gh-84016: Implement missing PyObject_CopyToObject in PEP3118

Doc/c-api/buffer.rst

@@ -517,6 +517,15 @@ Buffer-related functions
 
    ``0`` is returned on success, ``-1`` on error.
 
+.. c:function:: int PyObject_CopyToObject(PyObject *obj, void *buf, Py_ssize_t len, char fortran)
+
+   Copy data from *buf* to *obj* buffer. Can convert between C-style and
+   or Fortran-style buffers.
+
+   ``0`` is returned on success, ``-1`` on error.
+
+   .. versionadded:: 3.14
+
 .. c:function:: void PyBuffer_FillContiguousStrides(int ndims, Py_ssize_t *shape, Py_ssize_t *strides, int itemsize, char order)
 
    Fill the *strides* array with byte-strides of a :term:`contiguous` (C-style if

Include/pybuffer.h

@@ -75,6 +75,8 @@ PyAPI_FUNC(int) PyBuffer_FromContiguous(const Py_buffer *view, const void *buf,
    is 'A', then it does not matter and the copy will be made
    in whatever way is more efficient. */
 PyAPI_FUNC(int) PyObject_CopyData(PyObject *dest, PyObject *src);
+PyAPI_FUNC(int) PyObject_CopyToObject(PyObject *obj, void *buf,
+                                      Py_ssize_t len, char fort);
 
 /* Copy the data from the src buffer to the buffer of destination. */
 PyAPI_FUNC(int) PyBuffer_IsContiguous(const Py_buffer *view, char fort);

Misc/NEWS.d/next/C_API/2024-09-29-14-34-53.gh-issue-84016.f1ThMN.rst

@@ -0,0 +1 @@
+Added public :c:func:`PyObject_CopyToObject()` to ``pybuffer.h``

Objects/abstract.c

@@ -663,7 +663,8 @@ PyBuffer_FromContiguous(const Py_buffer *view, const void *buf, Py_ssize_t len,
     return 0;
 }
 
-int PyObject_CopyData(PyObject *dest, PyObject *src)
+int
+PyObject_CopyData(PyObject *dest, PyObject *src)
 {
     Py_buffer view_dest, view_src;
     int k;
@@ -733,6 +734,41 @@ int PyObject_CopyData(PyObject *dest, PyObject *src)
     return 0;
 }
 
+int
+PyObject_CopyToObject(PyObject *obj, void *buf, Py_ssize_t len,
+                      char Py_UNUSED(fort))
+{
+    Py_buffer view_obj;
+
+    if (!PyObject_CheckBuffer(obj)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "destination must be bytes-like objects");
+        return -1;
+    }
+
+    if (!buf) {
+        PyErr_SetString(PyExc_MemoryError, "buf pointer is null");
+        return -1;
+    }
+
+    if (PyObject_GetBuffer(obj, &view_obj, PyBUF_SIMPLE)) {
+        return -1;
+    }
+
+    if (view_obj.len < len) {
+        PyErr_SetString(PyExc_BufferError,
+                        "destination is too small to"
+                        "receive data from buf");
+        PyBuffer_Release(&view_obj);
+        return -1;
+    }
+
+    /* just copy it directly through memcpy */
+    memcpy(view_obj.buf, buf, len);
+    PyBuffer_Release(&view_obj);
+    return 0;
+}
+
 void
 PyBuffer_FillContiguousStrides(int nd, Py_ssize_t *shape,
                                Py_ssize_t *strides, int itemsize,