text: # Copyright 2013 The Chromium Authors. All rights reserved.
  # Use of this source code is governed by a BSD-style license that can be
  # found in the LICENSE file.
  
  
  import functools
  import logging
  import os
  import shlex
  import sys
  
  
  def memoize(default=None):
    """This decorator caches the return value of a parameterless pure function"""
    def memoizer(func):
      val = []
      @functools.wraps(func)
      def inner():
        if not val:
          ret = func()
          val.append(ret if ret is not None else default)
          if logging.getLogger().isEnabledFor(logging.INFO):
            print '%s -> %r' % (func.__name__, val[0])
        return val[0]
      return inner
    return memoizer
  
  
  @memoize()
  def IsWindows():
    return sys.platform in ['win32', 'cygwin']
  
  
  @memoize()
  def IsLinux():
    return sys.platform.startswith(('linux', 'freebsd', 'netbsd', 'openbsd'))
  
  
  @memoize()
  def IsMac():
    return sys.platform == 'darwin'
  
  
  @memoize()
  def gyp_defines():
    """Parses and returns GYP_DEFINES env var as a dictionary."""
    return dict(arg.split('=', 1)
        for arg in shlex.split(os.environ.get('GYP_DEFINES', '')))
  
  
  @memoize()
  def gyp_generator_flags():
    """Parses and returns GYP_GENERATOR_FLAGS env var as a dictionary."""
    return dict(arg.split('=', 1)
        for arg in shlex.split(os.environ.get('GYP_GENERATOR_FLAGS', '')))
  
  
  @memoize()
  def gyp_msvs_version():
    return os.environ.get('GYP_MSVS_VERSION', '')
  
  
  @memoize()
  def distributor():
    """
    Returns a string which is the distributed build engine in use (if any).
    Possible values: 'goma', None
    """
    if 'goma' in gyp_defines():
      return 'goma'
  
  
  @memoize()
  def platform():
    """
    Returns a string representing the platform this build is targetted for.
    Possible values: 'win', 'mac', 'linux', 'ios', 'android'
    """
    if 'OS' in gyp_defines():
      if 'android' in gyp_defines()['OS']:
        return 'android'
      else:
        return gyp_defines()['OS']
    elif IsWindows():
      return 'win'
    elif IsLinux():
      return 'linux'
    else:
      return 'mac'
  