[pypy-commit] pypy gmp: Move away rbigint.py to its own "one-possible-implementation" module.

arigo noreply at buildbot.pypy.org
Thu Oct 20 16:37:31 CEST 2011


Author: Armin Rigo <arigo at tunes.org>
Branch: gmp
Changeset: r48266:0bfa78d1c3c5
Date: 2011-10-20 15:41 +0200
http://bitbucket.org/pypy/pypy/changeset/0bfa78d1c3c5/

Log:	Move away rbigint.py to its own "one-possible-implementation"
	module.

diff --git a/pypy/objspace/std/longobject.py b/pypy/objspace/std/longobject.py
--- a/pypy/objspace/std/longobject.py
+++ b/pypy/objspace/std/longobject.py
@@ -6,7 +6,7 @@
 from pypy.objspace.std.multimethod import FailedToImplementArgs
 from pypy.objspace.std.intobject import W_IntObject
 from pypy.objspace.std.noneobject import W_NoneObject
-from pypy.rlib.rbigint import rbigint, SHIFT
+from pypy.rlib.rbigint import rbigint
 
 class W_LongObject(W_Object):
     """This is a wrapper of rbigint."""
diff --git a/pypy/rlib/rbigint.py b/pypy/rlib/_rbigint_native.py
copy from pypy/rlib/rbigint.py
copy to pypy/rlib/_rbigint_native.py
diff --git a/pypy/rlib/rbigint.py b/pypy/rlib/rbigint.py
--- a/pypy/rlib/rbigint.py
+++ b/pypy/rlib/rbigint.py
@@ -1,1904 +1,9 @@
-from pypy.rlib.rarithmetic import LONG_BIT, intmask, r_uint, r_ulonglong
-from pypy.rlib.rarithmetic import ovfcheck, r_longlong, widen
-from pypy.rlib.rarithmetic import most_neg_value_of_same_type
-from pypy.rlib.rfloat import isfinite
-from pypy.rlib.debug import make_sure_not_resized, check_regular_int
-from pypy.rlib.objectmodel import we_are_translated, specialize
-from pypy.rlib import jit
-from pypy.rpython.lltypesystem import lltype, rffi
-from pypy.rpython import extregistry
 
-import math, sys
 
-# note about digit sizes:
-# In division, the native integer type must be able to hold
-# a sign bit plus two digits plus 1 overflow bit.
+USE_GMP = False
 
-#SHIFT = (LONG_BIT // 2) - 1
-SHIFT = 31
 
-MASK = int((1 << SHIFT) - 1)
-FLOAT_MULTIPLIER = float(1 << SHIFT)
-
-
-# Debugging digit array access.
-#
-# False == no checking at all
-# True == check 0 <= value <= MASK
-
-
-# For long multiplication, use the O(N**2) school algorithm unless
-# both operands contain more than KARATSUBA_CUTOFF digits (this
-# being an internal Python long digit, in base BASE).
-
-USE_KARATSUBA = True # set to False for comparison
-KARATSUBA_CUTOFF = 70
-KARATSUBA_SQUARE_CUTOFF = 2 * KARATSUBA_CUTOFF
-
-# For exponentiation, use the binary left-to-right algorithm
-# unless the exponent contains more than FIVEARY_CUTOFF digits.
-# In that case, do 5 bits at a time.  The potential drawback is that
-# a table of 2**5 intermediate results is computed.
-
-## FIVEARY_CUTOFF = 8   disabled for now
-
-
-def _mask_digit(x):
-    if not we_are_translated():
-        assert type(x) is not long, "overflow occurred!"
-    return intmask(x & MASK)
-_mask_digit._annspecialcase_ = 'specialize:argtype(0)'
-
-def _widen_digit(x):
-    if not we_are_translated():
-        assert type(x) is int, "widen_digit() takes an int, got a %r" % type(x)
-    if SHIFT <= 15:
-        return int(x)
-    return r_longlong(x)
-
-def _store_digit(x):
-    if not we_are_translated():
-        assert type(x) is int, "store_digit() takes an int, got a %r" % type(x)
-    if SHIFT <= 15:
-        return rffi.cast(rffi.SHORT, x)
-    elif SHIFT <= 31:
-        return rffi.cast(rffi.INT, x)
-    else:
-        raise ValueError("SHIFT too large!")
-
-def _load_digit(x):
-    return rffi.cast(lltype.Signed, x)
-
-def _load_unsigned_digit(x):
-    return rffi.cast(lltype.Unsigned, x)
-
-NULLDIGIT = _store_digit(0)
-ONEDIGIT  = _store_digit(1)
-
-def _check_digits(l):
-    for x in l:
-        assert type(x) is type(NULLDIGIT)
-        assert intmask(x) & MASK == intmask(x)
-class Entry(extregistry.ExtRegistryEntry):
-    _about_ = _check_digits
-    def compute_result_annotation(self, s_list):
-        from pypy.annotation import model as annmodel
-        assert isinstance(s_list, annmodel.SomeList)
-        s_DIGIT = self.bookkeeper.valueoftype(type(NULLDIGIT))
-        assert s_DIGIT.contains(s_list.listdef.listitem.s_value)
-    def specialize_call(self, hop):
-        pass
-
-
-class rbigint(object):
-    """This is a reimplementation of longs using a list of digits."""
-
-    def __init__(self, digits=[], sign=0):
-        if len(digits) == 0:
-            digits = [NULLDIGIT]
-        _check_digits(digits)
-        make_sure_not_resized(digits)
-        self._digits = digits
-        self.sign = sign
-
-    def digit(self, x):
-        """Return the x'th digit, as an int."""
-        return _load_digit(self._digits[x])
-
-    def widedigit(self, x):
-        """Return the x'th digit, as a long long int if needed
-        to have enough room to contain two digits."""
-        return _widen_digit(_load_digit(self._digits[x]))
-
-    def udigit(self, x):
-        """Return the x'th digit, as an unsigned int."""
-        return _load_unsigned_digit(self._digits[x])
-
-    def setdigit(self, x, val):
-        val = _mask_digit(val)
-        assert val >= 0
-        self._digits[x] = _store_digit(val)
-    setdigit._annspecialcase_ = 'specialize:argtype(2)'
-
-    def numdigits(self):
-        return len(self._digits)
-
-    @staticmethod
-    @jit.elidable
-    def fromint(intval):
-        # This function is marked as pure, so you must not call it and
-        # then modify the result.
-        check_regular_int(intval)
-        if intval < 0:
-            sign = -1
-            ival = r_uint(-intval)
-        elif intval > 0:
-            sign = 1
-            ival = r_uint(intval)
-        else:
-            return rbigint()
-        # Count the number of Python digits.
-        # We used to pick 5 ("big enough for anything"), but that's a
-        # waste of time and space given that 5*15 = 75 bits are rarely
-        # needed.
-        t = ival
-        ndigits = 0
-        while t:
-            ndigits += 1
-            t >>= SHIFT
-        v = rbigint([NULLDIGIT] * ndigits, sign)
-        t = ival
-        p = 0
-        while t:
-            v.setdigit(p, t)
-            t >>= SHIFT
-            p += 1
-        return v
-
-    @staticmethod
-    @jit.elidable
-    def frombool(b):
-        # This function is marked as pure, so you must not call it and
-        # then modify the result.
-        if b:
-            return rbigint([ONEDIGIT], 1)
-        return rbigint()
-
-    @staticmethod
-    def fromlong(l):
-        "NOT_RPYTHON"
-        return rbigint(*args_from_long(l))
-
-    @staticmethod
-    def fromfloat(dval):
-        """ Create a new bigint object from a float """
-        # This function is not marked as pure because it can raise
-        if isfinite(dval):
-            return rbigint._fromfloat_finite(dval)
-        else:
-            raise OverflowError
-
-    @staticmethod
-    @jit.elidable
-    def _fromfloat_finite(dval):
-        sign = 1
-        if dval < 0.0:
-            sign = -1
-            dval = -dval
-        frac, expo = math.frexp(dval) # dval = frac*2**expo; 0.0 <= frac < 1.0
-        if expo <= 0:
-            return rbigint()
-        ndig = (expo-1) // SHIFT + 1 # Number of 'digits' in result
-        v = rbigint([NULLDIGIT] * ndig, sign)
-        frac = math.ldexp(frac, (expo-1) % SHIFT + 1)
-        for i in range(ndig-1, -1, -1):
-            # use int(int(frac)) as a workaround for a CPython bug:
-            # with frac == 2147483647.0, int(frac) == 2147483647L
-            bits = int(int(frac))
-            v.setdigit(i, bits)
-            frac -= float(bits)
-            frac = math.ldexp(frac, SHIFT)
-        return v
-
-    @staticmethod
-    @jit.elidable
-    @specialize.argtype(0)
-    def fromrarith_int(i):
-        # This function is marked as pure, so you must not call it and
-        # then modify the result.
