NAME

       Readonly::Tiny - Simple, correct readonly values

SYNOPSIS

           use Readonly::Tiny;

           my $x = readonly [1, 2, 3];
           # $x is not readonly, but the array it points to is.

           my @y = (4, 5, 6);
           readonly \@y;
           # @y is readonly, as well as its contents.

DESCRIPTION

       Readonly::Tiny provides a simple and correct way of making values readonly. Unlike
       Readonly it does not cause arrays and hashes to be tied, it just uses the core
       "SvREADONLY" flag.

FUNCTIONS

   readonly
           my $ro = readonly $ref, \%opts;

       Make a data structure readonly. $ref must be a reference; the referenced value, and any
       values referenced recursively, will be made readonly. $ref is returned, but it will not
       itself be readonly; it is possible to make a variable readonly by passing a reference to
       it, as in the "SYNOPSIS".

       %opts is a hashref of options:

       peek
           Normally blessed references will not be looked through. The scalar holding the
           reference will be made readonly (so a different object cannot be assigned) but the
           contents of the object itself will be left alone. Supplying "peek => 1" allows blessed
           refs to be looked through.

       skip
           This should be a hashref keyed by refaddr. Any object whose refaddr is in the hash
           will be skipped.

       Note that making a hash readonly has the same effect as calling "Hash::Util::lock_hash";
       in particular, it causes restricted hashes to be re-restricted to their current set of
       keys.

   readwrite
           my $rw = readwrite $ref, \%opts;

       Undo the effects of "readonly". %opts is the same. Note that making a hash readwrite will
       undo any restrictions put in place using Hash::Util.

       BE VERY CAREFUL calling this on values you have not made readonly yourself. It will
       silently ignore attempts to make the core values "PL_sv_undef", "PL_sv_yes" and "PL_sv_no"
       readwrite, but there are many other values the core makes readonly, usually with good
       reason.  Recent versions of perl will not allow you to make readwrite a value the core has
       set readonly, but you should probably not rely on this.

   Readonly
           Readonly my $x, 1;
           Readonly my @y, 2, 3, 4;
           Readonly my %z, foo => 5;

       This is a compatibility shim for Readonly. It is prototyped to take a reference to its
       first argument, and assigns the rest of the argument list to that argument before making
       the whole thing readonly.

EXPORTS

       "readonly" is exported by default. "readwrite" and "Readonly" are exported on request.

SEE ALSO

       Readonly was the first module to supply readonly values. It was written for Perl 5.6, and
       as a result the interface and implementation are both rather clunky. With Readonly::XS the
       performance is improved for scalar varuables, but arrays and hashes still use a tied
       implementation which is very slow.

       Const::Fast is a greatly improved reaoonly module which uses perl's internal "SvREADONLY"
       flag instead of ties. The differences between this module and Const::Fast are:

       •   The "readonly" function does not insist on performing an assignment, it just returns a
           readonly value. This is, IMHO, more useful, since it means a readonly value can be
           returned from a function. In particular, it is often useful to return a readonly value
           from a builder method.

       •   It does not attempt to clone deep structures. If "Clone::Fast" is applied to a
           structure with cross-links it will clone the whole thing, on the principle that parts
           of the graph may be shared with something else which should not be readonly. This
           module takes the approach that if you asked for something to be made readonly you
           meant it, and if it points to something it shouldn't that's your mistake.

BUGS

       Please report bugs to <bug-Readonly-Tiny@rt.cpan.org>.

AUTHOR

       Ben Morrow <ben@morrow.me.uk>

COPYRIGHT

       Copyright 2015 Ben Morrow.

       Released under the 2-clause BSD licence.