[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent/Handle.pm

Comparing AnyEvent/lib/AnyEvent/Handle.pm (file contents):
Revision 1.83 by root, Thu Aug 21 19:11:37 2008 UTC vs.
Revision 1.95 by root, Thu Oct 2 06:42:39 2008 UTC

 AnyEvent::Handle - non-blocking I/O on file handles via AnyEvent
 =cut
-our $VERSION = 4.232;
+our $VERSION = 4.3;
 =head1 SYNOPSIS
    use AnyEvent;
    use AnyEvent::Handle;
 This module is a helper module to make it easier to do event-based I/O on
 filehandles. For utility functions for doing non-blocking connects and accepts
 on sockets see L<AnyEvent::Util>.
+The L<AnyEvent::Intro> tutorial contains some well-documented
+AnyEvent::Handle examples.
 In the following, when the documentation refers to of "bytes" then this
 means characters. As sysread and syswrite are used for all I/O, their
 treatment of characters applies to this module as well.
 All callbacks will be invoked with the handle object as their first
 argument.
+=head2 SIGPIPE is not handled by this module
+SIGPIPE is not handled by this module, so one of the practical
+requirements of using it is to ignore SIGPIPE (C<$SIG{PIPE} =
+'IGNORE'>). At least, this is highly recommend in a networked program: If
+you use AnyEvent::Handle in a filter program (like sort), exiting on
+SIGPIPE is probably the right thing to do.
 =head1 METHODS
 =over 4
 occured, such as not being able to resolve the hostname, failure to
 connect or a read error.
 Some errors are fatal (which is indicated by C<$fatal> being true). On
 fatal errors the handle object will be shut down and will not be usable
-(but you are free to look at the current C< ->rbuf >). Examples of fatal
+(but you are free to look at the current C<< ->rbuf >>). Examples of fatal
 errors are an EOF condition with active (but unsatisifable) read watchers
 (C<EPIPE>) or I/O errors.
 Non-fatal errors can be retried by simply returning, but it is recommended
 to simply ignore this parameter and instead abondon the handle object
 =item timeout => $fractional_seconds
 If non-zero, then this enables an "inactivity" timeout: whenever this many
 seconds pass without a successful read or write on the underlying file
 handle, the C<on_timeout> callback will be invoked (and if that one is
-missing, an C<ETIMEDOUT> error will be raised).
+missing, a non-fatal C<ETIMEDOUT> error will be raised).
 Note that timeout processing is also active when you currently do not have
 any outstanding read or write requests: If you plan to keep the connection
 idle then you should disable the timout temporarily or ignore the timeout
-in the C<on_timeout> callback.
+in the C<on_timeout> callback, in which case AnyEvent::Handle will simply
+restart the timeout.
 Zero (the default) disables this timeout.
 =item on_timeout => $cb->($handle)
 =item rbuf_max => <bytes>
 If defined, then a fatal error will be raised (with C<$!> set to C<ENOSPC>)
 when the read buffer ever (strictly) exceeds this size. This is useful to
-avoid denial-of-service attacks.
+avoid some forms of denial-of-service attacks.
 For example, a server accepting connections from untrusted sources should
 be configured to accept only so-and-so much data that it cannot act on
 (for example, when expecting a line, an attacker could send an unlimited
 amount of data without a callback ever being called as long as the line
 isn't finished).
 =item autocork => <boolean>
 When disabled (the default), then C<push_write> will try to immediately
-write the data to the handle if possible. This avoids having to register
+write the data to the handle, if possible. This avoids having to register
-a write watcher and wait for the next event loop iteration, but can be
+a write watcher and wait for the next event loop iteration, but can
-inefficient if you write multiple small chunks (this disadvantage is
+be inefficient if you write multiple small chunks (on the wire, this
-usually avoided by your kernel's nagle algorithm, see C<low_delay>).
+disadvantage is usually avoided by your kernel's nagle algorithm, see
+C<no_delay>, but this option can save costly syscalls).
 When enabled, then writes will always be queued till the next event loop
 iteration. This is efficient when you do many small writes per iteration,
-but less efficient when you do a single write only.
+but less efficient when you do a single write only per iteration (or when
+the write buffer often is full). It also increases write latency.
