1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . V A L U E _ N --
9 -- Copyright (C) 2021-2023, 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 3, 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
32 -- This package is used to compute the Value attribute for enumeration types
33 -- other than those in packages Standard and System. See unit Exp_Imgv for
34 -- details of the format of constructed image tables.
38 type Index_Type
is range <>;
40 package System
.Value_N
is
43 type Hash_Function_Ptr
is access function (S
: String) return Natural;
45 function Value_Enumeration
47 Indexes
: System
.Address
;
48 Hash
: Hash_Function_Ptr
;
51 return Natural with Inline
;
52 -- Used to compute Enum'Value (Str) where Enum is some enumeration type
53 -- other than those defined in package Standard. Names is a string with
54 -- a lower bound of 1 containing the characters of all the enumeration
55 -- literals concatenated together in sequence. Indexes is the address
56 -- of an array of type array (0 .. N) of Index_Type, where N is the
57 -- number of enumeration literals in the type. The Indexes values are
58 -- the starting subscript of each enumeration literal, indexed by Pos
59 -- values, with an extra entry at the end containing Names'Length + 1.
60 -- The parameter Hash is a (perfect) hash function for Names and Indexes.
61 -- The parameter Num is the value N - 1 (i.e. Enum'Pos (Enum'Last)).
62 -- The reason that Indexes is passed by address is that the actual type
63 -- is created on the fly by the expander.
65 -- Str is the argument of the attribute function, and may have leading
66 -- and trailing spaces, and letters can be upper or lower case or mixed.
67 -- If the image is found in Names, then the corresponding Pos value is
68 -- returned. If not, Constraint_Error is raised.
70 function Valid_Value_Enumeration
72 Indexes
: System
.Address
;
73 Hash
: Hash_Function_Ptr
;
76 return Boolean with Inline
;
77 -- Returns True if Str is a valid Image of some enumeration literal, False
78 -- otherwise. That is, returns False if and only if Value_Enumeration would
79 -- raise Constraint_Error. The parameters have the same meaning as for