Add rindex() method

Author: atpalmer

README.md

@@ -51,6 +51,16 @@ Notes:
 * `start` and `end`, if provided, are _byte_ indexes.
 
 
+### rindex(substring [,start [,end]])
+
+See: https://docs.python.org/3/library/stdtypes.html#str.rindex
+
+Notes:
+
+* `substring` may be a `cstring` or Python `str` object.
+* `start` and `end`, if provided, are _byte_ indexes.
+
+
 ## TODO
 
 * Write docs (see `str` type docs)

src/cstring.c

@@ -321,6 +321,22 @@ PyObject *cstring_rfind(PyObject *self, PyObject *args) {
     return PyLong_FromSsize_t(p - CSTRING_VALUE(self));
 }
 
+PyDoc_STRVAR(rindex__doc__, "");
+PyObject *cstring_rindex(PyObject *self, PyObject *args) {
+    struct _substr_params params;
+
+    if(!_parse_substr_args(self, args, &params))
+        return NULL;
+
+    const char *p = _substr_params_rstr(&params);
+    if(!p) {
+        PyErr_SetString(PyExc_ValueError, "substring not found");
+        return NULL;
+    }
+
+    return PyLong_FromSsize_t(p - CSTRING_VALUE(self));
+}
+
 static PySequenceMethods cstring_as_sequence = {
     .sq_length = cstring_len,
     .sq_concat = cstring_concat,
@@ -339,6 +355,7 @@ static PyMethodDef cstring_methods[] = {
     {"find", cstring_find, METH_VARARGS, find__doc__},
     {"index", cstring_index, METH_VARARGS, index__doc__},
     {"rfind", cstring_rfind, METH_VARARGS, rfind__doc__},
+    {"rindex", cstring_rindex, METH_VARARGS, rindex__doc__},
     {0},
 };
 

test/test_methods.py

@@ -72,3 +72,24 @@ def test_rfind_missing():
     target = cstring('hello')
     assert target.rfind('lo', 0, 4) == -1
 
+
+def test_rindex():
+    target = cstring('hello')
+    assert target.rindex('o') == 4
+
+
+def test_rindex_empty():
+    target = cstring('hello')
+    assert target.rindex('') == 5
+
+
+def test_rindex_with_start():
+    target = cstring('hello')
+    assert target.rindex('lo', 3) == 3
+
+
+def test_rindex_missing():
+    target = cstring('hello')
+    with pytest.raises(ValueError):
+        return target.rindex('lo', 0, 4)
+