------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                         G N A T . R E G I S T R Y                        --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--          Copyright (C) 2001-2021, Free Software Foundation, Inc.         --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
--                                                                          --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception,   --
-- version 3.1, as published by the Free Software Foundation.               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

--  The registry is a Windows database to store key/value pair. It is used
--  to keep Windows operation system and applications configuration options.
--  The database is a hierarchal set of key and for each key a value can
--  be associated. This package provides high level routines to deal with
--  the Windows registry. For full registry API, but at a lower level of
--  abstraction, refer to the Win32.Winreg package provided with the
--  Win32Ada binding. For example this binding handle only key values of
--  type Standard.String.

--  This package is specific to the NT version of GNAT, and is not available
--  on any other platforms.

package GNAT.Registry is

   type HKEY is private;
   --  HKEY is a handle to a registry key, including standard registry keys:
   --  HKEY_CLASSES_ROOT, HKEY_CURRENT_CONFIG, HKEY_CURRENT_USER,
   --  HKEY_LOCAL_MACHINE, HKEY_USERS, HKEY_PERFORMANCE_DATA.

   HKEY_CLASSES_ROOT     : constant HKEY;
   HKEY_CURRENT_USER     : constant HKEY;
   HKEY_CURRENT_CONFIG   : constant HKEY;
   HKEY_LOCAL_MACHINE    : constant HKEY;
   HKEY_USERS            : constant HKEY;
   HKEY_PERFORMANCE_DATA : constant HKEY;

   type Key_Mode is
      (Read_Only, Read_Write,        -- operates on 32bit view of the registry
       Read_Only_64, Read_Write_64); -- operates on 64bit view of the registry
   --  Access mode for the registry key. The *_64 are only meaningful on
   --  Windows 64bit and ignored on Windows 32bit where _64 are equivalent to
   --  the non 64bit versions.

   Registry_Error : exception;
   --  Registry_Error is raises by all routines below if a problem occurs
   --  (key cannot be opened, key cannot be found etc).

   function Create_Key
     (From_Key : HKEY;
      Sub_Key  : String;
      Mode     : Key_Mode := Read_Write) return HKEY;
   --  Open or create a key (named Sub_Key) in the Windows registry database.
   --  The key will be created under key From_Key. It returns the key handle.
   --  From_Key must be a valid handle to an already opened key or one of
   --  the standard keys identified by HKEY declarations above.

   function Open_Key
     (From_Key : HKEY;
      Sub_Key  : String;
      Mode     : Key_Mode := Read_Only) return HKEY;
   --  Return a registry key handle for key named Sub_Key opened under key
   --  From_Key. It is possible to open a key at any level in the registry
   --  tree in a single call to Open_Key.

   procedure Close_Key (Key : HKEY);
   --  Close registry key handle. All resources used by Key are released

   function Key_Exists (From_Key : HKEY; Sub_Key : String) return Boolean;
   --  Returns True if Sub_Key is defined under From_Key in the registry

   function Query_Value
     (From_Key : HKEY;
      Sub_Key  : String;
      Expand   : Boolean := False) return String;
   --  Returns the registry key's value associated with Sub_Key in From_Key
   --  registry key. If Expand is set to True and the Sub_Key is a
   --  REG_EXPAND_SZ the returned value will have the %name% variables
   --  replaced by the corresponding environment variable value.

   procedure Set_Value
      (From_Key : HKEY;
       Sub_Key  : String;
       Value    : String;
       Expand   : Boolean := False);
   --  Add the pair (Sub_Key, Value) into From_Key registry key.
   --  By default the value created is of type REG_SZ, unless
   --  Expand is True in which case it is of type REG_EXPAND_SZ

   procedure Delete_Key (From_Key : HKEY; Sub_Key : String);
   --  Remove Sub_Key from the registry key From_Key

   procedure Delete_Value (From_Key : HKEY; Sub_Key : String);
   --  Remove the named value Sub_Key from the registry key From_Key

   generic
      with procedure Action
        (Index    : Positive;
         Key      : HKEY;
         Key_Name : String;
         Quit     : in out Boolean);
   procedure For_Every_Key (From_Key : HKEY; Recursive : Boolean := False);
   --  Iterates over all the keys registered under From_Key, recursively if
   --  Recursive is set to True. Index will be set to 1 for the first key and
   --  will be incremented by one in each iteration. The current key of an
   --  iteration is set in Key, and its name - in Key_Name. Quit can be set
   --  to True to stop iteration; its initial value is False.

   generic
      with procedure Action
        (Index   : Positive;
         Sub_Key : String;
         Value   : String;
         Quit    : in out Boolean);
   procedure For_Every_Key_Value (From_Key : HKEY; Expand : Boolean := False);
   --  Iterates over all the pairs (Sub_Key, Value) registered under
   --  From_Key. Index will be set to 1 for the first key and will be
   --  incremented by one in each iteration. Quit can be set to True to
   --  stop iteration; its initial value is False.
   --
   --  Key value that are not of type string (i.e. not REG_SZ / REG_EXPAND_SZ)
   --  are skipped. In this case, the iterator behaves exactly as if the key
   --  were not present. Note that you must use the Win32.Winreg API to deal
   --  with this case. Furthermore, if Expand is set to True and the Sub_Key
   --  is a REG_EXPAND_SZ the returned value will have the %name% variables
   --  replaced by the corresponding environment variable value.
   --
   --  This iterator can be used in conjunction with For_Every_Key in
   --  order to analyze all subkeys and values of a given registry key.

private

   type HKEY is mod 2 ** Standard'Address_Size;

   HKEY_CLASSES_ROOT     : constant HKEY := 16#80000000#;
   HKEY_CURRENT_USER     : constant HKEY := 16#80000001#;
   HKEY_LOCAL_MACHINE    : constant HKEY := 16#80000002#;
   HKEY_USERS            : constant HKEY := 16#80000003#;
   HKEY_PERFORMANCE_DATA : constant HKEY := 16#80000004#;
   HKEY_CURRENT_CONFIG   : constant HKEY := 16#80000005#;

end GNAT.Registry;