Add bin and edit workflow

bin/gems/hashery-2.1.2/lib/hashery/lru_hash.rb

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+require 'enumerator'
+
+module Hashery
+
+  # Hash with LRU expiry policy.  There are at most max_size elements in a
+  # LRUHash.  When adding more elements old elements are removed according
+  # to LRU policy.
+  #
+  # Based on Robert Klemme's LRUHash class.
+  #
+  # LRUHash, Copyright (c) 2010 Robert Klemme.
+  #
+  class LRUHash
+
+    include Enumerable
+
+    attr_reader :max_size
+
+    attr_accessor :default
+    attr_accessor :default_proc
+    attr_accessor :release_proc
+
+    #
+    # Initialize new LRUHash instance.
+    #
+    # max_size      -
+    # default_value -
+    # block         -
+    #
+    def initialize(max_size, default_value=nil, &block)
+      @max_size     = normalize_max(max_size)
+      @default      = default_value
+      @default_proc = block
+
+      @h = {}
+      @head = Node.new
+      @tail = front(Node.new)
+    end
+
+    #
+    # Iterate over each pair.
+    #
+    def each_pair
+      if block_given?
+        each_node do |n|
+          yield [n.key, n.value]
+        end
+      else
+        enum_for :each_pair
+      end
+    end
+
+    #
+    # Same as each pair.
+    #
+    alias each each_pair
+
+    #
+    # Iterate over each key.
+    #
+    def each_key
+      if block_given?
+        each_node do |n|
+          yield n.key
+        end
+      else
+        enum_for :each_key
+      end
+    end
+
+    #
+    # Iterate over each value.
+    #
+    def each_value
+      if block_given?
+        each_node do |n|
+          yield n.value
+        end
+      else
+        enum_for :each_value
+      end
+    end
+
+    #
+    # Size of the hash.
+    #
+    def size
+      @h.size
+    end
+
+    #
+    #
+    #
+    def empty?
+      @head.succ.equal? @tail
+    end
+
+    #
+    #
+    #
+    def fetch(key, &b)
+      n = @h[key]
+
+      if n
+        front(n).value
+      else
+        (b || FETCH)[key]
+      end
+    end
+
+    #
+    #
+    #
+    def [](key)
+      fetch(key) do |k|
+        @default_proc ? @default_proc[self, k] : default
+      end
+    end
+
+    #
+    #
+    #
+    def keys
+      @h.keys
+    end
+
+    #
+    #
+    #
+    def values
+      @h.map {|k,n| n.value}
+    end
+
+    #
+    #
+    #
+    def has_key?(key)
+      @h.has_key? key
+    end
+
+    alias key? has_key?
+    alias member? has_key?
+    alias include? has_key?
+
+    #
+    #
+    #
+    def has_value?(value)
+      each_pair do |k, v|
+        return true if value.eql? v
+      end
+
+      false
+    end
+
+    alias value? has_value?
+
+    def values_at(*key_list)
+      key_list.map {|k| self[k]}
+    end
+
+    #
+    #
+    #
+    def assoc(key)
+      n = @h[key]
+
+      if n
+        front(n)
+        [n.key, n.value]
+      end
+    end
+
+    #
+    #
+    #
+    def rassoc(value)
+      each_node do |n|
+        if value.eql? n.value
+          front(n)
+          return [n.key, n.value]
+        end
+      end
+      nil
+    end
+
+    #
+    #
+    #
+    def key(value)
+      pair = rassoc(value) and pair.first
+    end
+
+    #
+    #
+    #
+    def store(key, value)
+      # same optimization as in Hash
+      key = key.dup.freeze if String === key && !key.frozen?
+
+      n = @h[key]
+
+      unless n
+        if size == max_size
+          # reuse node to optimize memory usage
+          n = delete_oldest
+          n.key = key
+          n.value = value
+        else
+          n = Node.new key, value
+        end
+
+        @h[key] = n
+      end
+
+      front(n).value = value
+    end
+
+    alias []= store
+
+    #
+    #
+    #
+    def delete(key)
+      n = @h[key] and remove_node(n).value
+    end
+
+    #
+    #
+    #
+    def delete_if
+      each_node do |n|
+        remove_node n if yield n.key, n.value
+      end
+    end
+
+    #
+    #
+    #
+    def max_size=(limit)
+      limit = normalize_max(limit)
+
+      while size > limit
+        delete_oldest
+      end
+
+      @max_size = limit
+    end
+
+    #
+    #
+    #
+    def clear
+      until empty?
+        delete_oldest
+      end
+
+      self
+    end
+
+    #
+    #
+    #
+    def to_s
+      s = nil
+      each_pair {|k, v| (s ? (s << ', ') : s = '{') << k.to_s << '=>' << v.to_s}
+      s ? (s << '}') : '{}'
+    end
+
+    alias inspect to_s
+
+  private
+
+    #
+    # Iterate nodes.
+    #
+    def each_node
+      n = @head.succ
+
+      until n.equal? @tail
+        succ = n.succ
+        yield n
+        n = succ
+      end
+
+      self
+    end
+
+    #
+    # Move node to front.
+    #
+    # node - [Node]
+    #
+    def front(node)
+      node.insert_after(@head)
+    end
+
+    #
+    # Remove the node and invoke release_proc
+    # if set
+    #
+    # node - [Node]
+    #
+    def remove_node(node)
+      n = @h.delete(node.key)
+      n.unlink
+      release_proc and release_proc[n.key, n.value]
+      n
+    end
+
+    #
+    # Remove the oldest node returning the node
+    #
+    def delete_oldest
+      n = @tail.pred
+      raise "Cannot delete from empty hash" if @head.equal? n
+      remove_node n
+    end
+
+    #
+    # Normalize the argument in order to be usable as max_size
+    # criterion is that n.to_i must be an Integer and it must
+    # be larger than zero.
+    #
+    # n - [#to_i] max size
+    #
+    def normalize_max(n)
+      n = n.to_i
+      raise ArgumentError, 'Invalid max_size: %p' % n unless Integer === n && n > 0
+      n
+    end
+
+    #
+    FETCH = Proc.new {|k| raise KeyError, 'key not found'}
+
+    # A single node in the doubly linked LRU list of nodes.
+    Node = Struct.new :key, :value, :pred, :succ do
+      def unlink
+        pred.succ = succ if pred
+        succ.pred = pred if succ
+        self.succ = self.pred = nil
+        self
+      end
+
+      def insert_after(node)
+        raise 'Cannot insert after self' if equal? node
+        return self if node.succ.equal? self
+
+        unlink
+
+        self.succ = node.succ
+        self.pred = node
+
+        node.succ.pred = self if node.succ
+        node.succ = self
+
+        self
+      end
+    end
+
+  end
+
+end