Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl Monk, Perl Meditation
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??

I'm trying to write out a filehandle using Dancer2. The data may come from a live video stream, so the filehandle must be streamed in chunks, not returned all at once.

The documention for Dancer2::Manual has this to say about send_file():

"You can use around to get all the content (whether a filehandle if it's a regular file or a full string if it's a scalar ref) and decide what to do with it"

This and the example code suggests to me that I can pass the filehandle as the first argument to send_file(), and then the around callback will get the filehandle as its second argument. Here's an attempt at that:

return send_file( $in_fh, streaming => 1, content_type => $mime_type, callbacks => { around => sub { my ($writer, $content) = @_; my $buf = ''; while( read( $content, $buf, VID_READ_LENGTH ) ) { $writer->write( $buf ); } } }, );

This results in the error:

Device::WebIO::Dancer:5371] error @2014-08-13 18:01:28> Route exceptio +n: isa check for "path_info" failed: GLOB(0x222a5c8) is not a string! + at (eval 197) line 27.

OK, so the first argument can't be a filehandle. Maybe I can pass a dummy string as a scalar ref (which is documented to work) and then have the callback use $in_fh directly as a closure:

return send_file( \'foo', streaming => 1, content_type => $mime_type, callbacks => { around => sub { my ($writer, $content) = @_; my $buf = ''; while( read( $in_fh, $buf, VID_READ_LENGTH ) ) { $writer->write( $buf ); } } }, );

But the output of this is "foo", as if the callback is not being used at all.

OK, let's try passing a dummy file and see if the callback is called:

return send_file( '/dev/zero', streaming => 1, system_path => 1, content_type => $mime_type, callbacks => { around => sub { my ($writer, $content) = @_; my $buf = ''; while( read( $in_fh, $buf, VID_READ_LENGTH ) ) { $writer->write( $buf ); } } }, );

Even with system_path and /dev/zero existing on my system, this gives an HTTP 404 error.

Is there any way to coerce Dancer2 into streaming the filehandle? It feels like this shouldn't require callbacks at all, just:

return send_file( '$in_fh, streaming => 1, content_type => $mime_type, );

"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.


In reply to Write a Filehandle w/Dancer2 by hardburn

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others sharing their wisdom with the Monastery: (6)
As of 2024-03-28 22:57 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found