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module RGen
module Util
# WARNING: the mechanism of taking timestamps of directories in order to find out if the
# content has changed doesn't work reliably across all kinds of filesystems
#
class CachedGlob
def initialize(dir_glob, file_glob)
@dir_glob = dir_glob
@file_glob = file_glob
@root_dirs = []
@dirs = {}
@files = {}
@timestamps = {}
end
# returns all files contained in directories matched by +dir_glob+ which match +file_glob+.
# +file_glob+ must be relative to +dir_glob+.
# dir_glob "*/a" with file_glob "**/*.txt" is basically equivalent with Dir.glob("*/a/**/*.txt")
# the idea is that the file glob will only be re-eavluated when the content of one of the
# directories matched by dir_glob has changed.
# this will only be faster than a normal Dir.glob if the number of dirs matched by dir_glob is
# relatively large and changes in files affect only a few of them at a time.
def glob
root_dirs = Dir.glob(@dir_glob)
(@root_dirs - root_dirs).each do |d|
remove_root_dir(d)
end
(@root_dirs & root_dirs).each do |d|
update_root_dir(d) if dir_changed?(d)
end
(root_dirs - @root_dirs).each do |d|
update_root_dir(d)
end
@root_dirs = root_dirs
@root_dirs.sort.collect{|d| @files[d]}.flatten
end
private
def dir_changed?(dir)
@dirs[dir].any?{|d| File.mtime(d) != @timestamps[dir][d]}
end
def update_root_dir(dir)
@dirs[dir] = Dir.glob(dir+"/**/")
@files[dir] = Dir.glob(dir+"/"+@file_glob)
@timestamps[dir] = {}
@dirs[dir].each do |d|
@timestamps[dir][d] = File.mtime(d)
end
end
def remove_root_dir(dir)
@dirs.delete(dir)
@files.delete(dir)
@timestamps.delete(dir)
end
end
end
end
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