1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L _ U N S --
9 -- Copyright (C) 1992-2005, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with System.Unsigned_Types; use System.Unsigned_Types;
35 with System.Val_Util; use System.Val_Util;
37 package body System.Val_Uns is
43 function Scan_Unsigned
46 Max : Integer) return Unsigned
49 -- Local copy of the pointer
52 -- Accumulated unsigned integer result
57 Minus : Boolean := False;
58 -- Set to True if minus sign is present, otherwise to False. Note that
59 -- a minus sign is permissible for the singular case of -0, and in any
60 -- case the pointer is left pointing past a negative integer literal.
62 Overflow : Boolean := False;
63 -- Set True if overflow is detected at any point
66 -- Save location of first non-blank character
68 Base_Char : Character;
69 -- Base character (# or :) in based case
71 Base : Unsigned := 10;
72 -- Base value (reset in based case)
78 Scan_Sign (Str, Ptr, Max, Minus, Start);
80 if Str (Ptr.all) not in '0' .. '9' then
82 raise Constraint_Error;
86 Uval := Character'Pos (Str (P)) - Character'Pos ('0');
89 -- Scan out digits of what is either the number or the base.
90 -- In either case, we are definitely scanning out in base 10.
93 Umax : constant := (Unsigned'Last - 9) / 10;
94 -- Max value which cannot overflow on accumulating next digit
96 Umax10 : constant := Unsigned'Last / 10;
97 -- Numbers bigger than Umax10 overflow if multiplied by 10
100 -- Loop through decimal digits
104 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
106 -- Non-digit encountered
109 if Str (P) = '_' then
110 Scan_Underscore (Str, P, Ptr, Max, False);
115 -- Accumulate result, checking for overflow
119 Uval := 10 * Uval + Digit;
121 elsif Uval > Umax10 then
125 Uval := 10 * Uval + Digit;
127 if Uval < Umax10 then
139 -- Deal with based case
141 if P < Max and then (Str (P) = ':' or else Str (P) = '#') then
142 Base_Char := Str (P);
147 -- Check base value. Overflow is set True if we find a bad base, or
148 -- a digit that is out of range of the base. That way, we scan out
149 -- the numeral that is still syntactically correct, though illegal.
150 -- We use a safe base of 16 for this scan, to avoid zero divide.
152 if Base not in 2 .. 16 then
157 -- Scan out based integer
160 Umax : constant Unsigned := (Unsigned'Last - Base + 1) / Base;
161 -- Max value which cannot overflow on accumulating next digit
163 UmaxB : constant Unsigned := Unsigned'Last / Base;
164 -- Numbers bigger than UmaxB overflow if multiplied by base
167 -- Loop to scan out based integer value
170 -- We require a digit at this stage
172 if Str (P) in '0' .. '9' then
173 Digit := Character'Pos (Str (P)) - Character'Pos ('0');
175 elsif Str (P) in 'A' .. 'F' then
177 Character'Pos (Str (P)) - (Character'Pos ('A') - 10);
179 elsif Str (P) in 'a' .. 'f' then
181 Character'Pos (Str (P)) - (Character'Pos ('a') - 10);
183 -- If we don't have a digit, then this is not a based number
184 -- after all, so we use the value we scanned out as the base
185 -- (now in Base), and the pointer to the base character was
186 -- already stored in Ptr.all.
193 -- If digit is too large, just signal overflow and continue.
194 -- The idea here is to keep scanning as long as the input is
195 -- syntactically valid, even if we have detected overflow
197 if Digit >= Base then
200 -- Here we accumulate the value, checking overflow
202 elsif Uval <= Umax then
203 Uval := Base * Uval + Digit;
205 elsif Uval > UmaxB then
209 Uval := Base * Uval + Digit;
216 -- If at end of string with no base char, not a based number
217 -- but we signal Constraint_Error and set the pointer past
218 -- the end of the field, since this is what the ACVC tests
219 -- seem to require, see CE3704N, line 204.
225 raise Constraint_Error;
228 -- If terminating base character, we are done with loop
230 if Str (P) = Base_Char then
234 -- Deal with underscore
236 elsif Str (P) = '_' then
237 Scan_Underscore (Str, P, Ptr, Max, True);
244 -- Come here with scanned unsigned value in Uval. The only remaining
245 -- required step is to deal with exponent if one is present.
247 Expon := Scan_Exponent (Str, Ptr, Max);
249 if Expon /= 0 and then Uval /= 0 then
251 -- For non-zero value, scale by exponent value. No need to do this
252 -- efficiently, since use of exponent in integer literals is rare,
253 -- and in any case the exponent cannot be very large.
256 UmaxB : constant Unsigned := Unsigned'Last / Base;
257 -- Numbers bigger than UmaxB overflow if multiplied by base
260 for J in 1 .. Expon loop
271 -- Return result, dealing with sign and overflow
273 if Overflow or else (Minus and then Uval /= 0) then
274 raise Constraint_Error;
284 function Value_Unsigned (Str : String) return Unsigned is
286 P : aliased Integer := Str'First;
288 V := Scan_Unsigned (Str, P'Access, Str'Last);
289 Scan_Trailing_Blanks (Str, P);