lib/AnyEvent/Handle.pm

package AnyEvent::Handle;

no warnings;
use strict;

use AnyEvent ();
use AnyEvent::Util ();
use Scalar::Util ();
use Carp ();
use Fcntl ();
use Errno qw/EAGAIN EINTR/;

=head1 NAME

AnyEvent::Handle - non-blocking I/O on filehandles via AnyEvent

This module is experimental.

=cut

our $VERSION = '0.04';

=head1 SYNOPSIS

   use AnyEvent;
   use AnyEvent::Handle;

   my $cv = AnyEvent->condvar;

   my $ae_fh = AnyEvent::Handle->new (fh => \*STDIN);

   #TODO

   # or use the constructor to pass the callback:

   my $ae_fh2 =
      AnyEvent::Handle->new (
         fh => \*STDIN,
         on_eof => sub {
            $cv->broadcast;
         },
         #TODO
      );

   $cv->wait;

=head1 DESCRIPTION

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>.

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.

=head1 METHODS

=over 4

=item B<new (%args)>

The constructor supports these arguments (all as key => value pairs).

=over 4

=item fh => $filehandle [MANDATORY]

The filehandle this L<AnyEvent::Handle> object will operate on.

NOTE: The filehandle will be set to non-blocking (using
AnyEvent::Util::fh_nonblocking).

=item on_eof => $cb->($self)

Set the callback to be called on EOF.

While not mandatory, it is highly recommended to set an eof callback,
otherwise you might end up with a closed socket while you are still
waiting for data.

=item on_error => $cb->($self)

This is the fatal error callback, that is called when, well, a fatal error
ocurs, such as not being able to resolve the hostname, failure to connect
or a read error.

The object will not be in a usable state when this callback has been
called.

On callback entrance, the value of C<$!> contains the operating system
error (or C<ENOSPC> or C<EPIPE>).

While not mandatory, it is I<highly> recommended to set this callback, as
you will not be notified of errors otherwise. The default simply calls
die.

=item on_read => $cb->($self)

This sets the default read callback, which is called when data arrives
and no read request is in the queue.

To access (and remove data from) the read buffer, use the C<< ->rbuf >>
method or acces sthe C<$self->{rbuf}> member directly.

When an EOF condition is detected then AnyEvent::Handle will first try to
feed all the remaining data to the queued callbacks and C<on_read> before
calling the C<on_eof> callback. If no progress can be made, then a fatal
error will be raised (with C<$!> set to C<EPIPE>).

=item on_drain => $cb->()

This sets the callback that is called when the write buffer becomes empty
(or when the callback is set and the buffer is empty already).

To append to the write buffer, use the C<< ->push_write >> method.

=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.

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 read_size => <bytes>

The default read block size (the amount of bytes this module will try to read
on each [loop iteration). Default: C<4096>.

=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.

=back

=cut

sub new {
   my $class = shift;

   my $self = bless { @_ }, $class;

   $self->{fh} or Carp::croak "mandatory argument fh is missing";

   AnyEvent::Util::fh_nonblocking $self->{fh}, 1;

   $self->on_eof   (delete $self->{on_eof}  ) if $self->{on_eof};
   $self->on_error (delete $self->{on_error}) if $self->{on_error};
   $self->on_drain (delete $self->{on_drain}) if $self->{on_drain};
   $self->on_read  (delete $self->{on_read} ) if $self->{on_read};

   $self->start_read;

   $self
}

sub _shutdown {
   my ($self) = @_;

   delete $self->{rw};
   delete $self->{ww};
   delete $self->{fh};
}

sub error {
   my ($self) = @_;

   {
      local $!;
      $self->_shutdown;
   }

   if ($self->{on_error}) {
      $self->{on_error}($self);
   } else {
      die "AnyEvent::Handle uncaught fatal error: $!";
   }
}

=item $fh = $handle->fh

This method returns the filehandle of the L<AnyEvent::Handle> object.

=cut

sub fh { $_[0]->{fh} }

=item $handle->on_error ($cb)

Replace the current C<on_error> callback (see the C<on_error> constructor argument).

=cut

sub on_error {
   $_[0]{on_error} = $_[1];
}

=item $handle->on_eof ($cb)

Replace the current C<on_eof> callback (see the C<on_eof> constructor argument).

=cut

sub on_eof {
   $_[0]{on_eof} = $_[1];
}

#############################################################################

=back

=head2 WRITE QUEUE

AnyEvent::Handle manages two queues per handle, one for writing and one
for reading.