 =item no_delay => <boolean>
 When doing small writes on sockets, your operating system kernel might
 wait a bit for more data before actually sending it out. This is called
 the Nagle algorithm, and usually it is beneficial.
-In some situations you want as low a delay as possible, which cna be
+In some situations you want as low a delay as possible, which can be
-accomplishd by setting this option to true.
+accomplishd by setting this option to a true value.
-The default is your opertaing system's default behaviour, this option
+The default is your opertaing system's default behaviour (most likely
-explicitly enables or disables it, if possible.
+enabled), this option explicitly enables or disables it, if possible.
 =item read_size => <bytes>
-The default read block size (the amount of bytes this module will try to read
+The default read block size (the amount of bytes this module will
-during each (loop iteration). Default: C<8192>.
+try to read during each loop iteration, which affects memory
+requirements). Default: C<8192>.
 =item low_water_mark => <bytes>
 Sets the amount of bytes (default: C<0>) that make up an "empty" write
 buffer: If the write reaches this size or gets even samller it is
 considered empty.
+Sometimes it can be beneficial (for performance reasons) to add data to
+the write buffer before it is fully drained, but this is a rare case, as
+the operating system kernel usually buffers data as well, so the default
+is good in almost all cases.
 =item linger => <seconds>
 If non-zero (default: C<3600>), then the destructor of the
-AnyEvent::Handle object will check wether there is still outstanding write
+AnyEvent::Handle object will check whether there is still outstanding
-data and will install a watcher that will write out this data. No errors
+write data and will install a watcher that will write this data to the
-will be reported (this mostly matches how the operating system treats
+socket. No errors will be reported (this mostly matches how the operating
-outstanding data at socket close time).
+system treats outstanding data at socket close time).
-This will not work for partial TLS data that could not yet been
+This will not work for partial TLS data that could not be encoded
-encoded. This data will be lost.
+yet. This data will be lost. Calling the C<stoptls> method in time might
+help.
 =item tls => "accept" | "connect" | Net::SSLeay::SSL object
-When this parameter is given, it enables TLS (SSL) mode, that means it
+When this parameter is given, it enables TLS (SSL) mode, that means
-will start making tls handshake and will transparently encrypt/decrypt
+AnyEvent will start a TLS handshake as soon as the conenction has been
-data.
+established and will transparently encrypt/decrypt data afterwards.
 TLS mode requires Net::SSLeay to be installed (it will be loaded
-automatically when you try to create a TLS handle).
+automatically when you try to create a TLS handle): this module doesn't
+have a dependency on that module, so if your module requires it, you have
+to add the dependency yourself.
-For the TLS server side, use C<accept>, and for the TLS client side of a
+Unlike TCP, TLS has a server and client side: for the TLS server side, use
-connection, use C<connect> mode.
+C<accept>, and for the TLS client side of a connection, use C<connect>
+mode.
 You can also provide your own TLS connection object, but you have
 to make sure that you call either C<Net::SSLeay::set_connect_state>
 or C<Net::SSLeay::set_accept_state> on it before you pass it to
 AnyEvent::Handle.
-See the C<starttls> method if you need to start TLS negotiation later.
+See the C<< ->starttls >> method for when need to start TLS negotiation later.
 =item tls_ctx => $ssl_ctx
-Use the given Net::SSLeay::CTX object to create the new TLS connection
+Use the given C<Net::SSLeay::CTX> object to create the new TLS connection
 (unless a connection object was specified directly). If this parameter is
 missing, then AnyEvent::Handle will use C<AnyEvent::Handle::TLS_CTX>.
 =item json => JSON or JSON::XS object
 This is the json coder object used by the C<json> read and write types.
 If you don't supply it, then AnyEvent::Handle will create and use a
-suitable one, which will write and expect UTF-8 encoded JSON texts.
+suitable one (on demand), which will write and expect UTF-8 encoded JSON
+texts.
 Note that you are responsible to depend on the JSON module if you want to
 use this functionality, as AnyEvent does not have a dependency itself.
-=item filter_r => $cb
-=item filter_w => $cb
-These exist, but are undocumented at this time.
