Miscellany

# the first argument of this function is a filename
# the second argument is a reference to a hash of variables
# all variables in that hash will be written out to a file
# the format of the file is as follows
# SCALARS: s:name:value
# ARRAYS : a:name:value1:value2:value3
# HASHES : h:name:key1:value1:key2:value2
# newlines are the seperators! there is no terminating character
sub write_vars {
    my $filename = shift @_;
    my $vars = shift @_;
   
    open(FILE, ">$filename");
    
    foreach my $key (keys %{$vars}) {
    # this one is just for convienence
    my $i = \( $vars->{$key} );
        # this is a switch statement
        # make a reference to $vars->{$key} and pass it to ref
        for (ref $i) {
            # if it is scalar, ref will return SCALAR...
            if (/SCALAR/) {
                print FILE "s:$key:" . $vars->{$key} . ",\n";
            }
            # ...otherwise it returns an empty string
            # which means it is a hash or an array
            else {
                $j = $vars->{$key};
                $type = ref $j;
                # if it is an array, print out each element
                if ($type eq "ARRAY") {
                    print FILE "a:$key";
                    for my $element ( @{$j} ) {
                        print FILE ":$element";
                    }
                }
                # likewise for a hash, print out the key/value pairs
                elsif ($type eq "HASH") {
                    print FILE "h:$key";
                    for my $k ( keys %{$j} ) {
                        print FILE ":$k:" . $j->{$k};
                    }
                }
            }
        }
    }
   
    close(FILE);
        
    return;
}

# the first argument of this function is a filename
# function returns a hash
# see the above function for the format of the file
sub read_vars {
    my $filename = shift @_;
    my %vars;
    # these are used when extracting data from the fields
    my ($type, $name, $value, $key);

    open(FILE, $filename);
    my @data = <FILE>;
    close(FILE);

    # iterate through the array 
    foreach my $line (@data) {
        # retrieve the type
        $type = substr($line, 0, 1);
        for ($type) {
            # if it's a scalar...
            if (/s/) {
                (undef,$name,$value) = split(/:/, $line, 3);
                chomp $value;
                $vars{$name} = $value;
            }
            # if it's an array...
            if (/a/) {
                # stores the elements of the array, temporarily
                my ($values, @elements);
                (undef,$name,$values) = split(/:/, $line, 3);
                chomp $values;
                @elements = split(/:/, $values);

                # now we've got the values split up
                # time to write things to the hash
                $vars{$name} = (\@elements);
            }
            # if it's a hash...
            if (/h/) {
                # $k and $v are for key and value
                my ($k, $v, $pairs, %hash);
                (undef,$name,$pairs) = split(/:/, $line, 3);
                chomp $pairs;

                # extract all the pairs and put them in the hash
                while ($pairs ne "") {
                    ($k,$v,$pairs) = split(/:/, $pairs, 3);
                    $hash{$k} = $v;
                }

                # now shove a hash ref into our big hash!
                $vars{$name} = (\%hash);
            }
        }
    }
    
    return %vars;
}