Re: New way to do XS constants

[Tim Bunce <Tim.Bunce@ig.co.uk>]

On Fri, Jan 07, 2000 at 12:34:01AM -0600, Tye McQueen wrote:
> It looks like the makemaker e-mail list may have become defunct so
> I'm writing to p5p and CCing makemaker.  Since the only example module
> is Win32-specific, I'm also CCing Perl-Win32-Porters.
> 
> I've written a new way to deal with constants in XS modules.  The
> major advantages:
>
>   * No autoloading required [but could be used if you had a truely
>     huge list of constants and most users need few of them].
>   * No doing lots of strcmp()s at module run time when you have lots
>     of constants.
>   * The most efficient method [at module run time] if not tons of
>     unused constants
>   * No modifying big complex C case statements when you decide to
>     add more constants to your module.  To change which constants
>     you support, you simply update your @EXPORT, @EXPORT_OK, and/or
>     %EXPORT_TAGS entries and possibly make minor changes to your
>     Makefile.PL.
>   * Still uses C code to determine constant values -- not a
>     throw-back to h2ph.

FYI: All those advantages also apply to this very simple method:

  I32
  constant()
        PROTOTYPE:
    ALIAS:
        CONST_NAME_1 = 1
        CONST_NAME_2 = 2
        CONST_NAME_3 = 3
        CONST_NAME_4 = 4
    CODE:
    RETVAL = ix;
    OUTPUT:
    RETVAL

(The 1, 2, 3, 4 can be #defined values.)

Using a single XS sub and multiple XS aliases instead of multiple perl
subs uses very little memory (far less than multiple perl subs).
It also has a very low start-up overhead (just one newXS() call each).

Tim.

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Follow-Ups from:

Graham Barr <gbarr@pobox.com>

References to:

Tye McQueen <tye@metronet.com>

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