#!/usr/local/bin/perl -w

#
#  A very speedy min/max key finder for hashes keyed by integer values
+.
#
#  Requires Perl 5.004 or later, due to the hv_iterkeysv macro.
#
#  Copyright 2000,2001(c) J.C.Wren   jcwren@jcwren.com
#  A production of Twitching Monk Software
#  No rights reserved, use as you see fit.  I'd like to know about it,
+ though, just for kicks.
#
use strict;

{
   my %hash = (  8 => 'eight',
                22 => 'twenty-two',
                99 => 'ninety-nine',
                 4 => 'four',
                 0 => 'zero',
               -66 => 'negative sixty-six',
              );

   my ($min, $max) = minmaxhash (\%hash);

   printf ("min key=%d, min key value=%s\n", $min, $hash {$min});
   printf ("max key=%d, max key value=%s\n", $max, $hash {$max});
}

use Inline C => <<'END_OF_C_CODE';

void minmaxhash (SV* hash_ref)
{
   Inline_Stack_Vars;
   HV* hash;
   HE* hash_entry;
   int i;
   int num_keys;
   int temp, min, max;

   if (!SvROK(hash_ref))
      croak("hash_ref is not a reference");

   hash = (HV*)SvRV(hash_ref);
   num_keys = hv_iterinit(hash);

   for (min = INT_MAX, max = INT_MIN, i = 0; i < num_keys; i++)
   {
      /*
      ** This is a bug:  I should be able to eliminate hash_entry
      ** as a temporary varaible.  On my system, the statement
      ** "if ((temp = SvIV(hv_iterkeysv(hv_iternext(hash)))) > max)"
      ** causes a segfault.
      */
      hash_entry = hv_iternext(hash);
      if ((temp = SvIV(hv_iterkeysv(hash_entry))) > max)
         max = temp;
      if (temp < min)
         min = temp;
   }

   Inline_Stack_Reset;
   Inline_Stack_Push(sv_2mortal(newSViv(min)));
   Inline_Stack_Push(sv_2mortal(newSViv(max)));
   Inline_Stack_Done;
}

END_OF_C_CODE
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