RGen::Util::FileCacheMap

Implements a cache for storing and loading data associated with arbitrary files. The data is stored in cache files within a subfolder of the folder where the associated files exists. The cache files are protected with a checksum and loaded data will be invalid in case either the associated file are the cache file has changed.

Attributes

version_info[RW]

optional program version info to be associated with the cache files if the program version changes, cached data will also be invalid

Public Class Methods

new(cache_dir, postfix) click to toggle source

cache_dir is the name of the subfolder where cache files are created postfix is an extension appended to the original file name for creating the name of the cache file

# File lib/rgen/util/file_cache_map.rb, line 22
def initialize(cache_dir, postfix)
  @postfix = postfix
  @cache_dir = cache_dir
end

Public Instance Methods

clean_unused(root_path, key_paths) click to toggle source

remove cache files which are not associated with any file in key_paths will only remove files within root_path

# File lib/rgen/util/file_cache_map.rb, line 64
def clean_unused(root_path, key_paths)
  raise "key paths must be within root path" unless key_paths.all?{|p| p.index(root_path) == 0}
  used_files = key_paths.collect{|p| cache_file(p)}
  files = Dir[root_path+"/**/"+@cache_dir+"/*"+@postfix] 
  files.each do |f|
    FileUtils.rm(f) unless used_files.include?(f)
  end
end

load_data(key_path) click to toggle source

load data associated with file key_path returns :invalid in case either the associated file or the cache file has changed

# File lib/rgen/util/file_cache_map.rb, line 29
def load_data(key_path)
  cf = cache_file(key_path)
  return :invalid unless File.exist?(cf)
  result = nil
  File.open(cf, "rb") do |f|
    header = f.read(41)
    return :invalid unless header
    checksum = header[0..39]
    data = f.read
    if calc_sha1(data) == checksum
      if calc_sha1_keydata(key_path) == data[0..39]
        result = data[41..-1]
      else
        result = :invalid
      end
    else
      result = :invalid
    end
  end 
  result
end

store_data(key_path, value_data) click to toggle source

store data value_data associated with file key_path

# File lib/rgen/util/file_cache_map.rb, line 52
def store_data(key_path, value_data)
  data = calc_sha1_keydata(key_path) + "\n" + value_data
  data = calc_sha1(data) + "\n" + data
  cf = cache_file(key_path)
  FileUtils.mkdir(File.dirname(cf)) rescue Errno::EEXIST
  File.open(cf, "wb") do |f|
    f.write(data)
  end 
end

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RGen::Util::FileCacheMap

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Public Instance Methods