Add PyBytes_Join() function (#111)

Author: vstinner

docs/api.rst

@@ -33,6 +33,10 @@ Python 3.14
 
    See `PyLong_GetSign() documentation <https://docs.python.org/dev/c-api/long.html#c.PyLong_GetSign>`__.
 
+.. c:function:: PyObject* PyBytes_Join(PyObject *sep, PyObject *iterable)
+
+   See `PyBytes_Join() documentation <https://docs.python.org/dev/c-api/bytes.html#c.PyBytes_Join>`__.
+
 .. c:function:: int PyUnicode_Equal(PyObject *str1, PyObject *str2)
 
    See `PyUnicode_Equal() documentation <https://docs.python.org/dev/c-api/unicode.html#c.PyUnicode_Equal>`__.

docs/changelog.rst

@@ -1,7 +1,11 @@
 Changelog
 =========
 
-* 2024-10-09: Add ``PyUnicode_Equal()`` function.
+* 2024-10-09: Add functions:
+
+  * ``PyBytes_Join()``
+  * ``PyUnicode_Equal()``
+
 * 2024-07-18: Add functions:
 
   * ``PyUnicodeWriter_Create()``

pythoncapi_compat.h

@@ -1546,6 +1546,15 @@ static inline int PyUnicode_Equal(PyObject *str1, PyObject *str2)
 #endif
 
 
+// gh-121645 added PyBytes_Join() to Python 3.14.0a0
+#if PY_VERSION_HEX < 0x030E00A0
+static inline PyObject* PyBytes_Join(PyObject *sep, PyObject *iterable)
+{
+    return _PyBytes_Join(sep, iterable);
+}
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif

tests/test_pythoncapi_compat_cext.c

@@ -1881,6 +1881,36 @@ test_unicodewriter_format(PyObject *Py_UNUSED(self), PyObject *Py_UNUSED(args))
 #endif
 
 
+static PyObject *
+test_bytes(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
+{
+    PyObject *abc = PyBytes_FromString("a b c");
+    if (abc == NULL) {
+        return NULL;
+    }
+    PyObject *list = PyObject_CallMethod(abc, "split", NULL);
+    Py_DECREF(abc);
+    if (list == NULL) {
+        return NULL;
+    }
+    PyObject *sep = PyBytes_FromString("-");
+    if (sep == NULL) {
+        Py_DECREF(list);
+        return NULL;
+    }
+
+    PyObject *join = PyBytes_Join(sep, list);
+    assert(join != NULL);
+    assert(PyBytes_Check(join));
+    assert(memcmp(PyBytes_AS_STRING(join), "a-b-c", 5) == 0);
+    Py_DECREF(join);
+
+    Py_DECREF(list);
+    Py_DECREF(sep);
+    Py_RETURN_NONE;
+}
+
+
 static struct PyMethodDef methods[] = {
     {"test_object", test_object, METH_NOARGS, _Py_NULL},
     {"test_py_is", test_py_is, METH_NOARGS, _Py_NULL},
@@ -1924,6 +1954,7 @@ static struct PyMethodDef methods[] = {
     {"test_unicodewriter_widechar", test_unicodewriter_widechar, METH_NOARGS, _Py_NULL},
     {"test_unicodewriter_format", test_unicodewriter_format, METH_NOARGS, _Py_NULL},
 #endif
+    {"test_bytes", test_bytes, METH_NOARGS, _Py_NULL},
     {_Py_NULL, _Py_NULL, 0, _Py_NULL}
 };