package Scope::Upper;
+use 5.006_001;
+
use strict;
use warnings;
=head1 VERSION
-Version 0.16
+Version 0.31
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.16';
+ $VERSION = '0.31';
}
=head1 SYNOPSIS
package Scope;
- use Scope::Upper qw<reap localize localize_elem localize_delete :words>;
+ use Scope::Upper qw<
+ reap localize localize_elem localize_delete
+ :words
+ >;
sub new {
my ($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 *
-return values immediately to an upper level with L</unwind>, and know which context was in use then with L</want_at> ;
+return values immediately to an upper level with L</unwind>, L</yield> and L</leave> ;
=item *
-execute a subroutine in the setting of an upper subroutine stack frame with L</uplevel>.
+gather information about an upper context with L</want_at> and L</context_info> ;
+
+=item *
+
+execute a subroutine in the setting of an upper subroutine stack frame with L</uplevel> ;
+
+=item *
+
+uniquely identify contexts 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<$what> must be a string and the type of localization is inferred from its sigil.
If C<$what> is a string pointing to an undeclared variable, the variable will be vivified as soon as the localization occurs and emptied when it ends, although it will still exist in its glob.
-=head2 C<localize_delete $what, $key, $context>
+=head2 C<localize_delete>
+
+ localize_delete $what, $key;
+ localize_delete $what, $key, $context;
Introduces the deletion of a variable or an array/hash element delayed to the time of first return into the upper scope denoted by C<$context>.
C<$what> can be:
=item *
-A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectiveley C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
+A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectively C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
=item *
=back
-=head2 C<unwind @values, $context>
+=head2 C<unwind>
+
+ unwind;
+ 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<$context>, and immediately restart the program flow at this point - thus effectively returning to an upper scope.
+Returns C<@values> I<from> the subroutine, eval or format context pointed by or just above C<$context>, and immediately restarts the program flow at this point - thus effectively returning C<@values> to an upper scope.
+If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context (making the call equivalent to a bare C<return;>) ; otherwise it is mandatory.
The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
This means that
will set C<$num> to C<'z'>.
You can use L</want_at> to handle these cases.
-=head2 C<want_at $context>
+=head2 C<yield>
+
+ yield;
+ yield @values, $context;
+
+Returns C<@values> I<from> the context pointed by or just above C<$context>, and immediately restarts the program flow at this point.
+If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
+
+L</yield> differs from L</unwind> in that it can target I<any> upper scope (besides a C<s///e> substitution context) and not necessarily a sub, an eval or a format.
+Hence you can use it to return values from a C<do> or a C<map> block :
+
+ my $now = do {
+ local $@;
+ eval { require Time::HiRes } or yield time() => HERE;
+ Time::HiRes::time();
+ };
+
+ my @uniq = map {
+ yield if $seen{$_}++; # returns the empty list from the block
+ ...
+ } @things;
+
+Like for L</unwind>, the upper context isn't coerced onto C<@values>.
+You can use the fifth value returned by L</context_info> to handle context coercion.
+
+=head2 C<leave>
+
+ leave;
+ leave @values;
+
+Immediately returns C<@values> from the current block, whatever it may be (besides a C<s///e> substitution context).
+C<leave> is actually a synonym for C<yield HERE>, while C<leave @values> is a synonym for C<yield @values, HERE>.
+
+Like for L</yield>, you can use the fifth value returned by L</context_info> to handle context coercion.
+
+=head2 C<want_at>
-Like C<wantarray>, but for the subroutine/eval/format at or just above C<$context>.
+ my $want = want_at;
+ my $want = want_at $context;
-The previous example can then be "corrected" :
+Like L<perlfunc/wantarray>, but for the subroutine, eval or format context located at or just above C<$context>.
+
+It can be used to revise the example showed in L</unwind> :
my $num = sub {
my @a = ('a' .. 'z');
will rightfully set C<$num> to C<26>.
-=head2 C<uplevel $code, @args, $context>
+=head2 C<context_info>
+
+ my ($package, $filename, $line, $subroutine, $hasargs,
+ $wantarray, $evaltext, $is_require, $hints, $bitmask,
+ $hinthash) = context_info $context;
+
+Gives information about the context denoted by C<$context>, akin to what L<perlfunc/caller> provides but not limited only to subroutine, eval and format contexts.
+When C<$context> is omitted, it defaults to the current context.
+
+The returned values are, in order :
+
+=over 4
+
+=item *
+
+I<(index 0)> : the namespace in use when the context was created ;
+
+=item *
+
+I<(index 1)> : the name of the file at the point where the context was created ;
+
+=item *
+
+I<(index 2)> : the line number at the point where the context was created ;
+
+=item *
+
+I<(index 3)> : the name of the subroutine called for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 4)> : a boolean indicating whether a new instance of C<@_> was set up for this context, or C<undef> if this is not a subroutine context ;
+
+=item *
+
+I<(index 5)> : the context (in the sense of L<perlfunc/wantarray>) in which the context (in our sense) is executed ;
+
+=item *
+
+I<(index 6)> : the contents of the string being compiled for this context, or C<undef> if this is not an eval context ;
+
+=item *
+
+I<(index 7)> : a boolean indicating whether this eval context was created by C<require>, or C<undef> if this is not an eval context ;
+
+=item *
+
+I<(index 8)> : the value of the lexical hints in use when the context was created ;
+
+=item *
+
+I<(index 9)> : a bit string representing the warnings in use when the context was created ;
+
+=item *
+
+I<(index 10)> : a reference to the lexical hints hash in use when the context was created (only on perl 5.10 or greater).
