Provided by: libparanoid-perl_2.10-1_all 
NAME
Paranoid::IO::FileMultiplexer::Block::FileHeader - File Header Block
VERSION
$Id: lib/Paranoid/IO/FileMultiplexer/Block/FileHeader.pm, 2.10 2022/03/08 00:01:04
acorliss Exp $
SYNOPSIS
$obj = Paranoid::IO::FileMultiplexer::Block::FileHeader->new(
$filename, $bsize);
$count = $obj->blocks;
$version = $obj->version;
%streams = $obj->streams;
$max = $obj->maxStreams;
%model = $obj->model;
$rv = $obj->writeSig;
$rv = $obj->readSig;
$rv = $obj->writeBlocks;
$count = $obj->readBlocks;
$rv = $obj->incrBlocks;
$rv = $obj->validateBlocks;
$rv = $obj->writeStreams;
$rv = $obj->readStreams;
$rv = $obj->addStream($sname, $bn);
DESCRIPTION
This class is not meant to be used directly, but as part of the
Paranoid::IO::FileMultiplexer functionality. This provides functionality necessary for
manipulation of the file header block.
This module does presume that whatever file it is being used on has already been opened in
the appropriate mode, and that the Paranoid::IO flock stack has been enabled. For the
purposes of Paranoid::IO::FileMultiplexer, this is done in that class.
SUBROUTINES/METHODS
new
$obj =
Paranoid::IO::FileMultiplexer::Block::FileHeader->new($file, $blockSize);
This creates a new instance of a file header block object. It requires the filename in
order to retrieve the cached file handle from Paranoid::IO, and the size of the block.
This always writes to the first block of the file.
NOTE: creating an object does not automatically create the file and/or write a signature.
That must be done using the methods below.
blocks
$count = $obj->blocks;
This method returns the value of the blocks field in the file header. This is the total
number of blocks allocated in the file to date. Note that this is only the cached value
stored in the object. Other methods are provided for writing and reading the value from
the file.
version
$ver = $obj->version;
This method returns the file format version as a string.
streams
%streams = $obj->streams;
This method returns a hash of streams allocated in the file, in the format of stream name
=> block number.
maxStreams
$max = $obj->maxStreams;
This method returns the maximum number of streams supported by this file header.
model
$stats = $obj->model;
This method returns a hash with some basic statistical information on the file, in both
raw and human-friendly values. The information provided is as follows:
Key Description
---------------------------------------------------------------
intSize Size of Perl's native integers in bits
curFileSize Current file size in bytes
curFSHuman Current file size expressed w/unit suffixes
curStreams Current number of streams allocated
maxFileSize Maximum file size supported with Perl
maxFSHuman Maximum file size expressed w/unit suffixes
maxStreams Maximum number of streams that can be allocated
maxStreamSize Maximum stream size
maxSSHuman Maximum stream size expressed w/unit suffixes
writeSig
$rv = $obj->writeSig;
This method writes the file header signature to disk, returning a boolean value denoting
its success. Note that the signature contains the file format, version, block size, and
number of allocated blocks, but not the list of allocated streams.
readSig
$rv = $obj->readSig;
This method reads the file header signature from disk and performs basic validation that
the information in it is acceptable. It validates that the file size matches the block
size * block count, that the block size is an acceptable value, and the file format and
version are supported.
If the method call was successful it will update the cached values in the object. Note
that this is only the signature values, not the stream index records.
writeBlocks
$rv = $obj->writeBlocks($count);
This method writes the passed block count value to disk, and returns a boolean value
denoting success.
readBlocks
$count = $obj->readBlocks;
This method reads the block count field from disk and returns it. If there are any errors
reading or extracting the value, it will return undef.
incrBlocks
$rv = $obj->incrBlocks;
This method calls writeBlocks with a value of one greater that what's currently cached.
validateBlocks
$rv = $obj->validateBlocks;
This method compares the cached block count value to what's actually written in the file.
This is useful for determining whether an external process has potentially modified the
file.
writeStreams
$rv = $obj->writeStreams;
This method writes the stream index records to the header block, and returns a boolean
denoting success.
readStreams
$rv = $obj->readStreams;
This method reads the stream index records from the file, and returns a boolean value
denoting success. If the read is successful, this will update the cached streams
information in the object.
addStream
$rv = $obj->addStream($sname, $bn);
This method does some basic validation of the requested stream, and if it passes, updates
the stream indices on the disk.
DEPENDENCIES
o Fcntl
o Paranoid
o Paranoid::Debug
o Paranoid::Data
o Paranoid::IO
o Paranoid::IO::FileMultiplexer::Block
o Paranoid::IO::FileMultiplexer::Block::BATHeader
o Paranoid::IO::FileMultiplexer::Block::StreamHeader
BUGS AND LIMITATIONS
AUTHOR
Arthur Corliss (corliss@digitalmages.com)
LICENSE AND COPYRIGHT
This software is free software. Similar to Perl, you can redistribute it and/or modify it
under the terms of either:
a) the GNU General Public License
<https://www.gnu.org/licenses/gpl-1.0.html> as published by the
Free Software Foundation <http://www.fsf.org/>; either version 1
<https://www.gnu.org/licenses/gpl-1.0.html>, or any later version
<https://www.gnu.org/licenses/license-list.html#GNUGPL>, or
b) the Artistic License 2.0
<https://opensource.org/licenses/Artistic-2.0>,
subject to the following additional term: No trademark rights to "Paranoid" have been or
are conveyed under any of the above licenses. However, "Paranoid" may be used fairly to
describe this unmodified software, in good faith, but not as a trademark.
(c) 2005 - 2021, Arthur Corliss (corliss@digitalmages.com) (tm) 2008 - 2021, Paranoid Inc.
(www.paranoid.com)
perl v5.34.0 Paranoid::IO::FileMultiplexer::Block::FileHeader(3pm)