 =back
 =cut
 sub new {
    $self->{fh} or Carp::croak "mandatory argument fh is missing";
    AnyEvent::Util::fh_nonblocking $self->{fh}, 1;
-   if ($self->{tls}) {
-      require Net::SSLeay;
-      $self->starttls (delete $self->{tls}, delete $self->{tls_ctx});
+   $self->starttls (delete $self->{tls}, delete $self->{tls_ctx})
-   }
+      if $self->{tls};
    $self->{_activity} = AnyEvent->now;
    $self->_timeout;
    $self->on_drain (delete $self->{on_drain}) if exists $self->{on_drain};
    delete $self->{_tw};
    delete $self->{_rw};
    delete $self->{_ww};
    delete $self->{fh};
-   $self->stoptls;
+   &_freetls;
    delete $self->{on_read};
    delete $self->{_queue};
 }
    }
 }
 =item $fh = $handle->fh
-This method returns the file handle of the L<AnyEvent::Handle> object.
+This method returns the file handle used to create the L<AnyEvent::Handle> object.
 =cut
 sub fh { $_[0]{fh} }
    $_[0]{on_eof} = $_[1];
 }
 =item $handle->on_timeout ($cb)
-Replace the current C<on_timeout> callback, or disables the callback
+Replace the current C<on_timeout> callback, or disables the callback (but
-(but not the timeout) if C<$cb> = C<undef>. See C<timeout> constructor
+not the timeout) if C<$cb> = C<undef>. See the C<timeout> constructor
-argument.
+argument and method.
 =cut
 sub on_timeout {
    $_[0]{on_timeout} = $_[1];
    my ($self, $cb) = @_;
    $self->{on_drain} = $cb;
    $cb->($self)
-      if $cb && $self->{low_water_mark} >= length $self->{wbuf};
+      if $cb && $self->{low_water_mark} >= (length $self->{wbuf}) + (length $self->{_tls_wbuf});
 }
 =item $handle->push_write ($data)
 Queues the given scalar to be written. You can push as much data as you
             substr $self->{wbuf}, 0, $len, "";
             $self->{_activity} = AnyEvent->now;
             $self->{on_drain}($self)
-               if $self->{low_water_mark} >= length $self->{wbuf}
+               if $self->{low_water_mark} >= (length $self->{wbuf}) + (length $self->{_tls_wbuf})
                   && $self->{on_drain};
             delete $self->{_ww} unless length $self->{wbuf};
          } elsif ($! != EAGAIN && $! != EINTR && $! != WSAEWOULDBLOCK) {
             $self->_error ($!, 1);
       @_ = ($WH{$type} or Carp::croak "unsupported type passed to AnyEvent::Handle::push_write")
            ->($self, @_);
    }
-   if ($self->{filter_w}) {
+   if ($self->{tls}) {
-      $self->{filter_w}($self, \$_[0]);
+      $self->{_tls_wbuf} .= $_[0];
+      &_dotls ($self);
    } else {
       $self->{wbuf} .= $_[0];
       $self->_drain_wbuf;
    }
 }
             last; # more data might arrive
          }
       } else {
          # read side becomes idle
-         delete $self->{_rw};
+         delete $self->{_rw} unless $self->{tls};
          last;
       }
    }
    if ($self->{_eof}) {
 Note that AnyEvent::Handle will automatically C<start_read> for you when
 you change the C<on_read> callback or push/unshift a read callback, and it
 will automatically C<stop_read> for you when neither C<on_read> is set nor
 there are any read requests in the queue.
+These methods will have no effect when in TLS mode (as TLS doesn't support
+half-duplex connections).
