Switch dict lookup around to optimizing for unicode.

For now, unicode_eq() is static inside dictobject.c;
eventually we may have to move it into unicodeobject.c,
so as to support the same hacks from setobject.c.

None of this seems to affect performance much, but it's still the
right thing to do.

Objects/dictobject.c

@@ -149,7 +149,7 @@ _PyDict_Dummy(void)
 
 /* forward declarations */
 static dictentry *
-lookdict_string(dictobject *mp, PyObject *key, long hash);
+lookdict_unicode(dictobject *mp, PyObject *key, long hash);
 
 #ifdef SHOW_CONVERSION_COUNTS
 static long created = 0L;
@@ -218,7 +218,7 @@ PyDict_New(void)
 			return NULL;
 		EMPTY_TO_MINSIZE(mp);
 	}
-	mp->ma_lookup = lookdict_string;
+	mp->ma_lookup = lookdict_unicode;
 #ifdef SHOW_CONVERSION_COUNTS
 	++created;
 #endif
@@ -243,7 +243,7 @@ Christian Tismer.
 
 lookdict() is general-purpose, and may return NULL if (and only if) a
 comparison raises an exception (this was new in Python 2.5).
-lookdict_string() below is specialized to string keys, comparison of which can
+lookdict_unicode() below is specialized to string keys, comparison of which can
 never raise an exception; that function can never return NULL.  For both, when
 the key isn't found a dictentry* is returned for which the me_value field is
 NULL; this is the slot in the dict at which the key would have been found, and
@@ -325,17 +325,37 @@ lookdict(dictobject *mp, PyObject *key, register long hash)
 	return 0;
 }
 
+/* Return 1 if two unicode objects are equal, 0 if not. */
+static int
+unicode_eq(PyObject *aa, PyObject *bb)
+{
+	PyUnicodeObject *a = (PyUnicodeObject *)aa;
+	PyUnicodeObject *b = (PyUnicodeObject *)bb;
+
+	if (a->length != b->length)
+		return 0;
+	if (a->length == 0)
+		return 1;
+	if (a->str[0] != b->str[0])
+		return 0;
+	if (a->length == 1)
+		return 1;
+	return PyUnicode_Compare(aa, bb) == 0;
+}
+
+
 /*
- * Hacked up version of lookdict which can assume keys are always strings;
- * this assumption allows testing for errors during PyObject_RichCompareBool()
- * to be dropped; string-string comparisons never raise exceptions.  This also
- * means we don't need to go through PyObject_RichCompareBool(); we can always
- * use _PyString_Eq() directly.
+ * Hacked up version of lookdict which can assume keys are always
+ * unicodes; this assumption allows testing for errors during
+ * PyObject_RichCompareBool() to be dropped; unicode-unicode
+ * comparisons never raise exceptions.  This also means we don't need
+ * to go through PyObject_RichCompareBool(); we can always use
+ * unicode_eq() directly.
  *
- * This is valuable because dicts with only string keys are very common.
+ * This is valuable because dicts with only unicode keys are very common.
  */
 static dictentry *
-lookdict_string(dictobject *mp, PyObject *key, register long hash)
+lookdict_unicode(dictobject *mp, PyObject *key, register long hash)
 {
 	register size_t i;
 	register size_t perturb;
@@ -344,11 +364,11 @@ lookdict_string(dictobject *mp, PyObject *key, register long hash)
 	dictentry *ep0 = mp->ma_table;
 	register dictentry *ep;
 
-	/* Make sure this function doesn't have to handle non-string keys,
+	/* Make sure this function doesn't have to handle non-unicode keys,
 	   including subclasses of str; e.g., one reason to subclass
-	   strings is to override __eq__, and for speed we don't cater to
+	   unicodes is to override __eq__, and for speed we don't cater to
 	   that here. */
-	if (!PyString_CheckExact(key)) {
+	if (!PyUnicode_CheckExact(key)) {
 #ifdef SHOW_CONVERSION_COUNTS
 		++converted;
 #endif
@@ -362,7 +382,7 @@ lookdict_string(dictobject *mp, PyObject *key, register long hash)
 	if (ep->me_key == dummy)
 		freeslot = ep;
 	else {
-		if (ep->me_hash == hash && _PyString_Eq(ep->me_key, key))
+		if (ep->me_hash == hash && unicode_eq(ep->me_key, key))
 			return ep;
 		freeslot = NULL;
 	}
@@ -377,7 +397,7 @@ lookdict_string(dictobject *mp, PyObject *key, register long hash)
 		if (ep->me_key == key
 		    || (ep->me_hash == hash
 		        && ep->me_key != dummy
-			&& _PyString_Eq(ep->me_key, key)))
+			&& unicode_eq(ep->me_key, key)))
 			return ep;
 		if (ep->me_key == dummy && freeslot == NULL)
 			freeslot = ep;
@@ -615,8 +635,8 @@ PyDict_GetItemWithError(PyObject *op, PyObject *key)
 		PyErr_BadInternalCall();
 		return NULL;
 	}
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1)
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1)
 	{
 		hash = PyObject_Hash(key);
 		if (hash == -1) {
@@ -695,8 +715,8 @@ PyDict_DelItem(PyObject *op, PyObject *key)
 		return -1;
 	}
 	assert(key);
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return -1;
@@ -975,8 +995,8 @@ dict_subscript(dictobject *mp, register PyObject *key)
 	long hash;
 	dictentry *ep;
 	assert(mp->ma_table != NULL);
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return NULL;
@@ -1547,8 +1567,8 @@ dict_contains(register dictobject *mp, PyObject *key)
 	long hash;
 	dictentry *ep;
 
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return NULL;
@@ -1571,8 +1591,8 @@ dict_get(register dictobject *mp, PyObject *args)
 	if (!PyArg_UnpackTuple(args, "get", 1, 2, &key, &failobj))
 		return NULL;
 
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return NULL;
@@ -1600,8 +1620,8 @@ dict_setdefault(register dictobject *mp, PyObject *args)
 	if (!PyArg_UnpackTuple(args, "setdefault", 1, 2, &key, &failobj))
 		return NULL;
 
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return NULL;
@@ -1646,8 +1666,8 @@ dict_pop(dictobject *mp, PyObject *args)
 				"pop(): dictionary is empty");
 		return NULL;
 	}
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return NULL;
@@ -1842,8 +1862,8 @@ PyDict_Contains(PyObject *op, PyObject *key)
 	dictobject *mp = (dictobject *)op;
 	dictentry *ep;
 
-	if (!PyString_CheckExact(key) ||
-	    (hash = ((PyStringObject *) key)->ob_shash) == -1) {
+	if (!PyUnicode_CheckExact(key) ||
+	    (hash = ((PyUnicodeObject *) key)->hash) == -1) {
 		hash = PyObject_Hash(key);
 		if (hash == -1)
 			return -1;
@@ -1889,7 +1909,7 @@ dict_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 		/* It's guaranteed that tp->alloc zeroed out the struct. */
 		assert(d->ma_table == NULL && d->ma_fill == 0 && d->ma_used == 0);
 		INIT_NONZERO_DICT_SLOTS(d);
-		d->ma_lookup = lookdict_string;
+		d->ma_lookup = lookdict_unicode;
 #ifdef SHOW_CONVERSION_COUNTS
 		++created;
 #endif