File : s-strhas.ads


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--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
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--                    S Y S T E M . S T R I N G _ H A S H                   --
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--  This package provides a generic hashing function over strings, suitable for
--  use with a string keyed hash table. In particular, it is the basis for the
--  string hash functions in Ada.Containers.
--
--  The algorithm used here is not appropriate for applications that require
--  cryptographically strong hashes, or for application which wish to use very
--  wide hash values as pseudo unique identifiers. In such cases please refer
--  to GNAT.SHA1 and GNAT.MD5.

package System.String_Hash is
   pragma Pure;

   generic
      type Char_Type is (<>);
      --  The character type composing the key string type

      type Key_Type is array (Positive range <>) of Char_Type;
      --  The string type to use as a hash key

      type Hash_Type is mod <>;
      --  The type to be returned as a hash value. This must be a 32-bit
      --  unsigned type with full range 0 .. 2**32-1, no other type is allowed
      --  for this instantiation (checked in the body by Compile_Time_Error).

   function Hash (Key : Key_Type) return Hash_Type;
   pragma Inline (Hash);
   --  Compute a hash value for a key

end System.String_Hash;