-        return rbigint(*args_from_rarith_int(i))
-
-    @staticmethod
-    @jit.elidable
-    def fromdecimalstr(s):
-        # This function is marked as pure, so you must not call it and
-        # then modify the result.
-        return _decimalstr_to_bigint(s)
-
-    def toint(self):
-        """
-        Get an integer from a bigint object.
-        Raises OverflowError if overflow occurs.
-        """
-        x = self._touint_helper()
-        # Haven't lost any bits, but if the sign bit is set we're in
-        # trouble *unless* this is the min negative number.  So,
-        # trouble iff sign bit set && (positive || some bit set other
-        # than the sign bit).
-        sign = self.sign
-        if intmask(x) < 0 and (sign > 0 or (x << 1) != 0):
-            raise OverflowError
-        return intmask(x * sign)
-
-    def tolonglong(self):
-        return _AsLongLong(self)
-
-    def tobool(self):
-        return self.sign != 0
-
-    def touint(self):
-        if self.sign == -1:
-            raise ValueError("cannot convert negative integer to unsigned int")
-        return self._touint_helper()
-
-    def _touint_helper(self):
-        x = r_uint(0)
-        i = self.numdigits() - 1
-        while i >= 0:
-            prev = x
-            x = (x << SHIFT) + self.udigit(i)
-            if (x >> SHIFT) != prev:
-                raise OverflowError(
-                        "long int too large to convert to unsigned int")
-            i -= 1
-        return x
-
-    def toulonglong(self):
-        if self.sign == -1:
-            raise ValueError("cannot convert negative integer to unsigned int")
-        return _AsULonglong_ignore_sign(self)
-
-    def uintmask(self):
-        return _AsUInt_mask(self)
-
-    def ulonglongmask(self):
-        """Return r_ulonglong(self), truncating."""
-        return _AsULonglong_mask(self)
-
-    def tofloat(self):
-        return _AsDouble(self)
-
-    def format(self, digits, prefix='', suffix=''):
-        # 'digits' is a string whose length is the base to use,
-        # and where each character is the corresponding digit.
-        return _format(self, digits, prefix, suffix)
-
-    def repr(self):
-        return _format(self, BASE10, '', 'L')
-
-    def str(self):
-        return _format(self, BASE10)
-
-    def eq(self, other):
-        if (self.sign != other.sign or
-            self.numdigits() != other.numdigits()):
-            return False
-        i = 0
-        ld = self.numdigits()
-        while i < ld:
-            if self.digit(i) != other.digit(i):
-                return False
-            i += 1
-        return True
-
-    def ne(self, other):
-        return not self.eq(other)
-
-    def lt(self, other):
-        if self.sign > other.sign:
-            return False
-        if self.sign < other.sign:
-            return True
-        ld1 = self.numdigits()
-        ld2 = other.numdigits()
-        if ld1 > ld2:
-            if other.sign > 0:
-                return False
-            else:
-                return True
-        elif ld1 < ld2:
-            if other.sign > 0:
-                return True
-            else:
-                return False
-        i = ld1 - 1
-        while i >= 0:
-            d1 = self.digit(i)
-            d2 = other.digit(i)
-            if d1 < d2:
-                if other.sign > 0:
-                    return True
-                else:
-                    return False
-            elif d1 > d2:
-                if other.sign > 0:
-                    return False
-                else:
-                    return True
-            i -= 1
-        return False
-
-    def le(self, other):
-        return not other.lt(self)
-
-    def gt(self, other):
-        return other.lt(self)
-
-    def ge(self, other):
-        return not self.lt(other)
-
-    def hash(self):
-        return _hash(self)
-
-    def add(self, other):
-        if self.sign == 0:
-            return other
-        if other.sign == 0:
-            return self
-        if self.sign == other.sign:
-            result = _x_add(self, other)
-        else:
-            result = _x_sub(other, self)
-        result.sign *= other.sign
-        return result
-
-    def sub(self, other):
-        if other.sign == 0:
-            return self
-        if self.sign == 0:
-            return rbigint(other._digits[:], -other.sign)
-        if self.sign == other.sign:
-            result = _x_sub(self, other)
-        else:
-            result = _x_add(self, other)
-        result.sign *= self.sign
-        result._normalize()
-        return result
-
-    def mul(self, other):
-        if USE_KARATSUBA:
-            result = _k_mul(self, other)
-        else:
-            result = _x_mul(self, other)
-        result.sign = self.sign * other.sign
-        return result
-
-    def truediv(self, other):
-        div = _bigint_true_divide(self, other)
-        return div
-
-    def floordiv(self, other):
-        div, mod = self.divmod(other)
-        return div
-
-    def div(self, other):
-        return self.floordiv(other)
-
-    def mod(self, other):
-        div, mod = self.divmod(other)
-        return mod
-
-    def divmod(v, w):
-        """
-        The / and % operators are now defined in terms of divmod().
-        The expression a mod b has the value a - b*floor(a/b).
-        The _divrem function gives the remainder after division of
-        |a| by |b|, with the sign of a.  This is also expressed
-        as a - b*trunc(a/b), if trunc truncates towards zero.
-        Some examples:
-          a   b   a rem b     a mod b
-          13  10   3           3
-         -13  10  -3           7
-          13 -10   3          -7
-         -13 -10  -3          -3
-        So, to get from rem to mod, we have to add b if a and b
-        have different signs.  We then subtract one from the 'div'
-        part of the outcome to keep the invariant intact.
-        """
-        div, mod = _divrem(v, w)
-        if mod.sign * w.sign == -1:
-            mod = mod.add(w)
-            div = div.sub(rbigint([_store_digit(1)], 1))
-        return div, mod
-
-    def pow(a, b, c=None):
-        negativeOutput = False  # if x<0 return negative output
-
-        # 5-ary values.  If the exponent is large enough, table is
-        # precomputed so that table[i] == a**i % c for i in range(32).
-        # python translation: the table is computed when needed.
-
-        if b.sign < 0:  # if exponent is negative
-            if c is not None:
-                raise TypeError(
-                    "pow() 2nd argument "
-                    "cannot be negative when 3rd argument specified")
-            # XXX failed to implement
-            raise ValueError("bigint pow() too negative")
-
-        if c is not None:
-            if c.sign == 0:
-                raise ValueError("pow() 3rd argument cannot be 0")
-
-            # if modulus < 0:
-            #     negativeOutput = True
-            #     modulus = -modulus
-            if c.sign < 0:
-                negativeOutput = True
-                c = c.neg()
-
-            # if modulus == 1:
-            #     return 0
-            if c.numdigits() == 1 and c.digit(0) == 1:
-                return rbigint()
-
-            # if base < 0:
-            #     base = base % modulus
-            # Having the base positive just makes things easier.
-            if a.sign < 0:
-                a, temp = a.divmod(c)
-                a = temp
-
-        # At this point a, b, and c are guaranteed non-negative UNLESS
-        # c is NULL, in which case a may be negative. */
-
-        z = rbigint([_store_digit(1)], 1)
-
-        # python adaptation: moved macros REDUCE(X) and MULT(X, Y, result)
-        # into helper function result = _help_mult(x, y, c)
-        if 1:   ## b.numdigits() <= FIVEARY_CUTOFF:
-            # Left-to-right binary exponentiation (HAC Algorithm 14.79)
-            # http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf
-            i = b.numdigits() - 1
-            while i >= 0:
-                bi = b.digit(i)
-                j = 1 << (SHIFT-1)
-                while j != 0:
-                    z = _help_mult(z, z, c)
-                    if bi & j:
-                        z = _help_mult(z, a, c)
-                    j >>= 1
-                i -= 1
-##        else:
-##            This code is disabled for now, because it assumes that
-##            SHIFT is a multiple of 5.  It could be fixed but it looks
-##            like it's more troubles than benefits...
-##
-##            # Left-to-right 5-ary exponentiation (HAC Algorithm 14.82)
-##            # This is only useful in the case where c != None.
