Function offset_bounds_from_strides

numpy/core/src/common/mem_overlap.c:659–689

Gets a half-open range [start, end) of offsets from the data pointer */

/* Gets a half-open range [start, end) of offsets from the data pointer */
NPY_VISIBILITY_HIDDEN void
offset_bounds_from_strides(const int itemsize, const int nd,
                           const npy_intp *dims, const npy_intp *strides,
                           npy_intp *lower_offset, npy_intp *upper_offset)
{
    npy_intp max_axis_offset;
    npy_intp lower = 0;
    npy_intp upper = 0;
    int i;

    for (i = 0; i < nd; i++) {
        if (dims[i] == 0) {
            /* If the array size is zero, return an empty range */
            *lower_offset = 0;
            *upper_offset = 0;
            return;
        }
        /* Expand either upwards or downwards depending on stride */
        max_axis_offset = strides[i] * (dims[i] - 1);
        if (max_axis_offset > 0) {
            upper += max_axis_offset;
        }
        else {
            lower += max_axis_offset;
        }
    }
    /* Return a half-open range */
    upper += itemsize;
    *lower_offset = lower;
    *upper_offset = upper;
}


/* Gets a half-open range [start, end) which contains the array data */