The write queue is very simple: you can add data to its end, and
AnyEvent::Handle will automatically try to get rid of it for you.

When data could be writtena nd the write buffer is shorter then the low
water mark, the C<on_drain> callback will be invoked.

=over 4

=item $handle->on_drain ($cb)

Sets the C<on_drain> callback or clears it (see the description of
C<on_drain> in the constructor).

=cut

sub on_drain {
   my ($self, $cb) = @_;

   $self->{on_drain} = $cb;

   $cb->($self)
      if $cb && $self->{low_water_mark} >= length $self->{wbuf};
}

=item $handle->push_write ($data)

Queues the given scalar to be written. You can push as much data as you
want (only limited by the available memory), as C<AnyEvent::Handle>
buffers it independently of the kernel.

=cut

sub push_write {
   my ($self, $data) = @_;

   $self->{wbuf} .= $data;

   unless ($self->{ww}) {
      Scalar::Util::weaken $self;
      my $cb = sub {
         my $len = syswrite $self->{fh}, $self->{wbuf};

         if ($len > 0) {
            substr $self->{wbuf}, 0, $len, "";


            $self->{on_drain}($self)
               if $self->{low_water_mark} >= length $self->{wbuf}
                  && $self->{on_drain};

            delete $self->{ww} unless length $self->{wbuf};
         } elsif ($! != EAGAIN && $! != EINTR) {
            $self->error;
         }
      };

      $self->{ww} = AnyEvent->io (fh => $self->{fh}, poll => "w", cb => $cb);

      $cb->($self);
   };
}

#############################################################################

=back

=head2 READ QUEUE

AnyEvent::Handle manages two queues per handle, one for writing and one
for reading.

The read queue is more complex than the write queue. It can be used in two
ways, the "simple" way, using only C<on_read> and the "complex" way, using
a queue.

In the simple case, you just install an C<on_read> callback and whenever
new data arrives, it will be called. You can then remove some data (if
enough is there) from the read buffer (C<< $handle->rbuf >>) if you want
or not.

In the more complex case, you want to queue multiple callbacks. In this
case, AnyEvent::Handle will call the first queued callback each time new
data arrives and removes it when it has done its job (see C<push_read>,
below).

This way you can, for example, push three line-reads, followed by reading
a chunk of data, and AnyEvent::Handle will execute them in order.

Example 1: EPP protocol parser. EPP sends 4 byte length info, followed by
the specified number of bytes which give an XML datagram.

   # in the default state, expect some header bytes
   $handle->on_read (sub {
      # some data is here, now queue the length-header-read (4 octets)
      shift->unshift_read_chunk (4, sub {
         # header arrived, decode
         my $len = unpack "N", $_[1];

         # now read the payload
         shift->unshift_read_chunk ($len, sub {
            my $xml = $_[1];
            # handle xml
         });
      });
   });

Example 2: Implement a client for a protocol that replies either with
"OK" and another line or "ERROR" for one request, and 64 bytes for the
second request. Due tot he availability of a full queue, we can just
pipeline sending both requests and manipulate the queue as necessary in
the callbacks:

   # request one
   $handle->push_write ("request 1\015\012");

   # we expect "ERROR" or "OK" as response, so push a line read
   $handle->push_read_line (sub {
      # if we got an "OK", we have to _prepend_ another line,
      # so it will be read before the second request reads its 64 bytes
      # which are already in the queue when this callback is called
      # we don't do this in case we got an error
      if ($_[1] eq "OK") {
         $_[0]->unshift_read_line (sub {
            my $response = $_[1];
            ...
         });
      }
   });

   # request two
   $handle->push_write ("request 2\015\012");

   # simply read 64 bytes, always
   $handle->push_read_chunk (64, sub {
      my $response = $_[1];
      ...
   });

=over 4

=cut

sub _drain_rbuf {
   my ($self) = @_;

   return if $self->{in_drain};
   local $self->{in_drain} = 1;

   while (my $len = length $self->{rbuf}) {
      no strict 'refs';
      if (my $cb = shift @{ $self->{queue} }) {
         if (!$cb->($self)) {
            if ($self->{eof}) {
               # no progress can be made (not enough data and no data forthcoming)
               $! = &Errno::EPIPE; return $self->error;
            }

            unshift @{ $self->{queue} }, $cb;
            return;
         }
      } elsif ($self->{on_read}) {
         $self->{on_read}($self);

         if (
            $self->{eof}                    # if no further data will arrive
            && $len == length $self->{rbuf} # and no data has been consumed
            && !@{ $self->{queue} }         # and the queue is still empty
            && $self->{on_read}             # and we still want to read data
         ) {
            # then no progress can be made
            $! = &Errno::EPIPE; return $self->error;
         }
      } else {
         # read side becomes idle
         delete $self->{rw};
         return;
      }
   }

   if ($self->{eof}) {
      $self->_shutdown;
      $self->{on_eof}($self)
         if $self->{on_eof};
   }
}

=item $handle->on_read ($cb)

This replaces the currently set C<on_read> callback, or clears it (when
the new callback is C<undef>). See the description of C<on_read> in the
constructor.

