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# coding: utf-8
require 'hashery/lru_hash'
class PDF::Reader
# A Hash-like object for caching commonly used objects from a PDF file.
#
# This is an internal class, no promises about a stable API.
#
class ObjectCache # nodoc
# These object types use little memory and are accessed a heap of times as
# part of random page access, so we'll cache the unmarshalled objects and
# avoid lots of repetitive (and expensive) tokenising
CACHEABLE_TYPES = [:Catalog, :Page, :Pages]
attr_reader :hits, :misses
def initialize(lru_size = 1000)
@objects = {}
@lru_cache = Hashery::LRUHash.new(lru_size.to_i)
@hits = 0
@misses = 0
end
def [](key)
update_stats(key)
@objects[key] || @lru_cache[key]
end
def []=(key, value)
if cacheable?(value)
@objects[key] = value
else
@lru_cache[key] = value
end
end
def fetch(key, local_default = nil)
update_stats(key)
@objects[key] || @lru_cache.fetch(key, local_default)
end
def each(&block)
@objects.each(&block)
@lru_cache.each(&block)
end
alias :each_pair :each
def each_key(&block)
@objects.each_key(&block)
@lru_cache.each_key(&block)
end
def each_value(&block)
@objects.each_value(&block)
@lru_cache.each_value(&block)
end
def size
@objects.size + @lru_cache.size
end
alias :length :size
def empty?
@objects.empty? && @lru_cache.empty?
end
def include?(key)
@objects.include?(key) || @lru_cache.include?(key)
end
alias :has_key? :include?
alias :key? :include?
alias :member? :include?
def has_value?(value)
@objects.has_value?(value) || @lru_cache.has_value?(value)
end
def to_s
"<PDF::Reader::ObjectCache size: #{self.size}>"
end
def keys
@objects.keys + @lru_cache.keys
end
def values
@objects.values + @lru_cache.values
end
private
def update_stats(key)
if has_key?(key)
@hits += 1
else
@misses += 1
end
end
def cacheable?(obj)
obj.is_a?(Hash) && CACHEABLE_TYPES.include?(obj[:Type])
end
end
end
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