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=head1 NAME |
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Coro::Storable - offer a more fine-grained Storable interface |
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=head1 SYNOPSIS |
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use Coro::Storable; |
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=head1 DESCRIPTION |
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This module implements a few functions from the Storable module in a way |
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so that it cede's more often. Some applications (such as the Deliantra |
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game server) sometimes need to load large Storable objects without |
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blocking the server for a long time. |
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This is being implemented by using a perlio layer that feeds only small |
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amounts of data (512 bytes per call) into Storable, and C<Coro::cede>'ing |
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regularly (at most 100 times per second by default, though). |
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As it seems that Storable is not reentrant, this module also wraps most |
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functions of the Storable module so that only one freeze or thaw is done |
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at any one moment (recursive invocations are not currently supported). |
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=head1 FUNCTIONS |
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=over 4 |
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=item $ref = thaw $pst |
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Retrieve an object from the given $pst, which must have been created with |
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C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store> |
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(sorry, but Storable uses incompatible formats for disk/mem objects). |
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This works by calling C<Coro::cede> for every 4096 bytes read in. |
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=item $pst = freeze $ref |
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Freeze the given scalar into a Storable object. It uses the same format as |
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C<Storable::store_fd>. |
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This works by calling C<Coro::cede> for every write that Storable |
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issues. Unfortunately, Storable often makes many very small writes, so it |
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is rather inefficient. But it does keep the latency low. |
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=item $pst = nfreeze $ref |
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Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the |
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C<n>). |
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=item $pst = blocking_freeze $ref |
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Same as C<freeze> but is guaranteed to block. This is useful e.g. in |
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C<Coro::Util::fork_eval> when you want to serialise a data structure |
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for use with the C<thaw> function for this module. You cannot use |
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C<Storable::freeze> for this as Storable uses incompatible formats for |
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memory and file images. |
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=item $pst = blocking_nfreeze $ref |
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Same as C<blocking_freeze> but uses C<nfreeze> internally. |
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=item $guard = guard |
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Acquire the Storable lock, for when you want to call Storable yourself. |
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Note that this module already wraps the Storable functions, so there is |
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rarely the need to do this yourself. |
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=back |
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=cut |
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package Coro::Storable; |
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use strict qw(subs vars); |
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no warnings; |
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use Coro (); |
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use Coro::Semaphore (); |
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BEGIN { |
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# suppress warnings |
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local $^W = 0; |
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require Storable; |
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} |
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use Storable; |
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use base "Exporter"; |
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our $VERSION = 4.745; |
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our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze); |
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my $lock = new Coro::Semaphore; |
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sub guard { |
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$lock->guard |
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} |
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# wrap xs functions |
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for (qw(net_pstore mstore net_mstore pretrieve mretrieve dclone)) { |
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my $orig = \&{"Storable::$_"}; |
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*{"Storable::$_"} = sub { |
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my $guard = $lock->guard; |
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&$orig |
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}; |
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die if $@; |
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} |
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sub thaw($) { |
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open my $fh, "<:via(CoroCede)", \$_[0] |
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or die "cannot open pst via CoroCede: $!"; |
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Storable::fd_retrieve $fh |
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} |
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sub freeze($) { |
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open my $fh, ">:via(CoroCede)", \my $buf |
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or die "cannot open pst via CoroCede: $!"; |
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Storable::store_fd $_[0], $fh; |
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$buf |
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} |
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sub nfreeze($) { |
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open my $fh, ">:via(CoroCede)", \my $buf |
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or die "cannot open pst via CoroCede: $!"; |
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Storable::nstore_fd $_[0], $fh; |
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$buf |
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} |
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sub blocking_thaw($) { |
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open my $fh, "<", \$_[0] |
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or die "cannot open pst: $!"; |
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Storable::fd_retrieve $fh |
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} |
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sub blocking_freeze($) { |
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open my $fh, ">", \my $buf |
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or die "cannot open pst: $!"; |
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Storable::store_fd $_[0], $fh; |
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close $fh; |
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$buf |
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} |
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sub blocking_nfreeze($) { |
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open my $fh, ">", \my $buf |
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or die "cannot open pst: $!"; |
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Storable::nstore_fd $_[0], $fh; |
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close $fh; |
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$buf |
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} |
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package PerlIO::via::CoroCede; |
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# generic cede-on-read/write filtering layer |
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use Time::HiRes ("time"); |
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our $GRANULARITY = 0.01; |
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my $next_cede; |
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sub PUSHED { |
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__PACKAGE__ |
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} |
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sub FILL { |
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if ($next_cede <= time) { |
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$next_cede = time + $GRANULARITY; # calling time() twice usually is a net win |
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Coro::cede (); |
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} |
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read $_[1], my $buf, 512 |
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or return undef; |
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$buf |
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} |
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sub WRITE { |
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if ($next_cede <= time) { |
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$next_cede = time + $GRANULARITY; |
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Coro::cede (); |
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} |
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(print {$_[2]} $_[1]) ? length $_[1] : -1 |
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} |
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1; |
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=head1 AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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=cut |
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