=cut

sub on_read {
   my ($self, $cb) = @_;

   $self->{on_read} = $cb;
}

=item $handle->rbuf

Returns the read buffer (as a modifiable lvalue).

You can access the read buffer directly as the C<< ->{rbuf} >> member, if
you want.

NOTE: The read buffer should only be used or modified if the C<on_read>,
C<push_read> or C<unshift_read> methods are used. The other read methods
automatically manage the read buffer.

=cut

sub rbuf : lvalue {
   $_[0]{rbuf}
}

=item $handle->push_read ($cb)

=item $handle->unshift_read ($cb)

Append the given callback to the end of the queue (C<push_read>) or
prepend it (C<unshift_read>).

The callback is called each time some additional read data arrives.

It must check wether enough data is in the read buffer already.

If not enough data is available, it must return the empty list or a false
value, in which case it will be called repeatedly until enough data is
available (or an error condition is detected).

If enough data was available, then the callback must remove all data it is
interested in (which can be none at all) and return a true value. After returning
true, it will be removed from the queue.

=cut

sub push_read {
   my ($self, $cb) = @_;

   push @{ $self->{queue} }, $cb;
   $self->_drain_rbuf;
}

sub unshift_read {
   my ($self, $cb) = @_;

   push @{ $self->{queue} }, $cb;
   $self->_drain_rbuf;
}

=item $handle->push_read_chunk ($len, $cb->($self, $data))

=item $handle->unshift_read_chunk ($len, $cb->($self, $data))

Append the given callback to the end of the queue (C<push_read_chunk>) or
prepend it (C<unshift_read_chunk>).

The callback will be called only once C<$len> bytes have been read, and
these C<$len> bytes will be passed to the callback.

=cut

sub _read_chunk($$) {
   my ($self, $len, $cb) = @_;

   sub {
      $len <= length $_[0]{rbuf} or return;
      $cb->($_[0], substr $_[0]{rbuf}, 0, $len, "");
      1
   }
}

sub push_read_chunk {
   $_[0]->push_read (&_read_chunk);
}


sub unshift_read_chunk {
   $_[0]->unshift_read (&_read_chunk);
}

=item $handle->push_read_line ([$eol, ]$cb->($self, $line, $eol))

=item $handle->unshift_read_line ([$eol, ]$cb->($self, $line, $eol))

Append the given callback to the end of the queue (C<push_read_line>) or
prepend it (C<unshift_read_line>).

The callback will be called only once a full line (including the end of
line marker, C<$eol>) has been read. This line (excluding the end of line
marker) will be passed to the callback as second argument (C<$line>), and
the end of line marker as the third argument (C<$eol>).

The end of line marker, C<$eol>, can be either a string, in which case it
will be interpreted as a fixed record end marker, or it can be a regex
object (e.g. created by C<qr>), in which case it is interpreted as a
regular expression.

The end of line marker argument C<$eol> is optional, if it is missing (NOT
undef), then C<qr|\015?\012|> is used (which is good for most internet
protocols).

Partial lines at the end of the stream will never be returned, as they are
not marked by the end of line marker.

=cut

sub _read_line($$) {
   my $self = shift;
   my $cb = pop;
   my $eol = @_ ? shift : qr|(\015?\012)|;
   my $pos;

   $eol = quotemeta $eol unless ref $eol;
   $eol = qr|^(.*?)($eol)|s;

   sub {
      $_[0]{rbuf} =~ s/$eol// or return;

      $cb->($_[0], $1, $2);
      1
   }
}

sub push_read_line {
   $_[0]->push_read (&_read_line);
}

sub unshift_read_line {
   $_[0]->unshift_read (&_read_line);
}

=item $handle->stop_read

=item $handle->start_read

In rare cases you actually do not want to read anything form the
socket. In this case you can call C<stop_read>. Neither C<on_read> no
any queued callbacks will be executed then. To start readign again, call
C<start_read>.

