Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwm.edu!lll-winken!ames!haven!udel!princeton!phoenix!melon!viktor
From: viktor@melon.Princeton.EDU (Viktor Dukhovni)
Newsgroups: comp.lang.perl
Subject: Re: reverse of localtime()
Message-ID: <14243@phoenix.Princeton.EDU>
Date: 4 Mar 90 21:35:24 GMT
References: <1176@frankland-river.aaii.oz.au> <1990Mar4.034414.25460@pegasus.com>
Sender: news@phoenix.Princeton.EDU
Lines: 68


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#! /usr/bin/perl

;#
;#  depending on whether localtime takes signed or unsigned args,
;# this should work for years between ~1902 and ~2038 or
;# ~1970 and ~2106

sub cmpdate {
  local($tse,$tmi,$tho,$tda,$tmo,$tyr,$foo1,$foo2,$foo3,
         $se,$mi,$ho,$da,$mo,$yr) = @_;

  if ( $tyr != $yr ) {
    return($tyr - $yr) ;
  } 
  if ( $tmo != $mo ) {
    return($tmo - $mo) ;
  } 
  if ( $tda != $da ) {
    return($tda - $da) ;
  } 
  if ( $tho != $ho ) {
    return($tho - $ho) ;
  } 
  if ( $tmi != $mi ) {
    return($tmi - $mi) ;
  } 
  if ( $tse != $se ) {
    return($tse - $se) ;
  } 
}

sub unctime {
  local(@args) = @_;
  local($bit);
  local($t) = 0x0;
  local($maxtime,$mintime) ;

  if (do cmpdate(localtime(0x80000000),localtime(0)) > 0 ) {
    $maxtime=0x80000000;
    $mintime=0x0;
    $bit=0x80000000;
  } else { 
    $maxtime=0x7fffffff;
    $mintime=0x80000000;
    $bit=0x40000000;
    $t=$mintime if(do cmpdate(localtime(0),@args) > 0);
  }
  die "Date out of range\n" if (do cmpdate(localtime($maxtime),@args) < 0);
  die "Date out of range\n" if (do cmpdate(localtime($mintime),@args) > 0);

  while ( $bit != 0 ) {
    $t|=$bit if (do cmpdate(localtime($t|$bit),@args) <= 0) ;
    $bit >>= 1;
  }
  $t;
}

printf stderr "Please enter se/mi/ho/da/mo/yr ";
chop($date = <stdin>) ;
$time=do unctime(split(/\//,$date)) ;
print "$time <- ",join("/",localtime($time)),"\n" ;
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-- 
	Viktor Dukhovni <viktor%math@princeton.edu>	: ARPA
		<...!uunet!princeton!math!viktor>	: UUCP