-##            # z still holds 1L
-##            table = [z] * 32
-##            table[0] = z
-##            for i in range(1, 32):
-##                table[i] = _help_mult(table[i-1], a, c)
-##            i = b.numdigits() - 1
-##            while i >= 0:
-##                bi = b.digit(i)
-##                j = SHIFT - 5
-##                while j >= 0:
-##                    index = (bi >> j) & 0x1f
-##                    for k in range(5):
-##                        z = _help_mult(z, z, c)
-##                    if index:
-##                        z = _help_mult(z, table[index], c)
-##                    j -= 5
-##                i -= 1
-
-        if negativeOutput and z.sign != 0:
-            z = z.sub(c)
-        return z
-
-    def neg(self):
-        return rbigint(self._digits, -self.sign)
-
-    def abs(self):
-        return rbigint(self._digits, abs(self.sign))
-
-    def invert(self): #Implement ~x as -(x + 1)
-        return self.add(rbigint([_store_digit(1)], 1)).neg()
-
-    def lshift(self, int_other):
-        if int_other < 0:
-            raise ValueError("negative shift count")
-        elif int_other == 0:
-            return self
-
-        # wordshift, remshift = divmod(int_other, SHIFT)
-        wordshift = int_other // SHIFT
-        remshift  = int_other - wordshift * SHIFT
-
-        oldsize = self.numdigits()
-        newsize = oldsize + wordshift
-        if remshift:
-            newsize += 1
-        z = rbigint([NULLDIGIT] * newsize, self.sign)
-        accum = _widen_digit(0)
-        i = wordshift
-        j = 0
-        while j < oldsize:
-            accum |= self.widedigit(j) << remshift
-            z.setdigit(i, accum)
-            accum >>= SHIFT
-            i += 1
-            j += 1
-        if remshift:
-            z.setdigit(newsize - 1, accum)
-        else:
-            assert not accum
-        z._normalize()
-        return z
-
-    def rshift(self, int_other, dont_invert=False):
-        if int_other < 0:
-            raise ValueError("negative shift count")
-        elif int_other == 0:
-            return self
-        if self.sign == -1 and not dont_invert:
-            a1 = self.invert()
-            a2 = a1.rshift(int_other)
-            return a2.invert()
-
-        wordshift = int_other // SHIFT
-        newsize = self.numdigits() - wordshift
-        if newsize <= 0:
-            return rbigint()
-
-        loshift = int_other % SHIFT
-        hishift = SHIFT - loshift
-        lomask = intmask((r_uint(1) << hishift) - 1)
-        himask = MASK ^ lomask
-        z = rbigint([NULLDIGIT] * newsize, self.sign)
-        i = 0
-        j = wordshift
-        while i < newsize:
-            newdigit = (self.digit(j) >> loshift) & lomask
-            if i+1 < newsize:
-                newdigit |= intmask(self.digit(j+1) << hishift) & himask
-            z.setdigit(i, newdigit)
-            i += 1
-            j += 1
-        z._normalize()
-        return z
-
-    def and_(self, other):
-        return _bitwise(self, '&', other)
-
-    def xor(self, other):
-        return _bitwise(self, '^', other)
-
-    def or_(self, other):
-        return _bitwise(self, '|', other)
-
-    def oct(self):
-        if self.sign == 0:
-            return '0L'
-        else:
-            return _format(self, BASE8, '0', 'L')
-
-    def hex(self):
-        return _format(self, BASE16, '0x', 'L')
-
-    def log(self, base):
-        # base is supposed to be positive or 0.0, which means we use e
-        if base == 10.0:
-            return _loghelper(math.log10, self)
-        ret = _loghelper(math.log, self)
-        if base != 0.0:
-            ret /= math.log(base)
-        return ret
-
-    def tolong(self):
-        "NOT_RPYTHON"
-        l = 0L
-        digits = list(self._digits)
-        digits.reverse()
-        for d in digits:
-            l = l << SHIFT
-            l += intmask(d)
-        return l * self.sign
-
-    def _normalize(self):
-        if self.numdigits() == 0:
-            self.sign = 0
-            self._digits = [NULLDIGIT]
-            return
-        i = self.numdigits()
-        while i > 1 and self.digit(i - 1) == 0:
-            i -= 1
-        assert i >= 1
-        if i != self.numdigits():
-            self._digits = self._digits[:i]
-        if self.numdigits() == 1 and self.digit(0) == 0:
-            self.sign = 0
-
-    def bit_length(self):
-        i = self.numdigits()
-        if i == 1 and self.digit(0) == 0:
-            return 0
-        msd = self.digit(i - 1)
-        msd_bits = 0
-        while msd >= 32:
-            msd_bits += 6
-            msd >>= 6
-        msd_bits += [
-            0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
-            5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5
-            ][msd]
-        # yes, this can overflow: a huge number which fits 3 gigabytes of
-        # memory has around 24 gigabits!
-        bits = ovfcheck((i-1) * SHIFT) + msd_bits
-        return bits
-
-    def __repr__(self):
-        return "<rbigint digits=%s, sign=%s, %s>" % (self._digits,
-                                                     self.sign, self.str())
-
-#_________________________________________________________________
-
-# Helper Functions
-
-
-def _help_mult(x, y, c):
-    """
-    Multiply two values, then reduce the result:
-    result = X*Y % c.  If c is None, skip the mod.
-    """
-    res = x.mul(y)
-    # Perform a modular reduction, X = X % c, but leave X alone if c
-    # is NULL.
-    if c is not None:
-        res, temp = res.divmod(c)
-        res = temp
-    return res
-
-
-
-def digits_from_nonneg_long(l):
-    digits = []
-    while True:
-        digits.append(_store_digit(intmask(l & MASK)))
-        l = l >> SHIFT
-        if not l:
-            return digits[:] # to make it non-resizable
-digits_from_nonneg_long._annspecialcase_ = "specialize:argtype(0)"
-
-def digits_for_most_neg_long(l):
-    # This helper only works if 'l' is the most negative integer of its
-    # type, which in base 2 looks like: 1000000..0000
-    digits = []
-    while _mask_digit(l) == 0:
-        digits.append(NULLDIGIT)
-        l = l >> SHIFT
-    # now 'l' looks like: ...111100000
-    # turn it into:       ...000100000
-    # to drop the extra unwanted 1's introduced by the signed right shift
-    l = -intmask(l)
-    assert l & MASK == l
-    digits.append(_store_digit(l))
-    return digits[:] # to make it non-resizable
-digits_for_most_neg_long._annspecialcase_ = "specialize:argtype(0)"
-
-def args_from_rarith_int1(x):
-    if x > 0:
-        return digits_from_nonneg_long(x), 1
-    elif x == 0:
-        return [NULLDIGIT], 0
-    elif x != most_neg_value_of_same_type(x):
-        # normal case
-        return digits_from_nonneg_long(-x), -1
-    else:
-        # the most negative integer! hacks needed...
-        return digits_for_most_neg_long(x), -1
-args_from_rarith_int1._annspecialcase_ = "specialize:argtype(0)"
-
-def args_from_rarith_int(x):
-    return args_from_rarith_int1(widen(x))
-args_from_rarith_int._annspecialcase_ = "specialize:argtype(0)"
-# ^^^ specialized by the precise type of 'x', which is typically a r_xxx
-#     instance from rlib.rarithmetic
-
-def args_from_long(x):
-    "NOT_RPYTHON"
-    if x >= 0:
-        if x == 0:
-            return [NULLDIGIT], 0
-        else:
-            return digits_from_nonneg_long(x), 1
-    else:
-        return digits_from_nonneg_long(-x), -1
-
-def _x_add(a, b):
-    """ Add the absolute values of two bigint integers. """
-    size_a = a.numdigits()
-    size_b = b.numdigits()
-
-    # Ensure a is the larger of the two:
-    if size_a < size_b:
-        a, b = b, a
-        size_a, size_b = size_b, size_a
-    z = rbigint([NULLDIGIT] * (a.numdigits() + 1), 1)
-    i = 0
-    carry = r_uint(0)
-    while i < size_b:
-        carry += a.udigit(i) + b.udigit(i)
-        z.setdigit(i, carry)
-        carry >>= SHIFT
-        i += 1
-    while i < size_a:
-        carry += a.udigit(i)
-        z.setdigit(i, carry)
-        carry >>= SHIFT
-        i += 1
-    z.setdigit(i, carry)
-    z._normalize()
-    return z
-
-def _x_sub(a, b):
-    """ Subtract the absolute values of two integers. """
-    size_a = a.numdigits()
-    size_b = b.numdigits()
-    sign = 1
-
-    # Ensure a is the larger of the two:
-    if size_a < size_b:
-        sign = -1
-        a, b = b, a
-        size_a, size_b = size_b, size_a
-    elif size_a == size_b:
-        # Find highest digit where a and b differ:
-        i = size_a - 1
-        while i >= 0 and a.digit(i) == b.digit(i):
-            i -= 1
-        if i < 0:
-            return rbigint()
-        if a.digit(i) < b.digit(i):
-            sign = -1
-            a, b = b, a
-        size_a = size_b = i+1
-    z = rbigint([NULLDIGIT] * size_a, sign)
-    borrow = r_uint(0)
-    i = 0
-    while i < size_b:
-        # The following assumes unsigned arithmetic
-        # works modulo 2**N for some N>SHIFT.
