importing initial files

git-svn-id: svn+ssh://rubyforge.org/var/svn/timedcache/trunk@2 86bfafc1-3100-4244-9143-2200d8b62c5a

lib/timed_cache.rb

@@ -0,0 +1,147 @@
+require "pstore"
+
+# TimedCache implements a cache in which you can place objects
+# and specify a timeout value.
+# 
+# If you attempt to retrieve the object within the specified timeout
+# period, the object will be returned. If the timeout period has elapsed,
+# the TimedCache will return nil.
+# 
+# e.g.:
+#   cache = TimedCache.new
+#   cache.put :my_object_key, "Expensive data", 10 # => "Expensive data"
+#   cache.get :my_object_key # => "Expensive data"
+# 
+# ... 10 seconds later:
+#   cache.get :my_object_key # => nil
+# 
+# = Default timeout
+# 
+# When creating a new TimedCache, a default timeout value can be set. This value
+# will be used for each object added to the cache, unless a different timeout value
+# is specifically set for that object.
+# 
+# e.g.:
+# 
+#   cache = TimedCache.new(:default_timeout => 120)
+#   cache.default_timeout # => 120
+# 
+# = File-based cache
+# 
+# By default, TimedCache will use an in-memory store. A file-based store (using the 
+# PStore library) can also be used.
+# 
+# e.g.:
+# 
+#   TimedCache.new(:type => :file, :filename => "my_cache.db")
+# 
+class TimedCache
+  attr_reader :default_timeout
+
+  def initialize(opts = {})
+    opts[:type] ||= :memory
+    @default_timeout = opts[:default_timeout] || 60
+    @store = new_store(opts)
+  end
+
+  def put(key, value, timeout = @default_timeout)
+    @store.put(key, value, timeout)
+  end
+
+  def get(key)
+    @store.get(key)
+  end
+
+  def []=(key, value)
+    put(key, value)
+  end
+
+  def [](key)
+    get(key)
+  end
+
+  protected
+
+  def new_store(options)
+    self.class.const_get(options[:type].to_s.capitalize + "Store").new(options)
+  end
+
+  class Store #:nodoc:
+    def initialize(options)
+      @options = options
+    end
+  end
+
+  class MemoryStore < Store #:nodoc:
+    def initialize(options)
+      super
+      @cache = Hash.new
+    end
+
+    def put(key, value, timeout)
+      @cache[key.to_s.intern] = ObjectContainer.new(value, timeout)
+      # Return just the given value, so that references to the
+      # ObjectStore instance can't be held outside this TimedCache:
+      value
+    end
+
+    def get(key)
+      if object_store = @cache[key.to_s.intern]
+        if object_store.expired?
+          # Free up memory:
+          @cache[key.to_s.intern] = nil
+        else
+          object_store.object
+        end
+      end
+    end
+  end
+
+  class FileStore < Store #:nodoc:
+    def initialize(*args)
+      super(*args)
+      filename = @options[:filename]
+      unless filename
+        raise ArgumentError, ":filename option must be specified for :file type store."
+      end
+      @cache = PStore.new(filename)
+    end
+
+    def put(key, value, timeout = nil)
+      @cache.transaction do
+        @cache[key.to_s.intern] = ObjectContainer.new(value, timeout)
+      end
+
+      # Return just the given value, so that references to the
+      # ObjectStore instance can't be held outside this TimedCache:
+      value
+    end
+
+    def get(key)
+      @cache.transaction do
+        if object_store = @cache[key.to_s.intern]
+          if object_store.expired?
+            # Free up memory:
+            @cache[key.to_s.intern] = nil
+          else
+            object_store.object
+          end
+        end
+      end
+    end    
+  end
+
+  class ObjectContainer #:nodoc:
+    attr_reader :object
+
+    def initialize(object, timeout)
+      @created_at = Time.now.utc
+      @timeout    = timeout
+      @object     = object
+    end
+
+    def expired?
+      (Time.now.utc - @timeout) > @created_at
+    end
+  end
+end

specs/timed_cache_spec.rb

@@ -0,0 +1,67 @@
+require File.join(File.dirname(__FILE__), "../timed_cache")
+
+$filename = File.join(File.dirname(__FILE__), "specs.db")
+
+context "Adding and retrieving objects from the cache" do
+  setup do
+    @memory_cache = TimedCache.new
+    @file_cache   = TimedCache.new(:type => :file, :filename => $filename)
+    @caches = [@memory_cache, @file_cache]
+  end
+
+  teardown do
+    File.delete($filename)
+  end
+
+  specify "Can add an object to the cache, specifying a timeout value" do
+    @caches.each do |cache|
+      cache.put(:myobject, "This needs caching", 10).should_equal "This needs caching"
+    end
+  end
+
+  specify "Cache should hold seperate values for each key" do
+    @caches.each do |cache|    
+      cache.put(:myobject, "This needs caching", 10).should_equal "This needs caching"
+      cache.put(:my_other_object, "...and this too", 10).should_equal "...and this too"
+      cache.get(:myobject).should_equal "This needs caching"
+      cache.get(:my_other_object).should_equal "...and this too"
+    end
+  end
+
+  specify "After the specified timeout value has elapsed, nil should be returned" do
+    @caches.each do |cache|    
+      cache.put(:myobject, "This needs caching", 0).should_equal "This needs caching"
+      cache.get(:myobject).should_equal nil
+    end
+  end
+
+  specify "If no object matching the given key is found, nil should be returned" do
+    @caches.each do |cache|    
+      cache.get(:my_nonexistant_object).should_equal nil
+    end
+  end
+
+  specify "Should be able to use an array as a cache key" do
+    @caches.each do |cache|
+      cache.put([123,234], "Array").should_equal "Array"
+      cache.get([123,234]).should_equal "Array"
+    end
+  end
+end
+
+context "Specifying a default timeout" do
+  specify "Should be able to specify a default timeout when creating a TimedCache" do
+    cache = TimedCache.new(:default_timeout => 20)
+    cache.should_be_kind_of TimedCache
+    cache.default_timeout.should_equal 20
+  end
+
+  specify "If no default timeout is set, 60 seconds should be used" do
+    cache = TimedCache.new
+    cache.should_be_kind_of TimedCache
+    cache.default_timeout.should_equal 60
+  end
+
+  specify "Timeout specified when putting a new object into the cache should override default timeout" do
+  end
+end

svn-commit.2.tmp

@@ -0,0 +1,4 @@
+importing initial files
+--This line, and those below, will be ignored--
+
+A    .

svn-commit.tmp

@@ -0,0 +1,4 @@
+importing initial files
+--This line, and those below, will be ignored--
+
+A    .