Scroll to navigation

Feersum::Connection::Handle(3pm) User Contributed Perl Documentation Feersum::Connection::Handle(3pm)

NAME

Feersum::Connection::Handle - PSGI-style reader/writer objects.

SYNOPSIS

For read handles:

    my $buf;
    my $r = delete $env{'psgi.input'};
    $r->read($buf, 1, 1); # read the second byte of input without moving offset
    $r->read($buf, $env{CONTENT_LENGTH}); # append the whole input
    $r->close(); # discards any un-read() data
    # assuming the handle is "open":
    $r->seek(2,SEEK_CUR); # returns 1, discards skipped bytes
    $r->seek(-1,SEEK_CUR); # returns 0, can't seek back
    
    # not yet supported, throws exception:
    # $r->poll_cb(sub { .... });

For write handles:

    $w->write("scalar");
    $w->write(\"scalar ref");
    $w->write_array(\@some_stuff);
    $w->poll_cb(sub {
        # use $_[0] instead of $w to avoid a closure
        $_[0]->write(\"some data");
        # can close() or unregister the poll_cb in here
        $_[0]->close();
    });

For both:

    $h->response_guard(guard { response_is_complete() });

DESCRIPTION

See the PSGI spec for more information on how read/write handles are used (The Delayed Response and Streaming Body section has details on the writer).

METHODS

Reader methods

The reader is obtained via "$env->{'psgi.input'}".

"$r->read($buf, $len)"
Read the first $len bytes of the request body into the buffer specified by $buf (similar to how sysread works).

The calls to "$r->read()" will never block. Currently, the entire body is read into memory (or perhaps to a temp file) before the Feersum request handler is even called. This behaviour MAY change. Regardless, Feersum will be doing some buffering so "psgix.input.buffered" is set in the PSGI env hash.

"$r->seek(...)"
Seeking is partially supported. Feersum discards skipped-over bytes to conserve memory. 

    $r->seek(0,SEEK_CUR);  # returns 1
    $r->seek(-1,SEEK_CUR); # returns 0
    $r->seek(-1,SEEK_SET); # returns 0
    $r->seek(2,SEEK_CUR); # returns 1, discards skipped bytes
    $r->seek(42,SEEK_SET); # returns 1 if room, discards skipped bytes
    $r->seek(-8,SEEK_END); # returns 1 if room, discards skipped bytes
"$r->close()"
Discards the remainder of the input buffer.
"$r->poll_cb(sub { .... })"
NOT YET SUPPORTED. PSGI only defined poll_cb for the Writer object.

Writer methods.

The writer is obtained under PSGI by sending a code/headers pair to the "starter" callback. Under Feersum, calls to "$req->start_streaming" return one.

"$w->write("scalar")"
Send the scalar as a "T-E: chunked" chunk.

The calls to "$w->write()" will never block and data is buffered until transmitted. This behaviour is indicated by "psgix.output.buffered" in the PSGI env hash (Twiggy supports this too, for example).

"$w->write(\"scalar ref")"
Works just like "write("scalar")" above. This extension is indicated by "psgix.body.scalar_refs" in the PSGI env hash.
"$w->write_array(\@array)"
Pass in an array-ref and it works much like the two "write()" calls above, except it's way more efficient than calling "write()" over and over. Undefined elements of the array are ignored.
"$w->close()"
Close the HTTP response (which triggers the "T-E: chunked" terminating chunk to be sent). This method is implicitly called when the last reference to the writer is dropped.
"$w->poll_cb(sub { .... })"
Register a callback to be called when the write buffer is empty. Pass in "undef" to unset. The sub can call "close()".

A reference to the writer is passed in as the first and only argument to the sub. It's recommended that you use $_[0] rather than closing-over on $w to prevent a circular reference.

Common methods.

Methods in common to both types of handles.

"$h->response_guard($guard)"
Register a guard to be triggered when the response is completely sent and the socket is closed. A "guard" in this context is some object that will do something interesting in its DESTROY/DEMOLISH method. For example, Guard.

The guard is *not* attached to this handle object; the guard is attached to the response.

"psgix.output.guard" is the PSGI-env extension that indicates this method.

"$h->fileno"
Returns the file descriptor number for this connection.

AUTHOR

Jeremy Stashewsky, "stash@cpan.org"

COPYRIGHT AND LICENSE

Copyright (C) 2010 by Jeremy Stashewsky & Socialtext Inc.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.7 or, at your option, any later version of Perl 5 you may have available.

2018-03-22 perl v5.26.1