Class: Ramaze::LRUHash

Inherits:
Struct show all
Includes:
Enumerable
Defined in:
lib/ramaze/snippets/ramaze/lru_hash.rb

Overview

A Hash-alike LRU cache that provides fine-grained control over content restrictions.

It allows you to set:

  • a maximum number of elements

  • the maximum amount of memory used for all elements

  • the allowed memory-size per element

  • time to live

Differences to the original implementation include:

  • The Cache is now a Struct for speed

  • Object memory size is obtained via Marshal::dump instead of #to_s

Note that due to calculating object size with Marshal, you might have to do some evaluation as to how large your values will be when marshaled, for example a String will have String#size + 10. This differs from object to object and between versions of Marshal, so be generous.

Copyright © 2002 Yoshinori K. Okuji <[email protected]> Copyright © 2009 Michael Fellinger <[email protected]>

You may redistribute it and/or modify it under the same terms as Ruby.

Defined Under Namespace

Classes: CacheObject

Constant Summary collapse

VERSION = 
'0.3'
KeyError =

On 1.8 we raise IndexError, on 1.9 we raise KeyError

Module.const_defined?(:KeyError) ? KeyError : IndexError

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Struct

#values_at

Constructor Details

#initialize(options = {}, &hook) ⇒ LRUHash

Returns a new instance of LRUHash.



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 35

def initialize(options = {}, &hook)
  self.max_value  = options[:max_value]
  self.max_total  = options[:max_total]
  self.max_count  = options[:max_count]
  self.expiration = options[:expiration]

  avoid_insane_options

  self.hook = hook

  self.objs = {}
  self.list = []

  self.total_size = 0
  self.hits = self.misses = 0
end

Instance Attribute Details

#expiration ⇒ Object

Returns the value of attribute expiration

Returns:

  • (Object) —

    the current value of expiration



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def expiration
  @expiration
end

#hits ⇒ Object

Returns the value of attribute hits

Returns:

  • (Object) —

    the current value of hits



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def hits
  @hits
end

#hook ⇒ Object

Returns the value of attribute hook

Returns:

  • (Object) —

    the current value of hook



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def hook
  @hook
end

#list ⇒ Object

Returns the value of attribute list

Returns:

  • (Object) —

    the current value of list



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def list
  @list
end

#max_count ⇒ Object

Returns the value of attribute max_count

Returns:

  • (Object) —

    the current value of max_count



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def max_count
  @max_count
end

#max_total ⇒ Object

Returns the value of attribute max_total

Returns:

  • (Object) —

    the current value of max_total



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def max_total
  @max_total
end

#max_value ⇒ Object

Returns the value of attribute max_value

Returns:

  • (Object) —

    the current value of max_value



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def max_value
  @max_value
end

#misses ⇒ Object

Returns the value of attribute misses

Returns:

  • (Object) —

    the current value of misses



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def misses
  @misses
end

#objs ⇒ Object

Returns the value of attribute objs

Returns:

  • (Object) —

    the current value of objs



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def objs
  @objs
end

#total_size ⇒ Object

Returns the value of attribute total_size

Returns:

  • (Object) —

    the current value of total_size



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 25

def total_size
  @total_size
end

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 121

def [](key)
  expire

  unless objs.key?(key)
    self.misses += 1
    return
  end

  obj = objs[key]
  obj.atime = Time.now.to_i

  list.delete_if{|list_key| key == list_key }
  list << key

  self.hits += 1
  obj.content
end

#[]=(key, obj) ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 139

def []=(key, obj)
  expire

  invalidate key if key?(key)

  size = Marshal.dump(obj).size

  if max_value && max_value < max_total
    warn "%p isn't cached because it exceeds max_value %p" % [obj, max_value]
    return obj
  end

  if max_value.nil? && max_total && max_total < size
    warn "%p isn't cached because it exceeds max_total: %p" % [obj, max_total]
    return obj
  end

  invalidate list.first if max_count && max_count == list.size

  self.total_size += size

  if max_total
    invalidate list.first until total_size < max_total
  end

  objs[key] = CacheObject.new(obj, size, Time.now.to_i)
  list << key

  obj
end

#clear ⇒ Object Also known as: invalidate_all 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 103

def clear
  objs.each{|key, obj| hook.call(key, obj) } if hook
  objs.clear
  list.clear
  self.total_size = 0
end

#delete(key) ⇒ Object Also known as: invalidate 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 89

def delete(key)
  return unless objs.key?(key)
  obj = objs[key]

  hook.call(key, obj.content) if hook
  self.total_size -= obj.size
  objs.delete key

  list.delete_if{|list_key| key == list_key }

  obj.content
end

#each_key(&block) ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 180

def each_key(&block)
  return enum_for(:each_key) unless block_given?
  objs.each_key{|key| yield key }
  self
end

#each_pair ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 174

def each_pair
  return enum_for(:each_pair) unless block_given?
  objs.each{|key, obj| yield key, obj.content }
  self
end

#each_value ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 186

def each_value
  return enum_for(:each_value) unless block_given?
  objs.each_value{|obj| yield obj.content }
  self
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 192

def empty?
  objs.empty?
end

#expire ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 111

def expire
  return unless expiration
  now = Time.now.to_i

  list.each_with_index do |key, index|
    break unless (objs[key].atime + expiration) <= now
    invalidate key
  end
end

#fetch(key, default = (p_default = true; nil)) ⇒ Object

Note that this method diverges from the default behaviour of the Ruby Hash. If the cache doesn’t find content for the given key, it will store the given default instead. Optionally it also takes a block, the return value of the block is then stored and returned.



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 209

def fetch(key, default = (p_default = true; nil))
  if key?(key)
    value = self[key]
  elsif p_default.nil?
    value = self[key] = default
  elsif block_given?
    value = self[key] = yield(key)
  else
    raise KeyError, "key not found: %p" % [key]
  end

  value
end

#index(given_value) ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 64

def index(given_value)
  objs.each do |key, obj|
    return key if given_value == obj.content
  end

  nil
end

#key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 52

def key?(key)
  objs.key?(key)
end

#keys ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 72

def keys
  objs.keys
end

#size ⇒ Object Also known as: length 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 76

def size
  objs.size
end

#statistics ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 223

def statistics
  {:size => total_size, :count => list.size, :hits => hits, :misses => misses}
end

#store(key, value) ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 170

def store(key, value)
  self[key] = value
end

#to_hash ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 81

def to_hash
  objs.dup
end

#value?(given_value) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 56

def value?(given_value)
  objs.each do |key, obj|
    return true if given_value == obj.content
  end

  false
end

#values ⇒ Object 



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# File 'lib/ramaze/snippets/ramaze/lru_hash.rb', line 85

def values
  objs.map{|key, obj| obj.content }
end