SF Patch #864863: Bisect C implementation

(Contributed by Dmitry Vasiliev.)

1 files changed, 228 insertions, 0 deletions

diff --git a/Modules/_bisectmodule.c b/Modules/_bisectmodule.c
new file mode 100644
index 0000000..d336158
--- /dev/null
+++ b/Modules/_bisectmodule.c
@@ -0,0 +1,228 @@
+/* Bisection algorithms. Drop in replacement for bisect.py
+
+Converted to C by Dmitry Vasiliev (dima at hlabs.spb.ru).
+*/
+
+#include "Python.h"
+
+static int
+internal_bisect_right(PyObject *list, PyObject *item, int lo, int hi)
+{
+	PyObject *litem;
+	int mid, res;
+
+	if (hi == -1) {
+		hi = PySequence_Size(list);
+		if (hi < 0)
+			return -1;
+	}
+	while (lo < hi) {
+		mid = (lo + hi) / 2;
+		litem = PySequence_GetItem(list, mid);
+		if (litem == NULL)
+			return -1;
+		res = PyObject_RichCompareBool(item, litem, Py_LT);
+		Py_DECREF(litem);
+		if (res < 0)
+			return -1;
+		if (res)
+			hi = mid;
+		else
+			lo = mid + 1;
+	}
+	return lo;
+}
+
+static PyObject *
+bisect_right(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:bisect_right",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_right(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	return PyInt_FromLong(index);
+}
+
+PyDoc_STRVAR(bisect_right_doc,
+"bisect_right(list, item[, lo[, hi]]) -> index\n\
+\n\
+Return the index where to insert item x in list a, assuming a is sorted.\n\
+\n\
+The return value i is such that all e in a[:i] have e <= x, and all e in\n\
+a[i:] have e > x.  So if x already appears in the list, i points just\n\
+beyond the rightmost x already there\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static PyObject *
+insort_right(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:insort_right",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_right(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	if (PyList_Check(list)) {
+		if (PyList_Insert(list, index, item) < 0)
+			return NULL;
+	} else {
+		if (PyObject_CallMethod(list, "insert", "iO", index, item)
+			== NULL)
+			return NULL;
+	}
+
+	Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(insort_right_doc,
+"insort_right(list, item[, lo[, hi]])\n\
+\n\
+Insert item x in list a, and keep it sorted assuming a is sorted.\n\
+\n\
+If x is already in a, insert it to the right of the rightmost x.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static int
+internal_bisect_left(PyObject *list, PyObject *item, int lo, int hi)
+{
+	PyObject *litem;
+	int mid, res;
+
+	if (hi == -1) {
+		hi = PySequence_Size(list);
+		if (hi < 0)
+			return -1;
+	}
+	while (lo < hi) {
+		mid = (lo + hi) / 2;
+		litem = PySequence_GetItem(list, mid);
+		if (litem == NULL)
+			return -1;
+		res = PyObject_RichCompareBool(litem, item, Py_LT);
+		Py_DECREF(litem);
+		if (res < 0)
+			return -1;
+		if (res)
+			lo = mid + 1;
+		else
+			hi = mid;
+	}
+	return lo;
+}
+
+static PyObject *
+bisect_left(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:bisect_left",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_left(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	return PyInt_FromLong(index);
+}
+
+PyDoc_STRVAR(bisect_left_doc,
+"bisect_left(list, item[, lo[, hi]]) -> index\n\
+\n\
+Return the index where to insert item x in list a, assuming a is sorted.\n\
+\n\
+The return value i is such that all e in a[:i] have e < x, and all e in\n\
+a[i:] have e >= x.  So if x already appears in the list, i points just\n\
+before the leftmost x already there.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+static PyObject *
+insort_left(PyObject *self, PyObject *args)
+{
+	PyObject *list, *item;
+	int lo = 0;
+	int hi = -1;
+	int index;
+
+	if (!PyArg_ParseTuple(args, "OO|ii:insort_left",
+		&list, &item, &lo, &hi))
+		return NULL;
+	index = internal_bisect_left(list, item, lo, hi);
+	if (index < 0)
+		return NULL;
+	if (PyList_Check(list)) {
+		if (PyList_Insert(list, index, item) < 0)
+			return NULL;
+	} else {
+		if (PyObject_CallMethod(list, "insert", "iO", index, item)
+			== NULL)
+			return NULL;
+	}
+
+	Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(insort_left_doc,
+"insort_left(list, item[, lo[, hi]])\n\
+\n\
+Insert item x in list a, and keep it sorted assuming a is sorted.\n\
+\n\
+If x is already in a, insert it to the left of the leftmost x.\n\
+\n\
+Optional args lo (default 0) and hi (default len(a)) bound the\n\
+slice of a to be searched.\n");
+
+PyDoc_STRVAR(bisect_doc, "Alias for bisect_right().\n");
+PyDoc_STRVAR(insort_doc, "Alias for insort_right().\n");
+
+static PyMethodDef bisect_methods[] = {
+	{"bisect_right", (PyCFunction)bisect_right,
+		METH_VARARGS, bisect_right_doc},
+	{"bisect", (PyCFunction)bisect_right,
+		METH_VARARGS, bisect_doc},
+	{"insort_right", (PyCFunction)insort_right,
+		METH_VARARGS, insort_right_doc},
+	{"insort", (PyCFunction)insort_right,
+		METH_VARARGS, insort_doc},
+	{"bisect_left", (PyCFunction)bisect_left,
+		METH_VARARGS, bisect_left_doc},
+	{"insort_left", (PyCFunction)insort_left,
+		METH_VARARGS, insort_left_doc},
+	{NULL, NULL} /* sentinel */
+};
+
+PyDoc_STRVAR(module_doc,
+"Bisection algorithms.\n\
+\n\
+This module provides support for maintaining a list in sorted order without\n\
+having to sort the list after each insertion. For long lists of items with\n\
+expensive comparison operations, this can be an improvement over the more\n\
+common approach.\n");
+
+PyMODINIT_FUNC
+init_bisect(void)
+{
+	PyObject *m;
+
+	m = Py_InitModule3("_bisect", bisect_methods, module_doc);
+}
+