#
# Documentation is at the __END__
#

package DB;

# "private" globals

my ($running, $ready, $deep, $usrctxt, $evalarg, 
    @stack, @saved, @skippkg, @clients);
my $preeval = {};
my $posteval = {};
my $ineval = {};

####
#
# Globals - must be defined at startup so that clients can refer to 
# them right after a C<require DB;>
#
####

BEGIN {

  # these are hardcoded in perl source (some are magical)

  $DB::sub = '';        # name of current subroutine
  %DB::sub = ();        # "filename:fromline-toline" for every known sub
  $DB::single = 0;      # single-step flag (set it to 1 to enable stops in BEGIN/use)
  $DB::signal = 0;      # signal flag (will cause a stop at the next line)
  $DB::trace = 0;       # are we tracing through subroutine calls?
  @DB::args = ();       # arguments of current subroutine or @ARGV array
  @DB::dbline = ();     # list of lines in currently loaded file
  %DB::dbline = ();     # actions in current file (keyed by line number)
  @DB::ret = ();        # return value of last sub executed in list context
  $DB::ret = '';        # return value of last sub executed in scalar context

  # other "public" globals  

  $DB::package = '';    # current package space
  $DB::filename = '';   # current filename
  $DB::subname = '';    # currently executing sub (fullly qualified name)
  $DB::lineno = '';     # current line number

  $DB::VERSION = $DB::VERSION = '1.01';

  # initialize private globals to avoid warnings

  $running = 1;         # are we running, or are we stopped?
  @stack = (0);
  @clients = ();
  $deep = 100;
  $ready = 0;
  @saved = ();
  @skippkg = ();
  $usrctxt = '';
  $evalarg = '';
}

####
# entry point for all subroutine calls
#
sub sub {
  push(@stack, $DB::single);
  $DB::single &= 1;
  $DB::single |= 4 if $#stack == $deep;
  if ($DB::sub eq 'DESTROY' or substr($DB::sub, -9) eq '::DESTROY' or not defined wantarray) {
    &$DB::sub;
    $DB::single |= pop(@stack);
    $DB::ret = undef;
  }
  elsif (wantarray) {
    @DB::ret = &$DB::sub;
    $DB::single |= pop(@stack);
    @DB::ret;
  }
  else {
    $DB::ret = &$DB::sub;
    $DB::single |= pop(@stack);
    $DB::ret;
  }
}

####
# this is called by perl for every statement
#
sub DB {
  return unless $ready;
  &save;
  ($DB::package, $DB::filename, $DB::lineno) = caller;

  return if @skippkg and grep { $_ eq $DB::package } @skippkg;

  $usrctxt = "package $DB::package;";		# this won't let them modify, alas
  local(*DB::dbline) = "::_<$DB::filename";

  # we need to check for pseudofiles on Mac OS (these are files
  # not attached to a filename, but instead stored in Dev:Pseudo)
  # since this is done late, $DB::filename will be "wrong" after
  # skippkg
  if ($^O eq 'MacOS' && $#DB::dbline < 0) {