[spider.git] / perl / DXUser.pm

#
# DX cluster user routines
#
# Copyright (c) 1998-2020 - Dirk Koopman G1TLH
#
# The new internal structure of the users system looks like this:
#
# The users.v4 file formatted as a file of lines containing: <callsign>\t{json serialised version of user record}\n
#
# You can look at it with any text tools or your favourite editor :-)
#
# In terms of internal structure, the main user hash remains as %u, keyed on callsign as before.
#
# The value is a one or two element array [position] or [position, ref], depending on whether the record has been "get()ed"
# [i.e. got from disk] or not. The 'position' is simply the start of each line in the file. The function "get()" simply returns
# the stored reference in array[1], if present, or seeks to the  position from array[0], reads a line, json_decodes it,
# stores that reference into array[1] and returns that. That reference will be used from that time onwards.
#
# The routine writeoutjson() will (very) lazily write out a copy of %u WITHOUT STORING ANY EXTRA CURRENTLY UNREFERENCED CALLSIGN
# records to users.v4.n. It, in effect, does a sort of random accessed merge of the current user file and any "in memory"
# versions of any user record. This can be done with a spawned command because it will just be reading %u and merging
# loaded records, not altering the current users.v4 file in any way. 
#
# %u -> $u{call} -> [position of json line in users.v4 (, reference -> {call=>'G1TLH', ...} if this record is in use)].
#
# On my machine, it takes about 250mS to read the entire users.v4 file of 190,000 records and to create a
# $u{callsign}->[record position in users.v4] for every callsign in the users.v4 file. Loading ~19,000 records
# (read from disk, decode json, store reference) takes about 110mS (or 580nS/record).
#
# A periodic dump of users.v4.n, with said ~19,000 records in memory takes about 750mS to write (this can be speeded up,
# by at least a half, if it becomes a problem!). As this periodic dump will be spawned off, it will not interrupt the data
# stream.
#
# This is the first rewrite of DXUsers since inception. In the mojo branch we will no longer use Storable but use JSON instead.
# We will now be storing all the keys in memory and will use opportunistic loading of actual records in "get()". So out of
# say 200,000 known users it is unlikely that we will have more than 10% (more likely less) of the user records in memory.
# This will mean that there will be a increase in memory requirement, but it is modest. I estimate it's unlikely be more
# than 30 or so MB.
#
# At the moment that means that the working users.v4 is "immutable". 
#
# In normal operation, when first calling 'init()', the keys and positions will be read from the newer of users.v4.n and
# users.v4. If there is no users.v4.n, then users.v4 will be used. As time wears on, %u will then accrete active user records.
# Once an hour the current %u will be saved to users.v4.n.
#
# If it becomes too much of a problem then we are likely to chuck off "close()d" users onto the end of the current users.v4
# leaving existing users intact, but updating the pointer to the (now cleared out) user ref to the new location. This will
# be a sort of write behind log file. The users.v4 file is still immutable for the starting positions, but any chucked off
# records (or even "updates") will be written to the end of that file. If this has to be reread at any time, then the last
# entry for any callsign "wins". But this will only happen if I think the memory requirements over time become too much. 
#
# As there is no functional difference between the users.v4 and export_user generated "user_json" file(s), other than the latter
# will be in sorted order with the record elements in "canonical" order. There will now longer be any code to execute to
# "restore the users file". Simply copy one of the "user_json" files to users.v4, remove users.v4.n and restart. 
#
# Hopefully though, this will put to rest the need to do all that messing about ever again... Pigs may well be seen flying over
# your node as well :-)
#

package DXUser;

use DXLog;
use DB_File;
use Data::Dumper;
use Fcntl;
use IO::File;
use DXUtil;
use LRU;
use File::Copy;
use JSON;
use DXDebug;
use Data::Structure::Util qw(unbless);
use Time::HiRes qw(gettimeofday tv_interval);
use IO::File;

use strict;

use vars qw(%u  $filename %valid $lastoperinterval $lasttime $lru $lrusize $tooold $v3 $v4);

