1package VMS::DCLsym;
2
3use Carp;
4use DynaLoader;
5use vars qw( @ISA $VERSION );
6use strict;
7
8# Package globals
9@ISA = ( 'DynaLoader' );
10$VERSION = '1.05_01';
11my(%Locsyms) = ( ':ID' => 'LOCAL' );
12my(%Gblsyms) = ( ':ID' => 'GLOBAL');
13my $DoCache = 1;
14my $Cache_set = 0;
15
16
17#====> OO methods
18
19sub new {
20  my($pkg,$type) = @_;
21  $type ||= 'LOCAL';
22  $type = 'LOCAL' unless $type eq 'GLOBAL';
23  bless { TYPE => $type }, $pkg;
24}
25
26sub DESTROY { }
27
28sub getsym {
29  my($self,$name) = @_;
30  my($val,$table);
31
32  if (($val,$table) = _getsym($name)) {
33    if ($table eq 'GLOBAL') { $Gblsyms{$name} = $val; }
34    else                    { $Locsyms{$name} = $val; }
35  }
36  wantarray ? ($val,$table) : $val;
37}
38
39sub setsym {
40  my($self,$name,$val,$table) = @_;
41
42  $table = $self->{TYPE} unless $table;
43  if (_setsym($name,$val,$table)) {
44    if ($table eq 'GLOBAL') { $Gblsyms{$name} = $val; }
45    else                    { $Locsyms{$name} = $val; }
46    1;
47  }
48  else { 0; }
49}
50
51sub delsym {
52  my($self,$name,$table) = @_;
53
54  $table = $self->{TYPE} unless $table;
55  if (_delsym($name,$table)) {
56    if ($table eq 'GLOBAL') { delete $Gblsyms{$name}; }
57    else                    { delete $Locsyms{$name}; }
58    1;
59  }
60  else { 0; }
61}
62
63sub clearcache {
64  my($self,$perm) = @_;
65  my($old);
66
67  $Cache_set = 0;
68  %Locsyms = ( ':ID' => 'LOCAL');
69  %Gblsyms = ( ':ID' => 'GLOBAL');
70  $old = $DoCache;
71  $DoCache = $perm if defined($perm);
72  $old;
73}
74
75#====> TIEHASH methods
76
77sub TIEHASH {
78  shift->new(@_);
79}
80
81sub FETCH {
82  my($self,$name) = @_;
83  if    ($name eq ':GLOBAL') { $self->{TYPE} eq 'GLOBAL'; }
84  elsif ($name eq ':LOCAL' ) { $self->{TYPE} eq 'LOCAL';  }
85  else                       { scalar($self->getsym($name)); }
86}
87
88sub STORE {
89  my($self,$name,$val) = @_;
90  if    ($name eq ':GLOBAL') { $self->{TYPE} = 'GLOBAL'; }
91  elsif ($name eq ':LOCAL' ) { $self->{TYPE} = 'LOCAL';  }
92  else                       { $self->setsym($name,$val); }
93}
94
95sub DELETE {
96  my($self,$name) = @_;
97
98  $self->delsym($name);
99}
100
101sub FIRSTKEY {
102  my($self) = @_;
103  my($name,$eqs,$val);
104
105  if (!$DoCache || !$Cache_set) {
106    # We should eventually replace this with a C routine which walks the
107    # CLI symbol table directly.  If I ever get 'hold of an I&DS manual . . .
108    open(P,'Show Symbol * |');
109    while (<P>) {
110      ($name,$eqs,$val) = /^\s+(\S+) (=+) (.+)/
111        or carp "VMS::DCLsym: unparseable line $_";
112      $name =~ s#\*##;
113      $val =~ s/"(.*)"$/$1/ or $val =~ s/^(\S+).*/$1/;
114      if ($eqs eq '==') { $Gblsyms{$name} = $val; }
115      else              { $Locsyms{$name} = $val; }
116    }
117    close P;
118    $Cache_set = 1;
119  }
120  $self ->{IDX} = 0;
121  $self->{CACHE} = $self->{TYPE} eq 'GLOBAL' ? \%Gblsyms : \%Locsyms;
122  while (($name,$val) = each(%{$self->{CACHE}}) and !defined($name)) {
123    if ($self->{CACHE}{':ID'} eq 'GLOBAL') { return undef; }
124    $self->{CACHE} = \%Gblsyms;
125  }
126  $name;
127}
128
129sub NEXTKEY {
130  my($self) = @_;
131  my($name,$val);
132
133  while (($name,$val) = each(%{$self->{CACHE}}) and !defined($name)) {
134    if ($self->{CACHE}{':ID'} eq 'GLOBAL') { return undef; }
135    $self->{CACHE} = \%Gblsyms;
136  }
137  $name;
138}
139
140
141sub EXISTS { defined($_[0]->FETCH(@_)) ? 1 : 0 }
142
143sub CLEAR { }
144
145
146bootstrap VMS::DCLsym;
147
1481;
149
150__END__
151
152=head1 NAME
153
154VMS::DCLsym - Perl extension to manipulate DCL symbols
155
156=head1 SYNOPSIS
157
158  tie %allsyms, VMS::DCLsym;
159  tie %cgisyms, VMS::DCLsym, 'GLOBAL';
160
161
162  $handle = new VMS::DCLsym;
163  $value = $handle->getsym($name);
164  $handle->setsym($name, $value, 'GLOBAL')
165      or die "Can't create symbol: $!\n";
166  $handle->delsym($name, 'LOCAL') or die "Can't delete symbol: $!\n";
167  $handle->clearcache();
168
169=head1 DESCRIPTION
170
171The VMS::DCLsym extension provides access to DCL symbols using a
172tied hash interface.  This allows Perl scripts to manipulate symbols in
173a manner similar to the way in which logical names are manipulated via
174the built-in C<%ENV> hash.  Alternatively, one can call methods in this
175package directly to read, create, and delete symbols.