-        borrow = a.udigit(i) - b.udigit(i) - borrow
-        z.setdigit(i, borrow)
-        borrow >>= SHIFT
-        borrow &= 1 # Keep only one sign bit
-        i += 1
-    while i < size_a:
-        borrow = a.udigit(i) - borrow
-        z.setdigit(i, borrow)
-        borrow >>= SHIFT
-        borrow &= 1 # Keep only one sign bit
-        i += 1
-    assert borrow == 0
-    z._normalize()
-    return z
-
-
-def _x_mul(a, b):
-    """
-    Grade school multiplication, ignoring the signs.
-    Returns the absolute value of the product, or None if error.
-    """
-
-    size_a = a.numdigits()
-    size_b = b.numdigits()
-    z = rbigint([NULLDIGIT] * (size_a + size_b), 1)
-    if a is b:
-        # Efficient squaring per HAC, Algorithm 14.16:
-        # http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf
-        # Gives slightly less than a 2x speedup when a == b,
-        # via exploiting that each entry in the multiplication
-        # pyramid appears twice (except for the size_a squares).
-        i = 0
-        while i < size_a:
-            f = a.widedigit(i)
-            pz = i << 1
-            pa = i + 1
-            paend = size_a
-
-            carry = z.widedigit(pz) + f * f
-            z.setdigit(pz, carry)
-            pz += 1
-            carry >>= SHIFT
-            assert carry <= MASK
-
-            # Now f is added in twice in each column of the
-            # pyramid it appears.  Same as adding f<<1 once.
-            f <<= 1
-            while pa < paend:
-                carry += z.widedigit(pz) + a.widedigit(pa) * f
-                pa += 1
-                z.setdigit(pz, carry)
-                pz += 1
-                carry >>= SHIFT
-                assert carry <= (_widen_digit(MASK) << 1)
-            if carry:
-                carry += z.widedigit(pz)
-                z.setdigit(pz, carry)
-                pz += 1
-                carry >>= SHIFT
-            if carry:
-                z.setdigit(pz, z.widedigit(pz) + carry)
-            assert (carry >> SHIFT) == 0
-            i += 1
-    else:
-        # a is not the same as b -- gradeschool long mult
-        i = 0
-        while i < size_a:
-            carry = 0
-            f = a.widedigit(i)
-            pz = i
-            pb = 0
-            pbend = size_b
-            while pb < pbend:
-                carry += z.widedigit(pz) + b.widedigit(pb) * f
-                pb += 1
-                z.setdigit(pz, carry)
-                pz += 1
-                carry >>= SHIFT
-                assert carry <= MASK
-            if carry:
-                z.setdigit(pz, z.widedigit(pz) + carry)
-            assert (carry >> SHIFT) == 0
-            i += 1
-    z._normalize()
-    return z
-
-
-def _kmul_split(n, size):
-    """
-    A helper for Karatsuba multiplication (k_mul).
-    Takes a bigint "n" and an integer "size" representing the place to
-    split, and sets low and high such that abs(n) == (high << size) + low,
-    viewing the shift as being by digits.  The sign bit is ignored, and
-    the return values are >= 0.
-    """
-    size_n = n.numdigits()
-    size_lo = min(size_n, size)
-
-    lo = rbigint(n._digits[:size_lo], 1)
-    hi = rbigint(n._digits[size_lo:], 1)
-    lo._normalize()
-    hi._normalize()
-    return hi, lo
-
-def _k_mul(a, b):
-    """
-    Karatsuba multiplication.  Ignores the input signs, and returns the
-    absolute value of the product (or raises if error).
-    See Knuth Vol. 2 Chapter 4.3.3 (Pp. 294-295).
-    """
-    asize = a.numdigits()
-    bsize = b.numdigits()
-    # (ah*X+al)(bh*X+bl) = ah*bh*X*X + (ah*bl + al*bh)*X + al*bl
-    # Let k = (ah+al)*(bh+bl) = ah*bl + al*bh  + ah*bh + al*bl
-    # Then the original product is
-    #     ah*bh*X*X + (k - ah*bh - al*bl)*X + al*bl
-    # By picking X to be a power of 2, "*X" is just shifting, and it's
-    # been reduced to 3 multiplies on numbers half the size.
-
-    # We want to split based on the larger number; fiddle so that b
-    # is largest.
-    if asize > bsize:
-        a, b, asize, bsize = b, a, bsize, asize
-
-    # Use gradeschool math when either number is too small.
-    if a is b:
-        i = KARATSUBA_SQUARE_CUTOFF
-    else:
-        i = KARATSUBA_CUTOFF
-    if asize <= i:
-        if a.sign == 0:
-            return rbigint()     # zero
-        else:
-            return _x_mul(a, b)
-
-    # If a is small compared to b, splitting on b gives a degenerate
-    # case with ah==0, and Karatsuba may be (even much) less efficient
-    # than "grade school" then.  However, we can still win, by viewing
-    # b as a string of "big digits", each of width a->ob_size.  That
-    # leads to a sequence of balanced calls to k_mul.
-    if 2 * asize <= bsize:
-        return _k_lopsided_mul(a, b)
-
-    # Split a & b into hi & lo pieces.
-    shift = bsize >> 1
-    ah, al = _kmul_split(a, shift)
-    assert ah.sign == 1    # the split isn't degenerate
-
-    if a == b:
-        bh = ah
-        bl = al
-    else:
-        bh, bl = _kmul_split(b, shift)
-
-    # The plan:
-    # 1. Allocate result space (asize + bsize digits:  that's always
-    #    enough).
-    # 2. Compute ah*bh, and copy into result at 2*shift.
-    # 3. Compute al*bl, and copy into result at 0.  Note that this
-    #    can't overlap with #2.
-    # 4. Subtract al*bl from the result, starting at shift.  This may
-    #    underflow (borrow out of the high digit), but we don't care:
-    #    we're effectively doing unsigned arithmetic mod
-    #    BASE**(sizea + sizeb), and so long as the *final* result fits,
-    #    borrows and carries out of the high digit can be ignored.
-    # 5. Subtract ah*bh from the result, starting at shift.
-    # 6. Compute (ah+al)*(bh+bl), and add it into the result starting
-    #    at shift.
-
-    # 1. Allocate result space.
-    ret = rbigint([NULLDIGIT] * (asize + bsize), 1)
-
-    # 2. t1 <- ah*bh, and copy into high digits of result.
-    t1 = _k_mul(ah, bh)
-    assert t1.sign >= 0
-    assert 2*shift + t1.numdigits() <= ret.numdigits()
-    ret._digits[2*shift : 2*shift + t1.numdigits()] = t1._digits
-
-    # Zero-out the digits higher than the ah*bh copy. */
-    ## ignored, assuming that we initialize to zero
-    ##i = ret->ob_size - 2*shift - t1->ob_size;
-    ##if (i)
-    ##    memset(ret->ob_digit + 2*shift + t1->ob_size, 0,
-    ##           i * sizeof(digit));
-
-    # 3. t2 <- al*bl, and copy into the low digits.
-    t2 = _k_mul(al, bl)
-    assert t2.sign >= 0
-    assert t2.numdigits() <= 2*shift # no overlap with high digits
-    ret._digits[:t2.numdigits()] = t2._digits
-
-    # Zero out remaining digits.
-    ## ignored, assuming that we initialize to zero
-    ##i = 2*shift - t2->ob_size;  /* number of uninitialized digits */
-    ##if (i)
-    ##    memset(ret->ob_digit + t2->ob_size, 0, i * sizeof(digit));
-
-    # 4 & 5. Subtract ah*bh (t1) and al*bl (t2).  We do al*bl first
-    # because it's fresher in cache.
-    i = ret.numdigits() - shift  # # digits after shift
-    _v_isub(ret, shift, i, t2, t2.numdigits())
-    _v_isub(ret, shift, i, t1, t1.numdigits())
-    del t1, t2
-
-    # 6. t3 <- (ah+al)(bh+bl), and add into result.
