bpo-36957: Add _PyLong_Rshift() and _PyLong_Lshift(). (GH-13416)
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1d5bdef550
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a5119e7d75
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@ -230,6 +230,9 @@ PyAPI_FUNC(PyObject *) _PyLong_GCD(PyObject *, PyObject *);
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#ifndef Py_LIMITED_API
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PyAPI_DATA(PyObject *) _PyLong_Zero;
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PyAPI_DATA(PyObject *) _PyLong_One;
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PyAPI_FUNC(PyObject *) _PyLong_Rshift(PyObject *, size_t);
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PyAPI_FUNC(PyObject *) _PyLong_Lshift(PyObject *, size_t);
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#endif
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#ifdef __cplusplus
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@ -1671,18 +1671,13 @@ math_isqrt(PyObject *module, PyObject *n)
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}
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d = 0;
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while (--s >= 0) {
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PyObject *q, *shift;
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PyObject *q;
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size_t e = d;
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d = c >> s;
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/* q = (n >> 2*c - e - d + 1) // a */
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shift = PyLong_FromSize_t(2U*c - d - e + 1U);
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if (shift == NULL) {
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goto error;
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}
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q = PyNumber_Rshift(n, shift);
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Py_DECREF(shift);
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q = _PyLong_Rshift(n, 2U*c - d - e + 1U);
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if (q == NULL) {
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goto error;
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}
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@ -1692,13 +1687,7 @@ math_isqrt(PyObject *module, PyObject *n)
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}
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/* a = (a << d - 1 - e) + q */
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shift = PyLong_FromSize_t(d - 1U - e);
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if (shift == NULL) {
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Py_DECREF(q);
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goto error;
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}
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Py_SETREF(a, PyNumber_Lshift(a, shift));
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Py_DECREF(shift);
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Py_SETREF(a, _PyLong_Lshift(a, d - 1U - e));
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if (a == NULL) {
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Py_DECREF(q);
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goto error;
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@ -1939,9 +1928,9 @@ static PyObject *
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math_factorial(PyObject *module, PyObject *arg)
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/*[clinic end generated code: output=6686f26fae00e9ca input=6d1c8105c0d91fb4]*/
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{
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long x;
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long x, two_valuation;
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int overflow;
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PyObject *result, *odd_part, *two_valuation, *pyint_form;
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PyObject *result, *odd_part, *pyint_form;
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if (PyFloat_Check(arg)) {
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PyObject *lx;
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@ -1990,13 +1979,8 @@ math_factorial(PyObject *module, PyObject *arg)
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odd_part = factorial_odd_part(x);
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if (odd_part == NULL)
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return NULL;
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two_valuation = PyLong_FromLong(x - count_set_bits(x));
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if (two_valuation == NULL) {
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Py_DECREF(odd_part);
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return NULL;
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}
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result = PyNumber_Lshift(odd_part, two_valuation);
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Py_DECREF(two_valuation);
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two_valuation = x - count_set_bits(x);
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result = _PyLong_Lshift(odd_part, two_valuation);
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Py_DECREF(odd_part);
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return result;
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}
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@ -463,13 +463,13 @@ float_richcompare(PyObject *v, PyObject *w, int op)
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*/
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PyObject *temp;
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temp = PyNumber_Lshift(ww, _PyLong_One);
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temp = _PyLong_Lshift(ww, 1);
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if (temp == NULL)
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goto Error;
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Py_DECREF(ww);
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ww = temp;
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temp = PyNumber_Lshift(vv, _PyLong_One);
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temp = _PyLong_Lshift(vv, 1);
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if (temp == NULL)
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goto Error;
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Py_DECREF(vv);
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@ -4416,9 +4416,9 @@ long_bool(PyLongObject *v)
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/* wordshift, remshift = divmod(shiftby, PyLong_SHIFT) */
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static int
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divmod_shift(PyLongObject *shiftby, Py_ssize_t *wordshift, digit *remshift)
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divmod_shift(PyObject *shiftby, Py_ssize_t *wordshift, digit *remshift)
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{
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assert(PyLong_Check((PyObject *)shiftby));
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assert(PyLong_Check(shiftby));
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assert(Py_SIZE(shiftby) >= 0);
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Py_ssize_t lshiftby = PyLong_AsSsize_t((PyObject *)shiftby);
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if (lshiftby >= 0) {
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@ -4430,7 +4430,7 @@ divmod_shift(PyLongObject *shiftby, Py_ssize_t *wordshift, digit *remshift)
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be that PyLong_AsSsize_t raised an OverflowError. */
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assert(PyErr_ExceptionMatches(PyExc_OverflowError));
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PyErr_Clear();
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PyLongObject *wordshift_obj = divrem1(shiftby, PyLong_SHIFT, remshift);
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PyLongObject *wordshift_obj = divrem1((PyLongObject *)shiftby, PyLong_SHIFT, remshift);
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if (wordshift_obj == NULL) {
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return -1;
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}
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@ -4448,19 +4448,11 @@ divmod_shift(PyLongObject *shiftby, Py_ssize_t *wordshift, digit *remshift)
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}
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static PyObject *
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long_rshift(PyLongObject *a, PyLongObject *b)
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long_rshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
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{
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PyLongObject *z = NULL;
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Py_ssize_t newsize, wordshift, hishift, i, j;
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digit loshift, lomask, himask;
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CHECK_BINOP(a, b);
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if (Py_SIZE(b) < 0) {
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PyErr_SetString(PyExc_ValueError,
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"negative shift count");
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return NULL;
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}
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Py_ssize_t newsize, hishift, i, j;
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digit lomask, himask;
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if (Py_SIZE(a) < 0) {
