Function _new_sortlike

numpy/core/src/multiarray/item_selection.c:1142–1300

* These algorithms use special sorting. They are not called unless the * underlying sort function for the type is available. Note that axis is * already valid. The sort functions require 1-d contiguous and well-behaved * data. Therefore, a copy will be made of the data if needed before handing * it to the sorting routine. An iterator is constructed and adjusted to walk * over all but the

 * over all but the desired sorting axis.
 */
static int
_new_sortlike(PyArrayObject *op, int axis, PyArray_SortFunc *sort,
              PyArray_PartitionFunc *part, npy_intp const *kth, npy_intp nkth)
{
    npy_intp N = PyArray_DIM(op, axis);
    npy_intp elsize = (npy_intp)PyArray_ITEMSIZE(op);
    npy_intp astride = PyArray_STRIDE(op, axis);
    int swap = PyArray_ISBYTESWAPPED(op);
    int is_aligned = IsAligned(op);
    int needcopy = !is_aligned || swap || astride != elsize;
    int needs_api = PyDataType_FLAGCHK(PyArray_DESCR(op), NPY_NEEDS_PYAPI);

    char *buffer = NULL;

    PyArrayIterObject *it;
    npy_intp size;

    int ret = 0;

    PyArray_Descr *descr = PyArray_DESCR(op);
    PyArray_Descr *odescr = NULL;

    NPY_cast_info to_cast_info = {.func = NULL};
    NPY_cast_info from_cast_info = {.func = NULL};

    NPY_BEGIN_THREADS_DEF;

    /* Check if there is any sorting to do */
    if (N <= 1 || PyArray_SIZE(op) == 0) {
        return 0;
    }

    PyObject *mem_handler = PyDataMem_GetHandler();
    if (mem_handler == NULL) {
        return -1;
    }
    it = (PyArrayIterObject *)PyArray_IterAllButAxis((PyObject *)op, &axis);
    if (it == NULL) {
        Py_DECREF(mem_handler);
        return -1;
    }
    size = it->size;

    if (needcopy) {
        buffer = PyDataMem_UserNEW(N * elsize, mem_handler);
        if (buffer == NULL) {
            ret = -1;
            goto fail;
        }
        if (PyDataType_FLAGCHK(descr, NPY_NEEDS_INIT)) {
            memset(buffer, 0, N * elsize);
        }

        if (swap) {
            odescr = PyArray_DescrNewByteorder(descr, NPY_SWAP);
        }
        else {
            odescr = descr;