[m-rev.] for review: Implementation of time library in Java

[Fergus Henderson]

On 15-Dec-2003, James Goddard <goddardjames at yahoo.com> wrote:
> Implemented some library functions for the time library in java.
...
> +:- pragma foreign_proc("Java", time__clock(Ret::out, _IO0::di, _IO::uo),
> +        [will_not_call_mercury, promise_pure, tabled_for_io],
> +"
> +	// System.currentTimeMillis() returns a long (64 bit) integer which
> +	// represents the number of milliseconds since
> +	// January 1, 1970, 00:00:00 GMT.
> +	// This is cast to type int, discarding the high order bits, which is
> +	// ok since time__clock/3's base time is defined as being arbitrary.
>  
> +	Ret = (int) System.currentTimeMillis();

time__clock should return processor time, i.e. CPU usage, not wall clock time.

Apparently there is no way of doing this in Java short of using JNI or
the like.  So I suggest you leave this unimplemented for now, and just
put an XXX comment explaining the problem.  You can come back to this
once everything else is done.

> +:- pragma foreign_proc("Java", time__clk_tck = (Ret::out),
> +	[will_not_call_mercury, promise_pure],
> +"
> +	// Java only supports millisecond precision.
> +	Ret = 1000;
> +").

The time__clk_tck function is only used for interpreting the results of the
time__times procedure, which is unimplemented for the same reason as
time__clock.  It doesn't really make sense to implement this without
implementing time__times.  So I recommend leaving this unimplemented
for now.

> +:- pragma foreign_proc("Java",
> +	time__c_localtime(Time::in, Yr::out, Mnt::out, MD::out, Hrs::out,
> +		Min::out, Sec::out, YD::out, WD::out, N::out),
> +	[will_not_call_mercury, promise_pure],
> +"
...
> +		default:
> +			throw new RuntimeException(
> +				"DAY_OF_WEEK undefined in time__c_local_time");

s/DAY_OF_WEEK undefined/invalid DAY_OF_WEEK/

As discussed in person, the computation/use of N and DST_OFFSET in
localtime, gmtime, and mktime is not correct.

Please post another diff when you've addressed these review comments.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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