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(* $Id: IntConv.Mod,v 1.3 1999/09/02 13:07:24 acken Exp $ *)
MODULE IntConv;
(*
IntConv - Low-level integer/string conversions.
Copyright (C) 1995 Michael Griebling
This module is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This module is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
IMPORT
Char := CharClass, Str := Strings, Conv := ConvTypes;
TYPE
ConvResults = Conv.ConvResults; (* strAllRight, strOutOfRange, strWrongFormat, strEmpty *)
CONST
strAllRight*=Conv.strAllRight; (* the string format is correct for the corresponding conversion *)
strOutOfRange*=Conv.strOutOfRange; (* the string is well-formed but the value cannot be represented *)
strWrongFormat*=Conv.strWrongFormat; (* the string is in the wrong format for the conversion *)
strEmpty*=Conv.strEmpty; (* the given string is empty *)
VAR
W, S, SI: Conv.ScanState;
(* internal state machine procedures *)
PROCEDURE WState(inputCh: CHAR; VAR chClass: Conv.ScanClass; VAR nextState: Conv.ScanState);
BEGIN
IF Char.IsNumeric(inputCh) THEN chClass:=Conv.valid; nextState:=W
ELSE chClass:=Conv.terminator; nextState:=NIL
END
END WState;
PROCEDURE SState(inputCh: CHAR; VAR chClass: Conv.ScanClass; VAR nextState: Conv.ScanState);
BEGIN
IF Char.IsNumeric(inputCh) THEN chClass:=Conv.valid; nextState:=W
ELSE chClass:=Conv.invalid; nextState:=S
END
END SState;
PROCEDURE ScanInt*(inputCh: CHAR; VAR chClass: Conv.ScanClass; VAR nextState: Conv.ScanState);
(*
Represents the start state of a finite state scanner for signed whole
numbers - assigns class of inputCh to chClass and a procedure
representing the next state to nextState.
The call of ScanInt(inputCh,chClass,nextState) shall assign values to
`chClass' and `nextState' depending upon the value of `inputCh' as
shown in the following table.
Procedure inputCh chClass nextState (a procedure
with behaviour of)
--------- --------- -------- ---------
ScanInt space padding ScanInt
sign valid SState
decimal digit valid WState
other invalid ScanInt
SState decimal digit valid WState
other invalid SState
WState decimal digit valid WState
other terminator --
NOTE 1 -- The procedure `ScanInt' corresponds to the start state of a
finite state machine to scan for a character sequence that forms a
signed whole number. Like `ScanCard' and the corresponding procedures
in the other low-level string conversion modules, it may be used to
control the actions of a finite state interpreter. As long as the
value of `chClass' is other than `terminator' or `invalid', the
interpreter should call the procedure whose value is assigned to
`nextState' by the previous call, supplying the next character from
the sequence to be scanned. It may be appropriate for the interpreter
to ignore characters classified as `invalid', and proceed with the
scan. This would be the case, for example, with interactive input, if
only valid characters are being echoed in order to give interactive
users an immediate indication of badly-formed data.
If the character sequence end before one is classified as a
terminator, the string-terminator character should be supplied as
input to the finite state scanner. If the preceeding character
sequence formed a complete number, the string-terminator will be
classified as `terminator', otherwise it will be classified as
`invalid'.
For examples of how ScanInt is used, refer to the FormatInt and
ValueInt procedures below.
*)
BEGIN
IF Char.IsWhiteSpace(inputCh) THEN chClass:=Conv.padding; nextState:=SI
ELSIF (inputCh="+") OR (inputCh="-") THEN chClass:=Conv.valid; nextState:=S
ELSIF Char.IsNumeric(inputCh) THEN chClass:=Conv.valid; nextState:=W
ELSE chClass:=Conv.invalid; nextState:=SI
END
END ScanInt;
PROCEDURE FormatInt*(str: ARRAY OF CHAR): ConvResults;
(* Returns the format of the string value for conversion to LONGINT. *)
VAR
ch: CHAR;
int: LONGINT;
len, index, digit: INTEGER;
state: Conv.ScanState;
positive: BOOLEAN;
prev, class: Conv.ScanClass;
BEGIN
len:=Str.Length(str); index:=0;
class:=Conv.padding; prev:=class;
state:=SI; int:=0; positive:=TRUE;
LOOP
IF index=len THEN EXIT END;
ch:=str[index];
state.p(ch, class, state);
CASE class OF
| Conv.padding: (* nothing to do *)
| Conv.valid:
IF ch="-" THEN positive:=FALSE
ELSIF ch="+" THEN positive:=TRUE
ELSE (* must be a digit *)
digit:=ORD(ch)-ORD("0");
IF positive THEN
IF int>(MAX(LONGINT)-digit) DIV 10 THEN RETURN strOutOfRange END;
int:=int*10+digit
ELSE
IF int<(MIN(LONGINT)+digit) DIV 10 THEN RETURN strOutOfRange END;
int:=int*10-digit
END
END
| Conv.invalid, Conv.terminator: EXIT
END;
prev:=class; INC(index)
END;
IF class IN {Conv.invalid, Conv.terminator} THEN RETURN strWrongFormat
ELSIF prev=Conv.padding THEN RETURN strEmpty
ELSE RETURN strAllRight
END
END FormatInt;
PROCEDURE ValueInt*(str: ARRAY OF CHAR): LONGINT;
(*
Returns the value corresponding to the signed whole number string value
str if str is well-formed; otherwise raises the WholeConv exception.
*)
VAR
ch: CHAR;
len, index, digit: INTEGER;
int: LONGINT;
state: Conv.ScanState;
positive: BOOLEAN;
class: Conv.ScanClass;
BEGIN
IF FormatInt(str)=strAllRight THEN
len:=Str.Length(str); index:=0;
state:=SI; int:=0; positive:=TRUE;
FOR index:=0 TO len-1 DO
ch:=str[index];
state.p(ch, class, state);
IF class=Conv.valid THEN
IF ch="-" THEN positive:=FALSE
ELSIF ch="+" THEN positive:=TRUE
ELSE (* must be a digit *)
digit:=ORD(ch)-ORD("0");
IF positive THEN int:=int*10+digit
ELSE int:=int*10-digit
END
END
END
END;
RETURN int
ELSE RETURN 0 (* raise exception here *)
END
END ValueInt;
PROCEDURE LengthInt*(int: LONGINT): INTEGER;
(*
Returns the number of characters in the string representation of int.
This value corresponds to the capacity of an array `str' which is
of the minimum capacity needed to avoid truncation of the result in
the call IntStr.IntToStr(int,str).
*)
VAR
cnt: INTEGER;
BEGIN
IF int=MIN(LONGINT) THEN int:=-(int+1); cnt:=1 (* argh!! *)
ELSIF int<=0 THEN int:=-int; cnt:=1
ELSE cnt:=0
END;
WHILE int>0 DO INC(cnt); int:=int DIV 10 END;
RETURN cnt
END LengthInt;
PROCEDURE IsIntConvException*(): BOOLEAN;
(* Returns TRUE if the current coroutine is in the exceptional execution
state because of the raising of the IntConv exception; otherwise
returns FALSE.
*)
BEGIN
RETURN FALSE
END IsIntConvException;
BEGIN
(* kludge necessary because of recursive procedure declaration *)
NEW(S); NEW(W); NEW(SI);
S.p:=SState; W.p:=WState; SI.p:=ScanInt
END IntConv.
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