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# $Id: cache.rb,v 1.10 2003/07/25 22:51:25 sdalu Exp $
#
# CONTACT : zonecheck@nic.fr
# AUTHOR : Stephane D'Alu <sdalu@nic.fr>
#
# CREATED : 2002/08/02 13:58:17
# REVISION : $Revision: 1.10 $
# DATE : $Date: 2003/07/25 22:51:25 $
#
# CONTRIBUTORS: (see also CREDITS file)
#
#
# LICENSE : GPL v2 (or MIT/X11-like after agreement)
# COPYRIGHT : AFNIC (c) 2003
#
# This file is part of ZoneCheck.
#
# ZoneCheck 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
# (at your option) any later version.
#
# ZoneCheck 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 ZoneCheck; if not, write to the Free Software Foundation,
# Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
require 'sync'
require 'dbg'
##
##
##
class Cache
Nothing = Object::new # Another way to express nil
#
# Initialize the cache mechanisme
#
def initialize(name='0x%x'%__id__)
@name = name
@mutex = Sync::new
@list = {}
end
#
# Is caching enabled?
#
def enabled?
! $dbg.enabled?(DBG::NOCACHE)
end
#
# Clear the items (all if none specified)
#
def clear(*items)
@mutex.synchronize {
# Clear item content
list = items.empty? ? @list.keys : items
list.each { |item|
# Sanity check
if ! @list.has_key?(item)
raise ArgumentError, "Cache item '#{item}' not defined"
end
# Clear
@list[item] = {}
}
}
end
#
# Define cacheable item
#
def create(*items)
items.each { |item|
# Sanity check
if @list.has_key?(item)
raise ArgumentError, "Cache item '#{item}' already defined"
end
# Create item
@list[item] = {}
}
end
#
# Use a cacheable item
#
def use(item, args=nil, force=false)
# Sanity check
if ! @list.has_key?(item)
raise ArgumentError, "Cache item '#{item}' not defined"
end
# Caching enabled?
return yield unless enabled?
# Compute key to use for retrieval
key = case args
when NilClass then nil
when Array then case args.length
when 0 then nil
when 1 then args[0]
else args
end
else args
end
# Retrieve information
computed, r = nil, nil
@mutex.synchronize {
r = @list[item][key]
computed = force || r.nil?
if computed
r = yield
r = Nothing if r.nil?
@list[item][key] = r
end
r = nil if r == Nothing
}
# Debugging information
$dbg.msg(DBG::CACHE_INFO) {
l = case args
when NilClass then "#{item}"
when Array then case args.length
when 0 then "#{item}"
when 1 then "#{item}[#{args[0]}]"
else "#{item}[#{args.join(',')}]"
end
else "#{item}[#{args}]"
end
if computed
then "computed(#{@name}): #{l}=#{r}"
else "cached (#{@name}): #{l}=#{r}"
end
}
# Returns result
r
end
end
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