-    t1 = _x_add(ah, al)
-    del ah, al
-
-    if a == b:
-        t2 = t1
-    else:
-        t2 = _x_add(bh, bl)
-    del bh, bl
-
-    t3 = _k_mul(t1, t2)
-    del t1, t2
-    assert t3.sign >=0
-
-    # Add t3.  It's not obvious why we can't run out of room here.
-    # See the (*) comment after this function.
-    _v_iadd(ret, shift, i, t3, t3.numdigits())
-    del t3
-
-    ret._normalize()
-    return ret
-
-""" (*) Why adding t3 can't "run out of room" above.
-
-Let f(x) mean the floor of x and c(x) mean the ceiling of x.  Some facts
-to start with:
-
-1. For any integer i, i = c(i/2) + f(i/2).  In particular,
-   bsize = c(bsize/2) + f(bsize/2).
-2. shift = f(bsize/2)
-3. asize <= bsize
-4. Since we call k_lopsided_mul if asize*2 <= bsize, asize*2 > bsize in this
-   routine, so asize > bsize/2 >= f(bsize/2) in this routine.
-
-We allocated asize + bsize result digits, and add t3 into them at an offset
-of shift.  This leaves asize+bsize-shift allocated digit positions for t3
-to fit into, = (by #1 and #2) asize + f(bsize/2) + c(bsize/2) - f(bsize/2) =
-asize + c(bsize/2) available digit positions.
-
-bh has c(bsize/2) digits, and bl at most f(size/2) digits.  So bh+hl has
-at most c(bsize/2) digits + 1 bit.
-
-If asize == bsize, ah has c(bsize/2) digits, else ah has at most f(bsize/2)
-digits, and al has at most f(bsize/2) digits in any case.  So ah+al has at
-most (asize == bsize ? c(bsize/2) : f(bsize/2)) digits + 1 bit.
-
-The product (ah+al)*(bh+bl) therefore has at most
-
-    c(bsize/2) + (asize == bsize ? c(bsize/2) : f(bsize/2)) digits + 2 bits
-
-and we have asize + c(bsize/2) available digit positions.  We need to show
-this is always enough.  An instance of c(bsize/2) cancels out in both, so
-the question reduces to whether asize digits is enough to hold
-(asize == bsize ? c(bsize/2) : f(bsize/2)) digits + 2 bits.  If asize < bsize,
-then we're asking whether asize digits >= f(bsize/2) digits + 2 bits.  By #4,
-asize is at least f(bsize/2)+1 digits, so this in turn reduces to whether 1
-digit is enough to hold 2 bits.  This is so since SHIFT=15 >= 2.  If
-asize == bsize, then we're asking whether bsize digits is enough to hold
-c(bsize/2) digits + 2 bits, or equivalently (by #1) whether f(bsize/2) digits
-is enough to hold 2 bits.  This is so if bsize >= 2, which holds because
-bsize >= KARATSUBA_CUTOFF >= 2.
-
-Note that since there's always enough room for (ah+al)*(bh+bl), and that's
-clearly >= each of ah*bh and al*bl, there's always enough room to subtract
-ah*bh and al*bl too.
-"""
-
-def _k_lopsided_mul(a, b):
-    """
-    b has at least twice the digits of a, and a is big enough that Karatsuba
-    would pay off *if* the inputs had balanced sizes.  View b as a sequence
-    of slices, each with a->ob_size digits, and multiply the slices by a,
-    one at a time.  This gives k_mul balanced inputs to work with, and is
-    also cache-friendly (we compute one double-width slice of the result
-    at a time, then move on, never bactracking except for the helpful
-    single-width slice overlap between successive partial sums).
-    """
-    asize = a.numdigits()
-    bsize = b.numdigits()
-    # nbdone is # of b digits already multiplied
-
-    assert asize > KARATSUBA_CUTOFF
-    assert 2 * asize <= bsize
-
-    # Allocate result space, and zero it out.
-    ret = rbigint([NULLDIGIT] * (asize + bsize), 1)
-
-    # Successive slices of b are copied into bslice.
-    #bslice = rbigint([0] * asize, 1)
-    # XXX we cannot pre-allocate, see comments below!
-    bslice = rbigint([NULLDIGIT], 1)
-
-    nbdone = 0;
-    while bsize > 0:
-        nbtouse = min(bsize, asize)
-
-        # Multiply the next slice of b by a.
-
-        #bslice.digits[:nbtouse] = b.digits[nbdone : nbdone + nbtouse]
-        # XXX: this would be more efficient if we adopted CPython's
-        # way to store the size, instead of resizing the list!
-        # XXX change the implementation, encoding length via the sign.
-        bslice._digits = b._digits[nbdone : nbdone + nbtouse]
-        product = _k_mul(a, bslice)
-
-        # Add into result.
-        _v_iadd(ret, nbdone, ret.numdigits() - nbdone,
-                 product, product.numdigits())
-        del product
-
-        bsize -= nbtouse
-        nbdone += nbtouse
-
-    ret._normalize()
-    return ret
-
-
-def _inplace_divrem1(pout, pin, n, size=0):
-    """
-    Divide bigint pin by non-zero digit n, storing quotient
-    in pout, and returning the remainder. It's OK for pin == pout on entry.
-    """
-    rem = _widen_digit(0)
-    assert n > 0 and n <= MASK
-    if not size:
-        size = pin.numdigits()
-    size -= 1
-    while size >= 0:
-        rem = (rem << SHIFT) + pin.widedigit(size)
-        hi = rem // n
-        pout.setdigit(size, hi)
-        rem -= hi * n
-        size -= 1
-    return _mask_digit(rem)
-
-def _divrem1(a, n):
-    """
-    Divide a bigint integer by a digit, returning both the quotient
-    and the remainder as a tuple.
-    The sign of a is ignored; n should not be zero.
-    """
-    assert n > 0 and n <= MASK
-    size = a.numdigits()
-    z = rbigint([NULLDIGIT] * size, 1)
-    rem = _inplace_divrem1(z, a, n)
-    z._normalize()
-    return z, rem
-
-def _v_iadd(x, xofs, m, y, n):
-    """
-    x and y are rbigints, m >= n required.  x.digits[0:n] is modified in place,
-    by adding y.digits[0:m] to it.  Carries are propagated as far as
-    x[m-1], and the remaining carry (0 or 1) is returned.
-    Python adaptation: x is addressed relative to xofs!
-    """
-    carry = r_uint(0)
-
-    assert m >= n
-    i = xofs
-    iend = xofs + n
-    while i < iend:
-        carry += x.udigit(i) + y.udigit(i-xofs)
-        x.setdigit(i, carry)
-        carry >>= SHIFT
-        assert (carry & 1) == carry
-        i += 1
-    iend = xofs + m
-    while carry and i < iend:
-        carry += x.udigit(i)
-        x.setdigit(i, carry)
-        carry >>= SHIFT
-        assert (carry & 1) == carry
-        i += 1
-    return carry
-
-def _v_isub(x, xofs, m, y, n):
-    """
-    x and y are rbigints, m >= n required.  x.digits[0:n] is modified in place,
-    by substracting y.digits[0:m] to it. Borrows are propagated as
-    far as x[m-1], and the remaining borrow (0 or 1) is returned.
-    Python adaptation: x is addressed relative to xofs!
-    """
-    borrow = r_uint(0)
-
-    assert m >= n
-    i = xofs
-    iend = xofs + n
-    while i < iend:
-        borrow = x.udigit(i) - y.udigit(i-xofs) - borrow
-        x.setdigit(i, borrow)
-        borrow >>= SHIFT
-        borrow &= 1    # keep only 1 sign bit
-        i += 1
-    iend = xofs + m
-    while borrow and i < iend:
-        borrow = x.udigit(i) - borrow
-        x.setdigit(i, borrow)
-        borrow >>= SHIFT
-        borrow &= 1
-        i += 1
-    return borrow
-
-
-def _muladd1(a, n, extra=0):
-    """Multiply by a single digit and add a single digit, ignoring the sign.
