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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S E M _ M A P S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1996-2005, 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 2, 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains the operations on the renaming maps used for
-- generic analysis and instantiation. Renaming maps are created when
-- a generic unit is analyzed, in order to capture all references to
-- global variables within the unit. The renaming map of a generic unit
-- copied prior to each instantiation, and then updated by mapping the
-- formals into the actuals and the local entities into entities local to
-- the instance. When the generic tree is copied to produce the instance,
-- all references are updated by means of the renaming map.
-- Map composition of renaming maps takes place for nested instantiations,
-- for generic child units, and for formal packages.
-- For additional details, see the documentation in sem_ch12
with Table;
with Types; use Types;
package Sem_Maps is
type Map is new Int;
type Assoc is private;
type Scope_Kind is (S_Global, S_Formal, S_Local);
function New_Map (Num_Assoc : Int) return Map;
-- Build empty map with the given number of associations, and a
-- headers table of the appropriate size.
function Compose (Orig_Map : Map; New_Map : Map) return Map;
-- Update the associations in Orig_Map, so that if Orig_Map (e1) = e2
-- and New_Map (e2) = e3, then the image of e1 under the result is e3.
function Copy (M : Map) return Map;
-- Full copy of contents and headers
function Lookup (M : Map; E : Entity_Id) return Entity_Id;
-- Retrieve image of E under M, Empty if undefined
procedure Add_Association
(M : in out Map;
O_Id : Entity_Id;
N_Id : Entity_Id;
Kind : Scope_Kind := S_Local);
-- Update M in place. On entry M (O_Id) must not be defined
procedure Update_Association
(M : in out Map;
O_Id : Entity_Id;
N_Id : Entity_Id;
Kind : Scope_Kind := S_Local);
-- Update the entry in M for O_Id
function Build_Instance_Map (M : Map) return Map;
-- Copy renaming map of generic, and create new entities for all the
-- local entities within.
private
-- New maps are created when a generic is analyzed, and for each of
-- its instantiations. Maps are also updated for nested generics, for
-- child units, and for formal packages. As a result we need to allocate
-- maps dynamically.
-- When analyzing a generic, we do not know how many references are
-- in it. We build an initial map after generic analysis, using a static
-- structure that relies on the compiler's extensible table mechanism.
-- After constructing this initial map, all subsequent uses and updates
-- of this map do not modify its domain, so that dynamically allocated
-- maps have a fixed size and never need to be reallocated. Furthermore,
-- the headers of the hash table of a dynamically allocated map can be
-- chosen according to the total number of entries in the map, to
-- accommodate efficiently generic units of different sizes (Unchecked_
-- Conversion vs. Generic_Elementary_Functions, for example). So in
-- fact both components of a map have fixed size, and can be allocated
-- using the standard table mechanism. A Maps_Table holds records that
-- contain indices into the global Headers table and the Associations
-- table, and a Map is an index into the Maps_Table.
--
-- Maps_Table Headers_Table Associations_Table
--
-- |_____| |___________ |
-- |_____| | | | |
-- ------>|Map |------------------------------>|Associations|
-- |Info |------------->| |=========>| for one |
-- |_____| | |====| | unit |
-- | | | | |====>| |
-- |_____| |____________|
-- | | | |
type Header_Index is new Int;
type Assoc_Index is new Int;
No_Assoc : constant Assoc_Index := -1;
type Map_Info is record
Header_Offset : Header_Index;
Header_Num : Header_Index;
Assoc_Offset : Assoc_Index;
Assoc_Num : Assoc_Index;
Assoc_Next : Assoc_Index;
end record;
type Assoc is record
Old_Id : Entity_Id := Empty;
New_Id : Entity_Id := Empty;
Kind : Scope_Kind := S_Local;
Next : Assoc_Index := No_Assoc;
end record;
-- All maps are accessed through the following table. The map attribute
-- of a generic unit or an instance is an index into this table.
package Maps_Table is new Table.Table (
Table_Component_Type => Map_Info,
Table_Index_Type => Map,
Table_Low_Bound => 0,
Table_Initial => 100,
Table_Increment => 10,
Table_Name => "Maps_Table");
-- All headers for hash tables are allocated in one global table. Each
-- map stores the offset into this table at which its own headers start.
package Headers_Table is new Table.Table (
Table_Component_Type => Assoc_Index,
Table_Index_Type => Header_Index,
Table_Low_Bound => 0,
Table_Initial => 1000,
Table_Increment => 10,
Table_Name => "Headers_Table");
-- All associations are allocated in one global table. Each map stores
-- the offset into this table at which its own associations start.
package Associations_Table is new Table.Table (
Table_Component_Type => Assoc,
Table_Index_Type => Assoc_Index,
Table_Low_Bound => 1,
Table_Initial => 1000,
Table_Increment => 10,
Table_Name => "Associations_Table");
end Sem_Maps;
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