 =cut
 sub stop_read {
    my ($self) = @_;
-   delete $self->{_rw};
+   delete $self->{_rw} unless $self->{tls};
 }
 sub start_read {
    my ($self) = @_;
    unless ($self->{_rw} || $self->{_eof}) {
       Scalar::Util::weaken $self;
       $self->{_rw} = AnyEvent->io (fh => $self->{fh}, poll => "r", cb => sub {
-         my $rbuf = $self->{filter_r} ? \my $buf : \$self->{rbuf};
+         my $rbuf = \($self->{tls} ? my $buf : $self->{rbuf});
          my $len = sysread $self->{fh}, $$rbuf, $self->{read_size} || 8192, length $$rbuf;
          if ($len > 0) {
             $self->{_activity} = AnyEvent->now;
-            $self->{filter_r}
+            if ($self->{tls}) {
-               ? $self->{filter_r}($self, $rbuf)
+               Net::SSLeay::BIO_write ($self->{_rbio}, $$rbuf);
-               : $self->{_in_drain} || $self->_drain_rbuf;
+               &_dotls ($self);
+            } else {
+               $self->_drain_rbuf unless $self->{_in_drain};
+            }
          } elsif (defined $len) {
             delete $self->{_rw};
             $self->{_eof} = 1;
             $self->_drain_rbuf unless $self->{_in_drain};
       while ((my $len = Net::SSLeay::write ($self->{tls}, $self->{_tls_wbuf})) > 0) {
          substr $self->{_tls_wbuf}, 0, $len, "";
       }
    }
-   if (length ($buf = Net::SSLeay::BIO_read ($self->{_wbio}))) {
-      $self->{wbuf} .= $buf;
-      $self->_drain_wbuf;
-   }
    while (defined ($buf = Net::SSLeay::read ($self->{tls}))) {
-      if (length $buf) {
+      unless (length $buf) {
-         $self->{rbuf} .= $buf;
-         $self->_drain_rbuf unless $self->{_in_drain};
-      } else {
          # let's treat SSL-eof as we treat normal EOF
+         delete $self->{_rw};
          $self->{_eof} = 1;
-         $self->_shutdown;
+         &_freetls;
-         return;
       }
+      $self->{rbuf} .= $buf;
+      $self->_drain_rbuf unless $self->{_in_drain};
+      $self->{tls} or return; # tls session might have gone away in callback
    }
    my $err = Net::SSLeay::get_error ($self->{tls}, -1);
    if ($err!= Net::SSLeay::ERROR_WANT_READ ()) {
          return $self->_error (&Errno::EIO, 1);
       }
       # all others are fine for our purposes
    }
+   if (length ($buf = Net::SSLeay::BIO_read ($self->{_wbio}))) {
+      $self->{wbuf} .= $buf;
+      $self->_drain_wbuf;
+   }
 }
 =item $handle->starttls ($tls[, $tls_ctx])
 Instead of starting TLS negotiation immediately when the AnyEvent::Handle
 The TLS connection object will end up in C<< $handle->{tls} >> after this
 call and can be used or changed to your liking. Note that the handshake
 might have already started when this function returns.
+If it an error to start a TLS handshake more than once per
+AnyEvent::Handle object (this is due to bugs in OpenSSL).
 =cut
 sub starttls {
    my ($self, $ssl, $ctx) = @_;
-   $self->stoptls;
+   require Net::SSLeay;
+   Carp::croak "it is an error to call starttls more than once on an Anyevent::Handle object"
+      if $self->{tls};
    if ($ssl eq "accept") {
       $ssl = Net::SSLeay::new ($ctx || TLS_CTX ());
       Net::SSLeay::set_accept_state ($ssl);
    } elsif ($ssl eq "connect") {
       $ssl = Net::SSLeay::new ($ctx || TLS_CTX ());
    # basically, this is deep magic (because SSL_read should have the same issues)
    # but the openssl maintainers basically said: "trust us, it just works".
    # (unfortunately, we have to hardcode constants because the abysmally misdesigned
    # and mismaintained ssleay-module doesn't even offer them).
    # http://www.mail-archive.com/openssl-dev@openssl.org/msg22420.html
+   #
+   # in short: this is a mess.
+   #
+   # note that we do not try to keep the length constant between writes as we are required to do.
+   # we assume that most (but not all) of this insanity only applies to non-blocking cases,
+   # and we drive openssl fully in blocking mode here. Or maybe we don't - openssl seems to
+   # have identity issues in that area.