-    """
-    size_a = a.numdigits()
-    z = rbigint([NULLDIGIT] * (size_a+1), 1)
-    assert extra & MASK == extra
-    carry = _widen_digit(extra)
-    i = 0
-    while i < size_a:
-        carry += a.widedigit(i) * n
-        z.setdigit(i, carry)
-        carry >>= SHIFT
-        i += 1
-    z.setdigit(i, carry)
-    z._normalize()
-    return z
-
-
-def _x_divrem(v1, w1):
-    """ Unsigned bigint division with remainder -- the algorithm """
-    size_w = w1.numdigits()
-    d = (r_uint(MASK)+1) // (w1.udigit(size_w-1) + 1)
-    assert d <= MASK    # because the first digit of w1 is not zero
-    d = intmask(d)
-    v = _muladd1(v1, d)
-    w = _muladd1(w1, d)
-    size_v = v.numdigits()
-    size_w = w.numdigits()
-    assert size_v >= size_w and size_w > 1 # Assert checks by div()
-
-    size_a = size_v - size_w + 1
-    a = rbigint([NULLDIGIT] * size_a, 1)
-
-    j = size_v
-    k = size_a - 1
-    while k >= 0:
-        if j >= size_v:
-            vj = 0
-        else:
-            vj = v.widedigit(j)
-        carry = 0
-
-        if vj == w.widedigit(size_w-1):
-            q = MASK
-        else:
-            q = ((vj << SHIFT) + v.widedigit(j-1)) // w.widedigit(size_w-1)
-
-        while (w.widedigit(size_w-2) * q >
-                ((
-                    (vj << SHIFT)
-                    + v.widedigit(j-1)
-                    - q * w.widedigit(size_w-1)
-                                ) << SHIFT)
-                + v.widedigit(j-2)):
-            q -= 1
-        i = 0
-        while i < size_w and i+k < size_v:
-            z = w.widedigit(i) * q
-            zz = z >> SHIFT
-            carry += v.widedigit(i+k) - z + (zz << SHIFT)
-            v.setdigit(i+k, carry)
-            carry >>= SHIFT
-            carry -= zz
-            i += 1
-
-        if i+k < size_v:
-            carry += v.widedigit(i+k)
-            v.setdigit(i+k, 0)
-
-        if carry == 0:
-            a.setdigit(k, q)
-            assert not q >> SHIFT
-        else:
-            assert carry == -1
-            q -= 1
-            a.setdigit(k, q)
-            assert not q >> SHIFT
-
-            carry = 0
-            i = 0
-            while i < size_w and i+k < size_v:
-                carry += v.udigit(i+k) + w.udigit(i)
-                v.setdigit(i+k, carry)
-                carry >>= SHIFT
-                i += 1
-        j -= 1
-        k -= 1
-
-    a._normalize()
-    rem, _ = _divrem1(v, d)
-    return a, rem
-
-
-def _divrem(a, b):
-    """ Long division with remainder, top-level routine """
-    size_a = a.numdigits()
-    size_b = b.numdigits()
-
-    if b.sign == 0:
-        raise ZeroDivisionError("long division or modulo by zero")
-
-    if (size_a < size_b or
-        (size_a == size_b and
-         a.digit(size_a-1) < b.digit(size_b-1))):
-        # |a| < |b|
-        z = rbigint()   # result is 0
-        rem = a
-        return z, rem
-    if size_b == 1:
-        z, urem = _divrem1(a, b.digit(0))
-        rem = rbigint([_store_digit(urem)], int(urem != 0))
-    else:
-        z, rem = _x_divrem(a, b)
-    # Set the signs.
-    # The quotient z has the sign of a*b;
-    # the remainder r has the sign of a,
-    # so a = b*z + r.
-    if a.sign != b.sign:
-        z.sign = - z.sign
-    if a.sign < 0 and rem.sign != 0:
-        rem.sign = - rem.sign
-    return z, rem
-
-# ______________ conversions to double _______________
-
-def _AsScaledDouble(v):
-    """
-    NBITS_WANTED should be > the number of bits in a double's precision,
-    but small enough so that 2**NBITS_WANTED is within the normal double
-    range.  nbitsneeded is set to 1 less than that because the most-significant
-    Python digit contains at least 1 significant bit, but we don't want to
-    bother counting them (catering to the worst case cheaply).
-
-    57 is one more than VAX-D double precision; I (Tim) don't know of a double
-    format with more precision than that; it's 1 larger so that we add in at
-    least one round bit to stand in for the ignored least-significant bits.
-    """
-    NBITS_WANTED = 57
-    if v.sign == 0:
-        return 0.0, 0
-    i = v.numdigits() - 1
-    sign = v.sign
-    x = float(v.digit(i))
-    nbitsneeded = NBITS_WANTED - 1
-    # Invariant:  i Python digits remain unaccounted for.
-    while i > 0 and nbitsneeded > 0:
-        i -= 1
-        x = x * FLOAT_MULTIPLIER + float(v.digit(i))
-        nbitsneeded -= SHIFT
-    # There are i digits we didn't shift in.  Pretending they're all
-    # zeroes, the true value is x * 2**(i*SHIFT).
-    exponent = i
-    assert x > 0.0
-    return x * sign, exponent
-
-##def ldexp(x, exp):
-##    assert type(x) is float
-##    lb1 = LONG_BIT - 1
-##    multiplier = float(1 << lb1)
-##    while exp >= lb1:
-##        x *= multiplier
-##        exp -= lb1
-##    if exp:
-##        x *= float(1 << exp)
-##    return x
-
-# note that math.ldexp checks for overflows,
-# while the C ldexp is not guaranteed to do.
-# XXX make sure that we don't ignore this!
-# YYY no, we decided to do ignore this!
-
- at jit.dont_look_inside
-def _AsDouble(n):
-    """ Get a C double from a bigint object. """
-    # This is a "correctly-rounded" version from Python 2.7.
-    #
-    from pypy.rlib import rfloat
-    DBL_MANT_DIG = rfloat.DBL_MANT_DIG  # 53 for IEEE 754 binary64
-    DBL_MAX_EXP = rfloat.DBL_MAX_EXP    # 1024 for IEEE 754 binary64
-    assert DBL_MANT_DIG < r_ulonglong.BITS
-
-    # Reduce to case n positive.
-    sign = n.sign
-    if sign == 0:
-        return 0.0
-    elif sign < 0:
-        n = n.neg()
-
-    # Find exponent: 2**(exp - 1) <= n < 2**exp
-    exp = n.bit_length()
-
-    # Get top DBL_MANT_DIG + 2 significant bits of n, with a 'sticky'
-    # last bit: that is, the least significant bit of the result is 1
-    # iff any of the shifted-out bits is set.
-    shift = DBL_MANT_DIG + 2 - exp
-    if shift >= 0:
-        q = _AsULonglong_mask(n) << shift
-        if not we_are_translated():
-            assert q == n.tolong() << shift   # no masking actually done
-    else:
-        shift = -shift
-        n2 = n.rshift(shift)
-        q = _AsULonglong_mask(n2)
-        if not we_are_translated():
-            assert q == n2.tolong()           # no masking actually done
-        if not n.eq(n2.lshift(shift)):
-            q |= 1
-
-    # Now remove the excess 2 bits, rounding to nearest integer (with
-    # ties rounded to even).
-    q = (q >> 2) + (bool(q & 2) and bool(q & 5))
-
-    if exp > DBL_MAX_EXP or (exp == DBL_MAX_EXP and
-                             q == r_ulonglong(1) << DBL_MANT_DIG):
-        raise OverflowError("integer too large to convert to float")
-
-    ad = math.ldexp(float(q), exp - DBL_MANT_DIG)
-    if sign < 0:
-        ad = -ad
-    return ad
-
-def _loghelper(func, arg):
-    """
-    A decent logarithm is easy to compute even for huge bigints, but libm can't
-    do that by itself -- loghelper can.  func is log or log10.
-    Note that overflow isn't possible:  a bigint can contain
-    no more than INT_MAX * SHIFT bits, so has value certainly less than
-    2**(2**64 * 2**16) == 2**2**80, and log2 of that is 2**80, which is
-    small enough to fit in an IEEE single.  log and log10 are even smaller.
-    """
-    x, e = _AsScaledDouble(arg)
-    if x <= 0.0:
-        raise ValueError
-    # Value is ~= x * 2**(e*SHIFT), so the log ~=
-    # log(x) + log(2) * e * SHIFT.
-    # CAUTION:  e*SHIFT may overflow using int arithmetic,
-    # so force use of double. */
-    return func(x) + (e * float(SHIFT) * func(2.0))
-_loghelper._annspecialcase_ = 'specialize:arg(0)'
-
-# ____________________________________________________________
-
-BASE_AS_FLOAT = float(1 << SHIFT)     # note that it may not fit an int
-
-BitLengthTable = ''.join(map(chr, [
-    0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
-    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5]))
-
-def bits_in_digit(d):
-    # returns the unique integer k such that 2**(k-1) <= d <
-    # 2**k if d is nonzero, else 0.
