[Patches] [ python-Patches-876130 ] add C API to datetime module

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Patches item #876130, was opened at 2004-01-13 16:20
Message generated for change (Comment added) made by lemburg
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Category: Modules
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Anthony Tuininga (atuining)
Assigned to: M.-A. Lemburg (lemburg)
Summary: add C API to datetime module

Initial Comment:
The datetime module does not have a C API which means
that modules written in C cannot take advantage of the
datetime module without incurring significant overhead.
These patches supply this lack and are based on the C
API exported by the mxDateTime module and the cStringIO
module and enhanced as suggested by Guido.

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>Comment By: M.-A. Lemburg (lemburg)
Date: 2004-01-28 12:49

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Thanks for the clarification. I had forgotten about the
macros -- I'd suggest that you document them in the
datetimeapi.h include file to not cause the same confusion
on the developer side (the trick to achieve adoption is to
make things easy on the developer).

As for TimeFromTicks(): 
This should be rather straight forward to implement: you
take the time part of the ticks timestamp and create a time
object from it. This is the way the DB API constructor works.

Could you add C APIs for the three DB API ticks interface
methods ?

Other things that are missing:
* documentation of the way the CAPI object can be used in
datetimeapi.h
* documentation of the various CAPI entries
* documentation of the API magic number (there should be
some scheme for this)

I think that datetimeapi.h should be enough for a developer
to read in order to use the interface.


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Comment By: Anthony Tuininga (atuining)
Date: 2004-01-26 22:02

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I didn't think any additional API would be necessary for
extracting date time information since the following macros
are available:

PyDateTime_GET_YEAR(o)
PyDateTime_GET_MONTH(o)
PyDateTime_GET_DAY(o)
PyDateTime_DATE_GET_HOUR(o)
PyDateTime_DATE_GET_MINUTE(o)
PyDateTime_DATE_GET_SECOND(o)
PyDateTime_DATE_GET_MICROSECOND(o)
PyDateTime_TIME_GET_HOUR(o)
PyDateTime_TIME_GET_MINUTE(o)
PyDateTime_TIME_GET_SECOND(o)
PyDateTime_TIME_GET_MICROSECOND(o)

Were you thinking of something else that is needed?

As for interfacing at the C level for converting from Unix
ticks, the following method is already available and could
simply be used as a drop in replacement for DateFromTicks()
and TimestampFromTicks() from the DB API document.

DateFromTicks() --> datetime.date.fromtimestamp()
TimestampFromTicks() --> datetime.datetime.fromtimestamp()

TimeFromTicks() is not already exposed but discussions with
Tim Peters already suggested that would not happen since the
concept is rather strange. You'll have to discuss that with
him if you disagree! :-)

Any comments?

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Comment By: M.-A. Lemburg (lemburg)
Date: 2004-01-26 21:46

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This is a good start. However, you should add more APIs for
extracting date/time information to the C API. mxDateTime.h
from egenix-mx-base can provide a good basis for this. 

If you want to make the datetime module usable for database
interfacing at C level, you'll also have to add interfaces for
Unix ticks conversion, since these are often used by database
C level interfaces.


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Comment By: Anthony Tuininga (atuining)
Date: 2004-01-26 19:36

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I have no objection to providing patches for doc and test. A
quick look at _testcapimodule.c doesn't provide any obvious
ideas as to how to patch it. I looked for cStringIO which
has a C API already and found nothing in there at all. The
documentation also simply says "see the source for the
information you require". Any suggestions as to how to proceed?

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Comment By: Tim Peters (tim_one)
Date: 2004-01-26 04:17

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Marc-Andre, can you review this?  I think you have more 
experience building C APIs for modules than anyone else 
(while I don't have any).

There's certainly no objection to giving datetime a C API, and 
Guido already said he doesn't want to rely on that Martin 
changed datetime to be built as part of the core (in 2.3 on 
Windows, datetime.pyd was a distinct DLL; in CVS, datetime 
is compiled into the core DLL now).

Anthony, you probably need to add doc and test patches.  
_testcapimodule.c holds tests of things you can only get at 
from C.

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