%u = ();
$filename = undef;
$lastoperinterval = 60*24*60*60;
$lasttime = 0;
$lrusize = 2000;
$tooold = 86400 * 365 + 31;             # this marks an old user who hasn't given enough info to be useful
$v3 = 0;
$v4 = 0;
my $json;

our $maxconnlist = 3;                   # remember this many connection time (duration) [start, end] pairs

our $newusers = 0;                                      # per execution stats
our $modusers = 0;
our $totusers = 0;
our $delusers = 0;
our $cachedusers = 0;

my $ifh;                                                # the input file, initialised by readinjson()


# hash of valid elements and a simple prompt
%valid = (
                  call => '0,Callsign',
                  alias => '0,Real Callsign',
                  name => '0,Name',
                  qth => '0,Home QTH',
                  lat => '0,Latitude,slat',
                  long => '0,Longitude,slong',
                  qra => '0,Locator',
                  email => '0,E-mail Address,parray',
                  priv => '9,Privilege Level',
                  lastin => '0,Last Time in,cldatetime',
                  passwd => '9,Password,yesno',
                  passphrase => '9,Pass Phrase,yesno',
                  addr => '0,Full Address',
                  'sort' => '0,Type of User', # A - ak1a, U - User, S - spider cluster, B - BBS
                  xpert => '0,Expert Status,yesno',
                  bbs => '0,Home BBS',
                  node => '0,Last Node',
                  homenode => '0,Home Node',
                  lockout => '9,Locked out?,yesno',     # won't let them in at all
                  dxok => '9,Accept DX Spots?,yesno', # accept his dx spots?
                  annok => '9,Accept Announces?,yesno', # accept his announces?
                  lang => '0,Language',
                  hmsgno => '0,Highest Msgno',
                  group => '0,Group,parray',    # used to create a group of users/nodes for some purpose or other
                  buddies => '0,Buddies,parray',
                  isolate => '9,Isolate network,yesno',
                  wantbeep => '0,Req Beep,yesno',
                  wantann => '0,Req Announce,yesno',
                  wantwwv => '0,Req WWV,yesno',
                  wantwcy => '0,Req WCY,yesno',
                  wantecho => '0,Req Echo,yesno',
                  wanttalk => '0,Req Talk,yesno',
                  wantwx => '0,Req WX,yesno',
                  wantdx => '0,Req DX Spots,yesno',
                  wantemail => '0,Req Msgs as Email,yesno',
                  pagelth => '0,Current Pagelth',
                  pingint => '9,Node Ping interval',
                  nopings => '9,Ping Obs Count',
                  wantlogininfo => '0,Login Info Req,yesno',
          wantgrid => '0,Show DX Grid,yesno',
                  wantann_talk => '0,Talklike Anns,yesno',
                  wantpc16 => '9,Want Users from node,yesno',
                  wantsendpc16 => '9,Send PC16,yesno',
                  wantroutepc19 => '9,Route PC19,yesno',
                  wantusstate => '0,Show US State,yesno',
                  wantdxcq => '0,Show CQ Zone,yesno',
                  wantdxitu => '0,Show ITU Zone,yesno',
                  wantgtk => '0,Want GTK interface,yesno',
                  wantpc9x => '0,Want PC9X interface,yesno',
                  lastoper => '9,Last for/oper,cldatetime',
                  nothere => '0,Not Here Text',
                  registered => '9,Registered?,yesno',
                  prompt => '0,Required Prompt',
                  version => '1,Version',
                  build => '1,Build',
                  believe => '1,Believable nodes,parray',
                  lastping => '1,Last Ping at,ptimelist',
                  maxconnect => '1,Max Connections',
                  startt => '0,Start Time,cldatetime',
                  connlist => '1,Connections,parraydifft',
                 );

