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) [MANDATORY]

Set the callback to be called on EOF.

=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}  ) or Carp::croak "mandatory argument on_eof is missing");

   $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);
   }
}

=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:	1.15
Committed:	Sat May 17 21:34:15 2008 UTC (16 years ago) by root
Branch:	MAIN
CVS Tags:	rel-3_5
Changes since 1.14:	+3 -1 lines
Log Message:	* empty log message *
#	Content
1	package AnyEvent::Handle;
2
3	no warnings;
4	use strict;
5
6	use AnyEvent ();
7	use AnyEvent::Util ();
8	use Scalar::Util ();
9	use Carp ();
10	use Fcntl ();
11	use Errno qw/EAGAIN EINTR/;
12
13	=head1 NAME
14
15	AnyEvent::Handle - non-blocking I/O on filehandles via AnyEvent
16
17	This module is experimental.
18
19	=cut
20
21	our $VERSION = '0.04';
22
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	#TODO
33
34	# 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	#TODO
43	);
44
45	$cv->wait;
46
47	=head1 DESCRIPTION
48
49	This module is a helper module to make it easier to do event-based I/O on
50	filehandles. For utility functions for doing non-blocking connects and accepts
51	on sockets see L<AnyEvent::Util>.
52
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
57	All callbacks will be invoked with the handle object as their first
58	argument.
59
60	=head1 METHODS
61
62	=over 4
63
64	=item B<new (%args)>
65
66	The constructor supports these arguments (all as key => value pairs).
67
68	=over 4
69
70	=item fh => $filehandle [MANDATORY]
71
72	The filehandle this L<AnyEvent::Handle> object will operate on.
73
74	NOTE: The filehandle will be set to non-blocking (using
75	AnyEvent::Util::fh_nonblocking).
76
77	=item on_eof => $cb->($self) [MANDATORY]
78
79	Set the callback to be called on EOF.
80
81	=item on_error => $cb->($self)
82
83	This is the fatal error callback, that is called when, well, a fatal error
84	ocurs, such as not being able to resolve the hostname, failure to connect
85	or a read error.
86
87	The object will not be in a usable state when this callback has been
88	called.
89
90	On callback entrance, the value of C<$!> contains the operating system
91	error (or C<ENOSPC> or C<EPIPE>).
92
93	While not mandatory, it is I<highly> recommended to set this callback, as
94	you will not be notified of errors otherwise. The default simply calls
95	die.
96
97	=item on_read => $cb->($self)
98
99	This sets the default read callback, which is called when data arrives
100	and no read request is in the queue.
101
102	To access (and remove data from) the read buffer, use the C<< ->rbuf >>
103	method or acces sthe C<$self->{rbuf}> member directly.
104
105	When an EOF condition is detected then AnyEvent::Handle will first try to
106	feed all the remaining data to the queued callbacks and C<on_read> before
107	calling the C<on_eof> callback. If no progress can be made, then a fatal
108	error will be raised (with C<$!> set to C<EPIPE>).
109
110	=item on_drain => $cb->()
111
112	This sets the callback that is called when the write buffer becomes empty
113	(or when the callback is set and the buffer is empty already).
114
115	To append to the write buffer, use the C<< ->push_write >> method.
116
117	=item rbuf_max => <bytes>
118
119	If defined, then a fatal error will be raised (with C<$!> set to C<ENOSPC>)
120	when the read buffer ever (strictly) exceeds this size. This is useful to
121	avoid denial-of-service attacks.
122
123	For example, a server accepting connections from untrusted sources should
124	be configured to accept only so-and-so much data that it cannot act on
125	(for example, when expecting a line, an attacker could send an unlimited
126	amount of data without a callback ever being called as long as the line
127	isn't finished).
128
129	=item read_size => <bytes>
130
131	The default read block size (the amount of bytes this module will try to read
132	on each [loop iteration). Default: C<4096>.
133
134	=item low_water_mark => <bytes>
135
136	Sets the amount of bytes (default: C<0>) that make up an "empty" write
137	buffer: If the write reaches this size or gets even samller it is
138	considered empty.
