1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                               E L I S T S                                --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2019, 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 facilities for manipulating lists of nodes (see
33--  package Atree for format and implementation of tree nodes). Separate list
34--  elements are allocated to represent elements of these lists, so it is
35--  possible for a given node to be on more than one element list at a time.
36--  See also package Nlists, which provides another form that is threaded
37--  through the nodes themselves (using the Link field), which is more time
38--  and space efficient, but a node can be only one such list.
39
40with Types;  use Types;
41with System;
42
43package Elists is
44
45   --  An element list is represented by a header that is allocated in the
46   --  Elist header table. This header contains pointers to the first and
47   --  last elements in the list, or to No_Elmt if the list is empty.
48
49   --  The elements in the list each contain a pointer to the next element
50   --  and a pointer to the referenced node. Putting a node into an element
51   --  list causes no change at all to the node itself, so a node may be
52   --  included in multiple element lists, and the nodes thus included may
53   --  or may not be elements of node lists (see package Nlists).
54
55   procedure Initialize;
56   --  Initialize allocation of element list tables. Called at the start of
57   --  compiling each new main source file. Note that Initialize must not be
58   --  called if Tree_Read is used.
59
60   procedure Lock;
61   --  Lock tables used for element lists before calling backend
62
63   procedure Unlock;
64   --  Unlock list tables, in cases where the back end needs to modify them
65
66   procedure Tree_Read;
67   --  Initializes internal tables from current tree file using the relevant
68   --  Table.Tree_Read routines. Note that Initialize should not be called if
69   --  Tree_Read is used. Tree_Read includes all necessary initialization.
70
71   procedure Tree_Write;
72   --  Writes out internal tables to current tree file using the relevant
73   --  Table.Tree_Write routines.
74
75   function Last_Elist_Id return Elist_Id;
76   --  Returns Id of last allocated element list header
77
78   function Elists_Address return System.Address;
79   --  Return address of Elists table (used in Back_End for Gigi call)
80
81   function Num_Elists return Nat;
82   --  Number of currently allocated element lists
83
84   function Last_Elmt_Id return Elmt_Id;
85   --  Returns Id of last allocated list element
86
87   function Elmts_Address return System.Address;
88   --  Return address of Elmts table (used in Back_End for Gigi call)
89
90   function Node (Elmt : Elmt_Id) return Node_Or_Entity_Id;
91   pragma Inline (Node);
92   --  Returns the value of a given list element. Returns Empty if Elmt
93   --  is set to No_Elmt.
94
95   function New_Elmt_List return Elist_Id;
96   --  Creates a new empty element list. Typically this is used to initialize
97   --  a field in some other node which points to an element list where the
98   --  list is then subsequently filled in using Append calls.
99
100   function First_Elmt (List : Elist_Id) return Elmt_Id;
101   pragma Inline (First_Elmt);
102   --  Obtains the first element of the given element list or, if the list has
103   --  no items, then No_Elmt is returned.
104
105   function Last_Elmt (List : Elist_Id) return Elmt_Id;
106   pragma Inline (Last_Elmt);
107   --  Obtains the last element of the given element list or, if the list has
108   --  no items, then No_Elmt is returned.
109
110   function List_Length (List : Elist_Id) return Nat;
111   --  Returns number of elements in given List (zero if List = No_Elist)
112
113   function Next_Elmt (Elmt : Elmt_Id) return Elmt_Id;
114   pragma Inline (Next_Elmt);
115   --  This function returns the next element on an element list. The argument
116   --  must be a list element other than No_Elmt. Returns No_Elmt if the given
117   --  element is the last element of the list.
118
119   procedure Next_Elmt (Elmt : in out Elmt_Id);
120   pragma Inline (Next_Elmt);
121   --  Next_Elmt (Elmt) is equivalent to Elmt := Next_Elmt (Elmt)
122
123   function Is_Empty_Elmt_List (List : Elist_Id) return Boolean;
124   pragma Inline (Is_Empty_Elmt_List);
125   --  This function determines if a given tree id references an element list
126   --  that contains no items.
