Implement C API function 'PyIter_Next'.

Author: fangerer

graalpython/com.oracle.graal.python.cext/src/abstract.c

@@ -199,3 +199,12 @@ PyObject * PyNumber_Float(PyObject *o) {
     }
     return to_sulong(result);
 }
+
+PyObject * PyIter_Next(PyObject *iter) {
+	void* result = polyglot_invoke(PY_TRUFFLE_CEXT, "PyIter_Next", to_java(iter), ERROR_MARKER);
+	if (result == ERROR_MARKER && PyErr_Occurred() && PyErr_ExceptionMatches(PyExc_StopIteration)) {
+        PyErr_Clear();
+		return NULL;
+	}
+    return to_sulong(result);
+}

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_abstract.py

@@ -75,6 +75,17 @@ def _reference_asssize_t(args):
             return -1
 
 
+def _reference_next(args):
+    iterObj = args[0]
+    n = args[1]
+    try:
+        for i in range(n-1):
+            next(iterObj)
+        return next(iterObj)
+    except BaseException:
+        raise SystemError
+        
+
 class NoNumber():
     pass
 
@@ -495,3 +506,27 @@ def compile_module(self, name):
         arguments=["PyObject* sequence"],
     )
 
+    test_PyIter_Next = CPyExtFunction(
+        _reference_next,
+        lambda: (
+            (iter((1,2,3)),0),
+            (iter((1,2,3)),3),
+            (iter((None,)),1),
+            (iter([]),1),
+            (iter(['a','b','c']),2),
+            (iter({'a':0,'b':1,'c':2}),2)
+        ),
+        code='''PyObject* wrap_PyIter_Next(PyObject* iter, int n) {
+            for (int i = 0; i < n - 1; i++) {
+                PyIter_Next(iter);
+            } 
+            return PyIter_Next(iter);
+        }
+        ''',
+        resultspec="O",
+        argspec='Oi',
+        callfunction="wrap_PyIter_Next",
+        arguments=["PyObject* sequence", "int n"],
+        cmpfunc=unhandled_error_compare
+    )
+

graalpython/lib-graalpython/python_cext.py

@@ -452,6 +452,16 @@ def PyNumber_Long(v, error_marker):
     return error_marker
 
 
+def PyIter_Next(itObj, error_marker):
+    typ = val = tb = None
+    try:
+        return next(itObj)
+    except BaseException:
+        typ, val, tb = sys.exc_info()
+    PyErr_Restore(typ, val, tb)
+    return error_marker
+
+
 ##################### UNICODE