add writable method

Author: rhpvorderman

src/isal/isal_zlib.pyi

@@ -68,6 +68,7 @@ class _GzipReader():
     def __init__(self, fp: typing.BinaryIO, buffersize: int = 32 * 1024): ...
     def readinto(self, obj) -> int: ...
     def readable(self) -> bool: ...
+    def writable(self) -> bool: ...
     def seekable(self) -> bool: ...
     def tell(self) -> int: ...
     def seek(self, offset: int, whence: int): ...

src/isal/isal_zlibmodule.c

@@ -1773,6 +1773,12 @@ GzipReader_readable(GzipReader *self, PyObject *Py_UNUSED(ignore))
     Py_RETURN_TRUE;
 }
 
+static PyObject *
+GzipReader_writable(GzipReader *self, PyObject *Py_UNUSED(ignore))
+{
+    Py_RETURN_TRUE;
+}
+
 static PyObject *
 GzipReader_seekable(GzipReader *self, PyObject *Py_UNUSED(ignore)) {
     return PyObject_CallMethod(self->fp, "seekable", NULL);
@@ -1806,6 +1812,7 @@ GzipReader_get_closed(GzipReader *self, void *Py_UNUSED(closure))
 static PyMethodDef GzipReader_methods[] = {
     {"readinto", (PyCFunction)GzipReader_readinto, METH_O, NULL},
     {"readable", (PyCFunction)GzipReader_readable, METH_NOARGS, NULL},
+    {"writable", (PyCFunction)GzipReader_writable, METH_NOARGS, NULL},
     {"seekable", (PyCFunction)GzipReader_seekable, METH_NOARGS, NULL},
     {"tell", (PyCFunction)GzipReader_tell, METH_NOARGS, NULL},
     {"seek", (PyCFunction)GzipReader_seek, METH_VARARGS | METH_KEYWORDS, NULL},