PACKET convert DEFINES dec, hex, dsget2b, exhilo,    (* Stand: 87-01-13  *)
                       addc, subc, addl, subl, incl, (* Autor: G. Szalay *)
                       txt, CT, gethex, integ:

LET dectab = "0123456789", hextab="0123456789abcdef", mask16=15;
INT VAR number, digit, i;
TEXT VAR buffer, char;
INT CONST min 1     := dec ("ffff"),
          min 2     := dec ("fffe"),
          minint    := dec ("8000"),
          maxint    := dec ("7fff"),
       maxint min 1 := dec ("7ffe");

INT PROC integ (TEXT CONST text): (*only digits allowed*)
  number := 0;
  FOR i FROM 1 UPTO LENGTH text REP
    digit := pos (dectab, text SUB i);
    IF digit > 0
    THEN number := number * 10 + digit - 1
    FI
  UNTIL digit = 0 PER;
  number
END PROC integ;

TEXT PROC hex (INT CONST n):
  buffer := ""; number := n;
  FOR i FROM 1 UPTO 4 REP
    rotate (number,4);
    digit := number AND mask16;
    buffer CAT (hextab SUB (digit + 1))
  PER;
  buffer
END PROC hex;

INT PROC dec (TEXT CONST t):
  IF LENGTH t > 4 THEN leave with message FI;
  number := 0;
  FOR i FROM 1 UPTO LENGTH t
  REP char := t SUB i;
      digit := pos (hextab, char) - 1;
      IF digit<0 THEN leave with message FI;
      rotate (number, 4);
      number INCR digit
  PER;
  number.

  leave with message:
    error stop ("wrong param for dec");
    LEAVE dec WITH 0.

END PROC dec;

INT PROC exhilo (INT CONST val):
  INT VAR ex := val; rotate (ex, 8);
  ex
END PROC exhilo;

INT PROC dsget2b (INT CONST drid, off hi, off lo):
  INT VAR val := dsgetw (drid, off hi, off lo);
  IF drid <> 1 THEN rotate (val, 8) FI;
  val
END PROC dsget2b;

PROC addc (INT CONST a, b, INT VAR sum, BOOL VAR carry):
  INT VAR s;
  disable stop;
  s := a + b;
  IF a >= 0 AND b >= 0 THEN carry := FALSE
  ELIF a < 0 AND b < 0 THEN carry := TRUE
  ELSE carry := s >= 0
  FI;
  sum := s;
  clear error
END PROC addc;

PROC subc (INT CONST a, b, INT VAR diff, BOOL VAR carry):
  INT VAR d;
  disable stop;
  d := a - b;
  IF a >= 0 AND b < 0 THEN carry := TRUE
  ELIF a < 0 AND b >= 0 THEN carry := FALSE
  ELSE carry := d < 0
  FI;
  diff := d;
  clear error
END PROC subc;

PROC incl (INT VAR ah, al, INT CONST ainc):
  BOOL VAR ov;
  IF ainc = 1
  THEN IF al = min1 THEN al := 0; ah INCR 1
       ELIF al = maxint THEN al := minint
       ELSE al INCR 1
       FI
  ELIF ainc = 2
  THEN IF al = min2 THEN al := 0; ah INCR 1
       ELIF al = maxint min1 THEN al := minint
       ELSE al INCR 2
       FI
  ELSE addc (al, ainc, al, ov);
       IF ov THEN addc (ah, 1, ah, ov) FI
  FI
END PROC incl;

PROC addl (INT CONST ah, al, bh, bl, INT VAR sumh, suml, BOOL VAR carry):
  BOOL VAR low carry, high carry;
  addc (al, bl, suml, low carry);
  addc (ah, bh, sumh, high carry);
  IF low carry THEN addc (sumh, 1, sumh, low carry) FI;
  carry := low carry OR high carry
END PROC addl;

PROC subl (INT CONST ah, al, bh, bl, INT VAR diffh, diffl, BOOL VAR carry):
  BOOL VAR low carry, high carry;
  subc (al, bl, diffl, low carry);
  subc (ah, bh, diffh, high carry);
  IF low carry THEN subc (diffh, 1, diffh, low carry) FI;
  carry := low carry OR high carry
END PROC subl;

TEXT PROC txt (INT CONST num):
  IF   num = minint  THEN "-32768"
  ELIF num < 0       THEN "-" CT txt (-num)
  ELIF num <= 9      THEN code (num + 48)
  ELSE                    txt (num DIV 10) CT code (num MOD 10 + 48)
  FI
END PROC txt;

TEXT OP CT (TEXT CONST left, right):
  buffer := left; buffer CAT right; buffer
END OP CT;

PROC gethex (TEXT VAR hexline):
  buffer := "";
  REP inchar (char);
      SELECT pos (""13""12"0123456789abcdef", char) OF
        CASE 0: out(""7"")
        CASE 1: hexline := buffer; out (""13""10""); LEAVE gethex
        CASE 2: delete last char
        OTHERWISE buffer CAT char; out (char)
      ENDSELECT
  PER.

delete last char:
  IF buffer = ""
  THEN out (""7"")
  ELSE buffer := subtext (buffer, 1, LENGTH buffer - 1);
       out (""8" "8"")
  FI.

ENDPROC gethex;

END PACKET convert;