=cut

sub stop_read {
   my ($self) = @_;

   delete $self->{rw};
}

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 $len = sysread $self->{fh}, $self->{rbuf}, $self->{read_size} || 8192, length $self->{rbuf};

         if ($len > 0) {
            if (defined $self->{rbuf_max}) {
               if ($self->{rbuf_max} < length $self->{rbuf}) {
                  $! = &Errno::ENOSPC; return $self->error;
               }
            }

         } elsif (defined $len) {
            $self->{eof} = 1;
            delete $self->{rw};

         } elsif ($! != EAGAIN && $! != EINTR) {
            return $self->error;
         }

         $self->_drain_rbuf;
      });
   }
}

=back

=head1 AUTHOR

Robin Redeker C<< <elmex at ta-sa.org> >>, Marc Lehmann <schmorp@schmorp.de>.

=cut

1; # End of AnyEvent::Handle
Revision:	1.16
Committed:	Fri May 23 05:16:57 2008 UTC (16 years ago) by root
Branch:	MAIN
Changes since 1.15:	+8 -4 lines
Log Message:	implement vc support
#	User	Rev	Content
1	elmex	1.1	package AnyEvent::Handle;
2
3	elmex	1.6	no warnings;
4	elmex	1.1	use strict;
5
6	root	1.8	use AnyEvent ();
7			use AnyEvent::Util ();
8			use Scalar::Util ();
9			use Carp ();
10			use Fcntl ();
11	elmex	1.1	use Errno qw/EAGAIN EINTR/;
12
13			=head1 NAME
14
15			AnyEvent::Handle - non-blocking I/O on filehandles via AnyEvent
16
17	root	1.15	This module is experimental.
18
19	elmex	1.1	=cut
20
21	root	1.15	our $VERSION = '0.04';
22	elmex	1.1
23			=head1 SYNOPSIS
24
25			use AnyEvent;
26			use AnyEvent::Handle;
27
28			my $cv = AnyEvent->condvar;
29
30			my $ae_fh = AnyEvent::Handle->new (fh => \*STDIN);
31
32	root	1.8	#TODO
33	elmex	1.1
34	elmex	1.2	# or use the constructor to pass the callback:
35
36			my $ae_fh2 =
37			AnyEvent::Handle->new (
38			fh => \*STDIN,
39			on_eof => sub {
40			$cv->broadcast;
41			},
42	root	1.8	#TODO
43	elmex	1.2	);
44
45	elmex	1.1	$cv->wait;
46
47			=head1 DESCRIPTION
48
49	root	1.8	This module is a helper module to make it easier to do event-based I/O on
50	elmex	1.13	filehandles. For utility functions for doing non-blocking connects and accepts
51			on sockets see L<AnyEvent::Util>.
52	root	1.8
53			In the following, when the documentation refers to of "bytes" then this
54			means characters. As sysread and syswrite are used for all I/O, their
55			treatment of characters applies to this module as well.
56	elmex	1.1
57	root	1.8	All callbacks will be invoked with the handle object as their first
58			argument.
59	elmex	1.1
60			=head1 METHODS
61
62			=over 4
63
64			=item B<new (%args)>
65
66	root	1.8	The constructor supports these arguments (all as key => value pairs).
67	elmex	1.1
68			=over 4
69
70	root	1.8	=item fh => $filehandle [MANDATORY]
71	elmex	1.1
72			The filehandle this L<AnyEvent::Handle> object will operate on.
73
74	root	1.8	NOTE: The filehandle will be set to non-blocking (using
75			AnyEvent::Util::fh_nonblocking).
76
77	root	1.16	=item on_eof => $cb->($self)
78	root	1.10
79			Set the callback to be called on EOF.
80	root	1.8
81	root	1.16	While not mandatory, it is highly recommended to set an eof callback,
82			otherwise you might end up with a closed socket while you are still
83			waiting for data.
84
85	root	1.10	=item on_error => $cb->($self)
86
87			This is the fatal error callback, that is called when, well, a fatal error
88			ocurs, such as not being able to resolve the hostname, failure to connect
89			or a read error.
90	root	1.8
91			The object will not be in a usable state when this callback has been
92			called.
93
94	root	1.10	On callback entrance, the value of C<$!> contains the operating system
95	root	1.8	error (or C<ENOSPC> or C<EPIPE>).
96
97	root	1.10	While not mandatory, it is I<highly> recommended to set this callback, as
98			you will not be notified of errors otherwise. The default simply calls
99			die.
100	root	1.8
101			=item on_read => $cb->($self)
102
103			This sets the default read callback, which is called when data arrives
104	root	1.10	and no read request is in the queue.
