PerlIO::Via (Perl in a Nutshell, 2nd Edition)

8.172. PerlIO::Via

A helper class for PerlIO layers implemented in Perl. PerlIO::Via ships with the Perl 5.8 source kit.

For example, you can use PerlIO::Via to call MIME::Base64::encode_base64() via open():

#!/usr/local/bin/perl -w;
use MIME::Base64;
open(my $fh, ">Via(MIME::Base64)", "encode_base64");

PerlIO::Via implements the following methods.

CLOSE

CLOSE(fh)

Returns 0 on success and -1 on error.

EOF

EOF(fh)

Returns end-of-file state. The default behavior is to return a value of FILL() or READ().

ERROR

ERROR(fh)

Returns error state.

FILENO

FILENO(fh)

Returns a numeric value that represents the Unix-like file descriptor, or -1 if no file descriptor exists.

FILL

FILL(fh)

Returns a string that will be placed in the buffer.

FLUSH

FLUSH(fh)

Flushes any buffered write data. Returns 0 on success and -1 on error.

POPPED

POPPED([fh])

Removes a layer from PerlIO::Via.

PUSHED

$class->PUSHED([mode [,fh]])

Returns an object or the class, or -1 on failure. PUSHED takes optional arguments for file open mode—r, w, w+, etc.—and takes a mandatory filehandle for the PerlIO layer itself.

READ

READ(buffer, len, fh)

Returns the number of octets in buffer, which must be less than or equal to len.

SEEK

SEEK(posn, where, fh)

Returns 0 on success and -1 on error.

TELL

TELL(fh)

Returns the file position, without an available default.

UNREAD

UNREAD(buffer, fh)

Returns the number of octets from bufferthat have been successfully saved.

WRITE

WRITE(buffer, fh)

Returns the number of octets in buffer that have been written.