#no strict;
sub AUTOLOAD
{
        no strict;
        my $name = $AUTOLOAD;
  
        return if $name =~ /::DESTROY$/;
        $name =~ s/^.*:://o;
  
        confess "Non-existant field '$AUTOLOAD'" if !$valid{$name};
        # this clever line of code creates a subroutine which takes over from autoload
        # from OO Perl - Conway
        *$AUTOLOAD = sub {@_ > 1 ? $_[0]->{$name} = $_[1] : $_[0]->{$name}};
       goto &$AUTOLOAD;
}

#use strict;

#
# initialise the system
#
sub init
{
        my $mode = shift;
  
        my $ufn;
        my $convert;
        
        my $fn = "users";

        $json = JSON->new()->canonical(1);
        $filename = $ufn = localdata("$fn.v4");
        
        if (-e localdata("$fn.v4")) {
                $v4 = 1;
        } else {
                eval {
                        require Storable;
                };

                if ($@) {
                        if ( ! -e localdata("users.v3") && -e localdata("users.v2") ) {
                                $convert = 2;
                        }
                        LogDbg('',"the module Storable appears to be missing!!");
                        LogDbg('',"trying to continue in compatibility mode (this may fail)");
                        LogDbg('',"please install Storable from CPAN as soon as possible");
                } else {
                        import Storable qw(nfreeze thaw);
                        $convert = 3 if -e localdata("users.v3") && !-e $ufn;
                }
        }

        # do a conversion if required
        if ($convert) {
                my ($key, $val, $action, $count, $err) = ('','',0,0,0);
                my $ta = [gettimeofday];
                
                my %oldu;
                LogDbg('',"Converting the User File from V$convert to $fn.v4 ");
                LogDbg('',"This will take a while, I suggest you go and have cup of strong tea");
                my $odbm = tie (%oldu, 'DB_File', localdata("users.v$convert"), O_RDONLY, 0666, $DB_BTREE) or confess "can't open user file: $fn.v$convert ($!) [rebuild it from user_asc?]";
        for ($action = R_FIRST; !$odbm->seq($key, $val, $action); $action = R_NEXT) {
                        my $ref;
                        if ($convert == 3) {
                                eval { $ref = storable_decode($val) };
                        } else {
                                eval { $ref = asc_decode($val) };
                        }
                        unless ($@) {
                                if ($ref) {
                                        $u{$key} = $ref;
                                        $count++;
                                } else {
                                        $err++
                                }
                        } else {
                                Log('err', "DXUser: error decoding $@");
                        }
                } 
                undef $odbm;
                untie %oldu;
                my $t = _diffms($ta);
                LogDbg('',"Conversion from users.v$convert to users.v4 completed $count records $err errors $t mS");

                # now write it away for future use
                $ta = [gettimeofday];
                $err = 0;
                $count = writeoutjson();
                $t = _diffms($ta);
                LogDbg('',"New Userfile users.v4 write completed $count records $err errors $t mS");
                LogDbg('',"Now restarting..");
                $main::ending = 10;
        } else {
                # otherwise (i.e normally) slurp it in
                readinjson();
        }
        $filename = $ufn;
}

sub del_file
{
        # with extreme prejudice
        if ($v3) {
                unlink "$main::data/users.v3";
                unlink "$main::local_data/users.v3";
        }
        if ($v4) {
                unlink "$main::data/users.v4";
                unlink "$main::local_data/users.v4";
        }
}

#
# periodic processing
#
sub process
{
#       if ($main::systime > $lasttime + 15) {
#               #$dbm->sync if $dbm;
#               $lasttime = $main::systime;
#       }
}

#
# close the system
#

sub finish
{
        
        writeoutjson();
}

#
# new - create a new user
#

sub alloc
{
        my $pkg = shift;
        my $call = uc shift;
        my $self = bless {call => $call, 'sort'=>'U'}, $pkg;
        return $self;
}

sub new
{
        my $pkg = shift;
        my $call = shift;
        #  $call =~ s/-\d+$//o;
  
        confess "can't create existing call $call in User\n!" if $u{$call};

        my $self = $pkg->alloc($call);
        $u{$call} = [0, $self];
        $self->put;
        ++$newusers;
        ++$totusers;
        return $self;
}

