Function convert_datetime_to_datetimestruct

numpy/core/src/multiarray/datetime.c:448–602

* Converts a datetime based on the given metadata into a datetimestruct */

 * Converts a datetime based on the given metadata into a datetimestruct
 */
NPY_NO_EXPORT int
convert_datetime_to_datetimestruct(PyArray_DatetimeMetaData *meta,
                                    npy_datetime dt,
                                    npy_datetimestruct *out)
{
    npy_int64 days;

    /* Initialize the output to all zeros */
    memset(out, 0, sizeof(npy_datetimestruct));
    out->year = 1970;
    out->month = 1;
    out->day = 1;

    /* NaT is signaled in the year */
    if (dt == NPY_DATETIME_NAT) {
        out->year = NPY_DATETIME_NAT;
        return 0;
    }

    /* Datetimes can't be in generic units */
    if (meta->base == NPY_FR_GENERIC) {
        PyErr_SetString(PyExc_ValueError,
                    "Cannot convert a NumPy datetime value other than NaT "
                    "with generic units");
        return -1;
    }

    /* TODO: Change to a mechanism that avoids the potential overflow */
    dt *= meta->num;

    /*
     * Note that care must be taken with the / and % operators
     * for negative values.
     */
    switch (meta->base) {
        case NPY_FR_Y:
            out->year = 1970 + dt;
            break;

        case NPY_FR_M:
            out->year  = 1970 + extract_unit_64(&dt, 12);
            out->month = dt + 1;
            break;

        case NPY_FR_W:
            /* A week is 7 days */
            set_datetimestruct_days(dt * 7, out);
            break;

        case NPY_FR_D:
            set_datetimestruct_days(dt, out);
            break;

        case NPY_FR_h:
            days      = extract_unit_64(&dt, 24LL);
            set_datetimestruct_days(days, out);
            out->hour = (int)dt;
            break;