and 1 contributors
Genezzo::BufCa::BCFile.pm - A simple in-memory buffer cache for multiple files for a single process, without locking.
use Genezzo::BufCa::BCFile; # get a buffer cache my $bc = Genezzo::BufCa::BCFile->new(blocksize => 10, numblocks => 5); # register a file my $fileno = Genezzo::BufCa::BCFile->FileReg(FileName => 'file.dat'); # get back some block $bceref = $bc->ReadBlock(filenum => $fileno, blocknum => $blocknum); $bce = $$bceref;
The file buffer cache is a simple module designed to form the basis of a more complicated multi-process buffer cache with locking. The buffer cache contains a number of Buffer Cache Elements (BCEs), a special wrapper class for simple byte buffers (blocks). See L<Genezzo::BufCa::BufCa>. Note that this module does not perform space management or allocation within the files -- it only reads and writes the blocks. The caller is responsible for managing the contents of the file.
Takes arguments blocksize (required, in bytes), numblocks (10 by default). Returns a new buffer cache of the specified number of blocks of size blocksize.
- BCFileInfoByName Return the file state information.
- FileSetHeaderInfoByName Update the datafile header.
Register a file with the cache -- returns a file number. Reregistering a file should return the same number.
Takes argument blocknum, which must be a valid block number, and the argument filenum, which must be a valid file number. If the block is in memory it returns the bceref. If the block is not in the cache it fetches it from disk into an unused block. If the unused block is dirty, then ReadBlock writes it out first. Fails if all blocks are in use.
Write a block to disk. Not really necessary -- ReadBlock will flush some dirty blocks to disk automatically, and Flush will write all dirty blocks to disk.
Write all dirty blocks to disk.
Discard all dirty blocks and replace with blocks from disk..
None by default.
Currently requires 2 blocks per open file.
- note that _fileread could just be part of GetContrib
- need to move TSExtendFile functionality here if want to overload syswrite with encryption
- read_only database support
- buffer cache block zero should contain description of buffer cache layout
- need a way to free blocks associated with a file that is not currently in use
Jeffrey I. Cohen, email@example.com
Copyright (c) 2003-2006 Jeffrey I Cohen. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Address bug reports and comments to: firstname.lastname@example.org
For more information, please visit the Genezzo homepage at http://www.genezzo.com