#
# get - get an existing user - this seems to return a different reference everytime it is
#       called - see below
#

sub get
{
        my $call = uc shift;
        my $nodecode = shift;
        my $ref = $u{$call};
        return undef unless $ref;
        
        unless ($ref->[1]) {
                $ifh->seek($ref->[0], 0);
                my $l = $ifh->getline;
                if ($l) {
                        my ($k,$s) = split /\t/, $l;
                        return $s if $nodecode;
                        my $j = json_decode($s);
                        if ($j) {
                                $ref->[1] = $j;
                                ++$cachedusers;
                        }
                }
        } elsif ($nodecode) {
                return json_encode($ref->[1]);
        }
        return $ref->[1];
}

#
# get an "ephemeral" reference - i.e. this will give you new temporary copy of
# the call's user record, but without storing it (if it isn't already there)
#
# This is not as quick as get()! But it will allow safe querying of the
# user file. Probably in conjunction with get_some_calls feeding it.
#
# NOTE: for cached records this, in effect, is a faster version of Storable's
# dclone - only about 3.5 times as fast!
#

sub get_tmp
{
        my $call = uc shift;
        my $ref = $u{$call};
        if ($ref) {
                if ($ref->[1]) {
                        return json_decode(json_encode($ref->[1]));
                }
                $ifh->seek($ref->[0], 0);
                my $l = $ifh->getline;
                if ($l) {
                        my ($k,$s) = split /\t/, $l;
                        my $j = json_decode($s);
                        return $j;
                }
        }
        return undef;
}

#
# Master branch:
# get an existing record either from the channel (if there is one) or from the database
#
# It is important to note that if you have done a get (for the channel say) and you
# want access or modify that you must use this call (and you must NOT use get's all
# over the place willy nilly!)
#
# NOTE: mojo branch with newusers system:
# There is no longer any function difference between get_current()
# and get() as they will always reference the same record as held in %u. This is because
# there is no more (repeated) thawing of stored records from the underlying "database".
#
# BUT: notice the difference between this and the get_tmp() function. A get() will online an
# othewise unused record, so for poking around looking for that locked out user:
# MAKE SURE you use get_tmp(). It will likely still be quicker than DB_File and Storable!
#

sub get_current
{
        goto &get;
        
#       my $call = uc shift;
#  
#       my $dxchan = DXChannel::get($call);
#       if ($dxchan) {
#               my $ref = $dxchan->user;
#               return $ref if $ref && UNIVERSAL::isa($ref, 'DXUser');
#
#               dbg("DXUser::get_current: got invalid user ref for $call from dxchan $dxchan->{call} ". ref $ref. " ignoring");
#       }
#       return get($call);
}

#
# get all callsigns in the database 
#

sub get_all_calls
{
        return (sort keys %u);
}

#
# get some calls - provide a qr// style selector string as a partial key
#

sub get_some_calls
{
        my $pattern = shift || qr/.*/;
        return sort grep {$pattern} keys %u;
}

#
# if I understand the term correctly, this is a sort of monad.
#
# Scan through the whole user file and select records that you want
# to process further. This routine returns lines of json, yu
#
# the CODE ref should look like:
# sub {
#   my $key = shift;
#       my $line = shift;
#   # maybe do a rough check to see if this is a likely candidate
#   return unless $line =~ /something/;
#   my $r = json_decode($l);
#       return (condition ? wanted thing : ());
# }
#
        
sub scan
{
        my $c = shift;
        my @out;
        
        if (ref($c) eq 'CODE') {
                foreach my $k (get_all_calls()) {
                        my $l = get($k, 1);     # get the offline json line or the jsoned online version
                        push @out, $c->($k, $l) if $l;
                }
        } else {
                dbg("DXUser::scan supplied argument is not a code ref");
        }
        return @out;
}

