1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                    S Y S T E M . S T R I N G _ H A S H                   --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--             Copyright (C) 2009, Free Software Foundation, Inc.           --
10--                                                                          --
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.                                     --
17--                                                                          --
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.               --
21--                                                                          --
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/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This package provides a generic hashing function over strings, suitable for
33--  use with a string keyed hash table. In particular, it is the basis for the
34--  string hash functions in Ada.Containers.
35--
36--  The algorithm used here is not appropriate for applications that require
37--  cryptographically strong hashes, or for application which wish to use very
38--  wide hash values as pseudo unique identifiers. In such cases please refer
39--  to GNAT.SHA1 and GNAT.MD5.
40
41package System.String_Hash is
42   pragma Pure;
43
44   generic
45      type Char_Type is (<>);
46      --  The character type composing the key string type
47
48      type Key_Type is array (Positive range <>) of Char_Type;
49      --  The string type to use as a hash key
50
51      type Hash_Type is mod <>;
52      --  The type to be returned as a hash value. This must be a 32-bit
53      --  unsigned type with full range 0 .. 2**32-1, no other type is allowed
54      --  for this instantiation (checked in the body by Compile_Time_Error).
55
56   function Hash (Key : Key_Type) return Hash_Type;
57   pragma Inline (Hash);
58   --  Compute a hash value for a key
59
60end System.String_Hash;
61