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.