#
# put - put a user
#

sub put
{
        my $self = shift;
        confess "Trying to put nothing!" unless $self && ref $self;
        $self->{lastin} = $main::systime;
        ++$modusers;                            # new or existing, it's still been modified
}

# freeze the user
sub encode
{
        goto &json_encode if $v4;
        goto &asc_encode unless $v3;
        my $self = shift;
        return nfreeze($self);
}

# thaw the user
sub decode
{
        goto &json_decode if $v4;
        goto &storable_decode if $v3;
        goto &asc_decode;
}

# should now be obsolete for mojo branch build 238 and above
sub storable_decode
{
        my $ref;
        $ref = thaw(shift);
        return $ref;
}


#
# create a hash from a string (in ascii)
#
sub asc_decode
{
        my $s = shift;
        my $ref;
        $s =~ s/\%([0-9A-F][0-9A-F])/chr(hex($1))/eg;
        eval '$ref = ' . $s;
        if ($@) {
                LogDbg('err', "DXUser::asc_decode: on '$s' $@");
                $ref = undef;
        }
        return $ref;
}

sub json_decode
{
        my $s = shift;
    my $ref;
        eval { $ref = $json->decode($s) };
        if ($ref && !$@) {
        return bless $ref, 'DXUser';
        } else {
                LogDbg('err', "DXUser::json_decode: on '$s' $@");
        }
        return undef;
}

sub json_encode
{
        my $ref = shift;
        unbless($ref);
    my $s = $json->encode($ref);
        bless $ref, 'DXUser';
        return $s;
}
        
#
# del - delete a user
#

sub del
{
        my $self = shift;
        my $call = $self->{call};
        ++$delusers;
        --$totusers;
        --$cachedusers if $u{$call}->[1];
        delete $u{$call};
}

#
# close - close down a user
#

sub close
{
        my $self = shift;
        my $startt = shift;
        my $ip = shift;
        $self->{lastin} = $main::systime;
        # add a record to the connect list
#       $self->put();
}

#
# sync the database
#

sub sync
{
#       $dbm->sync;
}

#
# return a list of valid elements 
# 

sub fields
{
        return keys(%valid);
}


#
# export the database to an ascii file
#

sub export
{
        my $name = shift;

        my $fn = $name || localdata("user_json"); # force use of local_data
        
        # save old ones
        move "$fn.oooo", "$fn.ooooo" if -e "$fn.oooo";
        move "$fn.ooo", "$fn.oooo" if -e "$fn.ooo";
        move "$fn.oo", "$fn.ooo" if -e "$fn.oo";
        move "$fn.o", "$fn.oo" if -e "$fn.o";
        move "$fn", "$fn.o" if -e "$fn";

        my $json = JSON->new;
        $json->canonical(1);
        
        my $count = 0;
        my $err = 0;
        my $del = 0;
        my $fh = new IO::File ">$fn" or return "cannot open $fn ($!)";
        if ($fh) {
                my $key = 0;
                my $val = undef;
                foreach my $k (sort keys %u) {
                        my $r = $u{$k};
                        if ($r->{sort} eq 'U' && !$r->{priv} && $main::systime > $r->{lastin}+$tooold ) {
                                unless ($r->{lat} || $r->{long} || $r->{qra} || $r->{qth} || $r->{name}) {
                                        LogDbg('err', "DXUser::export deleting $k - too old, last in " . cldatetime($r->lastin) . " " . difft([$r->lastin, $main::systime]));
                                        delete $u{$k};
                                        ++$del;
                                        next;
                                }
                        }
                        eval {$val = json_encode($r);};
                        if ($@) {
                                LogDbg('err', "DXUser::export error encoding call: $k $@");
                                ++$err;
                                next;
                        } 
                        $fh->print("$k\t$val\n");
                        ++$count;
                }
        $fh->close;
    }
        my $s = qq{Exported users to $fn - $count Users $del Deleted $err Errors ('sh/log Export' for details)};
        LogDbg('command', $s);
        return $s;
}

