Binary Digit Sum in ABAP

report zz_test_binary.

parameters: x type x length 20 default '8060403A' visible length 40.

* Binary Digit Sums

* The following is an optimized algorithm to compute the binary digit sum
* of an hex string (should work for arbitrary length)

* If a bit sequence is used to model a set, the binary digit sum can be
* interpreted as the cardinality of the set.

* DSUM256 should be a CONSTANT, but a literal can only have 255 characters...
data gc_dsum256(256) type x.
perform build_dsum256 changing gc_dsum256.

data: sum   type i value 0,
      count type i,
      byte  type x.

write: / x.

count = xstrlen( x ).
while count > 0.
  subtract 1 from count.
  byte = x+count(1).
  sum = sum + gc_dsum256+byte(1).
endwhile.

write: / '... has binary digit sum', sum.

form build_dsum256 changing cv_dsum256 type raw256.

  data: part(32) type x,
        partoff type i value 0.
  define _build_dsum256.
    part = &1.
    cv_dsum256+partoff(32) = part.
    add 32 to partoff.
  end-of-definition.
  _build_dsum256 :
    '0001010201020203010202030203030401020203020303040203030403040405',
    '0102020302030304020303040304040502030304030404050304040504050506',
    '0102020302030304020303040304040502030304030404050304040504050506',
    '0203030403040405030404050405050603040405040505060405050605060607',
    '0102020302030304020303040304040502030304030404050304040504050506',
    '0203030403040405030404050405050603040405040505060405050605060607',
    '0203030403040405030404050405050603040405040505060405050605060607',
    '0304040504050506040505060506060704050506050606070506060706070708'.

* Digit sums of the first 256 numbers,
* computed in a JS console with the following code block:
*
*  t=[];s="'";for (var i=0;i<256;i++) { s+= "0"+(function(i){
*   s = 0; while (i > 0) { s += (i%2); i = i>>1; } return s;
*  })(i); if ((i+1)%32==0){t.push(s+"'");s="'"}};t.join(",\n")+"."
*

endform.