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Commit ffdb2c21 authored by Mark Dickinson's avatar Mark Dickinson
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Issue #16451: Refactor to remove duplication between range and slice in slice index computations.

parent c3afba10
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Showing with 87 additions and 269 deletions
Include/sliceobject.h
View file @ ffdb2c21
...@@ -34,6 +34,9 @@ PyAPI_FUNC(PyObject *) PySlice_New(PyObject* start, PyObject* stop, ...@@ -34,6 +34,9 @@ PyAPI_FUNC(PyObject *) PySlice_New(PyObject* start, PyObject* stop,
PyObject* step); PyObject* step);
#ifndef Py_LIMITED_API #ifndef Py_LIMITED_API
PyAPI_FUNC(PyObject *) _PySlice_FromIndices(Py_ssize_t start, Py_ssize_t stop); PyAPI_FUNC(PyObject *) _PySlice_FromIndices(Py_ssize_t start, Py_ssize_t stop);
PyAPI_FUNC(int) _PySlice_GetLongIndices(PySliceObject *self, PyObject *length,
PyObject **start_ptr, PyObject **stop_ptr,
PyObject **step_ptr);
#endif #endif
PyAPI_FUNC(int) PySlice_GetIndices(PyObject *r, Py_ssize_t length, PyAPI_FUNC(int) PySlice_GetIndices(PyObject *r, Py_ssize_t length,
Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step); Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step);
......
Objects/rangeobject.c
View file @ ffdb2c21
...@@ -318,195 +318,6 @@ range_item(rangeobject *r, Py_ssize_t i) ...@@ -318,195 +318,6 @@ range_item(rangeobject *r, Py_ssize_t i)
return res; return res;
} }
/* Additional helpers, since the standard slice helpers
* all clip to PY_SSIZE_T_MAX
*/
/* Replace _PyEval_SliceIndex */
static PyObject *
compute_slice_element(PyObject *obj)
{
PyObject *result = NULL;
if (obj != NULL) {
if (PyIndex_Check(obj)) {
result = PyNumber_Index(obj);
}
else {
PyErr_SetString(PyExc_TypeError,
"slice indices must be integers or "
"None or have an __index__ method");
}
}
return result;
}
/* Replace PySlice_GetIndicesEx
* Result indicates whether or not the slice is empty
* (-1 = error, 0 = empty slice, 1 = slice contains elements)
*/
static int
compute_slice_indices(rangeobject *r, PySliceObject *slice,
PyObject **start, PyObject **stop, PyObject **step)
{
int cmp_result, has_elements;
Py_ssize_t clamped_step = 0;
PyObject *zero = NULL, *one = NULL, *neg_one = NULL, *candidate = NULL;
PyObject *tmp_start = NULL, *tmp_stop = NULL, *tmp_step = NULL;
zero = PyLong_FromLong(0);
if (zero == NULL) goto Fail;
one = PyLong_FromLong(1);
if (one == NULL) goto Fail;
neg_one = PyLong_FromLong(-1);
if (neg_one == NULL) goto Fail;
/* Calculate step value */
if (slice->step == Py_None) {
clamped_step = 1;
tmp_step = one;
Py_INCREF(tmp_step);
} else {
if (!_PyEval_SliceIndex(slice->step, &clamped_step)) goto Fail;
if (clamped_step == 0) {
PyErr_SetString(PyExc_ValueError,
"slice step cannot be zero");
goto Fail;
}
tmp_step = compute_slice_element(slice->step);
if (tmp_step == NULL) goto Fail;
}
/* Calculate start value */
if (slice->start == Py_None) {
if (clamped_step < 0) {
tmp_start = PyNumber_Subtract(r->length, one);
if (tmp_start == NULL) goto Fail;
} else {
tmp_start = zero;
Py_INCREF(tmp_start);
}
} else {
candidate = compute_slice_element(slice->start);
if (candidate == NULL) goto Fail;
cmp_result = PyObject_RichCompareBool(candidate, zero, Py_LT);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* candidate < 0 */
tmp_start = PyNumber_Add(r->length, candidate);
if (tmp_start == NULL) goto Fail;
Py_CLEAR(candidate);
} else {
/* candidate >= 0 */
tmp_start = candidate;
candidate = NULL;
}
cmp_result = PyObject_RichCompareBool(tmp_start, zero, Py_LT);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* tmp_start < 0 */
Py_CLEAR(tmp_start);
if (clamped_step < 0) {
