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package IO::SigGuard; |
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=encoding utf-8 |
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=head1 NAME |
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IO::SigGuard - SA_RESTART in pure Perl |
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=head1 SYNOPSIS |
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IO::SigGuard::sysread( $fh, $buf, $size ); |
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IO::SigGuard::sysread( $fh, $buf, $size, $offset ); |
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IO::SigGuard::syswrite( $fh, $buf ); |
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IO::SigGuard::syswrite( $fh, $buf, $len ); |
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IO::SigGuard::syswrite( $fh, $buf, $len, $offset ); |
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IO::SigGuard::select( $read, $write, $exc, $timeout ); |
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=head1 DESCRIPTION |
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C describes how Perl versions from 5.8.0 onward disable |
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the OS’s SA_RESTART flag when installing Perl signal handlers. |
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This module imitates that pattern in pure Perl: it does an automatic |
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restart when a signal interrupts an operation so you can avoid |
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the generally-useless EINTR error when using |
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C, C, and C |
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For this to work, whatever signal handler you implement will need to break |
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out of this module, probably via either C or C. |
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=head1 ABOUT C and C |
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Other than that you’ll never see EINTR and that |
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there are no function prototypes used (i.e., you need parentheses on |
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all invocations), C and C |
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work exactly the same as Perl’s equivalent built-ins. |
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=head1 ABOUT C |
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To handle EINTR, C has to subtract the elapsed time |
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from the given timeout then repeat the internal C |
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the C |
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all platforms, we have to compute the elapsed time ourselves. By default the |
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only means of doing this is the C |
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individual seconds. |
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This works, but there are two ways to make it more accurate: |
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=over |
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=item * Have L loaded, and C will use that |
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module rather than the C |
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=item * Set C<$IO::SigGuard::TIME_CR> to a compatible code reference. This is |
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useful, e.g., if you have your own logic to do the equivalent of |
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L—for example, in Linux you may prefer to call the C |
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system call directly from Perl to avoid L’s XS overhead. |
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=back |
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In scalar contact, C is a drop-in replacement |
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for Perl’s 4-argument built-in. |
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In list context, there may be discrepancies re the C<$timeleft> value |
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that Perl returns from a call to C |
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this value is generally not reliable anyway, though, so that shouldn’t be a |
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big deal. In fact, on systems like MacOS where the built-in’s C<$timeleft> |
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is completely useless, IO::SigGuard’s return is actually B since it |
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does provide at least a rough estimate of how much of the given timeout value |
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is left. |
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See C for portability notes for C |
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=head1 TODO |
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This pattern could probably be extended to C, C, C, and |
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other system calls that can receive EINTR. If there’s a desire for that I’ll |
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consider adding it. |
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=cut |
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263257
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use strict; |
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use warnings; |
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use Errno (); |
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1549
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our $VERSION = '0.03-TRIAL2'; |
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#Set this in lieu of using Time::HiRes or built-in time(). |
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our $TIME_CR; |
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#Just in case someone has an actual reason to do this. |
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our $YES_I_REALLY_MEAN_TO_WRITE_ZERO_BYTES; |
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our $TOLERATE_NONERROR_ZERO_WRITE; |
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#As light as possible … |
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my $read; |
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sub sysread { |
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READ: { |
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$read = ( (@_ == 3) ? CORE::sysread( $_[0], $_[1], $_[2] ) : (@_ == 4) ? CORE::sysread( $_[0], $_[1], $_[2], $_[3] ) : die "Wrong args count! (@_)" ) or do { |
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redo READ if $! == Errno::EINTR(); |
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}; |
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} |
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return $read; |
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} |
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my $wrote; |
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sub syswrite { |
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WRITE: { |
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$wrote = ( (@_ == 2) ? CORE::syswrite( $_[0], $_[1] ) : (@_ == 3) ? CORE::syswrite( $_[0], $_[1], $_[2] ) : (@_ == 4) ? CORE::syswrite( $_[0], $_[1], $_[2], $_[3] ) : die "Wrong args count! (@_)" ) || do { |
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#EINTR means the file pointer is unchanged. |
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redo WRITE if $! == Errno::EINTR(); |
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}; |
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} |
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return $wrote; |
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} |
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my ($start, $last_loop_time, $os_error, $nfound, $timeleft, $timer_cr); |
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#pre-5.16 didn’t have \&CORE::time. |
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sub _time { time } |
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sub select { |
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die( (caller 0)[3] . ' must have 4 arguments!' ) if @_ != 4; |
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$os_error = $!; |
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$timer_cr = $TIME_CR || Time::HiRes->can('time') || \&_time; |
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$start = $timer_cr->(); |
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$last_loop_time = $start; |
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SELECT: { |
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($nfound, $timeleft) = CORE::select( $_[0], $_[1], $_[2], $_[3] - $last_loop_time + $start ); |
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if ($nfound == -1) { |
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#Use of %! will autoload Errno.pm, |
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#which can affect the value of $!. |
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my $select_error = $!; |
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if ($! == Errno::EINTR()) { |
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$last_loop_time = $timer_cr->(); |
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redo SELECT; |
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} |
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$! = $select_error; |
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} |
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else { |
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#select() doesn’t set $! on success, so let’s not clobber what |
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#value was there before. |
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$! = $os_error; |
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} |
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return wantarray ? ($nfound, $timeleft) : $nfound; |
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} |
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} |
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=head1 REPOSITORY |
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L |
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=head1 AUTHOR |
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173
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Felipe Gasper (FELIPE) |
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… with special thanks to Mario Roy (MARIOROY) for extra testing |
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and a few fixes/improvements. |
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178
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=head1 COPYRIGHT |
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Copyright 2017 by L |
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=head1 LICENSE |
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184
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This distribution is released under the same license as Perl. |
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186
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=cut |
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1; |