+
+=back
-Executes the code reference C<$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.
+=head2 C<uplevel>
+
+ my @ret = uplevel { ...; return @ret };
+ my @ret = uplevel { my @args = @_; ...; return @ret } @args, $context;
+ my @ret = &uplevel($callback, @args, $context);
+
+Executes the code reference C<$callback> 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>.
sub target {
my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
my $count = target(1, 2, 4); # $count is 3
+Note that if C<@args> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
+
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 *
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.
+When omitted, it defaults to 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>.
+If C<$from> points to the top-level scope in the current stack, then a warning is emitted and C<$from> is returned (see L</DIAGNOSTICS> for details).
+
+=head3 C<SUB>
-=head3 C<SUB $from>
+ my $sub_context = SUB;
+ my $sub_context = SUB $from;
The context of the closest subroutine above C<$from>.
-Note that C<$from> is returned if it is already a subroutine context ; hence C<SUB SUB == SUB>.
+If C<$from> already designates a subroutine context, then it is returned as-is ; hence C<SUB SUB == SUB>.
+If no subroutine context is present in the call stack, then a warning is emitted and the current context is returned (see L</DIAGNOSTICS> for details).
-=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<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.
+If C<$from> already designates an eval context, then it is returned as-is ; hence C<EVAL EVAL == EVAL>.
+If no eval context is present in the call stack, then a warning is emitted and the current context is returned (see L</DIAGNOSTICS> for details).
=head2 Getting a context from a level
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.
+If C<$level> points above the top-level scope in the current stack, then a warning is emitted and the top-level context is returned (see L</DIAGNOSTICS> for details).
+
+=head3 C<CALLER>
-=head3 C<CALLER $level>
+ 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 $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
+If C<$level> points above the top-level scope in the current stack, then a warning is emitted and the top-level context is returned (see L</DIAGNOSTICS> for details).
=head2 Examples
{
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>:
+Where L</unwind>, L</yield>, L</want_at>, L</context_info> and L</uplevel> point to depending on the C<$cxt>:
sub {
eval {
sub {
{
- unwind @things => $cxt; # or uplevel { ... } $cxt;
+ unwind @things => $cxt; # or yield @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 cannot target eval scopes.
+=head1 DIAGNOSTICS
+
+=head2 C<Cannot target a scope outside of the current stack>
+
+This warning is emitted when L</UP>, L</SCOPE> or L</CALLER> end up pointing to a context that is above the top-level context of the current stack.
+It indicates that you tried to go higher than the main scope, or to point across a C<DESTROY> method, a signal handler, an overloaded or tied method call, a C<require> statement or a C<sort> callback.
+In this case, the resulting context is the highest reachable one.
+
+=head2 C<No targetable %s scope in the current stack>
+
+This warning is emitted when you ask for an L</EVAL> or L</SUB> context and no such scope can be found in the call stack.
+The resulting context is the current one.
+
=head1 EXPORT
-The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind>, L</want_at> and L</uplevel> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
+The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind>, L</yield>, L</leave>, L</want_at>, L</context_info> and L</uplevel> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
The constant L</SU_THREADSAFE> is also only exported on request, individually or by the tags C<':consts'> and C<':all'>.
funcs => [ qw<
reap
localize localize_elem localize_delete
- unwind want_at
+ unwind yield leave
+ want_at context_info
uplevel
+ uid validate_uid
> ],
words => [ qw<TOP HERE UP SUB EVAL SCOPE CALLER> ],
consts => [ qw<SU_THREADSAFE> ],
=head1 CAVEATS
+It is not possible to act upon a scope that belongs to another perl 'stack', i.e. to target a scope across a C<DESTROY> method, a signal handler, an overloaded or tied method call, a C<require> statement or a C<sort> callback.
+
Be careful that local variables are restored in the reverse order in which they were localized.
Consider those examples:
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 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>.
+
+Starting from C<perl> 5.19.4, it is unfortunately no longer possible to reliably throw exceptions from L</uplevel>'d code while the debugger is in use.
+This may be solved in a future version depending on how the core evolves.
+
=head1 DEPENDENCIES
-L<XSLoader> (standard since perl 5.006).
+L<perl> 5.6.1.
+
+A C compiler.
+This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
+
+L<XSLoader> (core since perl 5.6.0).
=head1 SEE ALSO
=head1 AUTHOR
-Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
+Vincent Pit C<< <vpit at cpan.org> >>.
You can contact me by mail or on C<irc.perl.org> (vincent).
perldoc Scope::Upper
-Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Scope-Upper>.
-
=head1 ACKNOWLEDGEMENTS
Inspired by Ricardo Signes.
+The reimplementation of a large part of this module for perl 5.24 was provided by David Mitchell.
+His work was sponsored by the Perl 5 Core Maintenance Grant from The Perl Foundation.
+
Thanks to Shawn M. Moore for motivation.
=head1 COPYRIGHT & LICENSE
-Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019 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