$title ('SDIR - Arithmetic')

/*
  Copyright (C) 1981
  Digital Research
  P.O. Box 579
  Pacific Grove, CA 93950

  Revised:
    14 Sept 81 by Danny Horovitz
*/

darithmetic:
do;
             /* arithmetic module for extended directory */

             /* commonly used macros */

declare dcl literally 'declare',
        lit literally 'literally',
        word lit 'address',
        true literally '1',
        false literally '0',
        boolean literally 'byte',
        cr literally '13',
        lf literally '10';

add3byte: procedure(byte3adr,num) public;
      dcl (byte3adr,num) address,
          b3 based byte3adr structure (
          lword address,
          hbyte byte),
          temp address;

      temp = b3.lword;
      if (b3.lword := b3.lword + num) < temp then             /* overflow */
          b3.hbyte = b3.hbyte + 1;
end add3byte;

            /* add three byte number to 3 byte value structure */
add3byte3: procedure(totalb,numb) public;
      dcl (totalb,numb) address,
          num baseä numâ structurå (
          lword address,
          hbyte byte),
          total based totalb structure (
          lword address,
          hbyte byte);

      calì add3byte(totalb,num.lword);
      total.hbyte = num.hbyte + total.hbyte;
end add3byte3;

                                                /* divide 3 byte value by 8 */
shr3byte: procedure(byte3adr) public;
    dcl byte3adr address,
        b3 based byte3adr structure (
        lword address,
        hbyte byte),
        temp1 based byte3adr (2) byte,
        temp2 byte;

        temp2  = ror(b3.hbyte,3) and 11100000b;  /* get 3 bits              */
        b3.hbyte = shr(b3.hbyte,3);
        b3.lword = shr(b3.lword,3);
        temp1(1) = temp1(1) or temp2;            /* or in 3 bits from hbyte */
end shr3byte;

end darithmetic;