    Net::SSLeay::CTX_set_mode ($self->{tls},
       (eval { local $SIG{__DIE__}; Net::SSLeay::MODE_ENABLE_PARTIAL_WRITE () } || 1)
       | (eval { local $SIG{__DIE__}; Net::SSLeay::MODE_ACCEPT_MOVING_WRITE_BUFFER () } || 2));
    $self->{_rbio} = Net::SSLeay::BIO_new (Net::SSLeay::BIO_s_mem ());
    $self->{_wbio} = Net::SSLeay::BIO_new (Net::SSLeay::BIO_s_mem ());
    Net::SSLeay::set_bio ($ssl, $self->{_rbio}, $self->{_wbio});
-   $self->{filter_w} = sub {
+   &_dotls; # need to trigger the initial handshake
-      $_[0]{_tls_wbuf} .= ${$_[1]};
+   $self->start_read; # make sure we actually do read
-      &_dotls;
-   };
-   $self->{filter_r} = sub {
-      Net::SSLeay::BIO_write ($_[0]{_rbio}, ${$_[1]});
-      &_dotls;
-   };
 }
 =item $handle->stoptls
-Destroys the SSL connection, if any. Partial read or write data will be
+Shuts down the SSL connection - this makes a proper EOF handshake by
-lost.
+sending a close notify to the other side, but since OpenSSL doesn't
+support non-blocking shut downs, it is not possible to re-use the stream
+afterwards.
 =cut
 sub stoptls {
    my ($self) = @_;
+   if ($self->{tls}) {
+      Net::SSLeay::shutdown ($self->{tls});
+      &_dotls;
+      # we don't give a shit. no, we do, but we can't. no...
+      # we, we... have to use openssl :/
+      &_freetls;
+   }
+}
+sub _freetls {
+   my ($self) = @_;
+   return unless $self->{tls};
-   Net::SSLeay::free (delete $self->{tls}) if $self->{tls};
+   Net::SSLeay::free (delete $self->{tls});
-   delete $self->{_rbio};
+   delete @$self{qw(_rbio _wbio _tls_wbuf)};
-   delete $self->{_wbio};
-   delete $self->{_tls_wbuf};
-   delete $self->{filter_r};
-   delete $self->{filter_w};
 }
 sub DESTROY {
    my $self = shift;
-   $self->stoptls;
+   &_freetls;
    my $linger = exists $self->{linger} ? $self->{linger} : 3600;
    if ($linger && length $self->{wbuf}) {
       my $fh   = delete $self->{fh};
    }
 }
 =back
+=head1 NONFREQUENTLY ASKED QUESTIONS
+=over 4
+=item How do I read data until the other side closes the connection?
+If you just want to read your data into a perl scalar, the easiest way to achieve this is
+by setting an C<on_read> callback that does nothing, clearing the C<on_eof> callback
+and in the C<on_error> callback, the data will be in C<$_[0]{rbuf}>:
+   $handle->on_read (sub { });
+   $handle->on_eof (undef);
+   $handle->on_error (sub {
+      my $data = delete $_[0]{rbuf};
+      undef $handle;
+   });
+The reason to use C<on_error> is that TCP connections, due to latencies
+and packets loss, might get closed quite violently with an error, when in
+fact, all data has been received.
+It is usually better to use acknowledgements when transfering data,
+to make sure the other side hasn't just died and you got the data
+intact. This is also one reason why so many internet protocols have an
+explicit QUIT command.
+=item I don't want to destroy the handle too early - how do I wait until all data has been sent?
+After writing your last bits of data, set the C<on_drain> callback
+and destroy the handle in there - with the default setting of
+C<low_water_mark> this will be called precisely when all data has been
+written to the socket:
+   $handle->push_write (...);
+   $handle->on_drain (sub {
+      warn "all data submitted to the kernel\n";
+      undef $handle;
+   });
+=back
 =head1 SUBCLASSING AnyEvent::Handle
 In many cases, you might want to subclass AnyEvent::Handle.
 To make this easier, a given version of AnyEvent::Handle uses these

Diff Legend

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Comparing AnyEvent/lib/AnyEvent/Handle.pm (file contents): Revision 1.83 by root, Thu Aug 21 19:11:37 2008 UTC vs. Revision 1.95 by root, Thu Oct 2 06:42:39 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent/Handle.pm (file contents):
Revision 1.83 by root, Thu Aug 21 19:11:37 2008 UTC vs.
Revision 1.95 by root, Thu Oct 2 06:42:39 2008 UTC