#
# group handling
#

# add one or more groups
sub add_group
{
        my $self = shift;
        my $ref = $self->{group} || [ 'local' ];
        $self->{group} = $ref if !$self->{group};
        push @$ref, @_ if @_;
}

# remove one or more groups
sub del_group
{
        my $self = shift;
        my $ref = $self->{group} || [ 'local' ];
        my @in = @_;
        
        $self->{group} = $ref if !$self->{group};
        
        @$ref = map { my $a = $_; return (grep { $_ eq $a } @in) ? () : $a } @$ref;
}

# does this thing contain all the groups listed?
sub union
{
        my $self = shift;
        my $ref = $self->{group};
        my $n;
        
        return 0 if !$ref || @_ == 0;
        return 1 if @$ref == 0 && @_ == 0;
        for ($n = 0; $n < @_; ) {
                for (@$ref) {
                        my $a = $_;
                        $n++ if grep $_ eq $a, @_; 
                }
        }
        return $n >= @_;
}

# simplified group test just for one group
sub in_group
{
        my $self = shift;
        my $s = shift;
        my $ref = $self->{group};
        
        return 0 if !$ref;
        return grep $_ eq $s, $ref;
}

# set up a default group (only happens for them's that connect direct)
sub new_group
{
        my $self = shift;
        $self->{group} = [ 'local' ];
}

# set up empty buddies (only happens for them's that connect direct)
sub new_buddies
{
        my $self = shift;
        $self->{buddies} = [  ];
}

#
# return a prompt for a field
#

sub field_prompt
{ 
        my ($self, $ele) = @_;
        return $valid{$ele};
}

# some variable accessors
sub sort
{
        my $self = shift;
        @_ ? $self->{'sort'} = shift : $self->{'sort'} ;
}

# some accessors

# want is default = 1
sub _want
{
        my $n = shift;
        my $self = shift;
        my $val = shift;
        my $s = "want$n";
        $self->{$s} = $val if defined $val;
        return exists $self->{$s} ? $self->{$s} : 1;
}

# wantnot is default = 0
sub _wantnot
{
        my $n = shift;
        my $self = shift;
        my $val = shift;
        my $s = "want$n";
        $self->{$s} = $val if defined $val;
        return exists $self->{$s} ? $self->{$s} : 0;
}

sub wantbeep
{
        return _want('beep', @_);
}

sub wantann
{
        return _want('ann', @_);
}

sub wantwwv
{
        return _want('wwv', @_);
}

sub wantwcy
{
        return _want('wcy', @_);
}

sub wantecho
{
        return _want('echo', @_);
}

sub wantwx
{
        return _want('wx', @_);
}

sub wantdx
{
        return _want('dx', @_);
}

sub wanttalk
{
        return _want('talk', @_);
}

sub wantgrid
{
        return _want('grid', @_);
}

sub wantemail
{
        return _want('email', @_);
}

sub wantann_talk
{
        return _want('ann_talk', @_);
}

sub wantpc16
{
        return _want('pc16', @_);
}

sub wantsendpc16
{
        return _want('sendpc16', @_);
}

sub wantroutepc16
{
        return _want('routepc16', @_);
}

sub wantusstate
{
        return _want('usstate', @_);
}

sub wantdxcq
{
        return _want('dxcq', @_);
}

sub wantdxitu
{
        return _want('dxitu', @_);
}

sub wantgtk
{
        return _want('gtk', @_);
}

sub wantpc9x
{
        return _want('pc9x', @_);
}

sub wantlogininfo
{
        my $self = shift;
        my $val = shift;
        $self->{wantlogininfo} = $val if defined $val;
        return $self->{wantlogininfo};
}

sub is_node
{
        my $self = shift;
        return $self->{sort} =~ /^[ACRSX]$/;
}

sub is_local_node
{
        my $self = shift;
        return grep $_ eq 'local_node', @{$self->{group}};
}

sub is_user
{
        my $self = shift;
        return $self->{sort} =~ /^[UW]$/;
}

