#!./miniperl -w

$config_pm = $ARGV[0] || 'lib/Config.pm';
@ARGV = "./config.sh";

# list names to put first (and hence lookup fastest)
@fast = qw(archname osname osvers prefix libs libpth
	dynamic_ext static_ext extensions dlsrc so
	sig_name sig_num cc ccflags cppflags
	privlibexp archlibexp installprivlib installarchlib
	sharpbang startsh shsharp
);

# names of things which may need to have slashes changed to double-colons
@extensions = qw(dynamic_ext static_ext extensions known_extensions);


open CONFIG, ">$config_pm" or die "Can't open $config_pm: $!\n";
$myver = $];

print CONFIG <<"ENDOFBEG";
package Config;
use Exporter ();
\@ISA = (Exporter);
\@EXPORT = qw(%Config);
\@EXPORT_OK = qw(myconfig config_sh config_vars);

\$] == $myver
  or die "Perl lib version ($myver) doesn't match executable version (\$])";

# This file was created by configpm when Perl was built. Any changes
# made to this file will be lost the next time perl is built.

ENDOFBEG


@fast{@fast} = @fast;
@extensions{@extensions} = @extensions;
@non_v=();
@v_fast=();
@v_others=();
$in_v = 0;

while (<>) {
    next if m:^#!/bin/sh:;
    # Catch CONFIG=true and PATCHLEVEL=n line from Configure.
    s/^(\w+)=(true|\d+)\s*$/$1='$2'\n/;
    unless ($in_v or m/^(\w+)='(.*\n)/){
	push(@non_v, "#$_"); # not a name='value' line
	next;
    }
    if ($in_v) { $val .= $_;             }
    else       { ($name,$val) = ($1,$2); }
    $in_v = $val !~ /'\n/;
    next if $in_v;
    if ($extensions{$name}) { s,/,::,g }
    if (!$fast{$name}){ push(@v_others, "$name='$val"); next; }
    push(@v_fast,"$name='$val");
}

foreach(@non_v){ print CONFIG $_ }

print CONFIG "\n",
    "my \$config_sh = <<'!END!';\n",
    join("", @v_fast, sort @v_others),
    "!END!\n\n";

# copy config summary format from the myconfig script

print CONFIG "my \$summary = <<'!END!';\n";

open(MYCONFIG,"<myconfig") || die "open myconfig failed: $!";
1 while defined($_ = <MYCONFIG>) && !/^Summary of/;
do { print CONFIG $_ } until !defined($_ = <MYCONFIG>) || /^\s*$/;
close(MYCONFIG);

print CONFIG "\n!END!\n", <<'EOT';
my $summary_expanded = 0;

sub myconfig {
	return $summary if $summary_expanded;
	$summary =~ s/\$(\w+)/$Config{$1}/ge;
	$summary_expanded = 1;
	$summary;
}
EOT

# ----

print CONFIG <<'ENDOFEND';

sub FETCH { 
    # check for cached value (which may be undef so we use exists not defined)
    return $_[0]->{$_[1]} if (exists $_[0]->{$_[1]});

    # Search for it in the big string 
    my($value, $start, $marker);
    $marker = "$_[1]='";
    # return undef unless (($value) = $config_sh =~ m/^$_[1]='(.*)'\s*$/m);
    $start = index($config_sh, "\n$marker");
    return undef if ( ($start == -1) &&  # in case it's first 
        (substr($config_sh, 0, length($marker)) ne $marker) );
    if ($start == -1) { $start = length($marker) } 
        else { $start += length($marker) + 1 }
    $value = substr($config_sh, $start, 
        index($config_sh, qq('\n), $start) - $start);
 
    $value = undef if $value eq 'undef'; # So we can say "if $Config{'foo'}".
    $_[0]->{$_[1]} = $value; # cache it
    return $value;
}
 
my $prevpos = 0;

sub FIRSTKEY {
    $prevpos = 0;
    # my($key) = $config_sh =~ m/^(.*?)=/;
    substr($config_sh, 0, index($config_sh, '=') );
    # $key;
}

sub NEXTKEY {
    my $pos = index($config_sh, qq('\n), $prevpos) + 2;
    my $len = index($config_sh, "=", $pos) - $pos;
    $prevpos = $pos;
    $len > 0 ? substr($config_sh, $pos, $len) : undef;
}

