pypy / pypy / interpreter / nestedscope.py

from pypy.interpreter.error import OperationError
from pypy.interpreter import function, pycode, pyframe
from pypy.interpreter.baseobjspace import Wrappable
from pypy.interpreter.mixedmodule import MixedModule
from pypy.interpreter.astcompiler import consts
from pypy.rlib import jit
from pypy.tool.uid import uid

class Cell(Wrappable):
    "A simple container for a wrapped value."

    def __init__(self, w_value=None):
        self.w_value = w_value

    def clone(self):
        return self.__class__(self.w_value)

    def empty(self):
        return self.w_value is None

    def get(self):
        if self.w_value is None:
            raise ValueError, "get() from an empty cell"
        return self.w_value

    def set(self, w_value):
        self.w_value = w_value

    def delete(self):
        if self.w_value is None:
            raise ValueError, "delete() on an empty cell"
        self.w_value = None
  
    def descr__cmp__(self, space, w_other):
        other = space.interpclass_w(w_other)
        if not isinstance(other, Cell):
            return space.w_NotImplemented

        if self.w_value is None:
            if other.w_value is None:
                return space.newint(0)
            return space.newint(-1)
        elif other.w_value is None:
            return space.newint(1)

        return space.cmp(self.w_value, other.w_value)

    def descr__reduce__(self, space):
        w_mod    = space.getbuiltinmodule('_pickle_support')
        mod      = space.interp_w(MixedModule, w_mod)
        new_inst = mod.get('cell_new')
        if self.w_value is None:    #when would this happen?
            return space.newtuple([new_inst, space.newtuple([])])
        tup = [self.w_value]
        return space.newtuple([new_inst, space.newtuple([]),
                               space.newtuple(tup)])

    def descr__setstate__(self, space, w_state):
        self.w_value = space.getitem(w_state, space.wrap(0))
        
    def __repr__(self):
        """ representation for debugging purposes """
        if self.w_value is None:
            content = ""
        else:
            content = repr(self.w_value)
        return "<%s(%s) at 0x%x>" % (self.__class__.__name__,
                                     content, uid(self))

    def descr__cell_contents(self, space):
        try:
            return self.get()
        except ValueError:
            raise OperationError(space.w_ValueError, space.wrap("Cell is empty"))



super_initialize_frame_scopes = pyframe.PyFrame.initialize_frame_scopes
super_fast2locals             = pyframe.PyFrame.fast2locals
super_locals2fast             = pyframe.PyFrame.locals2fast


class __extend__(pyframe.PyFrame):
    """This class enhances a standard frame with nested scope abilities,
    i.e. handling of cell/free variables."""

    # Cell Vars:
    #     my local variables that are exposed to my inner functions
    # Free Vars:
    #     variables coming from a parent function in which i'm nested
    # 'closure' is a list of Cell instances: the received free vars.

    @jit.unroll_safe
    def initialize_frame_scopes(self, outer_func, code):
        super_initialize_frame_scopes(self, outer_func, code)
        ncellvars = len(code.co_cellvars)
        nfreevars = len(code.co_freevars)
        if not nfreevars:
            if not ncellvars:
                self.cells = []
                return            # no self.cells needed - fast path
        elif outer_func is None:
            space = self.space
            raise OperationError(space.w_TypeError,
                                 space.wrap("directly executed code object "
                                            "may not contain free variables"))
        if outer_func and outer_func.closure:
            closure_size = len(outer_func.closure)
        else:
            closure_size = 0
        if closure_size != nfreevars:
            raise ValueError("code object received a closure with "
                                 "an unexpected number of free variables")
        self.cells = [None] * (ncellvars + nfreevars)
        for i in range(ncellvars):
            self.cells[i] = Cell()
        for i in range(nfreevars):
            self.cells[i + ncellvars] = outer_func.closure[i]

    def _getcells(self):
        return self.cells

    def _setcellvars(self, cellvars):
        ncellvars = len(self.pycode.co_cellvars)
        if len(cellvars) != ncellvars:
            raise OperationError(self.space.w_TypeError,
                                 self.space.wrap("bad cellvars"))
        if self.cells is not None:
            self.cells[:ncellvars] = cellvars

    @jit.dont_look_inside
    def fast2locals(self):
        super_fast2locals(self)
        # cellvars are values exported to inner scopes
        # freevars are values coming from outer scopes 
        freevarnames = list(self.pycode.co_cellvars)
        if self.pycode.co_flags & consts.CO_OPTIMIZED:
            freevarnames.extend(self.pycode.co_freevars)
        for i in range(len(freevarnames)):
            name = freevarnames[i]
            cell = self.cells[i]
            try:
                w_value = cell.get()
            except ValueError:
                pass
            else:
                w_name = self.space.wrap(name)
                self.space.setitem(self.w_locals, w_name, w_value)

    @jit.dont_look_inside
    def locals2fast(self):
        super_locals2fast(self)
        freevarnames = self.pycode.co_cellvars + self.pycode.co_freevars
        for i in range(len(freevarnames)):
            name = freevarnames[i]
            cell = self.cells[i]
            w_name = self.space.wrap(name)
            try:
                w_value = self.space.getitem(self.w_locals, w_name)
            except OperationError, e:
                if not e.match(self.space, self.space.w_KeyError):
                    raise
            else:
                cell.set(w_value)

    @jit.unroll_safe
    def init_cells(self):
        if self.cells is None:
            return
        args_to_copy = self.pycode._args_as_cellvars
        for i in range(len(args_to_copy)):
            argnum = args_to_copy[i]
            if argnum >= 0:
                self.cells[i].set(self.locals_stack_w[argnum])

    def getfreevarname(self, index):
        freevarnames = self.pycode.co_cellvars + self.pycode.co_freevars
        return freevarnames[index]

    def iscellvar(self, index):
        # is the variable given by index a cell or a free var?
        return index < len(self.pycode.co_cellvars)

    ### extra opcodes ###

    def LOAD_CLOSURE(self, varindex, next_instr):
        # nested scopes: access the cell object
        cell = self.cells[varindex]
        w_value = self.space.wrap(cell)
        self.pushvalue(w_value)

    def LOAD_DEREF(self, varindex, next_instr):
        # nested scopes: access a variable through its cell object
        cell = self.cells[varindex]
        try:
            w_value = cell.get()
        except ValueError:
            varname = self.getfreevarname(varindex)
            if self.iscellvar(varindex):
                message = "local variable '%s' referenced before assignment"%varname
                w_exc_type = self.space.w_UnboundLocalError
            else:
                message = ("free variable '%s' referenced before assignment"
                           " in enclosing scope"%varname)
                w_exc_type = self.space.w_NameError
            raise OperationError(w_exc_type, self.space.wrap(message))
        else:
            self.pushvalue(w_value)

    def STORE_DEREF(self, varindex, next_instr):
        # nested scopes: access a variable through its cell object
        w_newvalue = self.popvalue()
        cell = self.cells[varindex]
        cell.set(w_newvalue)

    @jit.unroll_safe
    def MAKE_CLOSURE(self, numdefaults, next_instr):
        w_codeobj = self.popvalue()
        codeobj = self.space.interp_w(pycode.PyCode, w_codeobj)
        w_freevarstuple = self.popvalue()
        freevars = [self.space.interp_w(Cell, cell)
                    for cell in self.space.fixedview(w_freevarstuple)]
        defaultarguments = self.popvalues(numdefaults)
        fn = function.Function(self.space, codeobj, self.w_globals,
                               defaultarguments, freevars)
        self.pushvalue(self.space.wrap(fn))
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