text: #
  # __COPYRIGHT__
  #
  # Permission is hereby granted, free of charge, to any person obtaining
  # a copy of this software and associated documentation files (the
  # "Software"), to deal in the Software without restriction, including
  # without limitation the rights to use, copy, modify, merge, publish,
  # distribute, sublicense, and/or sell copies of the Software, and to
  # permit persons to whom the Software is furnished to do so, subject to
  # the following conditions:
  #
  # The above copyright notice and this permission notice shall be included
  # in all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
  # KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  # WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  # LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  #
  
  __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
  
  __doc__ = """
  CacheDir support
  """
  
  import json
  import os
  import stat
  import sys
  
  import SCons
  import SCons.Action
  import SCons.Warnings
  
  cache_enabled = True
  cache_debug = False
  cache_force = False
  cache_show = False
  cache_readonly = False
  
  def CacheRetrieveFunc(target, source, env):
      t = target[0]
      fs = t.fs
      cd = env.get_CacheDir()
      cd.requests += 1
      cachedir, cachefile = cd.cachepath(t)
      if not fs.exists(cachefile):
          cd.CacheDebug('CacheRetrieve(%s):  %s not in cache\n', t, cachefile)
          return 1
      cd.hits += 1
      cd.CacheDebug('CacheRetrieve(%s):  retrieving from %s\n', t, cachefile)
      if SCons.Action.execute_actions:
          if fs.islink(cachefile):
              fs.symlink(fs.readlink(cachefile), t.get_internal_path())
          else:
              env.copy_from_cache(cachefile, t.get_internal_path())
              try:
                  os.utime(cachefile, None)
              except OSError:
                  pass
          st = fs.stat(cachefile)
          fs.chmod(t.get_internal_path(), stat.S_IMODE(st[stat.ST_MODE]) | stat.S_IWRITE)
      return 0
  
  def CacheRetrieveString(target, source, env):
      t = target[0]
      fs = t.fs
      cd = env.get_CacheDir()
      cachedir, cachefile = cd.cachepath(t)
      if t.fs.exists(cachefile):
          return "Retrieved `%s' from cache" % t.get_internal_path()
      return None
  
  CacheRetrieve = SCons.Action.Action(CacheRetrieveFunc, CacheRetrieveString)
  
  CacheRetrieveSilent = SCons.Action.Action(CacheRetrieveFunc, None)
  
  def CachePushFunc(target, source, env):
      if cache_readonly:
          return
  
      t = target[0]
      if t.nocache:
          return
      fs = t.fs
      cd = env.get_CacheDir()
      cachedir, cachefile = cd.cachepath(t)
      if fs.exists(cachefile):
          # Don't bother copying it if it's already there.  Note that
          # usually this "shouldn't happen" because if the file already
          # existed in cache, we'd have retrieved the file from there,
          # not built it.  This can happen, though, in a race, if some
          # other person running the same build pushes their copy to
          # the cache after we decide we need to build it but before our
          # build completes.
          cd.CacheDebug('CachePush(%s):  %s already exists in cache\n', t, cachefile)
          return
  
      cd.CacheDebug('CachePush(%s):  pushing to %s\n', t, cachefile)
  
      tempfile = cachefile+'.tmp'+str(os.getpid())
      errfmt = "Unable to copy %s to cache. Cache file is %s"
  
      if not fs.isdir(cachedir):
          try:
              fs.makedirs(cachedir)
          except EnvironmentError:
              # We may have received an exception because another process
              # has beaten us creating the directory.
              if not fs.isdir(cachedir):
                  msg = errfmt % (str(target), cachefile)
                  raise SCons.Errors.SConsEnvironmentError(msg)
  
      try:
          if fs.islink(t.get_internal_path()):
              fs.symlink(fs.readlink(t.get_internal_path()), tempfile)
          else:
              fs.copy2(t.get_internal_path(), tempfile)
          fs.rename(tempfile, cachefile)
          st = fs.stat(t.get_internal_path())
          fs.chmod(cachefile, stat.S_IMODE(st[stat.ST_MODE]) | stat.S_IWRITE)
      except EnvironmentError:
          # It's possible someone else tried writing the file at the
          # same time we did, or else that there was some problem like
          # the CacheDir being on a separate file system that's full.
          # In any case, inability to push a file to cache doesn't affect
          # the correctness of the build, so just print a warning.
          msg = errfmt % (str(target), cachefile)
          SCons.Warnings.warn(SCons.Warnings.CacheWriteErrorWarning, msg)
  
  CachePush = SCons.Action.Action(CachePushFunc, None)
  
  
  class CacheDir(object):
  
      def __init__(self, path):
          """
          Initialize a CacheDir object.
  