105	root	1.8
106			To access (and remove data from) the read buffer, use the C<< ->rbuf >>
107			method or acces sthe C<$self->{rbuf}> member directly.
108
109			When an EOF condition is detected then AnyEvent::Handle will first try to
110			feed all the remaining data to the queued callbacks and C<on_read> before
111			calling the C<on_eof> callback. If no progress can be made, then a fatal
112			error will be raised (with C<$!> set to C<EPIPE>).
113	elmex	1.1
114	root	1.8	=item on_drain => $cb->()
115	elmex	1.1
116	root	1.8	This sets the callback that is called when the write buffer becomes empty
117			(or when the callback is set and the buffer is empty already).
118	elmex	1.1
119	root	1.8	To append to the write buffer, use the C<< ->push_write >> method.
120	elmex	1.2
121	root	1.8	=item rbuf_max => <bytes>
122	elmex	1.2
123	root	1.8	If defined, then a fatal error will be raised (with C<$!> set to C<ENOSPC>)
124			when the read buffer ever (strictly) exceeds this size. This is useful to
125			avoid denial-of-service attacks.
126	elmex	1.2
127	root	1.8	For example, a server accepting connections from untrusted sources should
128			be configured to accept only so-and-so much data that it cannot act on
129			(for example, when expecting a line, an attacker could send an unlimited
130			amount of data without a callback ever being called as long as the line
131			isn't finished).
132	elmex	1.2
133	root	1.8	=item read_size => <bytes>
134	elmex	1.2
135	root	1.8	The default read block size (the amount of bytes this module will try to read
136			on each [loop iteration). Default: C<4096>.
137
138			=item low_water_mark => <bytes>
139
140			Sets the amount of bytes (default: C<0>) that make up an "empty" write
141			buffer: If the write reaches this size or gets even samller it is
142			considered empty.
143	elmex	1.2
144	elmex	1.1	=back
145
146			=cut
147
148			sub new {
149	root	1.8	my $class = shift;
150
151			my $self = bless { @_ }, $class;
152
153			$self->{fh} or Carp::croak "mandatory argument fh is missing";
154
155			AnyEvent::Util::fh_nonblocking $self->{fh}, 1;
156	elmex	1.1
157	root	1.16	$self->on_eof (delete $self->{on_eof} ) if $self->{on_eof};
158	root	1.10	$self->on_error (delete $self->{on_error}) if $self->{on_error};
159	root	1.8	$self->on_drain (delete $self->{on_drain}) if $self->{on_drain};
160			$self->on_read (delete $self->{on_read} ) if $self->{on_read};
161	elmex	1.1
162	root	1.10	$self->start_read;
163
164	root	1.8	$self
165			}
166	elmex	1.2
167	root	1.8	sub _shutdown {
168			my ($self) = @_;
169	elmex	1.2
170	root	1.8	delete $self->{rw};
171			delete $self->{ww};
172			delete $self->{fh};
173			}
174
175			sub error {
176			my ($self) = @_;
177
178			{
179			local $!;
180			$self->_shutdown;
181	elmex	1.1	}
182
183	root	1.10	if ($self->{on_error}) {
184			$self->{on_error}($self);
185			} else {
186			die "AnyEvent::Handle uncaught fatal error: $!";
187			}
188	elmex	1.1	}
189
190	root	1.8	=item $fh = $handle->fh
191	elmex	1.1
192			This method returns the filehandle of the L<AnyEvent::Handle> object.
193
194			=cut
195
196			sub fh { $_[0]->{fh} }
197
198	root	1.8	=item $handle->on_error ($cb)
199	elmex	1.1
200	root	1.8	Replace the current C<on_error> callback (see the C<on_error> constructor argument).
201	elmex	1.1
202	root	1.8	=cut
203
204			sub on_error {
205			$_[0]{on_error} = $_[1];
206			}
207
208			=item $handle->on_eof ($cb)
209
210			Replace the current C<on_eof> callback (see the C<on_eof> constructor argument).
211	elmex	1.1
212			=cut
213
214	root	1.8	sub on_eof {
215			$_[0]{on_eof} = $_[1];
216			}
217
218	root	1.9	#############################################################################
219
220			=back
221
222			=head2 WRITE QUEUE
223
224			AnyEvent::Handle manages two queues per handle, one for writing and one
225			for reading.
226
227			The write queue is very simple: you can add data to its end, and
228			AnyEvent::Handle will automatically try to get rid of it for you.