tmp_start = neg_one;
} else {
tmp_start = zero;
}
Py_INCREF(tmp_start);
} else {
/* tmp_start >= 0 */
cmp_result = PyObject_RichCompareBool(tmp_start, r->length, Py_GE);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* tmp_start >= r->length */
Py_CLEAR(tmp_start);
if (clamped_step < 0) {
tmp_start = PyNumber_Subtract(r->length, one);
if (tmp_start == NULL) goto Fail;
} else {
tmp_start = r->length;
Py_INCREF(tmp_start);
}
}
}
}
/* Calculate stop value */
if (slice->stop == Py_None) {
if (clamped_step < 0) {
tmp_stop = neg_one;
} else {
tmp_stop = r->length;
}
Py_INCREF(tmp_stop);
} else {
candidate = compute_slice_element(slice->stop);
if (candidate == NULL) goto Fail;
cmp_result = PyObject_RichCompareBool(candidate, zero, Py_LT);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* candidate < 0 */
tmp_stop = PyNumber_Add(r->length, candidate);
if (tmp_stop == NULL) goto Fail;
Py_CLEAR(candidate);
} else {
/* candidate >= 0 */
tmp_stop = candidate;
candidate = NULL;
}
cmp_result = PyObject_RichCompareBool(tmp_stop, zero, Py_LT);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* tmp_stop < 0 */
Py_CLEAR(tmp_stop);
if (clamped_step < 0) {
tmp_stop = neg_one;
} else {
tmp_stop = zero;
}
Py_INCREF(tmp_stop);
} else {
/* tmp_stop >= 0 */
cmp_result = PyObject_RichCompareBool(tmp_stop, r->length, Py_GE);
if (cmp_result == -1) goto Fail;
if (cmp_result) {
/* tmp_stop >= r->length */
Py_CLEAR(tmp_stop);
if (clamped_step < 0) {
tmp_stop = PyNumber_Subtract(r->length, one);
if (tmp_stop == NULL) goto Fail;
} else {
tmp_stop = r->length;
Py_INCREF(tmp_stop);
}
}
}
}
/* Check if the slice is empty or not */
if (clamped_step < 0) {
has_elements = PyObject_RichCompareBool(tmp_start, tmp_stop, Py_GT);
} else {
has_elements = PyObject_RichCompareBool(tmp_start, tmp_stop, Py_LT);
}
if (has_elements == -1) goto Fail;
*start = tmp_start;
*stop = tmp_stop;
*step = tmp_step;
Py_DECREF(neg_one);
Py_DECREF(one);
Py_DECREF(zero);
return has_elements;
Fail:
Py_XDECREF(tmp_start);
Py_XDECREF(tmp_stop);
Py_XDECREF(tmp_step);
Py_XDECREF(candidate);
Py_XDECREF(neg_one);
Py_XDECREF(one);
Py_XDECREF(zero);
return -1;
}
static PyObject * static PyObject *
compute_slice(rangeobject *r, PyObject *_slice) compute_slice(rangeobject *r, PyObject *_slice)
{ {
...@@ -514,10 +325,11 @@ compute_slice(rangeobject *r, PyObject *_slice) ...@@ -514,10 +325,11 @@ compute_slice(rangeobject *r, PyObject *_slice)
rangeobject *result; rangeobject *result;
PyObject *start = NULL, *stop = NULL, *step = NULL; PyObject *start = NULL, *stop = NULL, *step = NULL;
PyObject *substart = NULL, *substop = NULL, *substep = NULL; PyObject *substart = NULL, *substop = NULL, *substep = NULL;
int has_elements; int error;
has_elements = compute_slice_indices(r, slice, &start, &stop, &step); error = _PySlice_GetLongIndices(slice, r->length, &start, &stop, &step);
if (has_elements == -1) return NULL; if (error == -1)
return NULL;
substep = PyNumber_Multiply(r->step, step); substep = PyNumber_Multiply(r->step, step);
if (substep == NULL) goto fail; if (substep == NULL) goto fail;
...@@ -527,13 +339,8 @@ compute_slice(rangeobject *r, PyObject *_slice) ...@@ -527,13 +339,8 @@ compute_slice(rangeobject *r, PyObject *_slice)
if (substart == NULL) goto fail; if (substart == NULL) goto fail;
Py_CLEAR(start); Py_CLEAR(start);
if (has_elements) { substop = compute_item(r, stop);
substop = compute_item(r, stop); if (substop == NULL) goto fail;
if (substop == NULL) goto fail;
} else {
substop = substart;
Py_INCREF(substop);
}
Py_CLEAR(stop); Py_CLEAR(stop);
result = make_range_object(Py_TYPE(r), substart, substop, substep); result = make_range_object(Py_TYPE(r), substart, substop, substep);
......
