[pacman-dev] [PATCH] Add a fetch callback to allow front-end download support

[Aaron Griffin]

On Sat, Mar 28, 2009 at 4:47 PM, Dan McGee <dpmcgee at gmail.com> wrote:
> On Sat, Mar 28, 2009 at 4:44 PM, Aaron Griffin <aaronmgriffin at gmail.com> wrote:
>> On Sat, Mar 28, 2009 at 4:34 PM, Dan McGee <dpmcgee at gmail.com> wrote:
>>> On Fri, Feb 20, 2009 at 2:31 AM, Sebastian Nowicki <sebnow at gmail.com> wrote:
>>>> +/** A callback for downloading files
>>>> + * @param url the URL of the file to be downloaded
>>>> + * @param localpath the directory to which the file should be downloaded
>>>> + * @param mtimeold the modification time of the file previously downloaded
>>>> + * @param mtimenew the modification time of the newly downloaded file.
>>>> + * This should be set by the callback.
>>>> + * @return 0 on success, 1 if the modification times are identical, -1 on
>>>> + * error.
>>>> + */
>>>> +typedef int (*alpm_cb_fetch)(const char *url, const char *localpath,
>>>> +               time_t mtimeold, time_t *mtimenew);
>>> Does everyone thing this is a good enough interface? I don't want to
>>> have to change this later after we release once.
>>
>> Hmmm I wonder... why do we need to pass the mtime stuff in? Doesn't it
>> make sense that most fetch callbacks would do the exact same
>> comparison? I can't see any other need for these - except maybe
>> mtimenew to set the download file's mtime to match the server's,
>> but... do we care that they are exact? If we don't set it, it should
>> always be greater than the server anyway.
>>
>> I'm kinda just talking here, not putting lots of thought into it, but
>> are those two points (mtime compare, and setting local file mtime)
>> sane? Is there something I'm missing?
>
> The mtime stuff is mainly used for database downloads, where we don't
> actually have the old file to compare against- we simply have the
> mtime stored in:
> $ cat /var/lib/pacman/sync/core/.lastupdate
> 1238199239
>
> We could probably simplify this by always keeping the db file we
> download around and just using the stat-ed mtime from that...

What about the compare? if(mtimenew > mtimeold) will be done in every
fetch callback, correct? Why don't e just do that before we call the
fetch callback?