Importing Variable-Magic-0.09.tar.gz

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

diff --git a/README b/README
index a626da01eb6c5a454204c4eb90abea31e75b80ca..5ca2936bd1302a122adac8c6bdf4bc35faa9e67e 100644 (file)
--- a/README
+++ b/README
@@ -2,7 +2,7 @@ NAME
     Variable::Magic - Associate user-defined magic to variables from Perl.
 
 VERSION
     Variable::Magic - Associate user-defined magic to variables from Perl.
 
 VERSION

-    Version 0.07_01
+    Version 0.09

 
 SYNOPSIS
         use Variable::Magic qw/wizard cast dispell/;
 
 SYNOPSIS
         use Variable::Magic qw/wizard cast dispell/;


@@ -46,9 +46,42 @@ DESCRIPTION
         prevent it to work before perl 5.9.5 - see the history).
 
     "free"
         prevent it to work before perl 5.9.5 - see the history).
 
     "free"

-        This last one can be considered as an object destructor. It happens
-        when the variable goes out of scope (with the exception of global
-        scope), but not when it is undefined.
+        This one can be considered as an object destructor. It happens when
+        the variable goes out of scope (with the exception of global scope),
+        but not when it is undefined.
+
+    "copy"
+        This magic only applies to tied arrays and hashes. It fires when you
+        try to access or change their elements. It is available on your perl
+        iff "MGf_COPY" is true.
+
+    "dup"
+        Invoked when the variable is cloned across threads. Currently not
+        available.
+
+    "local"
+        When this magic is set on a variable, all subsequent localizations
+        of the variable will trigger the callback. It is available on your
+        perl iff "MGf_LOCAL" is true.
+
+    The following actions only apply to hashes and are available iff
+    "VMG_UVAR" is true. They are referred to as "uvar" magics.
+
+    "fetch"
+        This magic happens each time an element is fetched from the hash.
+
+    "store"
+        This one is called when an element is stored into the hash.
+
+    "exists"
+        This magic fires when a key is tested for existence in the hash.
+
+    "delete"
+        This last one triggers when a key is deleted in the hash, regardless
+        of whether the key actually exists in it.
+
+    You can refer to the tests to have more insight of where the different
+    magics are invoked.

 
     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.


@@ -58,13 +91,18 @@ PERL MAGIC HISTORY
     The places where magic is invoked have changed a bit through perl
     history. Here's a little list of the most recent ones.
 
     The places where magic is invoked have changed a bit through perl
     history. Here's a little list of the most recent ones.
 

+  5.6.x
+    *p14416* : 'copy' and 'dup' magic.
+

   5.9.3
     'len' magic is no longer called when pushing an element into a magic
     array.
   5.9.3
     'len' magic is no longer called when pushing an element into a magic
     array.

+    *p26569* : 'local' magic.

 
   5.9.5
 
   5.9.5

-    'clear' magic wasn't invoked when undefining an array. The bug is fixed
-    as of this version.
+    *p31064* : Meaningful 'uvar' magic.
+    *p31473* : 'clear' magic wasn't invoked when undefining an array. The
+    bug is fixed as of this version.

 
 CONSTANTS
   "SIG_MIN"
 
 CONSTANTS
   "SIG_MIN"


@@ -77,42 +115,61 @@ CONSTANTS
         SIG_NBR = SIG_MAX - SIG_MIN + 1
 
   "MGf_COPY"
         SIG_NBR = SIG_MAX - SIG_MIN + 1
 
   "MGf_COPY"

-    True iff the 'copy' magic is available.
+    Evaluates to true iff the 'copy' magic is available.

 
   "MGf_DUP"
 
   "MGf_DUP"

-    True iff the 'dup' magic is available.
+    Evaluates to true iff the 'dup' magic is available.

 
   "MGf_LOCAL"
 
   "MGf_LOCAL"

-    True iff the 'local' magic is available.
+    Evaluates to true iff the 'local' magic is available.
+
+  "VMG_UVAR"
+    When this constant is true, you can use the "fetch,store,exists,delete"
+    callbacks on hashes.

 
 FUNCTIONS
   "wizard"
 
 FUNCTIONS
   "wizard"

-        wizard sig => .., data => ..., get => .., set => .., len => .., clear => .., free => ..
+        wizard sig    => ...,
+               data   => sub { ... },
+               get    => sub { my ($ref, $data) = @_; ... },
+               set    => sub { my ($ref, $data) = @_; ... },
+               len    => sub { my ($ref, $data, $len) = @_; ... ; return $newlen; },
+               clear  => sub { my ($ref, $data) = @_; ... },
+               free   => sub { my ($ref, $data) = @_, ... },
+               copy   => sub { my ($ref, $data, $elt) = @_; ... },
+               local  => sub { my ($ref, $data) = @_; ... },
+               fetch  => sub { my ($ref, $data, $key) = @_; ... },
+               store  => sub { my ($ref, $data, $key) = @_; ... },
+               exists => sub { my ($ref, $data, $key) = @_; ... },
+               delete => sub { my ($ref, $data, $key) = @_; ... }

 
     This function creates a 'wizard', an opaque type that holds the magic
     information. It takes a list of keys / values as argument, whose keys
     can be :
 
 
     This function creates a 'wizard', an opaque type that holds the magic
     information. It takes a list of keys / values as argument, whose keys
     can be :
 

-    'sig'
+    "sig"

         The numerical signature. If not specified or undefined, a random
         signature is generated. If the signature matches an already defined
         magic, then the existant magic object is returned.
 
