Class: FileCache

Inherits:
Object
  • Object
show all
Defined in:
lib/filecache.rb

Overview

A file-based caching library. It uses Marshal::dump and Marshal::load to serialize/deserialize cache values - so you should be OK to cache object values.

Constant Summary collapse

MAX_DEPTH = 
32

Instance Method Summary collapse

Constructor Details

#initialize(domain = "default", root_dir = "/tmp", expiry = 0, depth = 2) ⇒ FileCache

Create a new reference to a file cache system.

domain

A string that uniquely identifies this caching system on the given host

root_dir

The root directory of the cache file hierarchy The cache will be rooted at root_dir/domain/

expiry

The expiry time for cache entries, in seconds. Use 0 if you want cached values never to expire.

depth

The depth of the file tree storing the cache. Should be large enough that no cache directory has more than a couple of hundred objects in it



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# File 'lib/filecache.rb', line 21

def initialize(domain = "default", root_dir = "/tmp", expiry = 0, depth = 2)
  @domain  = domain
  @root_dir = root_dir
  @expiry  = expiry
  @depth   = depth > MAX_DEPTH ? MAX_DEPTH : depth
  FileUtils.mkdir_p(get_root)
end

Instance Method Details

#clear ⇒ Object

Delete ALL data from the cache, regardless of expiry time



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# File 'lib/filecache.rb', line 74

def clear
  if File.exist?(get_root)
    FileUtils.rm_r(get_root)
    FileUtils.mkdir_p(get_root)
  end
end

#delete(key) ⇒ Object

Delete the value for the given key from the cache



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

def delete(key)
  FileUtils.rm(get_path(key))
end

#get(key) ⇒ Object

Return the value for the specified key from the cache. Returns nil if the value isn’t found.



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# File 'lib/filecache.rb', line 39

def get(key)
  path = get_path(key)

  # expire
  if @expiry > 0 && File.exist?(path) && Time.new - File.new(path).mtime >= @expiry
    FileUtils.rm(path)
  end

  if File.exist?(path)
    f = File.open(path, "r")
    result = Marshal.load(f)
    f.close
    return result
  else
    return nil
  end
end

#get_or_set(key) ⇒ Object

Return the value for the specified key from the cache if the key exists in the cache, otherwise set the value returned by the block. Returns the value if found or the value from calling the block that was set.



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# File 'lib/filecache.rb', line 60

def get_or_set(key)
  value = get(key)
  return value if value
  value = yield
  set(key, value)
  value
end

#purge ⇒ Object

Delete all expired data from the cache



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# File 'lib/filecache.rb', line 82

def purge
  @t_purge = Time.new
  purge_dir(get_root) if @expiry > 0
end

#set(key, value) ⇒ Object

Set a cache value for the given key. If the cache contains an existing value for the key it will be overwritten.



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# File 'lib/filecache.rb', line 31

def set(key, value)
  f = File.open(get_path(key), "w")
  Marshal.dump(value, f)
  f.close
end