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Wrap

Text File | 2000-07-19 | 10KB | 299 lines

------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S Y S T E M . V A L _ U N S -- -- -- -- B o d y -- -- -- -- $Revision: 1.13 $ -- -- -- -- Copyright (C) 1992-1997 Free Software Foundation, Inc. -- -- -- -- GNAT is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 2, or (at your option) any later ver- -- -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- -- for more details. You should have received a copy of the GNU General -- -- Public License distributed with GNAT; see file COPYING. If not, write -- -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, USA. -- -- -- -- As a special exception, if other files instantiate generics from this -- -- unit, or you link this unit with other files to produce an executable, -- -- this unit does not by itself cause the resulting executable to be -- -- covered by the GNU General Public License. This exception does not -- -- however invalidate any other reasons why the executable file might be -- -- covered by the GNU Public License. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- -- -- ------------------------------------------------------------------------------ with System.Unsigned_Types; use System.Unsigned_Types; with System.Val_Util; use System.Val_Util; package body System.Val_Uns is ------------------- -- Scan_Unsigned -- ------------------- function Scan_Unsigned (Str : String; Ptr : access Integer; Max : Integer) return Unsigned is P : Integer; -- Local copy of the pointer Uval : Unsigned; -- Accumulated unsigned integer result Expon : Integer; -- Exponent value Minus : Boolean := False; -- Set to True if minus sign is present, otherwise to False. Note that -- a minus sign is permissible for the singular case of -0, and in any -- case the pointer is left pointing past a negative integer literal. Overflow : Boolean := False; -- Set True if overflow is detected at any point Start : Positive; -- Save location of first non-blank character Base_Char : Character; -- Base character (# or :) in based case Base : Unsigned := 10; -- Base value (reset in based case) Digit : Unsigned; -- Digit value begin Scan_Sign (Str, Ptr, Max, Minus, Start); if Str (Ptr.all) not in '0' .. '9' then Ptr.all := Start; raise Constraint_Error; end if; P := Ptr.all; Uval := Character'Pos (Str (P)) - Character'Pos ('0'); P := P + 1; -- Scan out digits of what is either the number or the base. -- In either case, we are definitely scanning out in base 10. declare Umax : constant := (Unsigned'Last - 9) / 10; -- Max value which cannot overflow on accumulating next digit Umax10 : constant := Unsigned'Last / 10; -- Numbers bigger than Umax10 overflow if multiplied by 10 begin -- Loop through decimal digits loop exit when P > Max; Digit := Character'Pos (Str (P)) - Character'Pos ('0'); -- Non-digit encountered if Digit > 9 then if Str (P) = '_' then Scan_Underscore (Str, P, Ptr, Max, False); else exit; end if; -- Accumulate result, checking for overflow else if Uval <= Umax then Uval := 10 * Uval + Digit; elsif Uval > Umax10 then Overflow := True; else Uval := 10 * Uval + Digit; if Uval < Umax10 then Overflow := True; end if; end if; P := P + 1; end if; end loop; end; Ptr.all := P; -- Deal with based case if P < Max and then (Str (P) = ':' or else Str (P) = '#') then Base_Char := Str (P); P := P + 1; Base := Uval; Uval := 0; -- Check base value. Overflow is set True if we find a bad base, or -- a digit that is out of range of the base. That way, we scan out -- the numeral that is still syntactically correct, though illegal. -- We use a safe base of 16 for this scan, to avoid zero divide. if Base not in 2 .. 16 then Overflow := True; Base := 16; end if; -- Scan out based integer declare Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base; -- Max value which cannot overflow on accumulating next digit UmaxB : constant Unsigned := Unsigned'Last / Base; -- Numbers bigger than UmaxB overflow if multiplied by base begin -- Loop to scan out based integer value loop -- We require a digit at this stage if Str (P) in '0' .. '9' then Digit := Character'Pos (Str (P)) - Character'Pos ('0'); elsif Str (P) in 'A' .. 'F' then Digit := Character'Pos (Str (P)) - (Character'Pos ('A') - 10); elsif Str (P) in 'a' .. 'f' then Digit := Character'Pos (Str (P)) - (Character'Pos ('a') - 10); -- If we don't have a digit, then this is not a based number -- after all, so we use the value we scanned out as the base -- (now in Base), and the pointer to the base character was -- already stored in Ptr.all. else Uval := Base; exit; end if; -- If digit is too large, just signal overflow and continue. -- The idea here is to keep scanning as long as the input is -- syntactically valid, even if we have detected overflow if Digit >= Base then Overflow := True; -- Here we accumulate the value, checking overflow elsif Uval <= Umax then Uval := Base * Uval + Digit; elsif Uval > UmaxB then Overflow := True; else Uval := Base * Uval + Digit; if Uval < UmaxB then Overflow := True; end if; end if; -- If at end of string with no base char, not a based number -- but we signal Constraint_Error and set the pointer past -- the end of the field, since this is what the ACVC tests -- seem to require, see CE3704N, line 204. P := P + 1; if P > Max then Ptr.all := P; raise Constraint_Error; end if; -- If terminating base character, we are done with loop if Str (P) = Base_Char then Ptr.all := P + 1; exit; -- Deal with underscore elsif Str (P) = '_' then Scan_Underscore (Str, P, Ptr, Max, True); end if; end loop; end; end if; -- Come here with scanned unsigned value in Uval. The only remaining -- required step is to deal with exponent if one is present. Expon := Scan_Exponent (Str, Ptr, Max); if Expon /= 0 and then Uval /= 0 then -- For non-zero value, scale by exponent value. No need to do this -- efficiently, since use of exponent in integer literals is rare, -- and in any case the exponent cannot be very large. declare UmaxB : constant Unsigned := Unsigned'Last / Base; -- Numbers bigger than UmaxB overflow if multiplied by base begin for J in 1 .. Expon loop if Uval > UmaxB then Overflow := True; exit; end if; Uval := Uval * Base; end loop; end; end if; -- Return result, dealing with sign and overflow if Overflow or else (Minus and then Uval /= 0) then raise Constraint_Error; else return Uval; end if; end Scan_Unsigned; -------------------- -- Value_Unsigned -- -------------------- function Value_Unsigned (Str : String) return Unsigned is V : Unsigned; P : aliased Integer := Str'First; begin V := Scan_Unsigned (Str, P'Access, Str'Last); Scan_Trailing_Blanks (Str, P); return V; end Value_Unsigned; end System.Val_Uns;