176
177=head2 Tied hash interface
178
179This interface lets you treat the DCL symbol table as a Perl associative array,
180in which the key of each element is the symbol name, and the value of the
181element is that symbol's value.  Case is not significant in the key string, as
182DCL converts symbol names to uppercase, but it is significant in the value
183string.  All of the usual operations on associative arrays are supported.
184Reading an element retrieves the current value of the symbol, assigning to it
185defines a new symbol (or overwrites the old value of an existing symbol), and
186deleting an element deletes the corresponding symbol.  Setting an element to
187C<undef>, or C<undef>ing it directly, sets the corresponding symbol to the null
188string. You may also read the special keys ':GLOBAL' and ':LOCAL' to find out
189whether a default symbol table has been specified for this hash (see C<table>
190below), or set either or these keys to specify a default symbol table.
191
192When you call the C<tie> function to bind an associative array to this package,
193you may specify as an optional argument the symbol table in which you wish to
194create and delete symbols.  If the argument is the string 'GLOBAL', then the
195global symbol table is used; any other string causes the local symbol table to
196be used.  Note that this argument does not affect attempts to read symbols; if
197a symbol with the specified name exists in the local symbol table, it is always
198returned in preference to a symbol by the same name in the global symbol table.
199
200=head2 Object interface
201
202Although it's less convenient in some ways than the tied hash interface, you
203can also call methods directly to manipulate individual symbols.  In some
204cases, this allows you finer control than using a tied hash aggregate.  The
205following methods are supported:
206
207=over 4
208
209=item new
210
211This creates a C<VMS::DCLsym> object which can be used as a handle for later
212method calls.  The single optional argument specifies the symbol table used
213by default in future method calls, in the same way as the optional argument to
214C<tie> described above.
215
216=item getsym
217
218If called in a scalar context, C<getsym> returns the value of the symbol whose
219name is given as the argument to the call, or C<undef> if no such symbol
220exists.  Symbols in the local symbol table are always used in preference to
221symbols in the global symbol table.  If called in a list context, C<getsym>
222returns a two-element list, whose first element is the value of the symbol, and
223whose second element is the string 'GLOBAL' or 'LOCAL', indicating the table
224from which the symbol's value was read.
225
226=item setsym
227
228The first two arguments taken by this method are the name of the symbol and the
229value which should be assigned to it.  The optional third argument is a string
230specifying the symbol table to be used; 'GLOBAL' specifies the global symbol
231table, and any other string specifies the local symbol table.  If this argument
232is omitted, the default symbol table for the object is used.  C<setsym> returns
233TRUE if successful, and FALSE otherwise.
234
235=item delsym
236
237This method deletes the symbol whose name is given as the first argument.  The
238optional second argument specifies the symbol table, as described above under
239C<setsym>.  It returns TRUE if the symbol was successfully deleted, and FALSE
240if it was not.
241
242=item clearcache
243
244Because of the overhead associated with obtaining the list of defined symbols
245for the tied hash iterator, it is only done once, and the list is reused for
246subsequent iterations.  Changes to symbols made through this package are
247recorded, but in the rare event that someone changes the process' symbol table
248from outside (as is possible using some software from the net), the iterator
249will be out of sync with the symbol table.  If you expect this to happen, you
250can reset the cache by calling this method.  In addition, if you pass a FALSE
251value as the first argument, caching will be disabled.  It can be re-enabled
252later by calling C<clearcache> again with a TRUE value as the first argument.
253It returns TRUE or FALSE to indicate whether caching was previously enabled or
254disabled, respectively.
255
256This method is a stopgap until we can incorporate code into this extension to
257traverse the process' symbol table directly, so it may disappear in a future
258version of this package.
259
260=back
261
262=head1 AUTHOR
263
264Charles Bailey  bailey@newman.upenn.edu
265
266=head1 VERSION
267
2681.05_01  16-Jun-2013
269
270=head1 BUGS
271
272The list of symbols for the iterator is assembled by spawning off a
273subprocess, which can be slow.  Ideally, we should just traverse the
274process' symbol table directly from C.
275
276