package FileCook;
$VERSION = '1.1';
use FileHandle;
use Exporter; 
use strict;
our @ISA = qw(Exporter);
our @EXPORT=qw(WriteStruct ReadStruct);

# NB: filehandles must be binmode!

# Writes structure to filehandle. Returns number of bytes written.
sub WriteStruct
{ 
  my ($filehandle, $record) = @_;
  $filehandle or return undef;
  $record or return undef;

  my $output = &StructToString( $record );

  if( defined( $output ) )
  {
    $output = &Write32( length $output ) . $output;
    print $filehandle $output;
	return length $output;
  }

  return 0;
}

# Reads structure from filehandle and returns it.
sub ReadStruct
{
  my ($filehandle) = @_;
  my $record;

  $filehandle or return undef;

  read( $filehandle, $record, 4 ) or return undef;
  $record = &Read32( $record );

  read( $filehandle, $record, $record );

  my ($result, $count) = &StringToStruct( $record );
  return $result;
}

# -----------------------

sub Write32
{
  (my $i) = @_;
  return (chr(($i)&0xFF). chr(($i>>8)&0xFF). chr(($i>>16)&0xFF). chr(($i>>24)&0xFF));
}

sub Read32
{
  (my $c) = @_;
  return unpack("V", $c);
}

sub StructToString
{
    (my $s)=@_;
    my $r = '';
    
    if (ref($s) eq 'ARRAY')
    {
		$r .= '[';
		foreach my $item (@$s)
		{
			$r.=&StructToString($item);
		}
		$r .= ']';
    }elsif (ref($s) eq 'HASH')
    {
		my @keys = keys %$s ;
		$r.='{';
		foreach my $key (@keys)
		{
			$r.=&StructToString($key);
			$r.=&StructToString($s->{$key});
		}
		$r.='}';
    }
	else
	{
	    $r.='$' . &Write32(length ($s)) . $s;
	}
	return $r;
}

sub StringToStruct
{
    (my $s)=@_;
    my $r = substr($s, 0, 1);
	my $count;

	length($s) or return undef;
    
    if ($r eq '[')
    {
		my @a = ( );
		my $i = 1;
		while(($i < length($s)) && (substr($s,$i,1) ne ']'))
		{
		  my ($t, $c) = &StringToStruct(substr($s, $i));
		  push @a, $t;
		  $i += $c;
		}
		$count = $i+1;
		$r = \@a;
	}
    elsif ($r eq '{')
    {
		my @a = ( );
		my %b;
		my $i = 1;
		while(($i < length($s)) && (substr($s,$i,1) ne '}'))
		{
		  my ($t, $c) = &StringToStruct(substr($s, $i));
		  push @a, $t;
		  $i += $c;
		}
		$count = $i+1;
		%b = @a;
		$r = \%b;
    }elsif ($r eq '$')
	{
		$count = &Read32(substr($s, 1, 4));
	    $r = substr($s, 5, $count);
		$count += 5;
	}
	else
	{
	    return undef;
	}
	return ($r, $count);
}

1;