229
230			When data could be writtena nd the write buffer is shorter then the low
231			water mark, the C<on_drain> callback will be invoked.
232
233			=over 4
234
235	root	1.8	=item $handle->on_drain ($cb)
236
237			Sets the C<on_drain> callback or clears it (see the description of
238			C<on_drain> in the constructor).
239
240			=cut
241
242			sub on_drain {
243	elmex	1.1	my ($self, $cb) = @_;
244
245	root	1.8	$self->{on_drain} = $cb;
246
247			$cb->($self)
248			if $cb && $self->{low_water_mark} >= length $self->{wbuf};
249			}
250
251			=item $handle->push_write ($data)
252
253			Queues the given scalar to be written. You can push as much data as you
254			want (only limited by the available memory), as C<AnyEvent::Handle>
255			buffers it independently of the kernel.
256
257			=cut
258
259			sub push_write {
260			my ($self, $data) = @_;
261
262			$self->{wbuf} .= $data;
263
264			unless ($self->{ww}) {
265			Scalar::Util::weaken $self;
266			my $cb = sub {
267			my $len = syswrite $self->{fh}, $self->{wbuf};
268
269			if ($len > 0) {
270			substr $self->{wbuf}, 0, $len, "";
271
272
273			$self->{on_drain}($self)
274			if $self->{low_water_mark} >= length $self->{wbuf}
275			&& $self->{on_drain};
276
277			delete $self->{ww} unless length $self->{wbuf};
278			} elsif ($! != EAGAIN && $! != EINTR) {
279			$self->error;
280	elmex	1.1	}
281	root	1.8	};
282
283			$self->{ww} = AnyEvent->io (fh => $self->{fh}, poll => "w", cb => $cb);
284
285			$cb->($self);
286			};
287			}
288
289			#############################################################################
290
291	root	1.9	=back
292
293			=head2 READ QUEUE
294
295			AnyEvent::Handle manages two queues per handle, one for writing and one
296			for reading.
297
298			The read queue is more complex than the write queue. It can be used in two
299			ways, the "simple" way, using only C<on_read> and the "complex" way, using
300			a queue.
301
302			In the simple case, you just install an C<on_read> callback and whenever
303			new data arrives, it will be called. You can then remove some data (if
304			enough is there) from the read buffer (C<< $handle->rbuf >>) if you want
305			or not.
306
307			In the more complex case, you want to queue multiple callbacks. In this
308			case, AnyEvent::Handle will call the first queued callback each time new
309			data arrives and removes it when it has done its job (see C<push_read>,
310			below).
311
312			This way you can, for example, push three line-reads, followed by reading
313			a chunk of data, and AnyEvent::Handle will execute them in order.
314
315			Example 1: EPP protocol parser. EPP sends 4 byte length info, followed by
316			the specified number of bytes which give an XML datagram.
317
318			# in the default state, expect some header bytes
319			$handle->on_read (sub {
320			# some data is here, now queue the length-header-read (4 octets)
321			shift->unshift_read_chunk (4, sub {
322			# header arrived, decode
323			my $len = unpack "N", $_[1];
324
325			# now read the payload
326			shift->unshift_read_chunk ($len, sub {
327			my $xml = $_[1];
328			# handle xml
329			});
330			});
331			});
332
333			Example 2: Implement a client for a protocol that replies either with
334			"OK" and another line or "ERROR" for one request, and 64 bytes for the
335			second request. Due tot he availability of a full queue, we can just
336			pipeline sending both requests and manipulate the queue as necessary in
337			the callbacks:
338
339			# request one
340			$handle->push_write ("request 1\015\012");
341
342			# we expect "ERROR" or "OK" as response, so push a line read
343			$handle->push_read_line (sub {
344			# if we got an "OK", we have to _prepend_ another line,
345			# so it will be read before the second request reads its 64 bytes
346			# which are already in the queue when this callback is called
347			# we don't do this in case we got an error
348			if ($_[1] eq "OK") {
349			$_[0]->unshift_read_line (sub {
