1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ U N S --
10 -- Copyright (C) 1992-1997 Free Software Foundation, Inc. --
12 -- GNAT is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNAT; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
21 -- MA 02111-1307, USA. --
23 -- As a special exception, if other files instantiate generics from this --
24 -- unit, or you link this unit with other files to produce an executable, --
25 -- this unit does not by itself cause the resulting executable to be --
26 -- covered by the GNU General Public License. This exception does not --
27 -- however invalidate any other reasons why the executable file might be --
28 -- covered by the GNU Public License. --
30 -- GNAT was originally developed by the GNAT team at New York University. --
31 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
33 ------------------------------------------------------------------------------
35 with System.Unsigned_Types; use System.Unsigned_Types;
36 with System.Val_Util; use System.Val_Util;
38 package body System.Val_Uns is
44 function Scan_Unsigned
51 -- Local copy of the pointer
54 -- Accumulated unsigned integer result
59 Minus : Boolean := False;
60 -- Set to True if minus sign is present, otherwise to False. Note that
61 -- a minus sign is permissible for the singular case of -0, and in any
62 -- case the pointer is left pointing past a negative integer literal.
64 Overflow : Boolean := False;
65 -- Set True if overflow is detected at any point
68 -- Save location of first non-blank character
70 Base_Char : Character;
71 -- Base character (# or :) in based case
73 Base : Unsigned := 10;
74 -- Base value (reset in based case)
80 Scan_Sign (Str, Ptr, Max, Minus, Start);
82 if Str (Ptr.all) not in '0' .. '9' then
84 raise Constraint_Error;
88 Uval := Character'Pos (Str (P)) - Character'Pos ('0');
91 -- Scan out digits of what is either the number or the base.
92 -- In either case, we are definitely scanning out in base 10.
95 Umax : constant := (Unsigned'Last - 9) / 10;
96 -- Max value which cannot overflow on accumulating next digit
98 Umax10 : constant := Unsigned'Last / 10;
99 -- Numbers bigger than Umax10 overflow if multiplied by 10
102 -- Loop through decimal digits
106 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
108 -- Non-digit encountered
111 if Str (P) = '_' then
112 Scan_Underscore (Str, P, Ptr, Max, False);
117 -- Accumulate result, checking for overflow
121 Uval := 10 * Uval + Digit;
123 elsif Uval > Umax10 then
127 Uval := 10 * Uval + Digit;
129 if Uval < Umax10 then
141 -- Deal with based case
143 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
144 Base_Char := Str (P);
149 -- Check base value. Overflow is set True if we find a bad base, or
150 -- a digit that is out of range of the base. That way, we scan out
151 -- the numeral that is still syntactically correct, though illegal.
152 -- We use a safe base of 16 for this scan, to avoid zero divide.
154 if Base not in 2 .. 16 then
159 -- Scan out based integer
162 Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base;
163 -- Max value which cannot overflow on accumulating next digit
165 UmaxB : constant Unsigned := Unsigned'Last / Base;
166 -- Numbers bigger than UmaxB overflow if multiplied by base
169 -- Loop to scan out based integer value
172 -- We require a digit at this stage
174 if Str (P) in '0' .. '9' then
175 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
177 elsif Str (P) in 'A' .. 'F' then
179 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
181 elsif Str (P) in 'a' .. 'f' then
183 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
185 -- If we don't have a digit, then this is not a based number
186 -- after all, so we use the value we scanned out as the base
187 -- (now in Base), and the pointer to the base character was
188 -- already stored in Ptr.all.
195 -- If digit is too large, just signal overflow and continue.
196 -- The idea here is to keep scanning as long as the input is
197 -- syntactically valid, even if we have detected overflow
199 if Digit >= Base then
202 -- Here we accumulate the value, checking overflow
204 elsif Uval <= Umax then
205 Uval := Base * Uval + Digit;
207 elsif Uval > UmaxB then
211 Uval := Base * Uval + Digit;
218 -- If at end of string with no base char, not a based number
219 -- but we signal Constraint_Error and set the pointer past
220 -- the end of the field, since this is what the ACVC tests
221 -- seem to require, see CE3704N, line 204.
227 raise Constraint_Error;
230 -- If terminating base character, we are done with loop
232 if Str (P) = Base_Char then
236 -- Deal with underscore
238 elsif Str (P) = '_' then
239 Scan_Underscore (Str, P, Ptr, Max, True);
246 -- Come here with scanned unsigned value in Uval. The only remaining
247 -- required step is to deal with exponent if one is present.
249 Expon := Scan_Exponent (Str, Ptr, Max);
251 if Expon /= 0 and then Uval /= 0 then
253 -- For non-zero value, scale by exponent value. No need to do this
254 -- efficiently, since use of exponent in integer literals is rare,
255 -- and in any case the exponent cannot be very large.
258 UmaxB : constant Unsigned := Unsigned'Last / Base;
259 -- Numbers bigger than UmaxB overflow if multiplied by base
262 for J in 1 .. Expon loop
273 -- Return result, dealing with sign and overflow
275 if Overflow or else (Minus and then Uval /= 0) then
276 raise Constraint_Error;
286 function Value_Unsigned (Str : String) return Unsigned is
288 P : aliased Integer := Str'First;
291 V := Scan_Unsigned (Str, P'Access, Str'Last);
292 Scan_Trailing_Blanks (Str, P);