sub is_web
{
        my $self = shift;
        return $self->{sort} eq 'W';
}

sub is_bbs
{
        my $self = shift;
        return $self->{sort} eq 'B';
}

sub is_spider
{
        my $self = shift;
        return $self->{sort} eq 'S';
}

sub is_clx
{
        my $self = shift;
        return $self->{sort} eq 'C';
}

sub is_dxnet
{
        my $self = shift;
        return $self->{sort} eq 'X';
}

sub is_arcluster
{
        my $self = shift;
        return $self->{sort} eq 'R';
}

sub is_ak1a
{
        my $self = shift;
        return $self->{sort} eq 'A';
}

sub unset_passwd
{
        my $self = shift;
        delete $self->{passwd};
        $self->put;
}

sub unset_passphrase
{
        my $self = shift;
        delete $self->{passphrase};
        $self->put;
}

sub set_believe
{
        my $self = shift;
        my $call = uc shift;
        $self->{believe} ||= [];
        unless (grep $_ eq $call, @{$self->{believe}}) {
                push @{$self->{believe}}, $call;
                $self->put;
        };
}

sub unset_believe
{
        my $self = shift;
        my $call = uc shift;
        if (exists $self->{believe}) {
                $self->{believe} = [grep {$_ ne $call} @{$self->{believe}}];
                delete $self->{believe} unless @{$self->{believe}};
                $self->put;
        }
}

sub believe
{
        my $self = shift;
        return exists $self->{believe} ? @{$self->{believe}} : ();
}

sub lastping
{
        my $self = shift;
        my $call = shift;
        $self->{lastping} ||= {};
        $self->{lastping} = {} unless ref $self->{lastping};
        my $b = $self->{lastping};
        $b->{$call} = shift if @_;
        return $b->{$call};     
}

#
# read in the latest version of the user file. As this file is immutable, the file one really wants is
# a later (generated) copy. But, if the plain users.v4 file is all we have, we'll use that.
#

sub readinjson
{
        my $fn = $filename;
        my $nfn = "$fn.n";
        my $ofn = "$fn.o";

        my $ta = [gettimeofday];
        my $count = 0;
        my $s;
        my $err = 0;

        unless (-r $fn) {
                dbg("DXUser $fn not found - probably about to convert");
                return;
        }

        if (-e $nfn && -e $fn && (stat($nfn))[9] > (stat($fn))[9]) {
                # move the old file to .o
                unlink $ofn;
                move($fn, $ofn);
                move($nfn, $fn);
        };

        if ($ifh) {
                $ifh->seek(0, 0);
        } else {
                $ifh = IO::File->new("+<$fn") or die "$fn read error $!";
        }
        my $pos = $ifh->tell;
        while (<$ifh>) {
                chomp;
                my @f = split /\t/;
                $u{$f[0]} = [$pos];
                $count++;
                $pos = $ifh->tell;
        }
        $ifh->seek(0, 0);

        # $ifh is "global" and should not be closed
        
        dbg("DXUser::readinjson $count record headers read from $fn in ". _diffms($ta) . " mS");
        return $totusers = $count;
}

#
# Write a newer copy of the users.v4 file to users.v4.n, which is what will be read in.
# This means that the existing users.v4 is not touched during a run of dxspider, or at least
# not yet.

sub writeoutjson
{
        my $ofn = shift || "$filename.n";
        my $ta = [gettimeofday];
        
        my $ofh = IO::File->new(">$ofn") or die "$ofn write error $!";
        my $count = 0;
        $ifh->seek(0, 0);
        for my $k (sort keys %u) {
                my $l = get($k, 1);
                if ($l) {
                        chomp $l;
                        print $ofh "$k\t$l\n";
                        ++$count;
                } else {
                        LogDbg('DXCommand', "DXUser::writeoutjson callsign $k not found")
                }
        }
        
        $ofh->close;
        dbg("DXUser::writeoutjson $count records written to $ofn in ". _diffms($ta) . " mS");
        return $count;
}
1;
__END__