Objects/sliceobject.c
View file @ ffdb2c21
...@@ -316,57 +316,41 @@ evaluate_slice_index(PyObject *v) ...@@ -316,57 +316,41 @@ evaluate_slice_index(PyObject *v)
} }
} }
/* Implementation of slice.indices. */ /* Compute slice indices given a slice and length. Return -1 on failure. Used
by slice.indices and rangeobject slicing. Assumes that `len` is a
nonnegative instance of PyLong. */
static PyObject* int
slice_indices(PySliceObject* self, PyObject* len) _PySlice_GetLongIndices(PySliceObject *self, PyObject *length,
PyObject **start_ptr, PyObject **stop_ptr,
PyObject **step_ptr)
{ {
PyObject *start=NULL, *stop=NULL, *step=NULL; PyObject *start=NULL, *stop=NULL, *step=NULL;
PyObject *length=NULL, *upper=NULL, *lower=NULL, *zero=NULL; PyObject *upper=NULL, *lower=NULL;
int step_is_negative, cmp; int step_is_negative, cmp_result;
zero = PyLong_FromLong(0L);
if (zero == NULL)
return NULL;
/* Compute step and length as integers. */
length = PyNumber_Index(len);
if (length == NULL)
goto error;
if (self->step == Py_None) /* Convert step to an integer; raise for zero step. */
if (self->step == Py_None) {
step = PyLong_FromLong(1L); step = PyLong_FromLong(1L);
else if (step == NULL)
step = evaluate_slice_index(self->step); goto error;
if (step == NULL) step_is_negative = 0;
goto error;
/* Raise ValueError for negative length or zero step. */
cmp = PyObject_RichCompareBool(length, zero, Py_LT);
if (cmp < 0) {
goto error;
}
if (cmp) {
PyErr_SetString(PyExc_ValueError,
"length should not be negative");
goto error;
}
cmp = PyObject_RichCompareBool(step, zero, Py_EQ);
if (cmp < 0) {
goto error;
} }
if (cmp) { else {
PyErr_SetString(PyExc_ValueError, int step_sign;
"slice step cannot be zero"); step = evaluate_slice_index(self->step);
goto error; if (step == NULL)
goto error;
step_sign = _PyLong_Sign(step);
if (step_sign == 0) {
PyErr_SetString(PyExc_ValueError,
"slice step cannot be zero");
goto error;
}
step_is_negative = step_sign < 0;
} }
/* Find lower and upper bounds for start and stop. */ /* Find lower and upper bounds for start and stop. */
step_is_negative = PyObject_RichCompareBool(step, zero, Py_LT);
if (step_is_negative < 0) {
goto error;
}
if (step_is_negative) { if (step_is_negative) {
lower = PyLong_FromLong(-1L); lower = PyLong_FromLong(-1L);
if (lower == NULL) if (lower == NULL)
...@@ -377,8 +361,10 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -377,8 +361,10 @@ slice_indices(PySliceObject* self, PyObject* len)
goto error; goto error;
} }
else { else {
lower = zero; lower = PyLong_FromLong(0L);
Py_INCREF(lower); if (lower == NULL)
goto error;
upper = length; upper = length;
Py_INCREF(upper); Py_INCREF(upper);
} }
...@@ -393,10 +379,7 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -393,10 +379,7 @@ slice_indices(PySliceObject* self, PyObject* len)
if (start == NULL) if (start == NULL)
goto error; goto error;
cmp = PyObject_RichCompareBool(start, zero, Py_LT); if (_PyLong_Sign(start) < 0) {
if (cmp < 0)
goto error;
if (cmp) {
/* start += length */ /* start += length */
PyObject *tmp = PyNumber_Add(start, length); PyObject *tmp = PyNumber_Add(start, length);
Py_DECREF(start); Py_DECREF(start);
...@@ -404,20 +387,20 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -404,20 +387,20 @@ slice_indices(PySliceObject* self, PyObject* len)
if (start == NULL) if (start == NULL)
goto error; goto error;
