implemented, tested reversed slice selector iterators

Author: flexatone

src/_arraykit.c

@@ -4253,12 +4253,12 @@ BIIterSeq_new(BlockIndexObject *bi, PyObject* selector, int8_t reversed) {
         PyArrayObject *a = (PyArrayObject *)selector;
         if (PyArray_NDIM(a) != 1) {
             PyErr_SetString(PyExc_TypeError, "Arrays must be 1-dimensional");
-            return NULL;
+            goto error;
         }
         char kind = PyArray_DESCR(a)->kind;
         if (kind != 'i' && kind != 'u') {
             PyErr_SetString(PyExc_TypeError, "Arrays must integer kind");
-            return NULL;
+            goto error;
         }
         bii->selector_len = PyArray_SIZE(a);
         bii->selector_is_array = 1;
@@ -4269,9 +4269,13 @@ BIIterSeq_new(BlockIndexObject *bi, PyObject* selector, int8_t reversed) {
     }
     else {
         PyErr_SetString(PyExc_TypeError, "Input type not supported");
-        return NULL;
+        goto error;
     }
     return (PyObject *)bii;
+error:
+    Py_DECREF(bii->bi);
+    Py_DECREF(bii->selector);
+    return NULL;
 }
 
 static void
@@ -4387,7 +4391,6 @@ typedef struct BIIterSliceObject {
     Py_ssize_t count; // count of , mutated in-place
     // these are the normalized values truncated to the span of the bir_count; len is the realized length after extraction; step is always set to 1 if missing; len is 0 if no realized values
     Py_ssize_t start;
-    Py_ssize_t stop;
     Py_ssize_t step;
     Py_ssize_t len;
 } BIIterSliceObject;
@@ -4405,14 +4408,14 @@ BIIterSlice_new(BlockIndexObject *bi, PyObject* slice, int8_t reversed) {
     Py_INCREF(slice);
     bii->slice = slice;
 
-    bii->reversed = reversed;
     bii->count = 0;
+    Py_ssize_t stop; // not needed
 
     if (PySlice_Check(slice)) {
         if (PySlice_GetIndicesEx(slice,
                 bi->bir_count,
                 &bii->start,
-                &bii->stop,
+                &stop,
                 &bii->step,
                 &bii->len)) {
             goto error;
@@ -4424,6 +4427,10 @@ BIIterSlice_new(BlockIndexObject *bi, PyObject* slice, int8_t reversed) {
         PyErr_SetString(PyExc_TypeError, "Input type not supported");
         goto error;
     }
+    if ((bii->reversed = reversed)) {
+        bii->start += (bii->step * (bii->len - 1));
+        bii->step *= -1;
+    }
     return (PyObject *)bii;
 error:
     Py_DECREF(bii->bi);

test/test_block_index.py

@@ -383,5 +383,19 @@ def test_block_index_iter_select_slice_b(self) -> None:
             )
 
         self.assertEqual(list(bi1.iter_select((slice(None, None, -1)))),
-            [(2, 4), (2, 3), (2, 2), (2, 1)]
+            [(2, 4), (2, 3), (2, 2), (2, 1), (2, 0), (1, 0), (0, 1), (0, 0)]
+            )
+
+    def test_block_index_iter_select_slice_c(self) -> None:
+        bi1 = BlockIndex()
+        bi1.register(np.arange(4).reshape(2,2))
+        bi1.register(np.arange(2))
+        bi1.register(np.arange(6).reshape(2,3))
+
+        self.assertEqual(list(bi1.iter_select(slice(1,5))),
+            [(0, 1), (1, 0), (2, 0), (2, 1)]
+            )
+
+        self.assertEqual(list(reversed(bi1.iter_select(slice(1,5)))),
+            [(2, 1), (2, 0), (1, 0), (0, 1)]
             )