         The numerical signature. If not specified or undefined, a random
         signature is generated. If the signature matches an already defined
         magic, then the existant magic object is returned.
 

-    'data'
+    "data"

         A code reference to a private data constructor. It is called each
         time this magic is cast on a variable, and the scalar returned is
         used as private data storage for it. $_[0] is a reference to the
         magic object and @_[1 .. @_-1] are all extra arguments that were
         passed to "cast".
 
         A code reference to a private data constructor. It is called each
         time this magic is cast on a variable, and the scalar returned is
         used as private data storage for it. $_[0] is a reference to the
         magic object and @_[1 .. @_-1] are all extra arguments that were
         passed to "cast".
 

-    'get', 'set', 'len', 'clear' and 'free'
+    "get", "set", "len", "clear", "free", "copy", "local", "fetch", "store",
+    "exists" and "delete"

         Code references to corresponding magic callbacks. You don't have to
         specify all of them : the magic associated with undefined entries
         Code references to corresponding magic callbacks. You don't have to
         specify all of them : the magic associated with undefined entries

-        simply won't be hooked. In those callbacks, $_[0] is a reference to
-        the magic object and $_[1] is the private data (or "undef" when no
-        private data constructor was supplied). In the special case of "len"
-        magic and when the variable is an array, $_[2] contains its normal
-        length.
+        simply won't be hooked. In those callbacks, $_[0] is always a
+        reference to the magic object and $_[1] is always the private data
+        (or "undef" when no private data constructor was supplied). In the
+        special case of "len" magic and when the variable is an array, $_[2]
+        contains its normal length. "copy" magic receives the current
+        element (i.e. the value) in $_[2]. $_[2] is also the current key in
+        "fetch", "store", "exists" and "delete" callbacks.

 
         # A simple scalar tracer
         my $wiz = wizard get  => sub { print STDERR "got ${$_[0]}\n" },
 
         # A simple scalar tracer
         my $wiz = wizard get  => sub { print STDERR "got ${$_[0]}\n" },


@@ -144,7 +201,8 @@ FUNCTIONS
     magic is already present, 0 on error, and "undef" when no magic
     corresponds to the given signature (in case $sig was supplied). All
     extra arguments specified after $wiz are passed to the private data
     magic is already present, 0 on error, and "undef" when no magic
     corresponds to the given signature (in case $sig was supplied). All
     extra arguments specified after $wiz are passed to the private data

-    constructor.
+    constructor. If the variable isn't a hash, any "uvar" callback of the
+    wizard is safely ignored.

 
         # Casts $wiz onto $x. If $wiz isn't a signature, undef can't be returned.
         my $x;
 
         # Casts $wiz onto $x. If $wiz isn't a signature, undef can't be returned.
         my $x;


@@ -178,19 +236,37 @@ EXPORT
     "dispell" are only exported on request. All of them are exported by the
     tags ':funcs' and ':all'.
 
     "dispell" are only exported on request. All of them are exported by the
     tags ':funcs' and ':all'.
 

-    The constants "SIG_MIN", "SIG_MAX" and "SIG_NBR" are also only exported
-    on request. They are all exported by the tags ':consts' and ':all'.
+    The constants "SIG_MIN", "SIG_MAX", "SIG_NBR", "MGf_COPY", "MGf_DUP",
+    "MGf_LOCAL" and "VMG_UVAR" are also only exported on request. They are
+    all exported by the tags ':consts' and ':all'.
+
+CAVEATS
+    If you store a magic object in the private data slot, the magic won't be
+    accessible by "getdata" since it's not copied by assignation. The only
+    way to address this would be to return a reference.
+
+    If you define a wizard with a "free" callback and cast it on itself,
+    this destructor won't be called because the wizard will be destroyed
+    first.

 
 DEPENDENCIES
     perl 5.7.3.
 
     Carp (standard since perl 5), XSLoader (standard since perl 5.006).
 
 
 DEPENDENCIES
     perl 5.7.3.
 
     Carp (standard since perl 5), XSLoader (standard since perl 5.006).
 

+    Copy tests need Tie::Array (standard since perl 5.005) and Tie::Hash
+    (since 5.002).
+
+    Some uvar tests need Hash::Util::FieldHash (standard since perl
+    5.009004).
+

     Glob tests need Symbol (standard since perl 5.002).
 
 SEE ALSO
     perlguts and perlapi for internal information about magic.
 
     Glob tests need Symbol (standard since perl 5.002).
 
 SEE ALSO
     perlguts and perlapi for internal information about magic.
 

+    perltie and overload for other ways of enhancing objects.
+

 AUTHOR
     Vincent Pit, "<perl at profvince.com>"
 
 AUTHOR
     Vincent Pit, "<perl at profvince.com>"
 


@@ -209,7 +285,7 @@ SUPPORT
         perldoc Variable::Magic
 
 COPYRIGHT & LICENSE
         perldoc Variable::Magic
 
 COPYRIGHT & LICENSE

-    Copyright 2007 Vincent Pit, all rights reserved.
+    Copyright 2007-2008 Vincent Pit, all rights reserved.

 
     This program is free software; you can redistribute it and/or modify it
     under the same terms as Perl itself.
 
     This program is free software; you can redistribute it and/or modify it
     under the same terms as Perl itself.