Remove obsolete ECOFF support.
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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- T A B L E --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 1992-2017, 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 ------------------------------------------------------------------------------
32 -- This package provides an implementation of dynamically resizable one
33 -- dimensional arrays. The idea is to mimic the normal Ada semantics for
34 -- arrays as closely as possible with the one additional capability of
35 -- dynamically modifying the value of the Last attribute.
37 -- This package uses a very efficient memory management scheme and any
38 -- change must be carefully evaluated on compilation of real software.
40 -- Note that this interface should remain synchronized with those in
41 -- GNAT.Table and GNAT.Dynamic_Tables to keep coherency between these
42 -- three related units.
44 with Types; use Types;
46 package Table is
47 pragma Elaborate_Body;
49 generic
50 type Table_Component_Type is private;
51 type Table_Index_Type is range <>;
53 Table_Low_Bound : Table_Index_Type;
54 Table_Initial : Pos;
55 Table_Increment : Nat;
56 Table_Name : String;
57 Release_Threshold : Nat := 0;
59 package Table is
61 -- Table_Component_Type and Table_Index_Type specify the type of the
62 -- array, Table_Low_Bound is the lower bound. Table_Index_Type must be
63 -- an integer type. The effect is roughly to declare:
65 -- Table : array (Table_Index_Type range Table_Low_Bound .. <>)
66 -- of Table_Component_Type;
68 -- Note: since the upper bound can be one less than the lower
69 -- bound for an empty array, the table index type must be able
70 -- to cover this range, e.g. if the lower bound is 1, then the
71 -- Table_Index_Type should be Natural rather than Positive.
73 -- Table_Component_Type may be any Ada type, except that controlled
74 -- types are not supported. Note however that default initialization
75 -- will NOT occur for array components.
77 -- The Table_Initial values controls the allocation of the table when
78 -- it is first allocated, either by default, or by an explicit Init
79 -- call. The value used is Opt.Table_Factor * Table_Initial.
81 -- The Table_Increment value controls the amount of increase, if the
82 -- table has to be increased in size. The value given is a percentage
83 -- value (e.g. 100 = increase table size by 100%, i.e. double it).
85 -- The Table_Name parameter is simply use in debug output messages it
86 -- has no other usage, and is not referenced in non-debugging mode.
88 -- The Last and Set_Last subprograms provide control over the current
89 -- logical allocation. They are quite efficient, so they can be used
90 -- freely (expensive reallocation occurs only at major granularity
91 -- chunks controlled by the allocation parameters).
93 -- Note: We do not make the table components aliased, since this would
94 -- restrict the use of table for discriminated types. If it is necessary
95 -- to take the access of a table element, use Unrestricted_Access.
97 -- WARNING: On HPPA, the virtual addressing approach used in this unit
98 -- is incompatible with the indexing instructions on the HPPA. So when
99 -- using this unit, compile your application with -mdisable-indexing.
101 -- WARNING: If the table is reallocated, then the address of all its
102 -- components will change. So do not capture the address of an element
103 -- and then use the address later after the table may be reallocated.
104 -- One tricky case of this is passing an element of the table to a
105 -- subprogram by reference where the table gets reallocated during
106 -- the execution of the subprogram. The best rule to follow is never
107 -- to pass a table element as a parameter except for the case of IN
108 -- mode parameters with scalar values.
110 type Table_Type is
111 array (Table_Index_Type range <>) of Table_Component_Type;
113 subtype Big_Table_Type is
114 Table_Type (Table_Low_Bound .. Table_Index_Type'Last);
115 -- We work with pointers to a bogus array type that is constrained
116 -- with the maximum possible range bound. This means that the pointer
117 -- is a thin pointer, which is more efficient. Since subscript checks
118 -- in any case must be on the logical, rather than physical bounds,
119 -- safety is not compromised by this approach.
121 type Table_Ptr is access all Big_Table_Type;
122 for Table_Ptr'Storage_Size use 0;
123 -- The table is actually represented as a pointer to allow reallocation
125 Table : aliased Table_Ptr := null;
126 -- The table itself. The lower bound is the value of Low_Bound.
127 -- Logically the upper bound is the current value of Last (although
128 -- the actual size of the allocated table may be larger than this).
129 -- The program may only access and modify Table entries in the range
130 -- First .. Last.
