Improve extended slicing support in builtin types and classes. Specifically:
- Specialcase extended slices that amount to a shallow copy the same way as
is done for simple slices, in the tuple, string and unicode case.
- Specialcase step-1 extended slices to optimize the common case for all
involved types.
- For lists, allow extended slice assignment of differing lengths as long
as the step is 1. (Previously, 'l[:2:1] = []' failed even though
'l[:2] = []' and 'l[:2:None] = []' do not.)
- Implement extended slicing for buffer, array, structseq, mmap and
UserString.UserString.
- Implement slice-object support (but not non-step-1 slice assignment) for
UserString.MutableString.
- Add tests for all new functionality.
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e3c5d04..db1e43d 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -7385,6 +7385,12 @@
if (slicelength <= 0) {
return PyUnicode_FromUnicode(NULL, 0);
+ } else if (start == 0 && step == 1 && slicelength == self->length &&
+ PyUnicode_CheckExact(self)) {
+ Py_INCREF(self);
+ return (PyObject *)self;
+ } else if (step == 1) {
+ return PyUnicode_FromUnicode(self->str + start, slicelength);
} else {
source_buf = PyUnicode_AS_UNICODE((PyObject*)self);
result_buf = (Py_UNICODE *)PyMem_MALLOC(slicelength*