=head1 VERSION
-Version 0.15
+Version 0.18
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.15';
+ $VERSION = '0.18';
}
=head1 SYNOPSIS
package Scope;
- use Scope::Upper qw<reap localize localize_elem localize_delete :words>;
+ use Scope::Upper qw<
+ reap localize localize_elem localize_delete
+ :words
+ >;
sub new {
my ($class, $name) = @_;
package UserLand;
{
- Scope->new("top"); # initializes $UserLand::tag
+ Scope->new("top"); # initializes $UserLand::tag
{
Scope->catch;
- my $one = 1 + undef; # prints "top: Use of uninitialized value..."
+ my $one = 1 + undef; # prints "top: Use of uninitialized value..."
{
Scope->private;
eval { require Cwd };
- print $@; # prints "Can't locate Cwd.pm in @INC (@INC contains:) at..."
- }
+ print $@; # prints "Can't locate Cwd.pm in @INC
+ } # (@INC contains:) at..."
- require Cwd; # loads Cwd.pm
+ require Cwd; # loads Cwd.pm
}
- } # prints "top: done"
+ } # prints "top: done"
L</unwind> and L</want_at> :
target('hello'); # "hello from Uplevel::target()"
+L</uid> and L</validate_uid> :
+
+ use Scope::Upper qw<uid validate_uid>;
+
+ my $uid;
+
+ {
+ $uid = uid();
+ {
+ if ($uid eq uid(UP)) { # yes
+ ...
+ }
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
=head1 DESCRIPTION
This module lets you defer actions I<at run-time> that will take place when the control flow returns into an upper scope.
=item *
-execute a subroutine in the context of an upper subroutine stack frame with L</uplevel>.
+execute a subroutine in the setting of an upper subroutine stack frame with L</uplevel> ;
+
+=item *
+
+uniquely identify contextes with L</uid> and L</validate_uid>.
=back
XSLoader::load(__PACKAGE__, $VERSION);
}
-=head2 C<reap $callback, $context>
+=head2 C<reap>
+
+ reap { ... };
+ reap { ... } $context;
+ &reap($callback, $context);
Adds a destructor that calls C<$callback> (in void context) when the upper scope represented by C<$context> ends.
-=head2 C<localize $what, $value, $context>
+=head2 C<localize>
+
+ localize $what, $value;
+ localize $what, $value, $context;
Introduces a C<local> delayed to the time of first return into the upper scope denoted by C<$context>.
C<$what> can be :
=back
-=head2 C<localize_elem $what, $key, $value, $context>
+=head2 C<localize_elem>
+
+ localize_elem $what, $key, $value;
+ localize_elem $what, $key, $value, $context;
Introduces a C<local $what[$key] = $value> or C<local $what{$key} = $value> delayed to the time of first return into the upper scope denoted by C<$context>.
Unlike L</localize>, C<$what> must be a string and the type of localization is inferred from its sigil.
=back
-=head2 C<unwind @values, $context>
+=head2 C<unwind>
+
+ unwind @values;
+ unwind @values, $context;
Returns C<@values> I<from> the context pointed by C<$context>, i.e. from the subroutine, eval or format at or just above C<$context>, and immediately restart the program flow at this point - thus effectively returning to an upper scope.
will set C<$num> to C<'z'>.
You can use L</want_at> to handle these cases.
-=head2 C<want_at $context>
+=head2 C<want_at>
+
+ my $want = want_at;
+ my $want = want_at $context;
Like C<wantarray>, but for the subroutine/eval/format at or just above C<$context>.
=head2 C<uplevel $code, @args, $context>
+ my @ret = uplevel { ...; return @ret };
+ my @ret = uplevel { my @args = @_; ...; return @ret } @args;
+ my @ret = uplevel { ... } @args, $context;
+ my @ret = &uplevel($callback, @args, $context);
+
Executes the code reference C<$code> with arguments C<@args> as if it were located at the subroutine stack frame pointed by C<$context>, effectively fooling C<caller> and C<die> into believing that the call actually happened higher in the stack.