139
140	=back
141
142	=cut
143
144	sub new {
145	my $class = shift;
146
147	my $self = bless { @_ }, $class;
148
149	$self->{fh} or Carp::croak "mandatory argument fh is missing";
150
151	AnyEvent::Util::fh_nonblocking $self->{fh}, 1;
152
153	$self->on_eof ((delete $self->{on_eof} ) or Carp::croak "mandatory argument on_eof is missing");
154
155	$self->on_error (delete $self->{on_error}) if $self->{on_error};
156	$self->on_drain (delete $self->{on_drain}) if $self->{on_drain};
157	$self->on_read (delete $self->{on_read} ) if $self->{on_read};
158
159	$self->start_read;
160
161	$self
162	}
163
164	sub _shutdown {
165	my ($self) = @_;
166
167	delete $self->{rw};
168	delete $self->{ww};
169	delete $self->{fh};
170	}
171
172	sub error {
173	my ($self) = @_;
174
175	{
176	local $!;
177	$self->_shutdown;
178	}
179
180	if ($self->{on_error}) {
181	$self->{on_error}($self);
182	} else {
183	die "AnyEvent::Handle uncaught fatal error: $!";
184	}
185	}
186
187	=item $fh = $handle->fh
188
189	This method returns the filehandle of the L<AnyEvent::Handle> object.
190
191	=cut
192
193	sub fh { $_[0]->{fh} }
194
195	=item $handle->on_error ($cb)
196
197	Replace the current C<on_error> callback (see the C<on_error> constructor argument).
198
199	=cut
200
201	sub on_error {
202	$_[0]{on_error} = $_[1];
203	}
204
205	=item $handle->on_eof ($cb)
206
207	Replace the current C<on_eof> callback (see the C<on_eof> constructor argument).
208
209	=cut
210
211	sub on_eof {
212	$_[0]{on_eof} = $_[1];
213	}
214
215	#############################################################################
216
217	=back
218
219	=head2 WRITE QUEUE
220
221	AnyEvent::Handle manages two queues per handle, one for writing and one
222	for reading.
223
224	The write queue is very simple: you can add data to its end, and
225	AnyEvent::Handle will automatically try to get rid of it for you.
226
227	When data could be writtena nd the write buffer is shorter then the low
228	water mark, the C<on_drain> callback will be invoked.
229
230	=over 4
231
232	=item $handle->on_drain ($cb)
233
234	Sets the C<on_drain> callback or clears it (see the description of
235	C<on_drain> in the constructor).
236
237	=cut
238
239	sub on_drain {
240	my ($self, $cb) = @_;
241
242	$self->{on_drain} = $cb;
243
244	$cb->($self)
245	if $cb && $self->{low_water_mark} >= length $self->{wbuf};
246	}
247
248	=item $handle->push_write ($data)
249
250	Queues the given scalar to be written. You can push as much data as you
251	want (only limited by the available memory), as C<AnyEvent::Handle>
252	buffers it independently of the kernel.
253
254	=cut
255
256	sub push_write {
257	my ($self, $data) = @_;
258
259	$self->{wbuf} .= $data;
260
261	unless ($self->{ww}) {
262	Scalar::Util::weaken $self;
263	my $cb = sub {
264	my $len = syswrite $self->{fh}, $self->{wbuf};
265
266	if ($len > 0) {
267	substr $self->{wbuf}, 0, $len, "";
268
269
270	$self->{on_drain}($self)
271	if $self->{low_water_mark} >= length $self->{wbuf}
272	&& $self->{on_drain};
273
274	delete $self->{ww} unless length $self->{wbuf};
275	} elsif ($! != EAGAIN && $! != EINTR) {
276	$self->error;
277	}
278	};
279
280	$self->{ww} = AnyEvent->io (fh => $self->{fh}, poll => "w", cb => $cb);
281
282	$cb->($self);
283	};
284	}
285
286	#############################################################################
287
288	=back
289
290	=head2 READ QUEUE
291
292	AnyEvent::Handle manages two queues per handle, one for writing and one
293	for reading.
294
295	The read queue is more complex than the write queue. It can be used in two
296	ways, the "simple" way, using only C<on_read> and the "complex" way, using
297	a queue.
298
299	In the simple case, you just install an C<on_read> callback and whenever
300	new data arrives, it will be called. You can then remove some data (if
301	enough is there) from the read buffer (C<< $handle->rbuf >>) if you want
302	or not.
303
304	In the more complex case, you want to queue multiple callbacks. In this
305	case, AnyEvent::Handle will call the first queued callback each time new
306	data arrives and removes it when it has done its job (see C<push_read>,
307	below).
308
309	This way you can, for example, push three line-reads, followed by reading
310	a chunk of data, and AnyEvent::Handle will execute them in order.
311
312	Example 1: EPP protocol parser. EPP sends 4 byte length info, followed by
313	the specified number of bytes which give an XML datagram.
