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Tatsuhiko Miyagawa
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Plack::Util - Utility subroutines for Plack server and framework developers


  my $true  = Plack::Util::TRUE;
  my $false = Plack::Util::FALSE;

Utility constants to include when you specify boolean variables in $env hash (e.g. psgi.multithread).

  my $class = Plack::Util::load_class($class [, $prefix ]);

Constructs a class name and require the class. Throws an exception if the .pm file for the class is not found, just with the built-in require.

If $prefix is set, the class name is prepended to the $class unless $class begins with + sign, which means the class name is already fully qualified.

  my $class = Plack::Util::load_class("Foo");                   # Foo
  my $class = Plack::Util::load_class("Baz", "Foo::Bar");       # Foo::Bar::Baz
  my $class = Plack::Util::load_class("+XYZ::ZZZ", "Foo::Bar"); # XYZ::ZZZ
  if ( Plack::Util::is_real_fh($fh) ) { }

returns true if a given $fh is a real file handle that has a file descriptor. It returns false if $fh is PerlIO handle that is not really related to the underlying file etc.

  my $cl = Plack::Util::content_length($body);

Returns the length of content from body if it can be calculated. If $body is an array ref it's a sum of length of each chunk, if $body is a real filehandle it's a remaining size of the filehandle, otherwise returns undef.

  Plack::Util::set_io_path($fh, "/path/to/foobar.txt");

Sets the (absolute) file path to $fh filehandle object, so you can call $fh->path on it. As a side effect $fh is blessed to an internal package but it can still be treated as a normal file handle.

This module doesn't normalize or absolutize the given path, and is intended to be used from Server or Middleware implementations. See also IO::File::WithPath.

  Plack::Util::foreach($body, $cb);

Iterate through $body which is an array reference or IO::Handle-like object and pass each line (which is NOT really guaranteed to be a line) to the callback function.

It internally sets the buffer length $/ to 4096 in case it reads the binary file, unless otherwise set in the caller's code.

  my $app = Plack::Util::load_psgi $app_psgi;

Load app.psgi file and evaluate the code to get PSGI application handler. If the file can't be loaded (e.g. file doesn't exist or has a perl syntax error), it will throw an exception.

  my $res = Plack::Util::run_app $app, $env;

Runs the $app by wrapping errors with eval and if an error is found, logs it to $env->{'psgi.errors'} and returns the template 500 Error response.

header_get, header_exists, header_set, header_push, header_remove
  my $hdrs = [ 'Content-Type' => 'text/plain' ];

  my $v = Plack::Util::header_get($hdrs, $key); # First found only
  my @v = Plack::Util::header_get($hdrs, $key);
  my $bool = Plack::Util::header_exists($hdrs, $key);
  Plack::Util::header_set($hdrs, $key, $val);   # overwrites existent header
  Plack::Util::header_push($hdrs, $key, $val);
  Plack::Util::header_remove($hdrs, $key);

Utility functions to manipulate PSGI response headers array reference. The methods that read existent header value handles header name as case insensitive.

  my $hdrs = [ 'Content-Type' => 'text/plain' ];
  my $v = Plack::Util::header_get('content-type'); # 'text/plain'
  my $headers = [ 'Content-Type' => 'text/plain' ];

  my $h = Plack::Util::headers($headers);
  if ($h->exists($key)) { ... }
  $h->set($key => $val);
  $h->push($key => $val);
  $h->headers; # same reference as $headers

Given a header array reference, returns a convenient object that has an instance methods to access header_* functions with an OO interface. The object holds a reference to the original given $headers argument and updates the reference accordingly when called write methods like set, push or remove. It also has headers method that would return the same reference.

  if (status_with_no_entity_body($res->[0])) { }

Returns true if the given status code doesn't have any Entity body in HTTP response, i.e. it's 100, 101, 204 or 304.

  my $o = Plack::Util::inline_object(
      write => sub { $h->push_write(@_) },
      close => sub { $h->push_shutdown },

Creates an instant object that can react to methods passed in the constructor. Handy to create when you need to create an IO stream object for input or errors.