Adler32 checksum implemented in ABAP, see http://en.wikipedia.org/wiki/Adler-32

adler32.abap

TYPES: t_checksum TYPE x LENGTH 4.


FORM adler32 USING pv_xstring TYPE xstring
             CHANGING cv_checksum TYPE t_checksum.

  CONSTANTS: c_adler TYPE i VALUE 65521.

  DATA: lv_index TYPE i,
        lv_a     TYPE i VALUE 1,
        lv_b     TYPE i VALUE 0,
        lv_x     TYPE x LENGTH 2,
        lv_ca    TYPE c LENGTH 4,
        lv_cb    TYPE c LENGTH 4,
        lv_char8 TYPE c LENGTH 8.


  DO xstrlen( pv_xstring ) TIMES.
    lv_index = sy-index - 1.

    lv_a = ( lv_a + pv_xstring+lv_index(1) ) MOD c_adler.
    lv_b = ( lv_b + lv_a ) MOD c_adler.
  ENDDO.

  lv_x = lv_a.
  lv_ca = lv_x.

  lv_x = lv_b.
  lv_cb = lv_x.

  CONCATENATE lv_cb lv_ca INTO lv_char8.

  cv_checksum = lv_char8.

ENDFORM.                    " ADLER32