C Parser: cleanup PyIter_Send backport

aiocsv/_parser.c

@@ -26,11 +26,62 @@ static inline PyObject* PyObject_CallMethodOneArg(PyObject* self, PyObject* name
 #define Py_TPFLAGS_IMMUTABLETYPE 0
 #define Py_TPFLAGS_DISALLOW_INSTANTIATION 0
 
+typedef enum {
+    PYGEN_RETURN = 0,
+    PYGEN_ERROR = -1,
+    PYGEN_NEXT = 1,
+} PySendResult;
+
 static inline PyObject* Py_NewRef(PyObject* o) {
     Py_INCREF(o);
     return o;
 }
 
+static PyObject* _fetch_stop_iteration_value(void) {
+    PyObject* exc_type;
+    PyObject* exc_value;
+    PyObject* exc_traceback;
+    PyErr_Fetch(&exc_type, &exc_value, &exc_traceback);
+
+    assert(exc_type);
+    assert(PyErr_ExceptionMatches(PyExc_StopIteration));
+
+    PyErr_NormalizeException(&exc_type, &exc_value, &exc_traceback);
+    assert(PyObject_TypeCheck(exc_value, (PyTypeObject*)PyExc_StopIteration));
+
+    PyErr_Clear();
+
+    PyObject* value = ((PyStopIterationObject*)exc_value)->value;
+    Py_INCREF(value);
+    Py_XDECREF(exc_type);
+    Py_XDECREF(exc_value);
+    Py_XDECREF(exc_traceback);
+    return value;
+}
+
+static PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult) {
+    assert(arg);
+    assert(presult);
+
+    // Ensure arg is Py_None
+    if (arg != Py_None) {
+        PyErr_SetString(PyExc_SystemError, "aiocsv's PyIter_Send backport doesn't support sending values other than None");
+        return PYGEN_ERROR;
+    }
+
+    // Ensure iter is an iterator
+    if (!PyIter_Check(iter)) {
+        PyErr_Format(PyExc_TypeError, "%R is not an iterable", Py_TYPE(iter));
+        return PYGEN_ERROR;
+    }
+
+    *presult = (Py_TYPE(iter)->tp_iternext)(iter);
+    if (*presult) return PYGEN_NEXT;
+    if (!PyErr_ExceptionMatches(PyExc_StopIteration)) return PYGEN_ERROR;
+    *presult = _fetch_stop_iteration_value();
+    return PYGEN_RETURN;
+}
+
 #endif
 
 typedef struct {
@@ -667,64 +718,6 @@ static int Parser_initiate_read(Parser* self) {
     return result;
 }
 
-// TODO: Simplify once support for 3.8 and 3.9 is dropped
-
-typedef enum {
-    AR_COMPLETE = 0,
-    AR_ERROR = -1,
-    AR_YIELD = 1,
-} AdvanceReadResult;
-
-// #if PY_VERSION_HEX < 0x030A0000
-#if 1
-
-static PyObject* PyErr_FetchStopIterationValue(void) {
-    PyObject* exc_type;
-    PyObject* exc_value;
-    PyObject* exc_traceback;
-    PyErr_Fetch(&exc_type, &exc_value, &exc_traceback);
-
-    assert(exc_type);
-    assert(PyErr_ExceptionMatches(PyExc_StopIteration));
-
-    PyErr_NormalizeException(&exc_type, &exc_value, &exc_traceback);
-    assert(PyObject_TypeCheck(exc_value, (PyTypeObject*)PyExc_StopIteration));
-
-    PyErr_Clear();
-
-    PyObject* value = ((PyStopIterationObject*)exc_value)->value;
-    Py_INCREF(value);
-    Py_XDECREF(exc_type);
-    Py_XDECREF(exc_value);
-    Py_XDECREF(exc_traceback);
-    return value;
-}
-
-static inline AdvanceReadResult Parser_advance_read(Parser* self, PyObject** str_or_yield) {
-    *str_or_yield = (Py_TYPE(self->current_read)->tp_iternext)(self->current_read);
-    if (*str_or_yield) return AR_YIELD;
-    if (!PyErr_ExceptionMatches(PyExc_StopIteration)) return AR_ERROR;
-    *str_or_yield = PyErr_FetchStopIterationValue();
-    return AR_COMPLETE;
-}
-
-#else
-
-static inline AdvanceReadResult Parser_advance_read(Parser* self, PyObject** str_or_yield) {
-    switch (PyIter_Send(self->current_read, Py_None, str_or_yield)) {
-        case PYGEN_RETURN:
-            return AR_COMPLETE;
-        case PYGEN_ERROR:
-            return AR_ERROR;
-        case PYGEN_NEXT:
-            return AR_YIELD;
-        default:
-            Py_UNREACHABLE();
-    }
-}
-
-#endif
-
 static int Parser_copy_to_buffer(Parser* self, PyObject* unicode) {
     int result = 1;
 
@@ -778,12 +771,12 @@ static PyObject* Parser_next(Parser* self) {
         // Await on the pending read
         if (self->current_read) {
             PyObject* read_str;
-            switch (Parser_advance_read(self, &read_str)) {
-                case AR_COMPLETE:
+            switch (PyIter_Send(self->current_read, Py_None, &read_str)) {
+                case PYGEN_RETURN:
                     break;
-                case AR_ERROR:
+                case PYGEN_ERROR:
                     return NULL;
-                case AR_YIELD:
+                case PYGEN_NEXT:
                     return read_str;
             }