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|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . V A L _ U N S --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2006, 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, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, 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. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with System.Unsigned_Types; use System.Unsigned_Types;
with System.Val_Util; use System.Val_Util;
package body System.Val_Uns is
-----------------------
-- Scan_Raw_Unsigned --
-----------------------
function Scan_Raw_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
Overflow : Boolean := False;
-- Set True if overflow is detected at any point
Base_Char : Character;
-- Base character (# or :) in based case
Base : Unsigned := 10;
-- Base value (reset in based case)
Digit : Unsigned;
-- Digit value
begin
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 then
raise Constraint_Error;
else
return Uval;
end if;
end Scan_Raw_Unsigned;
-------------------
-- Scan_Unsigned --
-------------------
function Scan_Unsigned
(Str : String;
Ptr : access Integer;
Max : Integer) return Unsigned
is
Start : Positive;
-- Save location of first non-blank character
begin
Scan_Plus_Sign (Str, Ptr, Max, Start);
if Str (Ptr.all) not in '0' .. '9' then
Ptr.all := Start;
raise Constraint_Error;
end if;
return Scan_Raw_Unsigned (Str, Ptr, Max);
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;
|
