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

Text File | 1989-11-25 | 1.1 KB | 28 lines

PROCEDURE vunpack(VAR intarray : I_ARRAY;
    start_index : INTEGER;
    VAR boolarray : B_ARRAY;
    lb, ub : INTEGER);
VAR i, j, end_index, unpack_index : INTEGER;
BEGIN
 { intarray IS THE ARRAY TO UNPACK FROM INTEGER BITS }
 { TO CHAR FORMAT;  boolarray IS THE UNPACKING 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 }
 { PACKED ARRAY ADDRESS; lb IS THE LOWER BOUND INDEX OF THE }
 { UNPACKED 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 UNPACKING INTO IT: }
 FOR i := lb TO ub DO boolarray[i] := FALSE;
 FOR i := start_index TO end_index DO
  BEGIN
   unpack_index := i DIV 16 + 1; j := i MOD 16;
   { 'OR' FOR INTEGERS IS 'LOGICAL OR'; SHL = 'SHIFT LEFT' }
   IF (intarray[unpack_index] AND (1 SHL (j-1))) <> 0 THEN
    boolarray[i] := TRUE
   ELSE boolarray[i] := FALSE
  END
END;