1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                              P R J . E X T                               --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 2000-2011, 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.  See the GNU General Public License --
17-- for  more details.  You should have  received  a copy of the GNU General --
18-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
19-- http://www.gnu.org/licenses for a complete copy of the license.          --
20--                                                                          --
21-- GNAT was originally developed  by the GNAT team at  New York University. --
22-- Extensive contributions were provided by Ada Core Technologies Inc.      --
23--                                                                          --
24------------------------------------------------------------------------------
25
26--  Subprograms to set, get and cache external references, to be used as
27--  External functions in project files.
28
29with GNAT.Dynamic_HTables;
30
31package Prj.Ext is
32
33   -------------------------
34   -- External References --
35   -------------------------
36
37   --  External references influence the way a project tree is processed (in
38   --  particular they provide the values for the typed string variables that
39   --  are then used in case constructions).
40
41   --  External references are project-tree specific, so that when multiple
42   --  trees are loaded in parallel we can have different scenarios (or even
43   --  load the same tree twice and see different views of it).
44
45   type External_References is private;
46   No_External_Refs : constant External_References;
47
48   procedure Initialize
49     (Self      : out External_References;
50      Copy_From : External_References := No_External_Refs);
51   --  Initialize Self, and copy all values from Copy_From if needed.
52   --  This has no effect if Self was already initialized.
53
54   procedure Free (Self : in out External_References);
55   --  Free memory used by Self
56
57   type External_Source is
58     (From_Command_Line,
59      From_Environment,
60      From_External_Attribute);
61   --  Indicates where was the value of an external reference defined. They are
62   --  prioritized in that order, so that a user can always use the command
63   --  line to override a value coming from his environment, or an environment
64   --  variable to override a value defined in an aggregate project through the
65   --  "for External()..." attribute.
66
67   procedure Add
68     (Self          : External_References;
69      External_Name : String;
70      Value         : String;
71      Source        : External_Source := External_Source'First);
72   --  Add an external reference (or modify an existing one). No overriding is
73   --  done if the Source's priority is less than the one used to previously
74   --  set the value of the variable. The default for Source is such that
75   --  overriding always occurs.
76
77   function Value_Of
78     (Self          : External_References;
79      External_Name : Name_Id;
80      With_Default  : Name_Id := No_Name)
81      return          Name_Id;
82   --  Get the value of an external reference, and cache it for future uses
83
84   function Check
85     (Self        : External_References;
86      Declaration : String) return Boolean;
87   --  Check that an external declaration <external>=<value> is correct.
88   --  If it is correct, the external reference is Added.
89
90   procedure Reset (Self : External_References);
91   --  Clear the internal data structure that stores the external references
92   --  and free any allocated memory.
93
94private
95   --  Use a Static_HTable, rather than a Simple_HTable
96
97   --  The issue is that we need to be able to copy the contents of the table
98   --  (in Initialize), but this isn't doable for Simple_HTable for which
99   --  iterators do not return the key.
100
101   type Name_To_Name;
102   type Name_To_Name_Ptr is access all Name_To_Name;
103   type Name_To_Name is record
104      Key    : Name_Id;
105      Value  : Name_Id;
106      Source : External_Source;
107      Next   : Name_To_Name_Ptr;
108   end record;
109
110   procedure Set_Next (E : Name_To_Name_Ptr; Next : Name_To_Name_Ptr);
111   function  Next     (E : Name_To_Name_Ptr) return Name_To_Name_Ptr;
112   function  Get_Key  (E : Name_To_Name_Ptr) return Name_Id;
113
114   package Name_To_Name_HTable is new GNAT.Dynamic_HTables.Static_HTable
115     (Header_Num => Header_Num,
116      Element    => Name_To_Name,
117      Elmt_Ptr   => Name_To_Name_Ptr,
118      Null_Ptr   => null,
119      Set_Next   => Set_Next,
120      Next       => Next,
121      Key        => Name_Id,
122      Get_Key    => Get_Key,
123      Hash       => Hash,
124      Equal      => "=");
125   --  General type for htables associating name_id to name_id. This is in
126   --  particular used to store the values of external references.
127
128   type Instance_Access is access all Name_To_Name_HTable.Instance;
129
130   type External_References is record
131      Refs : Instance_Access;
132      --  External references are stored in this hash table (and manipulated
133      --  through subprogrames in prj-ext.ads). External references are
134      --  project-tree specific so that one can load the same tree twice but
135      --  have two views of it, for instance.
136   end record;
137
138   No_External_Refs : constant External_References := (Refs => null);
139
140end Prj.Ext;
141