sub EXISTS { 
    # exists($_[0]->{$_[1]})  or  $config_sh =~ m/^$_[1]=/m;
    exists($_[0]->{$_[1]}) or
    index($config_sh, "\n$_[1]='") != -1 or
    substr($config_sh, 0, length($_[1])+2) eq "$_[1]='";
}

sub STORE  { die "\%Config::Config is read-only\n" }
sub DELETE { &STORE }
sub CLEAR  { &STORE }


sub config_sh {
    $config_sh
}

sub config_re {
    my $re = shift;
    my @matches = ($config_sh =~ /^$re=.*\n/mg);
    @matches ? (print @matches) : print "$re: not found\n";
}

sub config_vars {
    foreach(@_){
	config_re($_), next if /\W/;
	my $v=(exists $Config{$_}) ? $Config{$_} : 'UNKNOWN';
	$v='undef' unless defined $v;
	print "$_='$v';\n";
    }
}

ENDOFEND

if ($^O eq 'os2') {
  print CONFIG <<'ENDOFSET';
my %preconfig;
if ($OS2::is_aout) {
    my ($value, $v) = $config_sh =~ m/^used_aout='(.*)'\s*$/m;
    for (split ' ', $value) {
        ($v) = $config_sh =~ m/^aout_$_='(.*)'\s*$/m;
        $preconfig{$_} = $v eq 'undef' ? undef : $v;
    }
}
sub TIEHASH { bless {%preconfig} }
ENDOFSET
} else {
  print CONFIG <<'ENDOFSET';
sub TIEHASH { bless {} }
ENDOFSET
}

print CONFIG <<'ENDOFTAIL';

tie %Config, 'Config';

1;
__END__

=head1 NAME

Config - access Perl configuration information

=head1 SYNOPSIS

    use Config;
    if ($Config{'cc'} =~ /gcc/) {
	print "built by gcc\n";
    } 

    use Config qw(myconfig config_sh config_vars);

    print myconfig();

    print config_sh();

    config_vars(qw(osname archname));


=head1 DESCRIPTION

The Config module contains all the information that was available to
the C<Configure> program at Perl build time (over 900 values).

Shell variables from the F<config.sh> file (written by Configure) are
stored in the readonly-variable C<%Config>, indexed by their names.

Values stored in config.sh as 'undef' are returned as undefined
values.  The perl C<exists> function can be used to check if a
named variable exists.

=over 4

=item myconfig()

Returns a textual summary of the major perl configuration values.
See also C<-V> in L<perlrun/Switches>.

=item config_sh()

Returns the entire perl configuration information in the form of the
original config.sh shell variable assignment script.

=item config_vars(@names)

Prints to STDOUT the values of the named configuration variable. Each is
printed on a separate line in the form:

  name='value';

Names which are unknown are output as C<name='UNKNOWN';>.
See also C<-V:name> in L<perlrun/Switches>.

=back

=head1 EXAMPLE

Here's a more sophisticated example of using %Config:

    use Config;
    use strict;

    my %sig_num;
    my @sig_name;
    unless($Config{sig_name} && $Config{sig_num}) {
	die "No sigs?";
    } else {
	my @names = split ' ', $Config{sig_name};
	@sig_num{@names} = split ' ', $Config{sig_num};
	foreach (@names) {
	    $sig_name[$sig_num{$_}] ||= $_;
	}   
    }

    print "signal #17 = $sig_name[17]\n";
    if ($sig_num{ALRM}) { 
	print "SIGALRM is $sig_num{ALRM}\n";
    }   

=head1 WARNING

Because this information is not stored within the perl executable
itself it is possible (but unlikely) that the information does not
relate to the actual perl binary which is being used to access it.

The Config module is installed into the architecture and version
specific library directory ($Config{installarchlib}) and it checks the
perl version number when loaded.

=head1 NOTE

This module contains a good example of how to use tie to implement a
cache and an example of how to make a tied variable readonly to those
outside of it.

=cut

ENDOFTAIL

close(CONFIG);

# Now do some simple tests on the Config.pm file we have created
unshift(@INC,'lib');
require $config_pm;
import Config;

die "$0: $config_pm not valid"
	unless $Config{'CONFIG'} eq 'true';

die "$0: error processing $config_pm"
	if defined($Config{'an impossible name'})
	or $Config{'CONFIG'} ne 'true' # test cache
	;

die "$0: error processing $config_pm"
	if eval '$Config{"cc"} = 1'
	or eval 'delete $Config{"cc"}'
	;


exit 0;