parsers: add a C function to pack the dirstate

This is about 9 times faster than the Python dirstate packing code.
The relatively small speedup is due to the poor locality and memory
access patterns caused by traversing dicts and other boxed Python
values.

mercurial/dirstate.py

@@ -498,12 +498,24 b' class dirstate(object):'
             return
         st = self._opener("dirstate", "w", atomictemp=True)
 
+        def finish(s):
+            st.write(s)
+            st.close()
+            self._lastnormaltime = 0
+            self._dirty = self._dirtypl = False
+
         # use the modification time of the newly created temporary file as the
         # filesystem's notion of 'now'
-        now = int(util.fstat(st).st_mtime)
+        now = util.fstat(st).st_mtime
+        copymap = self._copymap
+        try:
+            finish(parsers.pack_dirstate(self._map, copymap, self._pl, now))
+            return
+        except AttributeError:
+            pass
 
+        now = int(now)
         cs = cStringIO.StringIO()
-        copymap = self._copymap
         pack = struct.pack
         write = cs.write
         write("".join(self._pl))
@@ -526,10 +538,7 b' class dirstate(object):'
             e = pack(_format, e[0], e[1], e[2], e[3], len(f))
             write(e)
             write(f)
-        st.write(cs.getvalue())
-        st.close()
-        self._lastnormaltime = 0
-        self._dirty = self._dirtypl = False
+        finish(cs.getvalue())
 
     def _dirignore(self, f):
         if f == '.':

