|new ( ARGS )||The constructor is exactly the same as that of FileHandle, except that you can also call it with an existing IO::Handle object to attach unget semantics to a pre-existing handle.|
|$fh->ungetc ( ORD )||Pushes a character with the given ordinal value back onto the given handles input stream. This method can be called more than once in a row to put multiple values back on the stream. Memory usage is equal to the total number of bytes pushed back.|
|$fh->ungets ( BUF )||
Pushes a buffer back onto the given handles input stream. This method can be
called more than once in a row to put multiple buffers of characters back on
the stream. Memory usage is equal to the total number of bytes pushed back.
The buffer is not processed in any waymanaging end-of-line characters and whatnot is your responsibility.
|$fh->buffer ( [BUF] )||Get or set the pushback buffer directly.|
|$fh->input_record_separator ( STRING )||
Get or set the per-filehandle input record separator. If an argument is
specified, the input record separator for the filehandle is made independent of
the global $/. Until this method is called (and after
clear_input_record_separator is called) the global $/ is used.
Note that a return value of undef is ambiguous. It can either mean that this method has never been called with an argument, or it can mean that it was called with an argument of undef.
|$fh->clear_input_record_separator ()||Clear the per-filehandle input record separator. This removes the per-filehandle input record separator semantics, reverting the filehandle to the normal global $/ semantics.|
|tell ( $fh )||
tell returns the actual file position minus the length of the unget buffer.
If you read three bytes, then unget three bytes, tell will report a file
position of 0.
Everything works as expected if you are careful to unget the exact same bytes which you read. However, things get tricky if you unget different bytes. First, the next bytes you read wont be the actual bytes on the filehandle at the position indicated by tell. Second, tell will return a negative number if you unget more bytes than you read. (This can be problematic since this function returns -1 on error.)
|seek ( $fh, [POSITION], [WHENCE] )||
seek defaults to the standard seek if possible, clearing the unget buffer
if it succeeds. If the standard seek fails, then seek will attempt to seek
within the unget buffer. Note that in this case, you will not be able to seek
backwardFileHandle::Unget will only save a buffer for the next bytes to be
For example, lets say you read 10 bytes from a pipe, then unget the 10 bytes. If you seek 5 bytes forward, you wont be able to read the first five bytes. (Otherwise this module would have to keep around a lot of probably useless data!)
To test that this module is indeed a drop-in replacement for FileHandle, the following modules were modified to use FileHandle::Unget, and tested using make test. They have all passed.
There is a bug in Perl on Windows that is exposed if you open a stream, then check for eof, then call binmode. For example:
One solution is to make sure that you only call binmode immediately after opening the filehandle. Im not aware of any workaround for this bug that FileHandle::Unget could implement. However, the module does detect this situation and prints a warning.
Contact email@example.com for bug reports and suggestions.
David Coppit <firstname.lastname@example.org>.
This code is distributed under the GNU General Public License (GPL) Version 2. See the file LICENSE in the distribution for details.
Mail::Mbox::MessageParser for an example of how to use this package.
|perl v5.20.3||FILEHANDLE::UNGET (3)||2015-05-03|