350			my $response = $_[1];
351			...
352			});
353			}
354			});
355
356			# request two
357			$handle->push_write ("request 2\015\012");
358
359			# simply read 64 bytes, always
360			$handle->push_read_chunk (64, sub {
361			my $response = $_[1];
362			...
363			});
364
365			=over 4
366
367	root	1.10	=cut
368
369	root	1.8	sub _drain_rbuf {
370			my ($self) = @_;
371	elmex	1.1
372	root	1.11	return if $self->{in_drain};
373	root	1.8	local $self->{in_drain} = 1;
374	elmex	1.1
375	root	1.8	while (my $len = length $self->{rbuf}) {
376			no strict 'refs';
377	root	1.10	if (my $cb = shift @{ $self->{queue} }) {
378			if (!$cb->($self)) {
379			if ($self->{eof}) {
380			# no progress can be made (not enough data and no data forthcoming)
381			$! = &Errno::EPIPE; return $self->error;
382			}
383
384			unshift @{ $self->{queue} }, $cb;
385	root	1.8	return;
386			}
387			} elsif ($self->{on_read}) {
388			$self->{on_read}($self);
389
390			if (
391			$self->{eof} # if no further data will arrive
392			&& $len == length $self->{rbuf} # and no data has been consumed
393			&& !@{ $self->{queue} } # and the queue is still empty
394			&& $self->{on_read} # and we still want to read data
395			) {
396			# then no progress can be made
397			$! = &Errno::EPIPE; return $self->error;
398	elmex	1.1	}
399	root	1.8	} else {
400			# read side becomes idle
401			delete $self->{rw};
402			return;
403			}
404			}
405
406			if ($self->{eof}) {
407			$self->_shutdown;
408	root	1.16	$self->{on_eof}($self)
409			if $self->{on_eof};
410	root	1.8	}
411	elmex	1.1	}
412
413	root	1.8	=item $handle->on_read ($cb)
414	elmex	1.1
415	root	1.8	This replaces the currently set C<on_read> callback, or clears it (when
416			the new callback is C<undef>). See the description of C<on_read> in the
417			constructor.
418	elmex	1.1
419	root	1.8	=cut
420
421			sub on_read {
422			my ($self, $cb) = @_;
423	elmex	1.1
424	root	1.8	$self->{on_read} = $cb;
425	elmex	1.1	}
426
427	root	1.8	=item $handle->rbuf
428
429			Returns the read buffer (as a modifiable lvalue).
430	elmex	1.1
431	root	1.8	You can access the read buffer directly as the C<< ->{rbuf} >> member, if
432			you want.
433	elmex	1.1
434	root	1.8	NOTE: The read buffer should only be used or modified if the C<on_read>,
435			C<push_read> or C<unshift_read> methods are used. The other read methods
436			automatically manage the read buffer.
437	elmex	1.1
438			=cut
439
440	elmex	1.2	sub rbuf : lvalue {
441	root	1.8	$_[0]{rbuf}
442	elmex	1.2	}
443	elmex	1.1
444	root	1.8	=item $handle->push_read ($cb)
445
446			=item $handle->unshift_read ($cb)
447
448			Append the given callback to the end of the queue (C<push_read>) or
449			prepend it (C<unshift_read>).
450
451			The callback is called each time some additional read data arrives.
452	elmex	1.1
453	root	1.8	It must check wether enough data is in the read buffer already.
454	elmex	1.1
455	root	1.8	If not enough data is available, it must return the empty list or a false
456			value, in which case it will be called repeatedly until enough data is
457			available (or an error condition is detected).
458
459			If enough data was available, then the callback must remove all data it is
460			interested in (which can be none at all) and return a true value. After returning
461			true, it will be removed from the queue.
462	elmex	1.1
463			=cut
464
465	root	1.8	sub push_read {
466			my ($self, $cb) = @_;
467	elmex	1.1
468	root	1.8	push @{ $self->{queue} }, $cb;
469			$self->_drain_rbuf;
470	elmex	1.1	}
471
472	root	1.8	sub unshift_read {
473			my ($self, $cb) = @_;
474
475			push @{ $self->{queue} }, $cb;
476			$self->_drain_rbuf;
477			}
478	elmex	1.1
479	root	1.8	=item $handle->push_read_chunk ($len, $cb->($self, $data))
480	elmex	1.1
481	root	1.8	=item $handle->unshift_read_chunk ($len, $cb->($self, $data))
482	elmex	1.1
483	root	1.8	Append the given callback to the end of the queue (C<push_read_chunk>) or
484			prepend it (C<unshift_read_chunk>).
485	elmex	1.1