mercurial/parsers.c

@@ -214,6 +214,154 b' quit:'
 	return ret;
 }
 
+static inline int getintat(PyObject *tuple, int off, uint32_t *v)
+{
+	PyObject *o = PyTuple_GET_ITEM(tuple, off);
+	long val;
+
+	if (PyInt_Check(o))
+		val = PyInt_AS_LONG(o);
+	else if (PyLong_Check(o)) {
+		val = PyLong_AsLong(o);
+		if (val == -1 && PyErr_Occurred())
+			return -1;
+	} else {
+		PyErr_SetString(PyExc_TypeError, "expected an int or long");
+		return -1;
+	}
+	if (LONG_MAX > INT_MAX && (val > INT_MAX || val < INT_MIN)) {
+		PyErr_SetString(PyExc_OverflowError,
+				"Python value to large to convert to uint32_t");
+		return -1;
+	}
+	*v = (uint32_t)val;
+	return 0;
+}
+
+static PyObject *dirstate_unset;
+
+/*
+ * Efficiently pack a dirstate object into its on-disk format.
+ */
+static PyObject *pack_dirstate(PyObject *self, PyObject *args)
+{
+	PyObject *packobj = NULL;
+	PyObject *map, *copymap, *pl;
+	Py_ssize_t nbytes, pos, l;
+	PyObject *k, *v, *pn;
+	char *p, *s;
+	double now;
+
+	if (!PyArg_ParseTuple(args, "O!O!Od:pack_dirstate",
+			      &PyDict_Type, &map, &PyDict_Type, &copymap,
+			      &pl, &now))
+		return NULL;
+
+	if (!PySequence_Check(pl) || PySequence_Size(pl) != 2) {
+		PyErr_SetString(PyExc_TypeError, "expected 2-element sequence");
+		return NULL;
+	}
+
+	/* Figure out how much we need to allocate. */
+	for (nbytes = 40, pos = 0; PyDict_Next(map, &pos, &k, &v);) {
+		PyObject *c;
+		if (!PyString_Check(k)) {
+			PyErr_SetString(PyExc_TypeError, "expected string key");
+			goto bail;
+		}
+		nbytes += PyString_GET_SIZE(k) + 17;
+		c = PyDict_GetItem(copymap, k);
+		if (c) {
+			if (!PyString_Check(c)) {
+				PyErr_SetString(PyExc_TypeError,
+						"expected string key");
+				goto bail;
+			}
+			nbytes += PyString_GET_SIZE(c) + 1;
+		}
+	}
+
+	packobj = PyString_FromStringAndSize(NULL, nbytes);
+	if (packobj == NULL)
+		goto bail;
+
+	p = PyString_AS_STRING(packobj);
+
+	pn = PySequence_ITEM(pl, 0);
+	if (PyString_AsStringAndSize(pn, &s, &l) == -1 || l != 20) {
+		PyErr_SetString(PyExc_TypeError, "expected a 20-byte hash");
+		goto bail;
+	}
+	memcpy(p, s, l);
+	p += 20;
+	pn = PySequence_ITEM(pl, 1);
+	if (PyString_AsStringAndSize(pn, &s, &l) == -1 || l != 20) {
+		PyErr_SetString(PyExc_TypeError, "expected a 20-byte hash");
+		goto bail;
+	}
+	memcpy(p, s, l);
+	p += 20;
+
+	for (pos = 0; PyDict_Next(map, &pos, &k, &v); ) {
+		uint32_t mode, size, mtime;
+		Py_ssize_t len, l;
+		PyObject *o;
+		char *s, *t;
+		int err;
+
+		if (!PyTuple_Check(v) || PyTuple_GET_SIZE(v) != 4) {
+			PyErr_SetString(PyExc_TypeError, "expected a 4-tuple");
+			goto bail;
+		}
+		o = PyTuple_GET_ITEM(v, 0);
+		if (PyString_AsStringAndSize(o, &s, &l) == -1 || l != 1) {
+			PyErr_SetString(PyExc_TypeError, "expected one byte");
+			goto bail;
+		}
+		*p++ = *s;
+		err = getintat(v, 1, &mode);
+		err |= getintat(v, 2, &size);
+		err |= getintat(v, 3, &mtime);
+		if (err)
+			goto bail;
+		if (*s == 'n' && mtime == (uint32_t)now) {
+			/* See dirstate.py:write for why we do this. */
+			if (PyDict_SetItem(map, k, dirstate_unset) == -1)
+				goto bail;
+			mode = 0, size = -1, mtime = -1;
+		}
+		putbe32(mode, p);
+		putbe32(size, p + 4);
+		putbe32(mtime, p + 8);
+		t = p + 12;
+		p += 16;
+		len = PyString_GET_SIZE(k);
+		memcpy(p, PyString_AS_STRING(k), len);
+		p += len;
+		o = PyDict_GetItem(copymap, k);
+		if (o) {
+			*p++ = '\0';
+			l = PyString_GET_SIZE(o);
+			memcpy(p, PyString_AS_STRING(o), l);
+			p += l;
+			len += l + 1;
+		}
+		putbe32((uint32_t)len, t);
+	}
+
+	pos = p - PyString_AS_STRING(packobj);
+	if (pos != nbytes) {
+		PyErr_Format(PyExc_SystemError, "bad dirstate size: %ld != %ld",
+                             (long)pos, (long)nbytes);
+		goto bail;
+	}
+
+	return packobj;
+bail:
+	Py_XDECREF(packobj);
+	return NULL;
+}
+
 /*
  * A base-16 trie for fast node->rev mapping.
  *
@@ -1356,6 +1504,7 b' bail:'
 static char parsers_doc[] = "Efficient content parsing.";
 
 static PyMethodDef methods[] = {
+	{"pack_dirstate", pack_dirstate, METH_VARARGS, "pack a dirstate\n"},
 	{"parse_manifest", parse_manifest, METH_VARARGS, "parse a manifest\n"},
 	{"parse_dirstate", parse_dirstate, METH_VARARGS, "parse a dirstate\n"},
 	{"parse_index2", parse_index2, METH_VARARGS, "parse a revlog index\n"},
@@ -1375,6 +1524,8 b' static void module_init(PyObject *mod)'
 				  -1, -1, -1, -1, nullid, 20);
 	if (nullentry)
 		PyObject_GC_UnTrack(nullentry);
+
+	dirstate_unset = Py_BuildValue("ciii", 'n', 0, -1, -1);
 }
 
 #ifdef IS_PY3K