-    d_bits = 0
-    while d >= 32:
-        d_bits += 6
-        d >>= 6
-    d_bits += ord(BitLengthTable[d])
-    return d_bits
-
-def _truediv_result(result, negate):
-    if negate:
-        result = -result
-    return result
-
-def _truediv_overflow():
-    raise OverflowError("integer division result too large for a float")
-
-def _bigint_true_divide(a, b):
-    # A longish method to obtain the floating-point result with as much
-    # precision as theoretically possible.  The code is almost directly
-    # copied from CPython.  See there (Objects/longobject.c,
-    # long_true_divide) for detailled comments.  Method in a nutshell:
-    #
-    #    0. reduce to case a, b > 0; filter out obvious underflow/overflow
-    #    1. choose a suitable integer 'shift'
-    #    2. use integer arithmetic to compute x = floor(2**-shift*a/b)
-    #    3. adjust x for correct rounding
-    #    4. convert x to a double dx with the same value
-    #    5. return ldexp(dx, shift).
-
-    from pypy.rlib import rfloat
-    DBL_MANT_DIG = rfloat.DBL_MANT_DIG  # 53 for IEEE 754 binary64
-    DBL_MAX_EXP = rfloat.DBL_MAX_EXP    # 1024 for IEEE 754 binary64
-    DBL_MIN_EXP = rfloat.DBL_MIN_EXP
-    MANT_DIG_DIGITS = DBL_MANT_DIG // SHIFT
-    MANT_DIG_BITS = DBL_MANT_DIG % SHIFT
-
-    # Reduce to case where a and b are both positive.
-    negate = (a.sign < 0) ^ (b.sign < 0)
-    if not b.tobool():
-        raise ZeroDivisionError("long division or modulo by zero")
-    if not a.tobool():
-        return _truediv_result(0.0, negate)
-
-    a_size = a.numdigits()
-    b_size = b.numdigits()
-
-    # Fast path for a and b small (exactly representable in a double).
-    # Relies on floating-point division being correctly rounded; results
-    # may be subject to double rounding on x86 machines that operate with
-    # the x87 FPU set to 64-bit precision.
-    a_is_small = (a_size <= MANT_DIG_DIGITS or
-                  (a_size == MANT_DIG_DIGITS+1 and
-                   a.digit(MANT_DIG_DIGITS) >> MANT_DIG_BITS == 0))
-    b_is_small = (b_size <= MANT_DIG_DIGITS or
-                  (b_size == MANT_DIG_DIGITS+1 and
-                   b.digit(MANT_DIG_DIGITS) >> MANT_DIG_BITS == 0))
-    if a_is_small and b_is_small:
-        a_size -= 1
-        da = float(a.digit(a_size))
-        while True:
-            a_size -= 1
-            if a_size < 0: break
-            da = da * BASE_AS_FLOAT + a.digit(a_size)
-
-        b_size -= 1
-        db = float(b.digit(b_size))
-        while True:
-            b_size -= 1
-            if b_size < 0: break
-            db = db * BASE_AS_FLOAT + b.digit(b_size)
-
-        return _truediv_result(da / db, negate)
-
-    # Catch obvious cases of underflow and overflow
-    diff = a_size - b_size
-    if diff > sys.maxint/SHIFT - 1:
-        return _truediv_overflow()           # Extreme overflow
-    elif diff < 1 - sys.maxint/SHIFT:
-        return _truediv_result(0.0, negate)  # Extreme underflow
-    # Next line is now safe from overflowing integers
-    diff = (diff * SHIFT + bits_in_digit(a.digit(a_size - 1)) -
-                           bits_in_digit(b.digit(b_size - 1)))
-    # Now diff = a_bits - b_bits.
-    if diff > DBL_MAX_EXP:
-        return _truediv_overflow()
-    elif diff < DBL_MIN_EXP - DBL_MANT_DIG - 1:
-        return _truediv_result(0.0, negate)
-
-    # Choose value for shift; see comments for step 1 in CPython.
-    shift = max(diff, DBL_MIN_EXP) - DBL_MANT_DIG - 2
-
-    inexact = False
-
-    # x = abs(a * 2**-shift)
-    if shift <= 0:
-        x = a.lshift(-shift)
-    else:
-        x = a.rshift(shift, dont_invert=True)
-        # set inexact if any of the bits shifted out is nonzero
-        if not a.eq(x.lshift(shift)):
-            inexact = True
-
-    # x //= b. If the remainder is nonzero, set inexact.
-    x, rem = _divrem(x, b)
-    if rem.tobool():
-        inexact = True
-
-    assert x.tobool()    # result of division is never zero
-    x_size = x.numdigits()
-    x_bits = (x_size-1)*SHIFT + bits_in_digit(x.digit(x_size-1))
-
-    # The number of extra bits that have to be rounded away.
-    extra_bits = max(x_bits, DBL_MIN_EXP - shift) - DBL_MANT_DIG
-    assert extra_bits == 2 or extra_bits == 3
-
-    # Round by remembering a modified copy of the low digit of x
-    mask = 1 << (extra_bits - 1)
-    low = x.udigit(0) | inexact
-    if (low & mask) != 0 and (low & (3*mask-1)) != 0:
-        low += mask
-    x_digit_0 = low & ~(mask-1)
-
-    # Convert x to a double dx; the conversion is exact.
-    x_size -= 1
-    dx = 0.0
-    while x_size > 0:
-        dx += x.digit(x_size)
-        dx *= BASE_AS_FLOAT
-        x_size -= 1
-    dx += x_digit_0
-
-    # Check whether ldexp result will overflow a double.
-    if (shift + x_bits >= DBL_MAX_EXP and
-        (shift + x_bits > DBL_MAX_EXP or dx == math.ldexp(1.0, x_bits))):
-        return _truediv_overflow()
-
-    return _truediv_result(math.ldexp(dx, shift), negate)
-
-# ____________________________________________________________
-
-BASE8  = '01234567'
-BASE10 = '0123456789'
-BASE16 = '0123456789abcdef'
-
-def _format(a, digits, prefix='', suffix=''):
-    """
-    Convert a bigint object to a string, using a given conversion base.
-    Return a string object.
-    """
-    size_a = a.numdigits()
-
-    base = len(digits)
-    assert base >= 2 and base <= 36
-
-    # Compute a rough upper bound for the length of the string
-    i = base
-    bits = 0
-    while i > 1:
-        bits += 1
-        i >>= 1
-    i = 5 + len(prefix) + len(suffix) + (size_a*SHIFT + bits-1) // bits
-    s = [chr(0)] * i
-    p = i
-    j = len(suffix)
-    while j > 0:
-        p -= 1
-        j -= 1
-        s[p] = suffix[j]
-
-    if a.sign == 0:
-        p -= 1
-        s[p] = '0'
-    elif (base & (base - 1)) == 0:
-        # JRH: special case for power-of-2 bases
-        accum = 0
-        accumbits = 0  # # of bits in accum 
-        basebits = 1   # # of bits in base-1
-        i = base
-        while 1:
-            i >>= 1
-            if i <= 1:
-                break
-            basebits += 1
-
-        for i in range(size_a):
-            accum |= a.widedigit(i) << accumbits
-            accumbits += SHIFT
-            assert accumbits >= basebits
-            while 1:
-                cdigit = intmask(accum & (base - 1))
-                p -= 1
-                assert p >= 0
-                s[p] = digits[cdigit]
-                accumbits -= basebits
-                accum >>= basebits
-                if i < size_a - 1:
-                    if accumbits < basebits:
-                        break
-                else:
-                    if accum <= 0:
-                        break
-    else:
-        # Not 0, and base not a power of 2.  Divide repeatedly by
-        # base, but for speed use the highest power of base that
-        # fits in a digit.
-        size = size_a
-        pin = a # just for similarity to C source which uses the array
-        # powbase <- largest power of base that fits in a digit.
-        powbase = _widen_digit(base)  # powbase == base ** power
-        power = 1
-        while 1:
-            newpow = powbase * base
-            if newpow >> SHIFT:  # doesn't fit in a digit
-                break
-            powbase = newpow
-            power += 1
-
-        # Get a scratch area for repeated division.
-        scratch = rbigint([NULLDIGIT] * size, 1)
-
-        # Repeatedly divide by powbase.
-        while 1:
-            ntostore = power
-            rem = _inplace_divrem1(scratch, pin, powbase, size)
-            pin = scratch  # no need to use a again
-            if pin.digit(size - 1) == 0:
-                size -= 1
-
-            # Break rem into digits.
-            assert ntostore > 0
-            while 1:
-                nextrem = rem // base
-                c = rem - nextrem * base
-                p -= 1
-                assert p >= 0
-                s[p] = digits[c]
-                rem = nextrem
-                ntostore -= 1
-                # Termination is a bit delicate:  must not
-                # store leading zeroes, so must get out if
-                # remaining quotient and rem are both 0.
