Optimize unicode_hash() by not calling
_PyUnicode_AsDefaultEncodedString() at all -- this saves two object
allocations (three block allocations!) and lots of redundant work.
By using the same hash algorithm as string_hash(), we maintain the
invariant that the hash of an ASCII string is the same whether
represented as a PyString or a PyUnicode.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 140ffaf..2a6a087 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6587,21 +6587,27 @@
return (PyObject*) PyUnicode_FromUnicode(&self->str[index], 1);
}
+/* Believe it or not, this produces the same value for ASCII strings
+ as string_hash(). */
static long
unicode_hash(PyUnicodeObject *self)
{
- if (self->hash != -1) {
- return self->hash;
- }
- else {
- /* Since Unicode objects compare equal to their UTF-8 string
- counterparts, we hash the UTF-8 string. */
- PyObject *v = _PyUnicode_AsDefaultEncodedString((PyObject*)self, NULL);
- if (v == NULL)
- return -1;
- assert(PyString_CheckExact(v));
- return self->hash = v->ob_type->tp_hash(v);
- }
+ Py_ssize_t len;
+ Py_UNICODE *p;
+ long x;
+
+ if (self->hash != -1)
+ return self->hash;
+ len = Py_Size(self);
+ p = self->str;
+ x = *p << 7;
+ while (--len >= 0)
+ x = (1000003*x) ^ *p++;
+ x ^= Py_Size(self);
+ if (x == -1)
+ x = -2;
+ self->hash = x;
+ return x;
}
PyDoc_STRVAR(index__doc__,