File : s-strhas.ads
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) 2009-2015, 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 -- --
19 -- --
20 -- --
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 --
41 -- Note: this package is in the System hierarchy so that it can be directly
42 -- be used by other predefined packages. User access to this package is via
43 -- a renaming of this package in GNAT.String_Hash (file g-strhas.ads).
44
45 package System.String_Hash is
46 pragma Pure;
47
48 generic
49 type Char_Type is (<>);
50 -- The character type composing the key string type
51
52 type Key_Type is array (Positive range <>) of Char_Type;
53 -- The string type to use as a hash key
54
55 type Hash_Type is mod <>;
56 -- The type to be returned as a hash value. This must be a 32-bit
57 -- unsigned type with full range 0 .. 2**32-1, no other type is allowed
58 -- for this instantiation (checked in the body by Compile_Time_Error).
59
60 function Hash (Key : Key_Type) return Hash_Type;
61 pragma Inline (Hash);
62 -- Compute a hash value for a key
63
64 end System.String_Hash;