text: # Local file checksum cache implementation
  #
  # Copyright (C) 2012 Intel Corporation
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU General Public License version 2 as
  # published by the Free Software Foundation.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
  #
  # You should have received a copy of the GNU General Public License along
  # with this program; if not, write to the Free Software Foundation, Inc.,
  # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  
  import glob
  import operator
  import os
  import stat
  import bb.utils
  import logging
  from bb.cache import MultiProcessCache
  
  logger = logging.getLogger("BitBake.Cache")
  
  try:
      import cPickle as pickle
  except ImportError:
      import pickle
      logger.info("Importing cPickle failed. "
                  "Falling back to a very slow implementation.")
  
  
  # mtime cache (non-persistent)
  # based upon the assumption that files do not change during bitbake run
  class FileMtimeCache(object):
      cache = {}
  
      def cached_mtime(self, f):
          if f not in self.cache:
              self.cache[f] = os.stat(f)[stat.ST_MTIME]
          return self.cache[f]
  
      def cached_mtime_noerror(self, f):
          if f not in self.cache:
              try:
                  self.cache[f] = os.stat(f)[stat.ST_MTIME]
              except OSError:
                  return 0
          return self.cache[f]
  
      def update_mtime(self, f):
          self.cache[f] = os.stat(f)[stat.ST_MTIME]
          return self.cache[f]
  
      def clear(self):
          self.cache.clear()
  
  # Checksum + mtime cache (persistent)
  class FileChecksumCache(MultiProcessCache):
      cache_file_name = "local_file_checksum_cache.dat"
      CACHE_VERSION = 1
  
      def __init__(self):
          self.mtime_cache = FileMtimeCache()
          MultiProcessCache.__init__(self)
  
      def get_checksum(self, f):
          entry = self.cachedata[0].get(f)
          cmtime = self.mtime_cache.cached_mtime(f)
          if entry:
              (mtime, hashval) = entry
              if cmtime == mtime:
                  return hashval
              else:
                  bb.debug(2, "file %s changed mtime, recompute checksum" % f)
  
          hashval = bb.utils.md5_file(f)
          self.cachedata_extras[0][f] = (cmtime, hashval)
          return hashval
  
      def merge_data(self, source, dest):
          for h in source[0]:
              if h in dest:
                  (smtime, _) = source[0][h]
                  (dmtime, _) = dest[0][h]
                  if smtime > dmtime:
                      dest[0][h] = source[0][h]
              else:
                  dest[0][h] = source[0][h]
  
      def get_checksums(self, filelist, pn):
          """Get checksums for a list of files"""
  
          def checksum_file(f):
              try:
                  checksum = self.get_checksum(f)
              except OSError as e:
                  bb.warn("Unable to get checksum for %s SRC_URI entry %s: %s" % (pn, os.path.basename(f), e))
                  return None
              return checksum
  
          def checksum_dir(pth):
              # Handle directories recursively
              dirchecksums = []
              for root, dirs, files in os.walk(pth):
                  for name in files:
                      fullpth = os.path.join(root, name)
                      checksum = checksum_file(fullpth)
                      if checksum:
                          dirchecksums.append((fullpth, checksum))
              return dirchecksums
  
          checksums = []
          for pth in filelist.split():
              exist = pth.split(":")[1]
              if exist == "False":
                  continue
              pth = pth.split(":")[0]
              if '*' in pth:
                  # Handle globs
                  for f in glob.glob(pth):
                      if os.path.isdir(f):
                          if not os.path.islink(f):
                              checksums.extend(checksum_dir(f))
                      else:
                          checksum = checksum_file(f)
                          checksums.append((f, checksum))
              elif os.path.isdir(pth):
                  if not os.path.islink(pth):
                      checksums.extend(checksum_dir(pth))
              else:
                  checksum = checksum_file(pth)
                  checksums.append((pth, checksum))
  
          checksums.sort(key=operator.itemgetter(1))
          return checksums
  