gcc/ada/libgnat/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) 2009-2017, 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 --
  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;