-                if not (ntostore and (size or rem)):
-                    break
-            if size == 0:
-                break
-
-    j = len(prefix)
-    while j > 0:
-        p -= 1
-        j -= 1
-        s[p] = prefix[j]
-
-    if a.sign < 0:
-        p -= 1
-        s[p] = '-'
-
-    assert p >= 0    # otherwise, buffer overflow (this is also a
-                     # hint for the annotator for the slice below)
-    return ''.join(s[p:])
-
-
-def _bitwise(a, op, b): # '&', '|', '^'
-    """ Bitwise and/or/xor operations """
-
-    if a.sign < 0:
-        a = a.invert()
-        maska = MASK
-    else:
-        maska = 0
-    if b.sign < 0:
-        b = b.invert()
-        maskb = MASK
-    else:
-        maskb = 0
-
-    negz = 0
-    if op == '^':
-        if maska != maskb:
-            maska ^= MASK
-            negz = -1
-    elif op == '&':
-        if maska and maskb:
-            op = '|'
-            maska ^= MASK
-            maskb ^= MASK
-            negz = -1
-    elif op == '|':
-        if maska or maskb:
-            op = '&'
-            maska ^= MASK
-            maskb ^= MASK
-            negz = -1
-
-    # JRH: The original logic here was to allocate the result value (z)
-    # as the longer of the two operands.  However, there are some cases
-    # where the result is guaranteed to be shorter than that: AND of two
-    # positives, OR of two negatives: use the shorter number.  AND with
-    # mixed signs: use the positive number.  OR with mixed signs: use the
-    # negative number.  After the transformations above, op will be '&'
-    # iff one of these cases applies, and mask will be non-0 for operands
-    # whose length should be ignored.
-
-    size_a = a.numdigits()
-    size_b = b.numdigits()
-    if op == '&':
-        if maska:
-            size_z = size_b
-        else:
-            if maskb:
-                size_z = size_a
-            else:
-                size_z = min(size_a, size_b)
-    else:
-        size_z = max(size_a, size_b)
-
-    z = rbigint([NULLDIGIT] * size_z, 1)
-
-    for i in range(size_z):
-        if i < size_a:
-            diga = a.digit(i) ^ maska
-        else:
-            diga = maska
-        if i < size_b:
-            digb = b.digit(i) ^ maskb
-        else:
-            digb = maskb
-        if op == '&':
-            z.setdigit(i, diga & digb)
-        elif op == '|':
-            z.setdigit(i, diga | digb)
-        elif op == '^':
-            z.setdigit(i, diga ^ digb)
-
-    z._normalize()
-    if negz == 0:
-        return z
-    return z.invert()
-_bitwise._annspecialcase_ = "specialize:arg(1)"
-
-
-ULONGLONG_BOUND = r_ulonglong(1L << (r_longlong.BITS-1))
-LONGLONG_MIN = r_longlong(-(1L << (r_longlong.BITS-1)))
-
-def _AsLongLong(v):
-    """
-    Get a r_longlong integer from a bigint object.
-    Raises OverflowError if overflow occurs.
-    """
-    x = _AsULonglong_ignore_sign(v)
-    # grr grr grr
-    if x >= ULONGLONG_BOUND:
-        if x == ULONGLONG_BOUND and v.sign < 0:
-            x = LONGLONG_MIN
-        else:
-            raise OverflowError
-    else:
-        x = r_longlong(x)
-        if v.sign < 0:
-            x = -x
-    return x
-
-def _AsULonglong_ignore_sign(v):
-    x = r_ulonglong(0)
-    i = v.numdigits() - 1
-    while i >= 0:
-        prev = x
-        x = (x << SHIFT) + v.widedigit(i)
-        if (x >> SHIFT) != prev:
-                raise OverflowError(
-                    "long int too large to convert to unsigned long long int")
-        i -= 1
-    return x
-
-def make_unsigned_mask_conversion(T):
-    def _As_unsigned_mask(v):
-        x = T(0)
-        i = v.numdigits() - 1
-        while i >= 0:
-            x = (x << SHIFT) + T(v.digit(i))
-            i -= 1
-        if v.sign < 0:
-            x = -x
-        return x
-    return _As_unsigned_mask
-
-_AsULonglong_mask = make_unsigned_mask_conversion(r_ulonglong)
-_AsUInt_mask = make_unsigned_mask_conversion(r_uint)
-
-def _hash(v):
-    # This is designed so that Python ints and longs with the
-    # same value hash to the same value, otherwise comparisons
-    # of mapping keys will turn out weird.  Moreover, purely
-    # to please decimal.py, we return a hash that satisfies
-    # hash(x) == hash(x % ULONG_MAX).  In particular, this
-    # implies that hash(x) == hash(x % (2**64-1)).
-    i = v.numdigits() - 1
-    sign = v.sign
-    x = r_uint(0)
-    LONG_BIT_SHIFT = LONG_BIT - SHIFT
-    while i >= 0:
-        # Force a native long #-bits (32 or 64) circular shift
-        x = (x << SHIFT) | (x >> LONG_BIT_SHIFT)
-        x += v.udigit(i)
-        # If the addition above overflowed we compensate by
-        # incrementing.  This preserves the value modulo
-        # ULONG_MAX.
-        if x < v.udigit(i):
-            x += 1
-        i -= 1
-    x = intmask(x * sign)
-    return x
-
-#_________________________________________________________________
-
-# a few internal helpers
-
-def digits_max_for_base(base):
-    dec_per_digit = 1
-    while base ** dec_per_digit < MASK:
-        dec_per_digit += 1
-    dec_per_digit -= 1
-    return base ** dec_per_digit
-
-BASE_MAX = [0, 0] + [digits_max_for_base(_base) for _base in range(2, 37)]
-DEC_MAX = digits_max_for_base(10)
-assert DEC_MAX == BASE_MAX[10]
-
-def _decimalstr_to_bigint(s):
-    # a string that has been already parsed to be decimal and valid,
-    # is turned into a bigint
-    p = 0
-    lim = len(s)
-    sign = False
-    if s[p] == '-':
-        sign = True
-        p += 1
-    elif s[p] == '+':
-        p += 1
-
-    a = rbigint()
-    tens = 1
-    dig = 0
-    ord0 = ord('0')
-    while p < lim:
-        dig = dig * 10 + ord(s[p]) - ord0
-        p += 1
-        tens *= 10
-        if tens == DEC_MAX or p == lim:
-            a = _muladd1(a, tens, dig)
-            tens = 1
-            dig = 0
-    if sign and a.sign == 1:
-        a.sign = -1
-    return a
-
-def parse_digit_string(parser):
-    # helper for objspace.std.strutil
-    a = rbigint()
-    base = parser.base
-    digitmax = BASE_MAX[base]
-    tens, dig = 1, 0
-    while True:
-        digit = parser.next_digit()
-        if tens == digitmax or digit < 0:
-            a = _muladd1(a, tens, dig)
-            if digit < 0:
-                break
-            dig = digit
-            tens = base
-        else:
-            dig = dig * base + digit
-            tens *= base
-    a.sign *= parser.sign
-    return a
+if USE_GMP:
+    xxx
+else:
+    from pypy.rlib._rbigint_native import rbigint, parse_digit_string
diff --git a/pypy/rlib/test/test_rbigint.py b/pypy/rlib/test/test_rbigint_native.py
rename from pypy/rlib/test/test_rbigint.py
rename to pypy/rlib/test/test_rbigint_native.py
--- a/pypy/rlib/test/test_rbigint.py
+++ b/pypy/rlib/test/test_rbigint_native.py
@@ -2,9 +2,9 @@
 import py
 import operator, sys
 from random import random, randint, sample
-from pypy.rlib.rbigint import rbigint, SHIFT, MASK, KARATSUBA_CUTOFF
-from pypy.rlib.rbigint import _store_digit
-from pypy.rlib import rbigint as lobj
+from pypy.rlib._rbigint_native import rbigint, SHIFT, MASK, KARATSUBA_CUTOFF
+from pypy.rlib._rbigint_native import _store_digit, parse_digit_string
+from pypy.rlib import _rbigint_native as lobj
 from pypy.rlib.rarithmetic import r_uint, r_longlong, r_ulonglong, intmask
 from pypy.rpython.test.test_llinterp import interpret
 
@@ -599,7 +599,6 @@
                 r_ulonglong(-9**50))
 
     def test_parse_digit_string(self):
-        from pypy.rlib.rbigint import parse_digit_string
         class Parser:
             def __init__(self, base, sign, digits):
                 self.base = base


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