cmp = PyObject_RichCompareBool(start, lower, Py_LT); cmp_result = PyObject_RichCompareBool(start, lower, Py_LT);
if (cmp < 0) if (cmp_result < 0)
goto error; goto error;
if (cmp) { if (cmp_result) {
Py_INCREF(lower); Py_INCREF(lower);
Py_DECREF(start); Py_DECREF(start);
start = lower; start = lower;
} }
} }
else { else {
cmp = PyObject_RichCompareBool(start, upper, Py_GT); cmp_result = PyObject_RichCompareBool(start, upper, Py_GT);
if (cmp < 0) if (cmp_result < 0)
goto error; goto error;
if (cmp) { if (cmp_result) {
Py_INCREF(upper); Py_INCREF(upper);
Py_DECREF(start); Py_DECREF(start);
start = upper; start = upper;
...@@ -435,10 +418,7 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -435,10 +418,7 @@ slice_indices(PySliceObject* self, PyObject* len)
if (stop == NULL) if (stop == NULL)
goto error; goto error;
cmp = PyObject_RichCompareBool(stop, zero, Py_LT); if (_PyLong_Sign(stop) < 0) {
if (cmp < 0)
goto error;
if (cmp) {
/* stop += length */ /* stop += length */
PyObject *tmp = PyNumber_Add(stop, length); PyObject *tmp = PyNumber_Add(stop, length);
Py_DECREF(stop); Py_DECREF(stop);
...@@ -446,20 +426,20 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -446,20 +426,20 @@ slice_indices(PySliceObject* self, PyObject* len)
if (stop == NULL) if (stop == NULL)
goto error; goto error;
cmp = PyObject_RichCompareBool(stop, lower, Py_LT); cmp_result = PyObject_RichCompareBool(stop, lower, Py_LT);
if (cmp < 0) if (cmp_result < 0)
goto error; goto error;
if (cmp) { if (cmp_result) {
Py_INCREF(lower); Py_INCREF(lower);
Py_DECREF(stop); Py_DECREF(stop);
stop = lower; stop = lower;
} }
} }
else { else {
cmp = PyObject_RichCompareBool(stop, upper, Py_GT); cmp_result = PyObject_RichCompareBool(stop, upper, Py_GT);
if (cmp < 0) if (cmp_result < 0)
goto error; goto error;
if (cmp) { if (cmp_result) {
Py_INCREF(upper); Py_INCREF(upper);
Py_DECREF(stop); Py_DECREF(stop);
stop = upper; stop = upper;
...@@ -467,23 +447,51 @@ slice_indices(PySliceObject* self, PyObject* len) ...@@ -467,23 +447,51 @@ slice_indices(PySliceObject* self, PyObject* len)
} }
} }
*start_ptr = start;
*stop_ptr = stop;
*step_ptr = step;
Py_DECREF(upper); Py_DECREF(upper);
Py_DECREF(lower); Py_DECREF(lower);
Py_DECREF(length); return 0;
Py_DECREF(zero);
return Py_BuildValue("(NNN)", start, stop, step);
error: error:
*start_ptr = *stop_ptr = *step_ptr = NULL;
Py_XDECREF(start); Py_XDECREF(start);
Py_XDECREF(stop); Py_XDECREF(stop);
Py_XDECREF(step); Py_XDECREF(step);
Py_XDECREF(upper); Py_XDECREF(upper);
Py_XDECREF(lower); Py_XDECREF(lower);
Py_XDECREF(length); return -1;
Py_XDECREF(zero);
return NULL;
} }
/* Implementation of slice.indices. */
static PyObject*
slice_indices(PySliceObject* self, PyObject* len)
{
PyObject *start, *stop, *step;
PyObject *length;
int error;
/* Convert length to an integer if necessary; raise for negative length. */
length = PyNumber_Index(len);
if (length == NULL)
return NULL;
if (_PyLong_Sign(length) < 0) {
PyErr_SetString(PyExc_ValueError,
"length should not be negative");
Py_DECREF(length);
return NULL;
}
error = _PySlice_GetLongIndices(self, length, &start, &stop, &step);
Py_DECREF(length);
if (error == -1)
return NULL;
else
return Py_BuildValue("(NNN)", start, stop, step);
}
PyDoc_STRVAR(slice_indices_doc, PyDoc_STRVAR(slice_indices_doc,
"S.indices(len) -> (start, stop, stride)\n\ "S.indices(len) -> (start, stop, stride)\n\
......
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