The code is executed in the context of the C<uplevel> call, and what it returns is returned as-is by C<uplevel>.
}
my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
- my $count = target(1, 2, 4); # $target is 3
+ my $count = target(1, 2, 4); # $count is 3
L<Sub::Uplevel> also implements a pure-Perl version of C<uplevel>.
Both are identical, with the following caveats :
=item *
The L<Sub::Uplevel> implementation of C<uplevel> may execute a code reference in the context of B<any> upper stack frame.
-The L<Scope::Upper> version only allows to uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
+The L<Scope::Upper> version can only uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
=item *
=item *
-L<Sub::Uplevel> globally overrides C<CORE::GLOBAL::caller>, while L<Scope::Upper> does not.
+L<Sub::Uplevel> globally overrides the Perl keyword C<caller>, while L<Scope::Upper> does not.
=back
Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
+=head2 C<uid>
+
+ my $uid = uid;
+ my $uid = uid $context;
+
+Returns an unique identifier (UID) for the context (or dynamic scope) pointed by C<$context>, or for the current context if C<$context> is omitted.
+This UID will only be valid for the life time of the context it represents, and another UID will be generated next time the same scope is executed.
+
+ my $uid;
+
+ {
+ $uid = uid;
+ if ($uid eq uid()) { # yes, this is the same context
+ ...
+ }
+ {
+ if ($uid eq uid()) { # no, we are one scope below
+ ...
+ }
+ if ($uid eq uid(UP)) { # yes, UP points to the same scope as $uid
+ ...
+ }
+ }
+ }
+
+ # $uid is now invalid
+
+ {
+ if ($uid eq uid()) { # no, this is another block
+ ...
+ }
+ }
+
+For example, each loop iteration gets its own UID :
+
+ my %uids;
+
+ for (1 .. 5) {
+ my $uid = uid;
+ $uids{$uid} = $_;
+ }
+
+ # %uids has 5 entries
+
+The UIDs are not guaranteed to be numbers, so you must use the C<eq> operator to compare them.
+
+To check whether a given UID is valid, you can use the L</validate_uid> function.
+
+=head2 C<validate_uid>
+
+ my $is_valid = validate_uid $uid;
+
+Returns true if and only if C<$uid> is the UID of a currently valid context (that is, it designates a scope that is higher than the current one in the call stack).
+
+ my $uid;
+
+ {
+ $uid = uid();
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ {
+ if (validate_uid($uid)) { # yes
+ ...
+ }
+ }
+ }
+
+ if (validate_uid($uid)) { # no
+ ...
+ }
+
=head1 CONSTANTS
=head2 C<SU_THREADSAFE>
=head3 C<TOP>
+ my $top_context = TOP;
+
Returns the context that currently represents the highest scope.
=head3 C<HERE>
+ my $current_context = HERE;
+
The context of the current scope.
=head2 Getting a context from a context
For any of those functions, C<$from> is expected to be a context.
When omitted, it defaults to the the current context.
-=head3 C<UP $from>
+=head3 C<UP>
+
+ my $upper_context = UP;
+ my $upper_context = UP $from;
The context of the scope just above C<$from>.
-=head3 C<SUB $from>
+=head3 C<SUB>
+
+ my $sub_context = SUB;
+ my $sub_context = SUB $from;
The context of the closest subroutine above C<$from>.
Note that C<$from> is returned if it is already a subroutine context ; hence C<SUB SUB == SUB>.
-=head3 C<EVAL $from>
+=head3 C<EVAL>
+
+ my $eval_context = EVAL;
+ my $eval_context = EVAL $from;
The context of the closest eval above C<$from>.
Note that C<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.
Here, C<$level> should denote a number of scopes above the current one.
When omitted, it defaults to C<0> and those functions return the same context as L</HERE>.
