#!/usr/bin/perl
############################################################################
#
#  gpp - general pre processor
#
#  This script is a pre-processor that can be used for parsing documents
#  and get #ifdef/#ifndef/#else/#endif to decide how the output looks.
#  Defines are set with the -D option.  The -nr option is for setting the
#  name regular expression that is used to convert infile-names to outfile-
#  names.  --help gives a short usage summary.
#
#  Hacked in perl by Lars J. Aas <larsa@sim.no>, 1998.
#

@options = ();
@files = ();

foreach $arg ( @ARGV ) {
    if ( -f $arg ) {
        push( @files, $arg );
    } else {
        push( @options, $arg ); # hopefully
    }
}

# parse options

%defines = ();
$nameexp = "";

foreach $opt ( @options ) {
    if ( $opt =~ /^-D/ ) { # define
        $define = substr( $opt, 2 );
        $defines{$define} = 1;
    } elsif ( $opt =~ /^-(h|-help)/ || $opt =~ /^--usage/ ) {
        print "USAGE: gpp -nr<expr> -D<define> <files>\n";
        exit 0;
    } elsif ( $opt =~ /^-nr/ ) {
        $nameexp = substr( $opt, 3 );
    } else {
        print STDERR "Error: unknown option \"", $opt,
            "\" (or no such file).\n";
        exit 0;
    }
}

if ( $nameexp =~ /^$/ ) {
    print STDERR "ERROR: no name-modifying regular expression.\n";
    exit 0;
}

foreach $file ( @files ) {
    $oldname = $file;
    $newname = $file;
    $string = '$newname =~ ' . $nameexp . ";";
    eval $string;
    print "old name: ", $oldname, "\nnew name: ", $newname, "\n";
    if ( $oldname eq $newname ) {
        print STDERR "ERROR: can't use same name for both input and output.\n";
        exit 0;
    }

    @inlines = ();
    @outlines = ();

    open( INPUT, $oldname ) || die "open( ", $oldname, " ): $!\n"; 
    @inlines = <INPUT>;
    close( INPUT );

    $copy = 1;
    for ( $linenum = 0; $linenum < $#inlines; $linenum++ ) {
        if ( $inlines[$linenum] =~ /^#/ ) {
            $directive = $inlines[$linenum];
            chop( $directive );
            if ( $directive =~ /^#else/ ) {
                $copy = ($copy + 1) % 2;
            } elsif ( $directive =~ /^#endif/ ) {
                $copy = 1;
            } elsif ( $directive =~ /^#ifdef / ) {
                $var = substr( $directive, 7 );
                if ( $defines{$var} == 1 ) {
                    $copy = 1;
                } else {
                    $copy = 0;
                }
            } elsif ( $directive =~ /^#ifndef / ) {
                $var = substr( $directive, 8 );
                if ( $defines{$var} == 1 ) {
                    $copy = 0;
                } else {
                    $copy = 1;
                }
            }
        } elsif ( $copy == 1 ) {
            push( @outlines, $inlines[$linenum] );
        }
    }

    open( OUTPUT, "> $newname" ) || die "open( > ", $newname, " ): $!\n";
    print OUTPUT @outlines;
    close( OUTPUT );
    @outlines = ();
}