Function _UpdateContiguousFlags

numpy/core/src/multiarray/flagsobject.c:114–159

* Check whether the given array is stored contiguously * in memory. And update the passed in ap flags appropriately. * * The traditional rule is that for an array to be flagged as C contiguous, * the following must hold: * * strides[-1] == itemsize * strides[i] == shape[i+1] * strides[i + 1] * * And for an array to be flagged as F contiguous, the obvious reversal: * * strides[0] == item

 * The above rules thus only apply when ignoring all size 1 dimensions.
 */
static void
_UpdateContiguousFlags(PyArrayObject *ap)
{
    npy_intp sd;
    npy_intp dim;
    int i;
    npy_bool is_c_contig = 1;

    sd = PyArray_ITEMSIZE(ap);
    for (i = PyArray_NDIM(ap) - 1; i >= 0; --i) {
        dim = PyArray_DIMS(ap)[i];
        /* contiguous by definition */
        if (dim == 0) {
            PyArray_ENABLEFLAGS(ap, NPY_ARRAY_C_CONTIGUOUS);
            PyArray_ENABLEFLAGS(ap, NPY_ARRAY_F_CONTIGUOUS);
            return;
        }
        if (dim != 1) {
            if (PyArray_STRIDES(ap)[i] != sd) {
                is_c_contig = 0;
            }
            sd *= dim;
        }
    }
    if (is_c_contig) {
        PyArray_ENABLEFLAGS(ap, NPY_ARRAY_C_CONTIGUOUS);
    }
    else {
        PyArray_CLEARFLAGS(ap, NPY_ARRAY_C_CONTIGUOUS);
    }

    /* check if fortran contiguous */
    sd = PyArray_ITEMSIZE(ap);
    for (i = 0; i < PyArray_NDIM(ap); ++i) {
        dim = PyArray_DIMS(ap)[i];
        if (dim != 1) {
            if (PyArray_STRIDES(ap)[i] != sd) {
                PyArray_CLEARFLAGS(ap, NPY_ARRAY_F_CONTIGUOUS);
                return;
            }
            sd *= dim;
        }
    }
    PyArray_ENABLEFLAGS(ap, NPY_ARRAY_F_CONTIGUOUS);
    return;
}

static void
arrayflags_dealloc(PyArrayFlagsObject *self)