132 Locked : Boolean := False;
133 -- Table expansion is permitted only if this switch is set to False. A
134 -- client may set Locked to True, in which case any attempt to expand
135 -- the table will cause an assertion failure. Note that while a table
136 -- is locked, its address in memory remains fixed and unchanging. This
137 -- feature is used to control table expansion during Gigi processing.
138 -- Gigi assumes that tables other than the Uint and Ureal tables do
139 -- not move during processing, which means that they cannot be expanded.
140 -- The Locked flag is used to enforce this restriction.
142 procedure Init;
143 -- This procedure allocates a new table of size Initial (freeing any
144 -- previously allocated larger table). It is not necessary to call
145 -- Init when a table is first instantiated (since the instantiation does
146 -- the same initialization steps). However, it is harmless to do so, and
147 -- Init is convenient in reestablishing a table for new use.
149 function Last return Table_Index_Type;
150 pragma Inline (Last);
151 -- Returns the current value of the last used entry in the table, which
152 -- can then be used as a subscript for Table. Note that the only way to
153 -- modify Last is to call the Set_Last procedure. Last must always be
154 -- used to determine the logically last entry.
156 procedure Release;
157 -- Storage is allocated in chunks according to the values given in the
158 -- Initial and Increment parameters. If Release_Threshold is 0 or the
159 -- length of the table does not exceed this threshold then a call to
160 -- Release releases all storage that is allocated, but is not logically
161 -- part of the current array value; otherwise the call to Release leaves
162 -- the current array value plus 0.1% of the current table length free
163 -- elements located at the end of the table (this parameter facilitates
164 -- reopening large tables and adding a few elements without allocating a
165 -- chunk of memory). In both cases current array values are not affected
166 -- by this call.
168 procedure Free;
169 -- Free all allocated memory for the table. A call to init is required
170 -- before any use of this table after calling Free.
172 First : constant Table_Index_Type := Table_Low_Bound;
173 -- Export First as synonym for Low_Bound (parallel with use of Last)
175 procedure Set_Last (New_Val : Table_Index_Type);
176 pragma Inline (Set_Last);
177 -- This procedure sets Last to the indicated value. If necessary the
178 -- table is reallocated to accommodate the new value (i.e. on return
179 -- the allocated table has an upper bound of at least Last). If Set_Last
180 -- reduces the size of the table, then logically entries are removed
181 -- from the table. If Set_Last increases the size of the table, then
182 -- new entries are logically added to the table.
184 procedure Increment_Last;
185 pragma Inline (Increment_Last);
186 -- Adds 1 to Last (same as Set_Last (Last + 1)
188 procedure Decrement_Last;
189 pragma Inline (Decrement_Last);
190 -- Subtracts 1 from Last (same as Set_Last (Last - 1)
192 procedure Append (New_Val : Table_Component_Type);
193 pragma Inline (Append);
194 -- Equivalent to:
195 -- x.Increment_Last;
196 -- x.Table (x.Last) := New_Val;
197 -- i.e. the table size is increased by one, and the given new item
198 -- stored in the newly created table element.
200 procedure Append_All (New_Vals : Table_Type);
201 -- Appends all components of New_Vals
203 procedure Set_Item
204 (Index : Table_Index_Type;
205 Item : Table_Component_Type);
206 pragma Inline (Set_Item);
207 -- Put Item in the table at position Index. The table is expanded if
208 -- current table length is less than Index and in that case Last is set
209 -- to Index. Item will replace any value already present in the table
210 -- at this position.
212 type Saved_Table is private;
213 -- Type used for Save/Restore subprograms
215 function Save return Saved_Table;
216 -- Resets table to empty, but saves old contents of table in returned
217 -- value, for possible later restoration by a call to Restore.
219 procedure Restore (T : Saved_Table);
220 -- Given a Saved_Table value returned by a prior call to Save, restores
221 -- the table to the state it was in at the time of the Save call.
223 procedure Tree_Write;
224 -- Writes out contents of table using Tree_IO
226 procedure Tree_Read;
227 -- Initializes table by reading contents previously written with the
228 -- Tree_Write call (also using Tree_IO).
230 private
232 Last_Val : Int;
233 -- Current value of Last. Note that we declare this in the private part
234 -- because we don't want the client to modify Last except through one of
235 -- the official interfaces (since a modification to Last may require a
236 -- reallocation of the table).
238 Max : Int;
239 -- Subscript of the maximum entry in the currently allocated table
241 type Saved_Table is record
242 Last_Val : Int;
243 Max : Int;
244 Table : Table_Ptr;
245 end record;
247 end Table;
248 end Table;