"""scons.Node.Python

Python nodes.

"""

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__revision__ = "src/engine/SCons/Node/Python.py 5023 2010/06/14 22:05:46 scons"

import SCons.Node

class ValueNodeInfo(SCons.Node.NodeInfoBase):
    current_version_id = 1

    field_list = ['csig']

    def str_to_node(self, s):
        return Value(s)

class ValueBuildInfo(SCons.Node.BuildInfoBase):
    current_version_id = 1

class Value(SCons.Node.Node):
    """A class for Python variables, typically passed on the command line 
    or generated by a script, but not from a file or some other source.
    """

    NodeInfo = ValueNodeInfo
    BuildInfo = ValueBuildInfo

    def __init__(self, value, built_value=None):
        SCons.Node.Node.__init__(self)
        self.value = value
        if built_value is not None:
            self.built_value = built_value

    def str_for_display(self):
        return repr(self.value)

    def __str__(self):
        return str(self.value)

    def make_ready(self):
        self.get_csig()

    def build(self, **kw):
        if not hasattr(self, 'built_value'):
            SCons.Node.Node.build(self, **kw)

    is_up_to_date = SCons.Node.Node.children_are_up_to_date

    def is_under(self, dir):
        # Make Value nodes get built regardless of 
        # what directory scons was run from. Value nodes
        # are outside the filesystem:
        return 1

    def write(self, built_value):
        """Set the value of the node."""
        self.built_value = built_value

    def read(self):
        """Return the value. If necessary, the value is built."""
        self.build()
        if not hasattr(self, 'built_value'):
            self.built_value = self.value
        return self.built_value

    def get_text_contents(self):
        """By the assumption that the node.built_value is a
        deterministic product of the sources, the contents of a Value
        are the concatenation of all the contents of its sources.  As
        the value need not be built when get_contents() is called, we
        cannot use the actual node.built_value."""
        ###TODO: something reasonable about universal newlines
        contents = str(self.value)
        for kid in self.children(None):
            contents = contents + kid.get_contents()
        return contents

    get_contents = get_text_contents    ###TODO should return 'bytes' value

    def changed_since_last_build(self, target, prev_ni):
        cur_csig = self.get_csig()
        try:
            return cur_csig != prev_ni.csig
        except AttributeError:
            return 1

    def get_csig(self, calc=None):
        """Because we're a Python value node and don't have a real
        timestamp, we get to ignore the calculator and just use the
        value contents."""
        try:
            return self.ninfo.csig
        except AttributeError:
            pass
        contents = self.get_contents()
        self.get_ninfo().csig = contents
        return contents

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