Power-Programmierung/CD1.mdf/pascal/interpre/p_pascal/samples/vpack.p

Text File | 1989-11-25 | 1.0 KB | 27 lines

PROCEDURE vpack(VAR boolarray : B_ARRAY;
    start_index : INTEGER;
    VAR intarray : I_ARRAY;
    lb, ub : INTEGER);
VAR    i, j, end_index, pack_index : INTEGER;
BEGIN
 { boolarray IS THE ARRAY TO PACK FROM CHAR FORMAT }
 { TO INTEGER BITS; intarray IS THE PACKING DESTINATION. }
 { ACTUAL UPPER ARRAY BOUNDS ARE IGNORED C-STYLE, AND IT }
 { IS ASSUMED THAT BOUNDS CHECKING HAS BEEN TURNED OFF TO }
 { PREVENT SPURIOUS 'ERROR' MESSAGES. start_index IS THE }
 { BEGINNING UNPACKED ARRAY ADDRESS; lb IS THE LOWER BOUND }
 { INDEX OF THE PACKED DESTINATION ARRAY, AND ub IS THE }
 { UPPER BOUND. A 16-bit WORD ARCHITECTURE IS ASSUMED }
 { FOR THIS VERSION OF THE ALGORITHM: }
 end_index := (ub - lb + 1) * 16 + start_index;
 { ZERO OUT THE ARRAY PRIOR TO PACKING IT: }
 FOR i := lb TO ub DO intarray[i] := 0;
 FOR i := start_index TO end_index DO
  BEGIN
   pack_index := i DIV 16 + 1; j := i MOD 16;
   { 'OR' FOR INTEGERS IS 'LOGICAL OR'; SHL = 'SHIFT LEFT' }
   intarray[pack_index] :=
    intarray[pack_index] OR (ORD(boolarray[i]) SHL (j-1))
  END
END;