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/* Right shifting negative numbers is harder */
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@ -4468,7 +4460,7 @@ long_rshift(PyLongObject *a, PyLongObject *b)
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a1 = (PyLongObject *) long_invert(a);
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if (a1 == NULL)
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return NULL;
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a2 = (PyLongObject *) long_rshift(a1, b);
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a2 = (PyLongObject *) long_rshift1(a1, wordshift, remshift);
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Py_DECREF(a1);
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if (a2 == NULL)
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return NULL;
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@ -4476,19 +4468,17 @@ long_rshift(PyLongObject *a, PyLongObject *b)
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Py_DECREF(a2);
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}
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else {
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if (divmod_shift(b, &wordshift, &loshift) < 0)
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return NULL;
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newsize = Py_SIZE(a) - wordshift;
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if (newsize <= 0)
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return PyLong_FromLong(0);
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hishift = PyLong_SHIFT - loshift;
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hishift = PyLong_SHIFT - remshift;
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lomask = ((digit)1 << hishift) - 1;
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himask = PyLong_MASK ^ lomask;
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z = _PyLong_New(newsize);
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if (z == NULL)
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return NULL;
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for (i = 0, j = wordshift; i < newsize; i++, j++) {
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z->ob_digit[i] = (a->ob_digit[j] >> loshift) & lomask;
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z->ob_digit[i] = (a->ob_digit[j] >> remshift) & lomask;
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if (i+1 < newsize)
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z->ob_digit[i] |= (a->ob_digit[j+1] << hishift) & himask;
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}
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@ -4498,15 +4488,10 @@ long_rshift(PyLongObject *a, PyLongObject *b)
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}
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static PyObject *
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long_lshift(PyObject *v, PyObject *w)
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long_rshift(PyObject *a, PyObject *b)
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{
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/* This version due to Tim Peters */
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PyLongObject *a = (PyLongObject*)v;
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PyLongObject *b = (PyLongObject*)w;
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PyLongObject *z = NULL;
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Py_ssize_t oldsize, newsize, wordshift, i, j;
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Py_ssize_t wordshift;
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digit remshift;
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twodigits accum;
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CHECK_BINOP(a, b);
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@ -4517,9 +4502,35 @@ long_lshift(PyObject *v, PyObject *w)
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if (Py_SIZE(a) == 0) {
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return PyLong_FromLong(0);
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}
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if (divmod_shift(b, &wordshift, &remshift) < 0)
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return NULL;
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return long_rshift1((PyLongObject *)a, wordshift, remshift);
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}
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/* Return a >> shiftby. */
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PyObject *
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_PyLong_Rshift(PyObject *a, size_t shiftby)
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{
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Py_ssize_t wordshift;
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digit remshift;
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assert(PyLong_Check(a));
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if (Py_SIZE(a) == 0) {
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return PyLong_FromLong(0);
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}
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wordshift = shiftby / PyLong_SHIFT;
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remshift = shiftby % PyLong_SHIFT;
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return long_rshift1((PyLongObject *)a, wordshift, remshift);
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}
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static PyObject *
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long_lshift1(PyLongObject *a, Py_ssize_t wordshift, digit remshift)
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{
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/* This version due to Tim Peters */
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PyLongObject *z = NULL;
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Py_ssize_t oldsize, newsize, i, j;
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twodigits accum;
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oldsize = Py_ABS(Py_SIZE(a));
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newsize = oldsize + wordshift;
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if (remshift)
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@ -4547,6 +4558,42 @@ long_lshift(PyObject *v, PyObject *w)
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return (PyObject *) maybe_small_long(z);
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}
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static PyObject *
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long_lshift(PyObject *a, PyObject *b)
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{
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Py_ssize_t wordshift;
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digit remshift;
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CHECK_BINOP(a, b);
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if (Py_SIZE(b) < 0) {
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PyErr_SetString(PyExc_ValueError, "negative shift count");
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return NULL;
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}
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if (Py_SIZE(a) == 0) {
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return PyLong_FromLong(0);
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}
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if (divmod_shift(b, &wordshift, &remshift) < 0)
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return NULL;
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return long_lshift1((PyLongObject *)a, wordshift, remshift);
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}
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/* Return a << shiftby. */
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PyObject *
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_PyLong_Lshift(PyObject *a, size_t shiftby)
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{
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Py_ssize_t wordshift;
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digit remshift;
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assert(PyLong_Check(a));
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if (Py_SIZE(a) == 0) {
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return PyLong_FromLong(0);
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}
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wordshift = shiftby / PyLong_SHIFT;
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remshift = shiftby % PyLong_SHIFT;
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return long_lshift1((PyLongObject *)a, wordshift, remshift);
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}
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/* Compute two's complement of digit vector a[0:m], writing result to
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z[0:m]. The digit vector a need not be normalized, but should not
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be entirely zero. a and z may point to the same digit vector. */
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@ -5552,7 +5599,7 @@ static PyNumberMethods long_as_number = {
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(inquiry)long_bool, /*tp_bool*/
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(unaryfunc)long_invert, /*nb_invert*/
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long_lshift, /*nb_lshift*/
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(binaryfunc)long_rshift, /*nb_rshift*/
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long_rshift, /*nb_rshift*/
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long_and, /*nb_and*/
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long_xor, /*nb_xor*/
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long_or, /*nb_or*/
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