127
128   procedure Append_Elmt (N : Node_Or_Entity_Id; To : Elist_Id);
129   --  Appends N at the end of To, allocating a new element. N must be a
130   --  non-empty node or entity Id, and To must be an Elist (not No_Elist).
131
132   procedure Append_New_Elmt (N : Node_Or_Entity_Id; To : in out Elist_Id);
133   pragma Inline (Append_New_Elmt);
134   --  Like Append_Elmt if Elist_Id is not No_List, but if Elist_Id is No_List,
135   --  then first assigns it an empty element list and then does the append.
136
137   procedure Append_Unique_Elmt (N : Node_Or_Entity_Id; To : Elist_Id);
138   --  Like Append_Elmt, except that a check is made to see if To already
139   --  contains N and if so the call has no effect.
140
141   procedure Prepend_Elmt (N : Node_Or_Entity_Id; To : Elist_Id);
142   --  Appends N at the beginning of To, allocating a new element
143
144   procedure Prepend_Unique_Elmt (N : Node_Or_Entity_Id; To : Elist_Id);
145   --  Like Prepend_Elmt, except that a check is made to see if To already
146   --  contains N and if so the call has no effect.
147
148   procedure Insert_Elmt_After (N : Node_Or_Entity_Id; Elmt : Elmt_Id);
149   --  Add a new element (N) right after the pre-existing element Elmt
150   --  It is invalid to call this subprogram with Elmt = No_Elmt.
151
152   function New_Copy_Elist (List : Elist_Id) return Elist_Id;
153   --  Replicate the contents of a list. Internal list nodes are not shared and
154   --  order of elements is preserved.
155
156   procedure Replace_Elmt (Elmt : Elmt_Id; New_Node : Node_Or_Entity_Id);
157   pragma Inline (Replace_Elmt);
158   --  Causes the given element of the list to refer to New_Node, the node
159   --  which was previously referred to by Elmt is effectively removed from
160   --  the list and replaced by New_Node.
161
162   procedure Remove (List : Elist_Id; N : Node_Or_Entity_Id);
163   --  Remove a node or an entity from a list. If the list does not contain the
164   --  item in question, the routine has no effect.
165
166   procedure Remove_Elmt (List : Elist_Id; Elmt : Elmt_Id);
167   --  Removes Elmt from the given list. The node itself is not affected,
168   --  but the space used by the list element may be (but is not required
169   --  to be) freed for reuse in a subsequent Append_Elmt call.
170
171   procedure Remove_Last_Elmt (List : Elist_Id);
172   --  Removes the last element of the given list. The node itself is not
173   --  affected, but the space used by the list element may be (but is not
174   --  required to be) freed for reuse in a subsequent Append_Elmt call.
175
176   function Contains (List : Elist_Id; N : Node_Or_Entity_Id) return Boolean;
177   --  Perform a sequential search to determine whether the given list contains
178   --  a node or an entity.
179
180   function No (List : Elist_Id) return Boolean;
181   pragma Inline (No);
182   --  Tests given Id for equality with No_Elist. This allows notations like
183   --  "if No (Statements)" as opposed to "if Statements = No_Elist".
184
185   function Present (List : Elist_Id) return Boolean;
186   pragma Inline (Present);
187   --  Tests given Id for inequality with No_Elist. This allows notations like
188   --  "if Present (Statements)" as opposed to "if Statements /= No_Elist".
189
190   function No (Elmt : Elmt_Id) return Boolean;
191   pragma Inline (No);
192   --  Tests given Id for equality with No_Elmt. This allows notations like
193   --  "if No (Operation)" as opposed to "if Operation = No_Elmt".
194
195   function Present (Elmt : Elmt_Id) return Boolean;
196   pragma Inline (Present);
197   --  Tests given Id for inequality with No_Elmt. This allows notations like
198   --  "if Present (Operation)" as opposed to "if Operation /= No_Elmt".
199
200end Elists;
201