Pseudo-Randomization and the logo of the day

In order to fresh up the daily work, a customs control for a picture was created on a dynpro. Details for doing so can be found in the sample report SAP_PICTURE_DEMO.

As it would be boring to watch the same picture (in this case: logo) all the time, ten different versions of the logo were uploaded to the SAP Web Repository using transaction SMW0 (binary objects, file type jpg) with the purpose of randomly selecting one of those ten after each start of the transaction.

The main problem was the random number function of SAP. Despite the fact one can initialize the randomization via calling function module RANDOM_INITIALIZE, each new call of the transaction will produce the same order of “random” numbers, therefore, in my case, always the same logo would be selected and displayed.

Within a session, there would be random numbers. The solution I chose was to add some “salt” by using a pseudo-randomization, based on SY-UZEIT. I limited it to minutes and seconds, so in the worst case, 5959 calls of the random function woud be executed.

The coding for doing this is provided below:

  DATA:

  gv_url            TYPE cndp_url,               “URL to logo

  cntrl_pict        TYPE REF TO cl_gui_picture,

  gv_index          TYPE datatype-integer2,      “Random index for picture

  gv_help           TYPE i,                      “Help variable for randomization

  gv_objid          TYPE w3objid.                “Object-ID in SAP-Web-Repository

…

  CLEAR gv_index.

  gv_help = sy-uzeit+2(4).      “Take only minutes and seconds, so max. 5959 calls

  DO gv_help TIMES.

    CALL FUNCTION ‘RANDOM_I2’   “Select one of ten stored pictures

      EXPORTING

        rnd_min   = 1

        rnd_max   = 10

      IMPORTING

        rnd_value = gv_index.

  ENDDO.

  WRITE gv_index TO gv_objid LEFT-JUSTIFIED NO-SIGN.

  IF gv_index < 10.

    CONCATENATE ‘RANDOM_PIC_0’ gv_objid INTO gv_objid.

  ELSE.

    CONCATENATE ”RANDOM_PIC_’ gv_objid INTO gv_objid.

  ENDIF.

  CALL FUNCTION ‘DP_PUBLISH_WWW_URL’

    EXPORTING

      objid    = gv_objid

      lifetime = cndp_lifetime_transaction

    IMPORTING

      url      = gv_url

    EXCEPTIONS

      OTHERS   = 1.

  IF sy-subrc = 0.

    CALL METHOD cntrl_pict->load_picture_from_url_async

      EXPORTING

        url = gv_url.

  ENDIF.