Expose preadv2 in os module

vstinner · Jan 27, 2018 · Jan 19, 2018 · Jan 19, 2018 · Jan 19, 2018 · Jan 19, 2018
commit ea21128d44dc31bc1cd2f9c285dbcf8e3ad1fe18
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
@@ -272,6 +272,19 @@ def test_pread(self):
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'pread'), "test needs posix.pread()")
+    def test_preadv2(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            os.write(fd, b'test1tt2t3')
+            os.lseek(fd, 0, os.SEEK_SET)
+            buf = [bytearray(i) for i in [5, 3, 2]]
+            self.assertEqual(posix.preadv2(fd, buf, 0, os.RWF_SYNC), 10)
+            self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
+        finally:
+            os.close(fd)
+
+
     @unittest.skipUnless(hasattr(posix, 'pwrite'), "test needs posix.pwrite()")
     def test_pwrite(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)

diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
@@ -3705,6 +3705,50 @@ os_pread(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 
 #endif /* defined(HAVE_PREAD) */
 
+#if defined(HAVE_PREAD)
+
+PyDoc_STRVAR(os_preadv2__doc__,
+"preadv2($module, fd, buffers, offset, flags, /)\n"
+"--\n"
+"\n"
+"Read a number of bytes from a file descriptor starting at a particular offset.\n"
+"\n"
+"Read length bytes from file descriptor fd, starting at offset bytes from\n"
+"the beginning of the file.  The file offset remains unchanged.");
+
+#define OS_PREADV2_METHODDEF    \
+    {"preadv2", (PyCFunction)os_preadv2, METH_FASTCALL, os_preadv2__doc__},
+
+static Py_ssize_t
+os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags);
+
+static PyObject *
+os_preadv2(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *return_value = NULL;
+    int fd;
+    PyObject *buffers;
+    Py_off_t offset;
+    int flags;
+    Py_ssize_t _return_value;
+
+    if (!_PyArg_ParseStack(args, nargs, "iOO&i:preadv2",
+        &fd, &buffers, Py_off_t_converter, &offset, &flags)) {
+        goto exit;
+    }
+    _return_value = os_preadv2_impl(module, fd, buffers, offset, flags);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromSsize_t(_return_value);
+
+exit:
+    return return_value;
+}
+
+#endif /* defined(HAVE_PREAD) */
+
 PyDoc_STRVAR(os_write__doc__,
 "write($module, fd, data, /)\n"
 "--\n"
@@ -6239,6 +6283,10 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
     #define OS_PREAD_METHODDEF
 #endif /* !defined(OS_PREAD_METHODDEF) */
 
+#ifndef OS_PREADV2_METHODDEF
+    #define OS_PREADV2_METHODDEF
+#endif /* !defined(OS_PREADV2_METHODDEF) */
+
 #ifndef OS_PIPE_METHODDEF
     #define OS_PIPE_METHODDEF
 #endif /* !defined(OS_PIPE_METHODDEF) */
@@ -6410,4 +6458,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=6345053cd5992caf input=a9049054013a1b77]*/
+/*[clinic end generated code: output=2b1fdec599a15ea9 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -8163,6 +8163,64 @@ os_pread_impl(PyObject *module, int fd, int length, Py_off_t offset)
 }
 #endif /* HAVE_PREAD */
 
+#ifdef HAVE_PREAD
+/*[clinic input]
+os.preadv2 -> Py_ssize_t
+
+    fd: int
+    buffers: object
+    offset: Py_off_t
+    flags: int
+    /
+
+Read a number of bytes from a file descriptor starting at a particular offset.
+
+Read length bytes from file descriptor fd, starting at offset bytes from
+the beginning of the file.  The file offset remains unchanged.
+[clinic start generated code]*/
+
+static Py_ssize_t
+os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags)
+/*[clinic end generated code: output=fd040c20cf504631 input=f4a633d90005eb65]*/
+{
+    Py_ssize_t cnt, n;
+    int async_err = 0;
+    struct iovec *iov;
+    Py_buffer *buf;
+
+    if (!PySequence_Check(buffers)) {
+        PyErr_SetString(PyExc_TypeError,
+            "preadv2() arg 2 must be a sequence");
+        return -1;
+    }
+
+    cnt = PySequence_Size(buffers);
+    if (cnt < 0)
+        return -1;
+
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
+        return -1;
+
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        n = preadv2(fd, iov, cnt, offset, flags);
+        Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+
+    iov_cleanup(iov, buf, cnt);
+    if (n < 0) {
+        if (!async_err)
+            posix_error();
+        return -1;
+    }
+
+    return n;
+}
+
+
+#endif /* HAVE PREADV2 */
+
 
 /*[clinic input]
 os.write -> Py_ssize_t
@@ -12506,6 +12564,7 @@ static PyMethodDef posix_methods[] = {
     OS_READ_METHODDEF
     OS_READV_METHODDEF
     OS_PREAD_METHODDEF
+    OS_PREADV2_METHODDEF
     OS_WRITE_METHODDEF
     OS_WRITEV_METHODDEF
     OS_PWRITE_METHODDEF
@@ -12953,6 +13012,13 @@ all_ins(PyObject *m)
     if (PyModule_AddIntMacro(m, F_TEST)) return -1;
 #endif
 
+#ifdef HAVE_READV
+    if (PyModule_AddIntConstant(m, "RWF_DSYNC", RWF_DSYNC)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_HIPRI", RWF_HIPRI)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_SYNC", RWF_SYNC)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_NOWAIT", RWF_NOWAIT)) return -1;
+#endif
+
 #ifdef HAVE_SPAWNV
     if (PyModule_AddIntConstant(m, "P_WAIT", _P_WAIT)) return -1;
     if (PyModule_AddIntConstant(m, "P_NOWAIT", _P_NOWAIT)) return -1;