Function _descriptor_from_pep3118_format_fast

numpy/core/src/multiarray/buffer.c:993–1066

 */

static int
_descriptor_from_pep3118_format_fast(char const *s, PyObject **result)
{
    PyArray_Descr *descr;

    int is_standard_size = 0;
    char byte_order = '=';
    int is_complex = 0;

    int type_num = NPY_BYTE;
    int item_seen = 0;

    for (; *s != '\0'; ++s) {
        is_complex = 0;
        switch (*s) {
        case '@':
        case '^':
            /* ^ means no alignment; doesn't matter for a single element */
            byte_order = '=';
            is_standard_size = 0;
            break;
        case '<':
            byte_order = '<';
            is_standard_size = 1;
            break;
        case '>':
        case '!':
            byte_order = '>';
            is_standard_size = 1;
            break;
        case '=':
            byte_order = '=';
            is_standard_size = 1;
            break;
        case 'Z':
            is_complex = 1;
            ++s;
        default:
            if (item_seen) {
                /* Not a single-element data type */
                return 0;
            }
            type_num = _pep3118_letter_to_type(*s, !is_standard_size,
                                               is_complex);
            if (type_num < 0) {
                /* Something unknown */
                return 0;
            }
            item_seen = 1;
            break;
        }
    }

    if (!item_seen) {
        return 0;
    }

    descr = PyArray_DescrFromType(type_num);