phase: compute phases in C

phase: compute phases in C

Previously, the phase computation would grow much slower as the oldest draft
commit in the repository grew older (which is very common in repos with evolve
on) and the number of commits increase.
By rewriting the computation in C we can speed it up from 700ms to 7ms on
a large repository whose oldest draft commit is a year old.

--- a/mercurial/parsers.c	Wed Mar 25 14:16:10 2015 -0500
+++ b/mercurial/parsers.c	Tue Mar 24 11:00:09 2015 -0700
@@ -911,6 +911,111 @@
 	}
 }
 
+static Py_ssize_t add_roots_get_min(indexObject *self, PyObject *list,
+                                    int marker, char *phases)
+{
+	PyObject *iter = NULL;
+	PyObject *iter_item = NULL;
+	Py_ssize_t min_idx = index_length(self) + 1;
+	long iter_item_long;
+
+	if (PyList_GET_SIZE(list) != 0) {
+		iter = PyObject_GetIter(list);
+		if (iter == NULL)
+			return -2;
+		while ((iter_item = PyIter_Next(iter)))
+		{
+			iter_item_long = PyInt_AS_LONG(iter_item);
+			Py_DECREF(iter_item);
+			if (iter_item_long < min_idx)
+				min_idx = iter_item_long;
+			phases[iter_item_long] = marker;
+		}
+		Py_DECREF(iter);
+	}
+
+	return min_idx;
+}
+
+static inline void set_phase_from_parents(char *phases, int parent_1,
+                                          int parent_2, int i)
+{
+	if (parent_1 >= 0 && phases[parent_1] > phases[i])
+		phases[i] = phases[parent_1];
+	if (parent_2 >= 0 && phases[parent_2] > phases[i])
+		phases[i] = phases[parent_2];
+}
+
+static PyObject *compute_phases(indexObject *self, PyObject *args)
+{
+	PyObject *roots = Py_None;
+	PyObject *phaseslist = NULL;
+	PyObject *phaseroots = NULL;
+	PyObject *rev = NULL;
+	PyObject *p1 = NULL;
+	PyObject *p2 = NULL;
+	Py_ssize_t addlen = self->added ? PyList_GET_SIZE(self->added) : 0;
+	Py_ssize_t len = index_length(self) - 1;
+	Py_ssize_t numphase = 0;
+	Py_ssize_t minrevallphases = 0;
+	Py_ssize_t minrevphase = 0;
+	Py_ssize_t i = 0;
+	long parent_1, parent_2;
+	char *phases = NULL;
+	const char *data;
+
+	if (!PyArg_ParseTuple(args, "O", &roots))
+		goto release_none;
+	if (roots == NULL || !PyList_Check(roots))
+		goto release_none;
+
+	phases = calloc(len, 1); /* phase per rev: {0: public, 1: draft, 2: secret} */
+	if (phases == NULL)
+		goto release_none;
+	/* Put the phase information of all the roots in phases */
+	numphase = PyList_GET_SIZE(roots)+1;
+	minrevallphases = len + 1;
+	for (i = 0; i < numphase-1; i++) {
+		phaseroots = PyList_GET_ITEM(roots, i);
+		if (!PyList_Check(phaseroots))
+			goto release_phases;
+		minrevphase = add_roots_get_min(self, phaseroots, i+1, phases);
+		if (minrevphase == -2) /* Error from add_roots_get_min */
+			goto release_phases;
+		minrevallphases = MIN(minrevallphases, minrevphase);
+	}
+	/* Propagate the phase information from the roots to the revs */
+	if (minrevallphases != -1) {
+		for (i = minrevallphases; i < self->raw_length; i++) {
+			data = index_deref(self, i);
+			set_phase_from_parents(phases, getbe32(data+24), getbe32(data+28), i);
+		}
+		for (i = 0; i < addlen; i++) {
+			rev = PyList_GET_ITEM(self->added, i);
+			p1 = PyTuple_GET_ITEM(rev, 5);
+			p2 = PyTuple_GET_ITEM(rev, 6);
+			if (!PyInt_Check(p1) || !PyInt_Check(p2)) {
+				PyErr_SetString(PyExc_TypeError, "revlog parents are invalid");
+				goto release_phases;
+			}
+			parent_1 = PyInt_AS_LONG(p1);
+			parent_2 = PyInt_AS_LONG(p2);
+			set_phase_from_parents(phases, parent_1, parent_2, i+self->raw_length);
+		}
+	}
+	/* Transform phase list to a python list */
+	phaseslist = PyList_New(len);
+	if (phaseslist == NULL)
+		goto release_phases;
+	for (i = 0; i < len; i++)
+		PyList_SET_ITEM(phaseslist, i, PyInt_FromLong(phases[i]));
+
+release_phases:
+	free(phases);
+release_none:
+	return phaseslist;
+}
+
 static PyObject *index_headrevs(indexObject *self, PyObject *args)
 {
 	Py_ssize_t i, len, addlen;
@@ -2043,6 +2148,8 @@
 	 "clear the index caches"},
 	{"get", (PyCFunction)index_m_get, METH_VARARGS,
 	 "get an index entry"},
+	{"computephases", (PyCFunction)compute_phases, METH_VARARGS,
+		"compute phases"},
 	{"headrevs", (PyCFunction)index_headrevs, METH_VARARGS,
 	 "get head revisions"}, /* Can do filtering since 3.2 */
 	{"headrevsfiltered", (PyCFunction)index_headrevs, METH_VARARGS,

--- a/mercurial/util.h	Wed Mar 25 14:16:10 2015 -0500
+++ b/mercurial/util.h	Tue Mar 24 11:00:09 2015 -0700
@@ -209,6 +209,7 @@
 	return ret;
 }
 
+#define MIN(a, b) (((a)<(b))?(a):(b))
 /* VC9 doesn't include bool and lacks stdbool.h based on my searching */
 #ifdef _MSC_VER
 #define true 1