Dropping in software construction toolkit.

site_scons/site_tools/component_bits.py

Index: site_scons/site_tools/component_bits.py
===================================================================
--- site_scons/site_tools/component_bits.py	(revision 0)
+++ site_scons/site_tools/component_bits.py	(revision 0)
@@ -0,0 +1,212 @@
+#!/usr/bin/python2.4
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Environment bit support for software construction toolkit.
+
+This module is automatically included by the component_setup tool.
+"""
+
+
+import __builtin__
+import SCons
+
+
+_bit_descriptions = {}
+_bits_with_options = set()
+_bit_exclusive_groups = {}
+
+#------------------------------------------------------------------------------
+
+
+def DeclareBit(bit_name, desc, exclusive_groups=tuple()):
+  """Declares and describes the bit.
+
+  Args:
+    bit_name: Name of the bit being described.
+    desc: Description of bit.
+    exclusive_groups: Bit groups which this bit belongs to.  At most one bit
+        may be set in each exclusive group.
+
+  Raises:
+    ValueError: The bit has already been defined with a different description,
+        or the description is empty.
+
+  Adds a description for the bit in the global dictionary of bit names.  All
+  bits should be described before being used in Bit()/AllBits()/AnyBits().
+  """
+
+  if not desc:
+    raise ValueError('Must supply a description for bit "%s"' % bit_name)
+
+  existing_desc = _bit_descriptions.get(bit_name)
+  if existing_desc and desc != existing_desc:
+    raise ValueError('Cannot describe bit "%s" as "%s" because it has already'
+                     'been described as "%s".' %
+                     (bit_name, desc, existing_desc))
+
+  _bit_descriptions[bit_name] = desc
+
+  # Add bit to its exclusive groups
+  for g in exclusive_groups:
+    if g not in _bit_exclusive_groups:
+      _bit_exclusive_groups[g] = set()
+    _bit_exclusive_groups[g].add(bit_name)
+
+#------------------------------------------------------------------------------
+
+
+def Bit(env, bit_name):
+  """Checks if the environment has the bit.
+
+  Args:
+    env: Environment to check.
+    bit_name: Name of the bit to check.
+
+  Returns:
+    True if the bit is present in the environment.
+  """
+  # TODO(rspangler): Add bit sanity checking (description exists, exclusive
+  # groups not violated).
+  return bit_name in env['_BITS']
+
+#------------------------------------------------------------------------------
+
+
+def AllBits(env, *args):
+  """Checks if the environment has all the bits.
+
+  Args:
+    env: Environment to check.
+    args: List of bit names to check.
+
+  Returns:
+    True if every bit listed is present in the environment.
+  """
+  # TODO(rspangler): Add bit sanity checking
+  return set(args).issubset(env['_BITS'])
+
+#------------------------------------------------------------------------------
+
+
+def AnyBits(env, *args):
+  """Checks if the environment has at least one of the bits.
+
+  Args:
+    env: Environment to check.
+    args: List of bit names to check.
+
+  Returns:
+    True if at least one bit listed is present in the environment.
+  """
+  # TODO(rspangler): Add bit sanity checking
+  return set(args).intersection(env['_BITS'])
+
+#------------------------------------------------------------------------------
+
+
+def SetBits(env, *args):
+  """Sets the bits in the environment.
+
+  Args:
+    env: Environment to check.
+    args: List of bit names to set.
+  """
+  # TODO(rspangler): Add bit sanity checking
+  env['_BITS'] = env['_BITS'].union(args)
+
+#------------------------------------------------------------------------------
+
+
+def ClearBits(env, *args):
+  """Sets the bits in the environment.
+
+  Args:
+    env: Environment to check.
+    args: List of bit names to set.
+  """
+  # TODO(rspangler): Add bit sanity checking
+  env['_BITS'] = env['_BITS'].difference(args)
+
+#------------------------------------------------------------------------------
+
+
+def SetBitFromOption(env, bit_name, default):
+  """Sets the bit in the environment from a command line option.
+
+  Args:
+    env: Environment to check.
+    bit_name: Name of the bit to set from a command line option.
+    default: Default value for bit if command line option is not present.
+  """
+  # TODO(rspangler): Add bit sanity checking
+
+  # Add the command line option, if not already present
+  if bit_name not in _bits_with_options:
+    _bits_with_options.add(bit_name)
+    SCons.Script.AddOption('--' + bit_name,
+                           dest=bit_name,
+                           action='store_true',
+                           help='set bit:' + _bit_descriptions[bit_name])
+    SCons.Script.AddOption('--no-' + bit_name,
+                           dest=bit_name,
+                           action='store_false',
+                           help='clear bit:' + _bit_descriptions[bit_name])
+
+  bit_set = env.GetOption(bit_name)
+  if bit_set is None:
+    # Not specified on command line, so use default
+    bit_set = default
+
+  if bit_set:
+    env['_BITS'].add(bit_name)
+  elif bit_name in env['_BITS']:
+    env['_BITS'].remove(bit_name)
+
+#------------------------------------------------------------------------------
+
+
+def generate(env):
+  # NOTE: SCons requires the use of this name, which fails gpylint.
+  """SCons entry point for this tool."""
+
+  # Add methods to builtin
+  # TODO(rspangler): These really belong in site_init.py - but if we do that,
+  # what's the right way to access the bit global variables?
+  __builtin__.DeclareBit = DeclareBit
+
+  # Add methods to environment
+  env.AddMethod(AllBits)
+  env.AddMethod(AnyBits)
+  env.AddMethod(Bit)
+  env.AddMethod(ClearBits)
+  env.AddMethod(SetBitFromOption)
+  env.AddMethod(SetBits)
+
+  env['_BITS'] = set()