Class: Cache

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/cache.rb

Overview

Cache manager based on the LRU algorithm.

Defined Under Namespace

Classes: CACHE_OBJECT

Constant Summary collapse

CACHE_VERSION = 
'0.3'

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(*args, &hook) ⇒ Cache

initialize(max_obj_size = nil, max_size = nil, max_num = nil,

expiration = nil, &hook)

initialize(hash, &hook)



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# File 'lib/cache.rb', line 22

def initialize(*args, &hook)
  if args.size == 1 and args[0].kind_of?(Hash)
    @max_obj_size = @max_size = @max_num = @expiration = nil
    args[0].each do |k, v|
	k = k.intern if k.respond_to?(:intern)
	case k
	when :max_obj_size
 @max_obj_size = v
	when :max_size
 @max_size = v
	when :max_num
 @max_num = v
	when :expiration
 @expiration = v
	end
    end
  else
    @max_obj_size, @max_size, @max_num, @expiration = args
  end

  # Sanity checks.
  if @max_obj_size and @max_size and @max_obj_size > @max_size
    raise ArgumentError, "max_obj_size exceeds max_size (#{@max_obj_size} > #{@max_size})"
  end
  if @max_obj_size and @max_obj_size <= 0
    raise ArgumentError, "invalid max_obj_size `#{@max_obj_size}'"
  end
  if @max_size and @max_size <= 0
    raise ArgumentError, "invalid max_size `#{@max_size}'"
  end
  if @max_num and @max_num <= 0
    raise ArgumentError, "invalid max_num `#{@max_num}'"
  end
  if @expiration and @expiration <= 0
    raise ArgumentError, "invalid expiration `#{@expiration}'"
  end
  
  @hook = hook
  
  @objs = {}
  @size = 0
  @list = []
  
  @hits = 0
  @misses = 0
end

Instance Attribute Details

#expiration ⇒ Object (readonly)

Returns the value of attribute expiration.



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# File 'lib/cache.rb', line 69

def expiration
  @expiration
end

#max_num ⇒ Object (readonly)

Returns the value of attribute max_num.



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# File 'lib/cache.rb', line 69

def max_num
  @max_num
end

#max_obj_size ⇒ Object (readonly)

Returns the value of attribute max_obj_size.



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# File 'lib/cache.rb', line 69

def max_obj_size
  @max_obj_size
end

#max_size ⇒ Object (readonly)

Returns the value of attribute max_size.



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# File 'lib/cache.rb', line 69

def max_size
  @max_size
end

Class Method Details

.version ⇒ Object 



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# File 'lib/cache.rb', line 15

def self.version
  CACHE_VERSION
end

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/cache.rb', line 159

def [](key)
  self.expire()
  
  unless @objs.include?(key)
    @misses += 1
    return nil
  end
  
  obj = @objs[key]
  obj.atime = Time.now.to_i

  @list.each_index do |i|
    if @list[i] == key
	@list.delete_at(i)
	break
    end
  end
  @list.push(key)

  @hits += 1
  obj.content
end

#[]=(key, obj) ⇒ Object 



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# File 'lib/cache.rb', line 182

def []=(key, obj)
  self.expire()
  
  if self.cached?(key)
    self.invalidate(key)
  end

  size = obj.to_s.size
  if @max_obj_size and @max_obj_size < size
    if $DEBUG
	$stderr.puts("warning: `#{obj.inspect}' isn't cached because its size exceeds #{@max_obj_size}")
    end
    return obj
  end
  if @max_obj_size.nil? and @max_size and @max_size < size
    if $DEBUG
	$stderr.puts("warning: `#{obj.inspect}' isn't cached because its size exceeds #{@max_size}")
    end
    return obj
  end
    
  if @max_num and @max_num == @list.size
    self.invalidate(@list.first)
  end

  @size += size
  if @max_size
    while @max_size < @size
	self.invalidate(@list.first)
    end
  end

  @objs[key] = CACHE_OBJECT.new(obj, size, Time.now.to_i)
  @list.push(key)

  obj
end

#cached?(key) ⇒ Boolean Also known as: include?, member?, key?, has_key?

Returns:

  • (Boolean) 


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# File 'lib/cache.rb', line 71

def cached?(key)
  @objs.include?(key)
end

#cached_value?(val) ⇒ Boolean Also known as: has_value?, value?

Returns:

  • (Boolean) 


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# File 'lib/cache.rb', line 79

def cached_value?(val)
  self.each_value do |v|
    return true if v == val
  end
  false
end

#each_key ⇒ Object 



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# File 'lib/cache.rb', line 232

def each_key
  @objs.each_key do |key|
    yield key
  end
  self
end

#each_pair ⇒ Object Also known as: each 



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# File 'lib/cache.rb', line 224

def each_pair
  @objs.each do |key, obj|
    yield key, obj.content
  end
  self
end

#each_value ⇒ Object 



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# File 'lib/cache.rb', line 239

def each_value
  @objs.each_value do |obj|
    yield obj.content
  end
  self
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/cache.rb', line 246

def empty?
  @objs.empty?
end

#expire ⇒ Object 



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# File 'lib/cache.rb', line 146

def expire()
  if @expiration
    now = Time.now.to_i
    @list.each_index do |i|
	key = @list[i]
	
	break unless @objs[key].atime + @expiration <= now
	self.invalidate(key)
    end
  end
#    GC.start
end

#fetch(key, default = nil) ⇒ Object 



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# File 'lib/cache.rb', line 250

def fetch(key, default = nil)
  val = self[key]
  if val.nil?
    if default
	val = self[key] = default
    elsif block_given?
	val = self[key] = yield(key)
    else
	raise IndexError, "invalid key `#{key}'"
    end
  end
  val
end

#index(val) ⇒ Object 



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# File 'lib/cache.rb', line 88

def index(val)
  self.each_pair do |k,v|
    return k if v == val
  end
  nil
end

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



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# File 'lib/cache.rb', line 112

def invalidate(key)
  obj = @objs[key]
  if obj
    if @hook
	@hook.call(key, obj.content)
    end
    @size -= obj.size
    @objs.delete(key)
    @list.each_index do |i|
	if @list[i] == key
 @list.delete_at(i)
 break
	end
    end
  elsif block_given?
    return yield(key)
  end
  obj.content
end

#invalidate_all ⇒ Object Also known as: clear 



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# File 'lib/cache.rb', line 133

def invalidate_all()
  if @hook
    @objs.each do |key, obj|
	@hook.call(key, obj)
    end
  end

  @objs.clear
  @list.clear
  @size = 0
end

#keys ⇒ Object 



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# File 'lib/cache.rb', line 95

def keys
  @objs.keys
end

#length ⇒ Object Also known as: size 



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# File 'lib/cache.rb', line 99

def length
  @objs.length
end

#statistics ⇒ Object

The total size of cached objects, the number of cached objects, the number of cache hits, and the number of cache misses.



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# File 'lib/cache.rb', line 266

def statistics()
  [@size, @list.size, @hits, @misses]
end

#store(key, value) ⇒ Object 



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# File 'lib/cache.rb', line 220

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

#to_hash ⇒ Object 



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# File 'lib/cache.rb', line 104

def to_hash
  @objs.dup
end

#values ⇒ Object 



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# File 'lib/cache.rb', line 108

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