class Sprockets::Cache::FileStore


ActiveSupport::Cache::FileStore
See Also
environment.cache = Sprockets::Cache::FileStore.new(“/tmp”)
Assign the instance to the Environment#cache.
Public: A file system cache store that automatically cleans up old keys.

def self.default_logger

Returns a Logger.

Internal: Default standard error fatal logger. 
def self.default_logger
  logger = Logger.new($stderr)
  logger.level = Logger::FATAL
  logger
end

def clear(options=nil)

Returns true

as @root because everything in that directory will be deleted.
file store directory except for .keep or .gitkeep. Be careful which directory is specified
Deletes all items from the cache. In this case it deletes all the entries in the specified

adapted from ActiveSupport::Cache::FileStore#clear

Public: Clear the cache 
def clear(options=nil)
  root_dirs = Dir.entries(@root).reject { |f| (EXCLUDED_DIRS + GITKEEP_FILES).include?(f) }
  FileUtils.rm_r(root_dirs.collect{ |f| File.join(@root, f) })
  true
end

def compute_size(caches) 

def compute_size(caches)
  caches.inject(0) { |sum, (_, stat)| sum + stat.size }
end

def find_caches

mtime.
Returns an Array of [String filename, File::Stat] pairs sorted by

Internal: Get all cache files along with stats. 
def find_caches
  Dir.glob(File.join(@root, '**/*.cache')).reduce([]) { |stats, filename|
    stat = safe_stat(filename)
    # stat maybe nil if file was removed between the time we called
    # dir.glob and the next stat
    stats << [filename, stat] if stat
    stats
  }.sort_by { |_, stat| stat.mtime.to_i }
end

def gc! 

def gc!
  start_time = Time.now
  caches = find_caches
  size = compute_size(caches)
  delete_caches, keep_caches = caches.partition { |filename, stat|
    deleted = size > @gc_size
    size -= stat.size
    deleted
  }
  return if delete_caches.empty?
  FileUtils.remove(delete_caches.map(&:first), force: true)
  @size = compute_size(keep_caches)
  @logger.warn do
    secs = Time.now.to_f - start_time.to_f
    "#{self.class}[#{@root}] garbage collected " +
      "#{delete_caches.size} files (#{(secs * 1000).to_i}ms)"
  end
end

def get(key)

Returns Object or nil or the value is not set.

key - String cache key.

This API should not be used directly, but via the Cache wrapper API.

Public: Retrieve value from cache. 
def get(key)
  path = File.join(@root, "#{key}.cache")
  value = safe_open(path) do |f|
    begin
      EncodingUtils.unmarshaled_deflated(f.read, Zlib::MAX_WBITS)
    rescue Exception => e
      @logger.error do
        "#{self.class}[#{path}] could not be unmarshaled: " +
          "#{e.class}: #{e.message}"
      end
      nil
    end
  end
  if value
    FileUtils.touch(path)
    value
  end
end

def initialize(root, max_size = DEFAULT_MAX_SIZE, logger = self.class.default_logger)

(default: 1000).
max_size - A Integer of the maximum number of keys the store will hold.
root - A String path to a directory to persist cached values to.

Public: Initialize the cache store. 
def initialize(root, max_size = DEFAULT_MAX_SIZE, logger = self.class.default_logger)
  @root     = root
  @max_size = max_size
  @gc_size  = max_size * 0.75
  @logger   = logger
end

def inspect

Returns String.

Public: Pretty inspect 
def inspect
  "#<#{self.class} size=#{size}/#{@max_size}>"
end

def safe_open(path, &block) 

def safe_open(path, &block)
  if File.exist?(path)
    File.open(path, 'rb', &block)
  end
rescue Errno::ENOENT
end

def safe_stat(fn) 

def safe_stat(fn)
  File.stat(fn)
rescue Errno::ENOENT
  nil
end

def set(key, value)

Returns Object value.

value - Object value.
key - String cache key.

This API should not be used directly, but via the Cache wrapper API.

Public: Set a key and value in the cache. 
def set(key, value)
  path = File.join(@root, "#{key}.cache")
  # Ensure directory exists
  FileUtils.mkdir_p File.dirname(path)
  # Check if cache exists before writing
  exists = File.exist?(path)
  # Serialize value
  marshaled = Marshal.dump(value)
  # Compress if larger than 4KB
  if marshaled.bytesize > 4 * 1024
    deflater = Zlib::Deflate.new(
      Zlib::BEST_COMPRESSION,
      Zlib::MAX_WBITS,
      Zlib::MAX_MEM_LEVEL,
      Zlib::DEFAULT_STRATEGY
    )
    deflater << marshaled
    raw = deflater.finish
  else
    raw = marshaled
  end
  # Write data
  PathUtils.atomic_write(path) do |f|
    f.write(raw)
    @size = size + f.size unless exists
  end
  # GC if necessary
  gc! if size > @max_size
  value
end

def size 

def size
  @size ||= compute_size(find_caches)
end