Variable::Magic - Associate user-defined magic to variables from Perl.
VERSION
- Version 0.22
+ Version 0.30
SYNOPSIS
use Variable::Magic qw/wizard cast dispell/;
*p14416* : 'copy' and 'dup' magic.
+ * 5.8.9
+
+ *p28160* : Integration of *p25854* (see below).
+
+ *p32542* : Integration of *p31473* (see below).
+
* 5.9.3
*p25854* : 'len' magic is no longer called when pushing an element
*p32969* : 'len' magic is no longer invoked when calling "length"
with a magical scalar.
+ *p34908* : 'len' magic is no longer called when pushing / unshifting
+ an element into a magical array in void context. The "push" part was
+ already covered by *p25854*.
+
CONSTANTS
"SIG_MIN"
The minimum integer used as a signature for user-defined magic.
True for perls that don't call 'len' magic when you push an element in a
magical array.
+ "VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID"
+ True for perls that don't call 'len' magic when you unshift in void
+ context an element in a magical array.
+
"VMG_COMPAT_ARRAY_UNDEF_CLEAR"
True for perls that call 'clear' magic when undefining magical arrays.
True iff this module could have been built with thread-safety features
enabled.
+ "VMG_OP_INFO_NAME"
+ Value to pass with "op_info" to get the current op name in the magic
+ callbacks.
+
+ "VMG_OP_INFO_OBJECT"
+ Value to pass with "op_info" to get a "B::OP" object representing the
+ current op in the magic callbacks.
+
FUNCTIONS
"wizard"
- 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, $key, $elt) = @_; ... },
- local => sub { my ($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, $key) = @_; ... }
+ wizard sig => ...,
+ data => sub { ... },
+ get => sub { my ($ref, $data [, $op]) = @_; ... },
+ set => sub { my ($ref, $data [, $op]) = @_; ... },
+ len => sub { my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen; },
+ clear => sub { my ($ref, $data [, $op]) = @_; ... },
+ free => sub { my ($ref, $data [, $op]) = @_, ... },
+ copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
+ local => sub { my ($ref, $data [, $op]) = @_; ... },
+ fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
+ copy_key => $bool,
+ op_info => [ 0 | VMG_OP_INFO_NAME | VMG_OP_INFO_OBJECT ]
This function creates a 'wizard', an opaque type that holds the magic
information. It takes a list of keys / values as argument, whose keys
* "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 the 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 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. $_[2] is the current key in "copy",
- "fetch", "store", "exists" and "delete" callbacks, although for
- "copy" it may just be a copy of the actual key so it's useless to
- (for example) cast magic on it. "copy" magic also receives the
- current element (i.e. the value) in $_[3].
+ (or "undef" when no private data constructor was supplied).
+
+ Moreover, when you pass "op_info => $num" to "wizard", the last
+ element of @_ will be the current op name if "$num ==
+ VMG_OP_INFO_NAME" and a "B::OP" object representing the current op
+ if "$num == VMG_OP_INFO_OBJECT". Both have a performance hit, but
+ just getting the name is lighter than getting the op object.
+
+ Other arguments are specific to the magic hooked :
+
+ * "len"
+
+ When the variable is an array or a scalar, $_[2] contains
+ the non-magical length. The callback can return the new
+ scalar or array length to use, or "undef" to default to the
+ normal length.
+
+ * "copy"
+
+ $_[2] is a either a copy or an alias of the current key,
+ which means that it is useless to try to change or cast
+ magic on it. $_[3] is an alias to the current element (i.e.
+ the value).
+
+ * "fetch", "store", "exists" and "delete"
+
+ $_[2] is an alias to the current key. Nothing prevents you
+ from changing it, but be aware that there lurk dangerous
+ side effects. For example, it may righteously be readonly if
+ the key was a bareword. You can get a copy instead by
+ passing "copy_key => 1" to "wizard", which allows you to
+ safely assign to $_[2] in order to e.g. redirect the action
+ to another key. This however has a little performance
+ drawback because of the copy.
+
+ All the callbacks are expected to return an integer, which is passed
+ straight to the perl magic API. However, only the return value of
+ the "len" callback currently holds a meaning.
# A simple scalar tracer
my $wiz = wizard get => sub { print STDERR "got ${$_[0]}\n" },
my $x;
die 'error' unless cast $x, $wiz;
+ The "var" argument can be an array or hash value. Magic for those
+ behaves like for any other scalar, except that it is dispelled when the
+ entry is deleted from the container. For example, if you want to call
+ "POSIX::tzset" each time the 'TZ' environment variable is changed in
+ %ENV, you can use :
+
+ use POSIX;
+ cast $ENV{TZ}, wizard set => sub { POSIX::tzset(); () };
+
+ If you want to overcome the possible deletion of the 'TZ' entry, you
+ have no choice but to rely on "store" uvar magic.
+
"getdata"
getdata [$@%&*]var, [$wiz|$sig]
first.
DEPENDENCIES
- perl 5.7.3.
+ perl 5.8.
Carp (standard since perl 5), XSLoader (standard since perl 5.006).
AUTHOR
Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
- You can contact me by mail or on #perl @ FreeNode (vincent or
- Prof_Vince).
+ You can contact me by mail or on "irc.perl.org" (vincent).
BUGS
Please report any bugs or feature requests to "bug-variable-magic at
<http://www.profvince.com/perl/cover/Variable-Magic>.
COPYRIGHT & LICENSE
- Copyright 2007-2008 Vincent Pit, all rights reserved.
+ Copyright 2007-2009 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.
projects / perl / modules / Variable-Magic.git / blobdiff