lib/geminabox/disk_cache.rb
# frozen_string_literal: true
require "fileutils"
module Geminabox
class Geminabox::DiskCache
attr_reader :root_path
def initialize(root_path)
@root_path = root_path
ensure_dir_exists!
end
def flush_key(key)
path = path(key_hash(key))
FileUtils.rm_f(path)
end
def flush
FileUtils.rm_rf(root_path)
ensure_dir_exists!
end
def cache(key)
key_hash = key_hash(key)
read(key_hash) || write(key_hash, yield)
end
def marshal_cache(key)
key_hash = key_hash(key)
marshal_read(key_hash) || marshal_write(key_hash, yield)
end
protected
def ensure_dir_exists!
FileUtils.mkdir_p(root_path)
end
def key_hash(key)
Digest::MD5.hexdigest(key)
end
def path(key_hash)
File.join(root_path, key_hash)
end
def read(key_hash)
read_int(key_hash) do |path|
begin
File.read(path)
rescue Errno::ENOENT
# There is a possibility that the file is removed by another process
# after checking File.exist?. Return nil if the file does not exist.
nil
end
end
end
def marshal_read(key_hash)
read_int(key_hash) do |path|
begin
File.open(path) {|fp| Marshal.load(fp) }
rescue Errno::ENOENT, EOFError
# There is a possibility that the file is removed by another process.
# Marshal.load raises EOFError if the file is removed after File.open(path) succeeds.
# Return nil if the file does not exist.
nil
end
end
end
def read_int(key_hash)
path = path(key_hash)
yield(path) if File.exist?(path)
end
def write(key_hash, value)
write_int(key_hash) { |f| f << value }
value
end
def marshal_write(key_hash, value)
write_int(key_hash) { |f| Marshal.dump(value, f) }
value
end
def write_int(key_hash)
File.open(path(key_hash), 'wb') { |f| yield(f) }
end
end
end