314
315	# in the default state, expect some header bytes
316	$handle->on_read (sub {
317	# some data is here, now queue the length-header-read (4 octets)
318	shift->unshift_read_chunk (4, sub {
319	# header arrived, decode
320	my $len = unpack "N", $_[1];
321
322	# now read the payload
323	shift->unshift_read_chunk ($len, sub {
324	my $xml = $_[1];
325	# handle xml
326	});
327	});
328	});
329
330	Example 2: Implement a client for a protocol that replies either with
331	"OK" and another line or "ERROR" for one request, and 64 bytes for the
332	second request. Due tot he availability of a full queue, we can just
333	pipeline sending both requests and manipulate the queue as necessary in
334	the callbacks:
335
336	# request one
337	$handle->push_write ("request 1\015\012");
338
339	# we expect "ERROR" or "OK" as response, so push a line read
340	$handle->push_read_line (sub {
341	# if we got an "OK", we have to _prepend_ another line,
342	# so it will be read before the second request reads its 64 bytes
343	# which are already in the queue when this callback is called
344	# we don't do this in case we got an error
345	if ($_[1] eq "OK") {
346	$_[0]->unshift_read_line (sub {
347	my $response = $_[1];
348	...
349	});
350	}
351	});
352
353	# request two
354	$handle->push_write ("request 2\015\012");
355
356	# simply read 64 bytes, always
357	$handle->push_read_chunk (64, sub {
358	my $response = $_[1];
359	...
360	});
361
362	=over 4
363
364	=cut
365
366	sub _drain_rbuf {
367	my ($self) = @_;
368
369	return if $self->{in_drain};
370	local $self->{in_drain} = 1;
371
372	while (my $len = length $self->{rbuf}) {
373	no strict 'refs';
374	if (my $cb = shift @{ $self->{queue} }) {
375	if (!$cb->($self)) {
376	if ($self->{eof}) {
377	# no progress can be made (not enough data and no data forthcoming)
378	$! = &Errno::EPIPE; return $self->error;
379	}
380
381	unshift @{ $self->{queue} }, $cb;
382	return;
383	}
384	} elsif ($self->{on_read}) {
385	$self->{on_read}($self);
386
387	if (
388	$self->{eof} # if no further data will arrive
389	&& $len == length $self->{rbuf} # and no data has been consumed
390	&& !@{ $self->{queue} } # and the queue is still empty
391	&& $self->{on_read} # and we still want to read data
392	) {
393	# then no progress can be made
394	$! = &Errno::EPIPE; return $self->error;
395	}
396	} else {
397	# read side becomes idle
398	delete $self->{rw};
399	return;
400	}
401	}
402
403	if ($self->{eof}) {
404	$self->_shutdown;
405	$self->{on_eof}($self);
406	}
407	}
408
409	=item $handle->on_read ($cb)
410
411	This replaces the currently set C<on_read> callback, or clears it (when
412	the new callback is C<undef>). See the description of C<on_read> in the
413	constructor.
414
415	=cut
416
417	sub on_read {
418	my ($self, $cb) = @_;
419
420	$self->{on_read} = $cb;
421	}
422
423	=item $handle->rbuf
424
425	Returns the read buffer (as a modifiable lvalue).
426
427	You can access the read buffer directly as the C<< ->{rbuf} >> member, if
428	you want.
429
430	NOTE: The read buffer should only be used or modified if the C<on_read>,
431	C<push_read> or C<unshift_read> methods are used. The other read methods
432	automatically manage the read buffer.
433
434	=cut
435
436	sub rbuf : lvalue {
437	$_[0]{rbuf}
438	}
439
440	=item $handle->push_read ($cb)
441
442	=item $handle->unshift_read ($cb)
443
444	Append the given callback to the end of the queue (C<push_read>) or
445	prepend it (C<unshift_read>).
446
447	The callback is called each time some additional read data arrives.
448
449	It must check wether enough data is in the read buffer already.
450
451	If not enough data is available, it must return the empty list or a false
452	value, in which case it will be called repeatedly until enough data is
453	available (or an error condition is detected).
454
455	If enough data was available, then the callback must remove all data it is
456	interested in (which can be none at all) and return a true value. After returning
457	true, it will be removed from the queue.
