Re: Question regarding the python binding

Hi Роман,

On Thu, Mar 25, 2010 at 06:56:26PM +0300, Роман Донченко wrote:

>> Back to python: I managed to use the Python bindings to get a value from
>> the config file (I didn't want to reinvent the wheel) like this:
>>
>> ***
>> from svn import repos, fs, delta, core, client
>>
>> def main(pool, repos_dir):
>>
>> # for now, store client configuration in repository root
>> cfgfile = repos_dir+'/conf/client.conf'
>>
>> svncfg = core.svn_config_read (cfgfile, True, pool)
>>
>> global_ignores = core.svn_config_get (svncfg,
>> core.SVN_CONFIG_SECTION_GLOBAL, core.SVN_CONFIG_OPTION_GLOBAL_IGNORES,
>> None)
>>
>> ***
>>
>> Now I'd like to verify our default set of required MIME types, so I need
>> to get the contents of the [auto-props] section from the config file.
>>
>> libsvn provides the following function which should be suitable for my
>> needs:
>>
>> svn_config_enumerate2(svn_config_t cfg, char section,
>> svn_config_enumerator2_t callback, void baton, apr_pool_t pool) -> int
>>
>> Two questions arise:
>>
>> 1. How do I define an appropiate callback in Python? Looking at the SWIG
>> documentation, I see examples on how to implement Python callbacks but
>> they don't seem to match the current SVN bindings. I tried passing a
>> Python method, deriving from svn_config_enumerator2_t etc. -> Segfault.
>
> I took a look, and unfortunately this callback is not supported. The
> reason for that is that SWIG can't automatically figure out how to call
> Python callbacks, so a chunk of boring code must be written for each
> callback type - and I guess no developers needed to scratch this
> particular itch.
>
> If it was supported, however, the call would look like this (and it
> *will* look like this, after I become un-busy again and implement it):
>
> def enumerator(name, value, pool):
> print "%s: %s" % (name, value)
>
> core.svn_config_enumerate2(svncfg, core.SVN_CONFIG_SECTION_AUTO_PROPS,
> enumerator)

Thanks a lot for the answer - I already suspected something like this... ;-|
So, back to good old "do it yourself"... ;-) Not that it's complicated,
I just wanted to stay within Subversion as far as possible. :-)

>> 2. What's the baton good for? Is it just some kind of additional data, I
>> don't need to care about?
>
> The baton argument is used up by the bindings themselves, you neither
> should nor can supply your own (this applies to all callbacks).

> > Additional question: I can't seem to find an equivalent of "svnlook
> > cat" anywhere... I wanted to avoid calling external programs - commits
> > are slow enough already...
>
> You basically need to apply repos.open, then repos.fs, then
> fs.revision_root, then fs.file_contents.

I'm seeing the following example code:

  fs_ptr = repos.svn_repos_fs(repos.svn_repos_open(repos_dir, pool))
  root = fs.txn_root(fs.open_txn(fs_ptr, txn, pool), pool)
  cc = repos.ChangeCollector(fs_ptr, root, pool)

-> shall I use fs.txn_root or fs.revision_root (the revision is not
complete yet, it's just being committed)

Thanks again,

Tino.

-- 
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