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require 'thread_safe'
require 'action_view/dependency_tracker'
require 'monitor'
module ActionView
class Digestor
cattr_reader(:cache)
@@cache = ThreadSafe::Cache.new
@@digest_monitor = Monitor.new
class << self
def digest(name, format, finder, options = {})
cache_key = ([name, format] + Array.wrap(options[:dependencies])).join('.')
# this is a correctly done double-checked locking idiom
# (ThreadSafe::Cache's lookups have volatile semantics)
@@cache[cache_key] || @@digest_monitor.synchronize do
@@cache.fetch(cache_key) do # re-check under lock
compute_and_store_digest(cache_key, name, format, finder, options)
end
end
end
private
def compute_and_store_digest(cache_key, name, format, finder, options) # called under @@digest_monitor lock
klass = if options[:partial] || name.include?("/_")
# Prevent re-entry or else recursive templates will blow the stack.
# There is no need to worry about other threads seeing the +false+ value,
# as they will then have to wait for this thread to let go of the @@digest_monitor lock.
pre_stored = @@cache.put_if_absent(cache_key, false).nil? # put_if_absent returns nil on insertion
PartialDigestor
else
Digestor
end
@@cache[cache_key] = digest = klass.new(name, format, finder, options).digest # Store the actual digest
ensure
@@cache.delete_pair(cache_key, false) if pre_stored && !digest # something went wrong, make sure not to corrupt the @@cache
end
end
attr_reader :name, :format, :finder, :options
def initialize(name, format, finder, options={})
@name, @format, @finder, @options = name, format, finder, options
end
def digest
Digest::MD5.hexdigest("#{source}-#{dependency_digest}").tap do |digest|
logger.try :info, "Cache digest for #{name}.#{format}: #{digest}"
end
rescue ActionView::MissingTemplate
logger.try :error, "Couldn't find template for digesting: #{name}.#{format}"
''
end
def dependencies
DependencyTracker.find_dependencies(name, template)
rescue ActionView::MissingTemplate
[] # File doesn't exist, so no dependencies
end
def nested_dependencies
dependencies.collect do |dependency|
dependencies = PartialDigestor.new(dependency, format, finder).nested_dependencies
dependencies.any? ? { dependency => dependencies } : dependency
end
end
private
def logger
ActionView::Base.logger
end
def logical_name
name.gsub(%r|/_|, "/")
end
def partial?
false
end
def template
@template ||= finder.find(logical_name, [], partial?, formats: [ format ])
end
def source
template.source
end
def dependency_digest
template_digests = dependencies.collect do |template_name|
Digestor.digest(template_name, format, finder, partial: true)
end
(template_digests + injected_dependencies).join("-")
end
def injected_dependencies
Array.wrap(options[:dependencies])
end
end
class PartialDigestor < Digestor # :nodoc:
def partial?
true
end
end
end
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