458
459	=cut
460
461	sub push_read {
462	my ($self, $cb) = @_;
463
464	push @{ $self->{queue} }, $cb;
465	$self->_drain_rbuf;
466	}
467
468	sub unshift_read {
469	my ($self, $cb) = @_;
470
471	push @{ $self->{queue} }, $cb;
472	$self->_drain_rbuf;
473	}
474
475	=item $handle->push_read_chunk ($len, $cb->($self, $data))
476
477	=item $handle->unshift_read_chunk ($len, $cb->($self, $data))
478
479	Append the given callback to the end of the queue (C<push_read_chunk>) or
480	prepend it (C<unshift_read_chunk>).
481
482	The callback will be called only once C<$len> bytes have been read, and
483	these C<$len> bytes will be passed to the callback.
484
485	=cut
486
487	sub _read_chunk($$) {
488	my ($self, $len, $cb) = @_;
489
490	sub {
491	$len <= length $_[0]{rbuf} or return;
492	$cb->($_[0], substr $_[0]{rbuf}, 0, $len, "");
493	1
494	}
495	}
496
497	sub push_read_chunk {
498	$_[0]->push_read (&_read_chunk);
499	}
500
501
502	sub unshift_read_chunk {
503	$_[0]->unshift_read (&_read_chunk);
504	}
505
506	=item $handle->push_read_line ([$eol, ]$cb->($self, $line, $eol))
507
508	=item $handle->unshift_read_line ([$eol, ]$cb->($self, $line, $eol))
509
510	Append the given callback to the end of the queue (C<push_read_line>) or
511	prepend it (C<unshift_read_line>).
512
513	The callback will be called only once a full line (including the end of
514	line marker, C<$eol>) has been read. This line (excluding the end of line
515	marker) will be passed to the callback as second argument (C<$line>), and
516	the end of line marker as the third argument (C<$eol>).
517
518	The end of line marker, C<$eol>, can be either a string, in which case it
519	will be interpreted as a fixed record end marker, or it can be a regex
520	object (e.g. created by C<qr>), in which case it is interpreted as a
521	regular expression.
522
523	The end of line marker argument C<$eol> is optional, if it is missing (NOT
524	undef), then C<qr\|\015?\012\|> is used (which is good for most internet
525	protocols).
526
527	Partial lines at the end of the stream will never be returned, as they are
528	not marked by the end of line marker.
529
530	=cut
531
532	sub _read_line($$) {
533	my $self = shift;
534	my $cb = pop;
535	my $eol = @_ ? shift : qr\|(\015?\012)\|;
536	my $pos;
537
538	$eol = quotemeta $eol unless ref $eol;
539	$eol = qr\|^(.*?)($eol)\|s;
540
541	sub {
542	$_[0]{rbuf} =~ s/$eol// or return;
543
544	$cb->($_[0], $1, $2);
545	1
546	}
547	}
548
549	sub push_read_line {
550	$_[0]->push_read (&_read_line);
551	}
552
553	sub unshift_read_line {
554	$_[0]->unshift_read (&_read_line);
555	}
556
557	=item $handle->stop_read
558
559	=item $handle->start_read
560
561	In rare cases you actually do not want to read anything form the
562	socket. In this case you can call C<stop_read>. Neither C<on_read> no
563	any queued callbacks will be executed then. To start readign again, call
564	C<start_read>.
565
566	=cut
567
568	sub stop_read {
569	my ($self) = @_;
570
571	delete $self->{rw};
572	}
573
574	sub start_read {
575	my ($self) = @_;
576
577	unless ($self->{rw} \|\| $self->{eof}) {
578	Scalar::Util::weaken $self;
579
580	$self->{rw} = AnyEvent->io (fh => $self->{fh}, poll => "r", cb => sub {
581	my $len = sysread $self->{fh}, $self->{rbuf}, $self->{read_size} \|\| 8192, length $self->{rbuf};
582
583	if ($len > 0) {
584	if (defined $self->{rbuf_max}) {
585	if ($self->{rbuf_max} < length $self->{rbuf}) {
586	$! = &Errno::ENOSPC; return $self->error;
587	}
588	}
589
590	} elsif (defined $len) {
591	$self->{eof} = 1;
592	delete $self->{rw};
593
594	} elsif ($! != EAGAIN && $! != EINTR) {
595	return $self->error;
596	}
597
598	$self->_drain_rbuf;
599	});
600	}
601	}
602
603	=back
604
605	=head1 AUTHOR
606
607	Robin Redeker C<< <elmex at ta-sa.org> >>, Marc Lehmann <schmorp@schmorp.de>.
608
609	=cut
610
611	1; # End of AnyEvent::Handle