Genezzo::BufCa::BufCa.pm - A simple in-memory buffer cache for a single process, without locking.
use Genezzo::BufCa::BufCa; # get a buffer cache my $bc = Genezzo::BufCa::BufCa->new(blocksize => 10, numblocks => 5); # find a free block my $free_arr = $bc->GetFree(); # get the block number and a reference to a Buffer Cache Element my $blocknum = shift (@{$free_arr}); my $bceref = shift (@{$free_arr}); # obtain the actual Buffer Cache Element my $bce = $$bceref; # can later use the block number to revisit this Buffer Cache Element . . . # get back the same block $bceref = $bc->ReadBlock(blocknum => $blocknum); $bce = $$bceref;
The in-memory buffer cache is a simple module designed to form the basis of a more complicated, file-based, 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). The BCE has two callback functions or closures of note:
A block is pinned as long as the bceref (returned via GetFree or ReadBlock) is in scope. BufCa uses a scalar tie class to unpin the block when the bceref is garbage collected. The basic pin function acts as a form of advisory locking, and could be upgraded to a true locking mechanism.
a block is marked as dirty if it is modified.
Takes arguments blocksize (required, in bytes), numblocks (10 by default). Returns a new buffer cache of the specified number of blocks of size blocksize.
Returns an array @free = (block number, bceref). The bceref and its associated blocknumber are for a block that is currently not in use. Note that the block might be dirty. Also, GetFree is not a space allocator -- it only indicates that a block is not in use.
Takes argument blocknum, which must be a valid block number. Returns a bceref
None by default.
Jeffrey I. Cohen, jcohen@genezzo.com
perl(1).
Copyright (c) 2003, 2004 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: jcohen@genezzo.com
For more information, please visit the Genezzo homepage at http://www.genezzo.com
To install Genezzo, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Genezzo
CPAN shell
perl -MCPAN -e shell install Genezzo
For more information on module installation, please visit the detailed CPAN module installation guide.