unified build scheme: give util/dofile.pl the possibility to output selectively

Under certain conditions, one might not want to output certain
sections of a template file.  This adds the functions output_off() and
output_on(), reachable inside the templates.  And example usage in a
Makefile template could be this:

	@ : {- output_off() if $config{no_shared}; "" -}
	... lines dealing with shared libraries
	@ : {- output_on() -}
Reviewed-by: NRich Salz <rsalz@openssl.org>

util/dofile.pl

@@ -10,23 +10,76 @@ use warnings;
 
 use Getopt::Std;
 
-# Because we know that Text::Template isn't a core Perl module, we use
-# a fallback in case it's not installed on the system
-use File::Basename;
-use File::Spec::Functions;
-use lib catdir(dirname(__FILE__));
-use with_fallback qw(Text::Template);
-
 # We actually expect to get the following hash tables from configdata:
 #
 #    %config
 #    %target
 #    %withargs
+#    %unified_info
 #
 # We just do a minimal test to see that we got what we expected.
 # $config{target} must exist as an absolute minimum.
 die "You must run this script with -Mconfigdata\n" if !exists($config{target});
 
+# Make a subclass of Text::Template to override append_text_to_result,
+# as recommended here:
+#
+# http://search.cpan.org/~mjd/Text-Template-1.46/lib/Text/Template.pm#Automatic_postprocessing_of_template_hunks
+
+package OpenSSL::Template;
+
+# Because we know that Text::Template isn't a core Perl module, we use
+# a fallback in case it's not installed on the system
+use File::Basename;
+use File::Spec::Functions;
+use lib catdir(dirname(__FILE__));
+use with_fallback qw(Text::Template);
+
+use parent qw/Text::Template/;
+
+# Override constructor
+sub new {
+    my ($class) = shift;
+
+    # Call the constructor of the parent class, Person.
+    my $self = $class->SUPER::new( @_ );
+    # Add few more attributes
+    $self->{_output_off}   = 0;	# Default to output hunks
+    bless $self, $class;
+    return $self;
+}
+
+sub append_text_to_output {
+    my $self = shift;
+
+    if ($self->{_output_off} == 0) {
+	$self->SUPER::append_text_to_output(@_);
+    }
+
+    return;
+}
+
+sub output_reset_on {
+    my $self = shift;
+    $self->{_output_off} = 0;
+}
+
+sub output_on {
+    my $self = shift;
+    if (--$self->{_output_off} < 0) {
+	$self->{_output_off} = 0;
+    }
+}
+
+sub output_off {
+    my $self = shift;
+    $self->{_output_off}++;
+}
+
+# Come back to main
+
+package main;
+
 # Helper functions for the templates #################################
 
 # It might be practical to quotify some strings and have them protected
@@ -98,7 +151,7 @@ my @autowarntext = ("WARNING: do not edit!",
 my $prev_linecount = 0;
 my $text =
     @ARGV
-    ? join("", map { my $x = Text::Template::_load_text($_);
+    ? join("", map { my $x = "{- output_reset_on() -}".Text::Template::_load_text($_);
                      my $linecount = $x =~ tr/\n//;
                      $prev_linecount = ($linecount += $prev_linecount);
                      $lines{$linecount} = $_;
@@ -110,13 +163,31 @@ my $text =
 # Load the full template (combination of files) into Text::Template
 # and fill it up with our data.  Output goes directly to STDOUT
 
-my $template = Text::Template->new(TYPE => 'STRING', SOURCE => $text );
+my $template = OpenSSL::Template->new(TYPE => 'STRING', SOURCE => $text );
+
+sub output_reset_on {
+    $template->output_reset_on();
+    "";
+}
+sub output_on {
+    $template->output_on();
+    "";
+}
+sub output_off {
+    $template->output_off();
+    "";
+}
+
 $template->fill_in(OUTPUT => \*STDOUT,
                    HASH => { config => \%config,
                              target => \%target,
                              withargs => \%withargs,
+                             unified_info => \%unified_info,
                              autowarntext => \@autowarntext,
                              quotify1 => \&quotify1,
-                             quotify_l => \&quotify_l },
+                             quotify_l => \&quotify_l,
+                             output_reset_on => \&output_reset_on,
+                             output_on => \&output_on,
+                             output_off => \&output_off },
                    DELIMITERS => [ "{-", "-}" ],
                    BROKEN => \&broken);