class PDF::Reader::SynchronizedCache

interchangeable thread-safe cache implementations:
same time, we don’t want to throw away thread safety We have two
only save CPU cycles but also greatly reduce memory requirements But at the
from caching are made In some cases, caching and reusing results can not
Throughout the pdf-reader codebase, repeated calculations which can benefit

def [](key) 

def [](key)
  @mutex.synchronize { @cache[key] }
end

def []=(key,value) 

def []=(key,value)
  @mutex.synchronize { @cache[key] = value }
end

def initialize 

def initialize
  @cache = {}
  @mutex = Mutex.new
end