option --metalink-file will be added.
>
>
> Hm, do you really need a separate option for that? Won't it just be a
> file:// URL instead pretty much?
>

Agree.
The attached patch does what we discussed here: --metalink is now
non-argument option and if it is specified, process given URI as
Metalink XML file.

I dropped Content-Type sniffing because now users has total control of
whether parsing or not parsing file as Metalink. If URI is file://,
then we don't have Content-Type at the first place.

This patch also takes into account of Gunter's concern:

> perhaps lets store the metalink data in a temp file, and remove it afterwards;
> there's no need to clutter local disk with that stuff once the download finished
> successfully ...

I think this makes sense because if --metalink is given, user wants
the URI described in Metalink file and not Metalink file itself.
In this patch, Metalink specific write function is passed to libcurl
CURLOPT_WRITEFUNCTION option and downloaded data is directly fed into
libmetalink's XML parser. So no local file involved this time.

So you can now download remote metalink like this:

$ curl --metalink 'http://curl.haxx.se/metalink.cgi?curl=tar.bz2'

No worry about '?' characters this time, because it is not written to the disk.

You can also process local file using file://:

$ curl --metalink file://curl.metalink

0001 patch contains referctoring to reduce memory copy when multiple
checksum is provided.
0002 patch contains the changes I mentioned above.
0003 patch restores noprogress and isatty config values in each download.
This might be a bug fix.
0004 patch adds Metalink test case. Please forget about my previous
mail about Metalink test cases.

# It turns out that --metalink cannot be used to enable Metalink/HTTP
feature, so it
# seems we need another option for it, but it is another story.

Best regards,

Tatsuhiro Tsujikawa

>
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>
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