486	root	1.8	The callback will be called only once C<$len> bytes have been read, and
487			these C<$len> bytes will be passed to the callback.
488	elmex	1.1
489			=cut
490
491	root	1.8	sub _read_chunk($$) {
492	root	1.10	my ($self, $len, $cb) = @_;
493	elmex	1.1
494	root	1.8	sub {
495			$len <= length $_[0]{rbuf} or return;
496	elmex	1.12	$cb->($_[0], substr $_[0]{rbuf}, 0, $len, "");
497	root	1.8	1
498			}
499			}
500
501			sub push_read_chunk {
502	root	1.10	$_[0]->push_read (&_read_chunk);
503	root	1.8	}
504	elmex	1.1
505	elmex	1.5
506	root	1.8	sub unshift_read_chunk {
507	root	1.10	$_[0]->unshift_read (&_read_chunk);
508	elmex	1.1	}
509
510	root	1.8	=item $handle->push_read_line ([$eol, ]$cb->($self, $line, $eol))
511	elmex	1.1
512	root	1.8	=item $handle->unshift_read_line ([$eol, ]$cb->($self, $line, $eol))
513	elmex	1.1
514	root	1.8	Append the given callback to the end of the queue (C<push_read_line>) or
515			prepend it (C<unshift_read_line>).
516	elmex	1.1
517	root	1.8	The callback will be called only once a full line (including the end of
518			line marker, C<$eol>) has been read. This line (excluding the end of line
519			marker) will be passed to the callback as second argument (C<$line>), and
520			the end of line marker as the third argument (C<$eol>).
521	elmex	1.1
522	root	1.8	The end of line marker, C<$eol>, can be either a string, in which case it
523			will be interpreted as a fixed record end marker, or it can be a regex
524			object (e.g. created by C<qr>), in which case it is interpreted as a
525			regular expression.
526	elmex	1.1
527	root	1.8	The end of line marker argument C<$eol> is optional, if it is missing (NOT
528			undef), then C<qr\|\015?\012\|> is used (which is good for most internet
529			protocols).
530	elmex	1.1
531	root	1.8	Partial lines at the end of the stream will never be returned, as they are
532			not marked by the end of line marker.
533	elmex	1.1
534	root	1.8	=cut
535	elmex	1.1
536	root	1.8	sub _read_line($$) {
537	root	1.10	my $self = shift;
538	root	1.8	my $cb = pop;
539			my $eol = @_ ? shift : qr\|(\015?\012)\|;
540			my $pos;
541	elmex	1.1
542	root	1.14	$eol = quotemeta $eol unless ref $eol;
543			$eol = qr\|^(.*?)($eol)\|s;
544	elmex	1.1
545	root	1.8	sub {
546			$_[0]{rbuf} =~ s/$eol// or return;
547	elmex	1.1
548	elmex	1.12	$cb->($_[0], $1, $2);
549	root	1.8	1
550			}
551			}
552	elmex	1.1
553	root	1.8	sub push_read_line {
554	root	1.10	$_[0]->push_read (&_read_line);
555			}
556
557			sub unshift_read_line {
558			$_[0]->unshift_read (&_read_line);
559			}
560
561			=item $handle->stop_read
562
563			=item $handle->start_read
564
565			In rare cases you actually do not want to read anything form the
566			socket. In this case you can call C<stop_read>. Neither C<on_read> no
567			any queued callbacks will be executed then. To start readign again, call
568			C<start_read>.
569
570			=cut
571
572			sub stop_read {
573			my ($self) = @_;
574	elmex	1.1
575	root	1.10	delete $self->{rw};
576	root	1.8	}
577	elmex	1.1
578	root	1.10	sub start_read {
579			my ($self) = @_;
580
581			unless ($self->{rw} \|\| $self->{eof}) {
582			Scalar::Util::weaken $self;
583
584			$self->{rw} = AnyEvent->io (fh => $self->{fh}, poll => "r", cb => sub {
585			my $len = sysread $self->{fh}, $self->{rbuf}, $self->{read_size} \|\| 8192, length $self->{rbuf};
586
587			if ($len > 0) {
588	root	1.11	if (defined $self->{rbuf_max}) {
589	root	1.10	if ($self->{rbuf_max} < length $self->{rbuf}) {
590			$! = &Errno::ENOSPC; return $self->error;
591			}
592			}
593
594			} elsif (defined $len) {
595			$self->{eof} = 1;
596			delete $self->{rw};
597
598			} elsif ($! != EAGAIN && $! != EINTR) {
599			return $self->error;
600			}
601	elmex	1.1
602	root	1.10	$self->_drain_rbuf;
603			});
604			}
605	elmex	1.1	}
606
607			=back
608
609			=head1 AUTHOR
610
611	root	1.8	Robin Redeker C<< <elmex at ta-sa.org> >>, Marc Lehmann <schmorp@schmorp.de>.
612	elmex	1.1
613			=cut
614
615			1; # End of AnyEvent::Handle