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

sub Exclude
{
 my $cfile = shift;
 if (open(C,"<$cfile"))
  {
   while (<C>)
    {
     if (/{\s*"[^"]+"\s*,\s*(\w+)\s*}/)
      {
       $Exclude{$1} = $cfile;
      }
    }
   close(C);
  }
 else
  {
   warn "Cannot open $cfile:$!";
  }
}

sub Vfunc
{
 my $hfile = shift;
 my %VFunc = ();
 my %VVar  = ();
 my %VError= ();
 open(H,"<$hfile") || die "Cannot open $hfile:$!";

 while (<H>)
  {
   if (/^\s*(EXTERN|extern)\s*(.*?)\s*(\w+)\s+_\s*\(\(/)
    {
     my ($type,$name) = ($2,$3);
     my $defn =  "VFUNC($type,$name,V_$name,_((";
     $_ = $';
     until (/\)\);\s*$/)
      {
       $defn .= $_;
       $_ = <H>;
       if (/^\S/)
        {
         chomp($_);
         die $_;
        }
      }
     s/\)\);\s*$/)))\n/;
     $defn .= $_;
     $VFunc{$name} = $defn;
    }
   elsif (/^\s*(EXTERN|extern)\s*(.*?)\s*(\w+)\s*;/)
    {
     my ($type,$name) = ($2,$3);
     $VVar{$name} = "VVAR($type,$name,V_$name)\n";
    }
   elsif (/\b(EXTERN|extern)\b/)
    {
     die "$hfile:$.: $_" unless (/^\s*#\s*define/);
    }
  }
 close(H);


 if (keys %VFunc || keys %VVar)
  {
   my $gard = "\U$hfile";
   $gard =~ s/\..*$//;
   $gard =~ s#/#_#g;
   my $name = "\u\L${gard}\UV";
   $fdef = $hfile;
   $fdef =~ s/\..*$/.t/;
   $mdef = $hfile;
   $mdef =~ s/\..*$/.m/;

   my $htfile = $hfile;
   $htfile =~ s/\..*$/_f.h/;
   unless (-r $htfile)
    {
     open(C,">$htfile") || die "Cannot open $htfile:$!";
     print C "#ifndef ${gard}_VT\n";
     print C "#define ${gard}_VT\n";
     print C "#include \"$hfile\"\n";
     print C "typedef struct ${name}tab\n{\n";
     print C "#define VFUNC(type,name,mem,args) type (*mem) args;\n";
     print C "#define VVAR(type,name,mem)       type (*mem);\n";
     print C "#include \"$fdef\"\n";
     print C "#undef VFUNC\n";
     print C "#undef VVAR\n";
     print C "} ${name}tab;\n";
     print C "extern ${name}tab *${name}ptr;\n";
     print C "extern ${name}tab *${name}Get _((void));\n";
     print C "#endif /* ${gard}_VT */\n";
     close(C);
    }

   my $cfile = $hfile;
   $cfile =~ s/\..*$/_f.c/;
   unless (-r $cfile)
    {
     open(C,">$cfile") || die "Cannot open $cfile:$!";
     print C "#include \"$hfile\"\n";
     print C "#include \"$htfile\"\n";
     print C "static ${name}tab ${name}table =\n{\n";
     print C "#define VFUNC(type,name,mem,args) name,\n";
     print C "#define VVAR(type,name,mem)      &name,\n";
     print C "#include \"$fdef\"\n";
     print C "#undef VFUNC\n";
     print C "#undef VVAR\n";
     print C "};\n";
     print C "${name}tab *${name}ptr;\n";
     print C "${name}tab *${name}Get() { return ${name}ptr = &${name}table;}\n";
     close(C);
    }

   print STDERR "$gard\n";
   chmod(0666,$fdef) unless -w $fdef;
   open(VFUNC,">$fdef")   || die "Cannot open $fdef:$!";
   chmod(0666,$mdef) unless -w $mdef;
   open(VMACRO,">$mdef")  || die "Cannot open $mdef:$!";
   print VFUNC  "#ifdef _$gard\n";
   print VMACRO "#ifndef _${gard}_VM\n";
   print VMACRO "#define _${gard}_VM\n";
   print VMACRO "#include \"$htfile\"\n";
   foreach $func (sort keys %VVar)
    {
     if (!exists $Exclude{$func})
      {
       print VFUNC $VVar{$func};
       print VMACRO "#define $func (*${name}ptr->V_$func)\n"
      }
    }
   foreach $func (sort keys %VFunc)
    {
     if (!exists $Exclude{$func})
      {
       print VFUNC $VFunc{$func};
       print VMACRO "#define $func (*${name}ptr->V_$func)\n"
      }
    }
   print VMACRO "#endif /* _${gard}_VM */\n";
   close(VMACRO);
   print VFUNC  "#endif /* _$gard */\n";
   close(VFUNC); # Close this last - Makefile dependancy
  }
}

foreach (<tk*Tab.c>)
 {
  Exclude($_);
 }

foreach (@ARGV)
 {
  Vfunc($_);
 }

__END__

=head1 NAME

mkVFunc - Support for "nested" dynamic loading

=head1 SYNOPSIS

 mkVFunc xxx.h

=head1 DESCRIPTION

B<perl/Tk> is designed so that B<Tk> can be dynamically loaded 'on top of'
perl. That is the easy bit. What it also does is allow Tk::Xxxx to be
dynamically loaded 'on top of' the B<perl/Tk> composite. Thus when
you 'require Tk::HList' the shared object F<.../HList.so> needs to be
able to call functions defined in perl I<and> functions defined in loadable
.../Tk.so . Now functions in 'base executable' are a well known problem,
and are solved by DynaLoader. However most of dynamic loading schemes
cannot handle one loadable calling another loadable.

Thus what Tk does is build a table of functions that should be callable.
This table is auto-generated from the .h file by looking for
'extern' (and EXTERN which is #defined to 'extern').
Thus any function marked as 'extern' is 'referenced' by the table.
The address of the table is then stored in a perl variable when Tk is loaded.
When HList is loaded it looks in the perl variable (via functions
in perl - the 'base executable') to get the address of the table.

The same utility that builds the table also builds a set of #define's.
HList.c (and any other .c files which comprise HList) #include these
#define's. So that

  Tk_SomeFunc(x,y,z)

Is actually compiled as

  (*TkVptr->V_Tk_SomeFunc)(x,y,z)

Where Tk_ptr is pointer to the table.

See:

 Tk-b*/pTk/mkVFunc - perl script that produces tables
          /tk.h        - basis from which table is generated
          /tk.m        - #define's to include in sub-extension
          /tk_f.h      - #included both sides.
          /tk_f.c      - Actual table definition.
          /tk.t        - 'shared' set of macros which produce table
                         included in tk_f.c and tk_f.h
          /tkVMacro.h  - Wrapper to include *.m files

In addition to /tk* there are /tkInt*, /Lang* and /tix*

=cut