This is 0.32

[perl/modules/Variable-Magic.git] / README

diff --git a/README b/README
index 171a7ca2cfdc055fb271a679d72d6ecb4e74198f..030eb08661306cc3101e6060724468f299272440 100644 (file)
--- a/README
+++ b/README
@@ -2,17 +2,32 @@ NAME
     Variable::Magic - Associate user-defined magic to variables from Perl.
 
 VERSION
     Variable::Magic - Associate user-defined magic to variables from Perl.
 
 VERSION

-    Version 0.31
+    Version 0.32

 
 SYNOPSIS
 
 SYNOPSIS

-        use Variable::Magic qw/wizard cast dispell/;
-
-        my $wiz = wizard set => sub { print STDERR "now set to ${$_[0]}!\n" };
-        my $a = 1;
-        cast $a, $wiz;
-        $a = 2;          # "now set to 2!"
-        dispell $a, $wiz;
-        $a = 3           # (nothing)
+        use Variable::Magic qw/wizard cast VMG_OP_INFO_NAME/;
+
+        { # A variable tracer
+         my $wiz = wizard set  => sub { print "now set to ${$_[0]}!\n" },
+                          free => sub { print "destroyed!\n" };
+
+         my $a = 1;
+         cast $a, $wiz;
+         $a = 2;        # "now set to 2!"
+        }               # "destroyed!"
+
+        { # A hash with a default value
+         my $wiz = wizard data     => sub { $_[1] },
+                          fetch    => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
+                          store    => sub { print "key $_[2] stored in $_[-1]\n" },
+                          copy_key => 1,
+                          op_info  => VMG_OP_INFO_NAME;
+
+         my %h = (_default => 0, apple => 2);
+         cast %h, $wiz, '_default';
+         print $h{banana}, "\n"; # "0", because the 'banana' key doesn't exist in %h
+         $h{pear} = 1;           # "key pear stored in helem"
+        }

 
 DESCRIPTION
     Magic is Perl way of enhancing objects. This mechanism lets the user add
 
 DESCRIPTION
     Magic is Perl way of enhancing objects. This mechanism lets the user add


@@ -25,7 +40,7 @@ DESCRIPTION
     variables. It's not surprising, as tied variables are implemented as a
     special kind of magic, just like any 'irregular' Perl variable : scalars
     like $!, $( or $^W, the %ENV and %SIG hashes, the @ISA array, "vec()"
     variables. It's not surprising, as tied variables are implemented as a
     special kind of magic, just like any 'irregular' Perl variable : scalars
     like $!, $( or $^W, the %ENV and %SIG hashes, the @ISA array, "vec()"

-    and "substr()" lvalues, thread::shared variables... They all share the
+    and "substr()" lvalues, threads::shared variables... They all share the

     same underlying C API, and this module gives you direct access to it.
 
     Still, the magic made available by this module differs from tieing and
     same underlying C API, and this module gives you direct access to it.
 
     Still, the magic made available by this module differs from tieing and


@@ -83,11 +98,12 @@ DESCRIPTION
 
     *   "clear"
 
 
     *   "clear"
 

-        This magic is invoked when the variable is reset, such as when an
-        array is emptied. Please note that this is different from undefining
-        the variable, even though the magic is called when the clearing is a
-        result of the undefine (e.g. for an array, but actually a bug
-        prevent it to work before perl 5.9.5 - see the history).
+        This magic is invoked when a container variable is reset, i.e. when
+        an array or a hash is emptied. Please note that this is different
+        from undefining the variable, even though the magic is called when
+        the clearing is a result of the undefine (e.g. for an array, but
+        actually a bug prevent it to work before perl 5.9.5 - see the
+        history).

 
     *   "free"
 
 
     *   "free"
 


@@ -137,7 +153,10 @@ DESCRIPTION
 
     To prevent any clash between different magics defined with this module,
     an unique numerical signature is attached to each kind of magic (i.e.
 
     To prevent any clash between different magics defined with this module,
     an unique numerical signature is attached to each kind of magic (i.e.

-    each set of callbacks for magic operations).
+    each set of callbacks for magic operations). At the C level, magic
+    tokens owned by magic created by this module have their "mg->mg_private"
+    field set to 0x3891 or 0x3892, so please don't use these magic (sic)
+    numbers in other extensions.

 
 FUNCTIONS
   "wizard"
 
 FUNCTIONS
   "wizard"


@@ -226,6 +245,10 @@ FUNCTIONS
                          set  => sub { print STDERR "set to ${$_[0]}\n" },
                          free => sub { print STDERR "${$_[0]} was deleted\n" }
 
                          set  => sub { print STDERR "set to ${$_[0]}\n" },
                          free => sub { print STDERR "${$_[0]} was deleted\n" }
 

+    Note that "free" callbacks are *never* called during global destruction,
+    as there's no way to ensure that the wizard and the "free" callback
+    weren't destroyed before the variable.
+

   "gensig"
     With this tool, you can manually generate random magic signature between
     SIG_MIN and SIG_MAX inclusive. That's the way "wizard" creates them when
   "gensig"
     With this tool, you can manually generate random magic signature between
     SIG_MIN and SIG_MAX inclusive. That's the way "wizard" creates them when


@@ -270,6 +293,50 @@ FUNCTIONS
     If you want to overcome the possible deletion of the 'TZ' entry, you
     have no choice but to rely on "store" uvar magic.
 
     If you want to overcome the possible deletion of the 'TZ' entry, you
     have no choice but to rely on "store" uvar magic.
 

+    "cast" can be called from any magical callback, and in particular from
+    "data". This allows you to recursively cast magic on datastructures :
+
+        my $wiz;
+        $wiz = wizard
+                data => sub {
+                 my ($var, $depth) = @_;
+                 $depth ||= 0;
+                 my $r = ref $var;
+                 if ($r eq 'ARRAY') {
+                  &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for @$var;
+                 } elsif ($r eq 'HASH') {
+                  &cast((ref() ? $_ : \$_), $wiz, $depth + 1) for values %$var;
+                 }
+                 return $depth;
+                },
+                free => sub {
+                 my ($var, $depth) = @_;
+                 my $r = ref $var;
+                 print "free $r at depth $depth\n";
+                 ();
+                };
+
+        {
+         my %h = (
+          a => [ 1, 2 ],
+          b => { c => 3 }
+         );
+         cast %h, $wiz;
+        }
+
+    When %h goes out of scope, this will print something among the lines of
+    :
+
+        free HASH at depth 0
+        free HASH at depth 1
+        free SCALAR at depth 2
+        free ARRAY at depth 1
+        free SCALAR at depth 3
+        free SCALAR at depth 3
+
+    Of course, this example does nothing with the values that are added
+    after the "cast".
+

   "getdata"
         getdata [$@%&*]var, [$wiz|$sig]
 
   "getdata"
         getdata [$@%&*]var, [$wiz|$sig]