          The cache configuration is stored in the object. It
          is read from the config file in the supplied path if
          one exists,  if not the config file is created and
          the default config is written, as well as saved in the object.
          """
          self.requests = 0
          self.hits = 0
          self.path = path
          self.current_cache_debug = None
          self.debugFP = None
          self.config = dict()
          if path is None:
              return
  
          self._readconfig(path)
  
  
      def _readconfig(self, path):
          """
          Read the cache config.
  
          If directory or config file do not exist, create.  Take advantage
          of Py3 capability in os.makedirs() and in file open(): just try
          the operation and handle failure appropriately.
  
          Omit the check for old cache format, assume that's old enough
          there will be none of those left to worry about.
  
          :param path: path to the cache directory
          """
          config_file = os.path.join(path, 'config')
          try:
              os.makedirs(path, exist_ok=True)
          except FileExistsError:
              pass
          except OSError:
              msg = "Failed to create cache directory " + path
              raise SCons.Errors.SConsEnvironmentError(msg)
  
          try:
              with open(config_file, 'x') as config:
                  self.config['prefix_len'] = 2
                  try:
                      json.dump(self.config, config)
                  except Exception:
                      msg = "Failed to write cache configuration for " + path
                      raise SCons.Errors.SConsEnvironmentError(msg)
          except FileExistsError:
              try:
                  with open(config_file) as config:
                      self.config = json.load(config)
              except ValueError:
                  msg = "Failed to read cache configuration for " + path
                  raise SCons.Errors.SConsEnvironmentError(msg)
  
  
      def CacheDebug(self, fmt, target, cachefile):
          if cache_debug != self.current_cache_debug:
              if cache_debug == '-':
                  self.debugFP = sys.stdout
              elif cache_debug:
                  self.debugFP = open(cache_debug, 'w')
              else:
                  self.debugFP = None
              self.current_cache_debug = cache_debug
          if self.debugFP:
              self.debugFP.write(fmt % (target, os.path.split(cachefile)[1]))
              self.debugFP.write("requests: %d, hits: %d, misses: %d, hit rate: %.2f%%\n" %
                                 (self.requests, self.hits, self.misses, self.hit_ratio))
  
      @property
      def hit_ratio(self):
          return (100.0 * self.hits / self.requests if self.requests > 0 else 100)
  
      @property
      def misses(self):
          return self.requests - self.hits
  
      def is_enabled(self):
          return cache_enabled and self.path is not None
  
      def is_readonly(self):
          return cache_readonly
  
      def cachepath(self, node):
          """
          """
          if not self.is_enabled():
              return None, None
  
          sig = node.get_cachedir_bsig()
  
          subdir = sig[:self.config['prefix_len']].upper()
  
          dir = os.path.join(self.path, subdir)
          return dir, os.path.join(dir, sig)
  
      def retrieve(self, node):
          """
          This method is called from multiple threads in a parallel build,
          so only do thread safe stuff here. Do thread unsafe stuff in
          built().
  
          Note that there's a special trick here with the execute flag
          (one that's not normally done for other actions).  Basically
          if the user requested a no_exec (-n) build, then
          SCons.Action.execute_actions is set to 0 and when any action
          is called, it does its showing but then just returns zero
          instead of actually calling the action execution operation.
          The problem for caching is that if the file does NOT exist in
          cache then the CacheRetrieveString won't return anything to
          show for the task, but the Action.__call__ won't call
          CacheRetrieveFunc; instead it just returns zero, which makes
          the code below think that the file *was* successfully
          retrieved from the cache, therefore it doesn't do any
          subsequent building.  However, the CacheRetrieveString didn't
          print anything because it didn't actually exist in the cache,
          and no more build actions will be performed, so the user just
          sees nothing.  The fix is to tell Action.__call__ to always
          execute the CacheRetrieveFunc and then have the latter
          explicitly check SCons.Action.execute_actions itself.
          """
          if not self.is_enabled():
              return False
  
          env = node.get_build_env()
          if cache_show:
              if CacheRetrieveSilent(node, [], env, execute=1) == 0:
                  node.build(presub=0, execute=0)
                  return True
          else:
              if CacheRetrieve(node, [], env, execute=1) == 0:
                  return True
  
          return False
  
      def push(self, node):
          if self.is_readonly() or not self.is_enabled():
              return
          return CachePush(node, [], node.get_build_env())
  
      def push_if_forced(self, node):
          if cache_force:
              return self.push(node)
  
  # Local Variables:
  # tab-width:4
  # indent-tabs-mode:nil
  # End:
  # vim: set expandtab tabstop=4 shiftwidth=4:
  