-=head3 C<SCOPE $level>
+=head3 C<SCOPE>
+
+ my $context = SCOPE;
+ my $context = SCOPE $level;
The C<$level>-th upper context, regardless of its type.
-=head3 C<CALLER $level>
+=head3 C<CALLER>
+
+ my $context = CALLER;
+ my $context = CALLER $level;
The context of the C<$level>-th upper subroutine/eval/format.
It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
{
reap \&cleanup => $cxt;
...
- } # $cxt = SCOPE(0), or HERE
+ } # $cxt = SCOPE(0) = HERE
...
- }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ }->(); # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
Where L</localize>, L</localize_elem> and L</localize_delete> act depending on the C<$cxt> :
sub {
{
localize '$x' => 1 => $cxt;
- # $cxt = SCOPE(0), or HERE
+ # $cxt = SCOPE(0) = HERE
...
}
- # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+ # $cxt = SCOPE(1) = UP = SUB = CALLER(0)
...
}->();
- # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+ # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1)
...
};
- # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
}->();
- # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP
+ # $cxt = SCOPE(4), UP SUB UP SUB = UP SUB EVAL = UP CALLER(2) = TOP
...
Where L</unwind>, L</want_at> and L</uplevel> point to depending on the C<$cxt>:
eval {
sub {
{
- unwind @things => $cxt; # or uplevel { ... } $cxt;
+ unwind @things => $cxt; # or uplevel { ... } $cxt;
...
}
...
- }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0)
+ }->(); # $cxt = SCOPE(0) = SCOPE(1) = HERE = UP = SUB = CALLER(0)
...
- }; # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) (*)
+ }; # $cxt = SCOPE(2) = UP UP = UP SUB = EVAL = CALLER(1) (*)
...
- }->(); # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+ }->(); # $cxt = SCOPE(3) = SUB UP SUB = SUB EVAL = CALLER(2)
...
# (*) Note that uplevel() will croak if you pass that scope frame,
- # because it can't target eval scopes.
+ # because it cannot target eval scopes.
=head1 EXPORT
localize localize_elem localize_delete
unwind want_at
uplevel
+ uid validate_uid
> ],
words => [ qw<TOP HERE UP SUB EVAL SCOPE CALLER> ],
consts => [ qw<SU_THREADSAFE> ],
Some rare oddities may still happen when running inside the debugger.
It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context-related fixes.
+Calling C<goto> to replace an L</uplevel>'d code frame does not work :
+
+=over 4
+
+=item *
+
+for a C<perl> older than the 5.8 series ;
+
+=item *
+
+for a C<DEBUGGING> C<perl> run with debugging flags set (as in C<perl -D ...>) ;
+
+=item *
+
+when the runloop callback is replaced by another module.
+
+=back
+
+In those three cases, L</uplevel> will look for a C<goto &sub> statement in its callback and, if there is one, throw an exception before executing the code.
+
+Moreover, in order to handle C<goto> statements properly, L</uplevel> currently has to suffer a run-time overhead proportional to the size of the the callback in every case (with a small ratio), and proportional to the size of B<all> the code executed as the result of the L</uplevel> call (including subroutine calls inside the callback) when a C<goto> statement is found in the L</uplevel> callback.
+Despite this shortcoming, this XS version of L</uplevel> should still run way faster than the pure-Perl version from L<Sub::Uplevel>.
+
=head1 DEPENDENCIES
L<XSLoader> (standard since perl 5.006).
L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
+L<Sub::Uplevel>.
+
L<Continuation::Escape> is a thin wrapper around L<Scope::Upper> that gives you a continuation passing style interface to L</unwind>.
It's easier to use, but it requires you to have control over the scope where you want to return.
L<Scope::Escape>.
-L<Sub::Uplevel> provides a pure-Perl implementation of L</uplevel>.
-
=head1 AUTHOR
Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
=head1 COPYRIGHT & LICENSE
-Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011,2012 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 / Scope-Upper.git / blobdiff