1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- G N A T . T A B L E --
9 -- Copyright (C) 1998-2007, AdaCore --
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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with System; use System;
35 with System.Memory; use System.Memory;
37 with Ada.Unchecked_Conversion;
39 package body GNAT.Table is
41 Min : constant Integer := Integer (Table_Low_Bound);
42 -- Subscript of the minimum entry in the currently allocated table
45 -- Subscript of the maximum entry in the currently allocated table
47 Length : Integer := 0;
48 -- Number of entries in currently allocated table. The value of zero
49 -- ensures that we initially allocate the table.
52 -- Current value of Last
54 -----------------------
55 -- Local Subprograms --
56 -----------------------
59 -- Reallocate the existing table according to the current value stored
60 -- in Max. Works correctly to do an initial allocation if the table
63 pragma Warnings (Off);
64 -- Turn off warnings. The following unchecked conversions are only used
65 -- internally in this package, and cannot never result in any instances
66 -- of improperly aliased pointers for the client of the package.
68 function To_Address is new Ada.Unchecked_Conversion (Table_Ptr, Address);
69 function To_Pointer is new Ada.Unchecked_Conversion (Address, Table_Ptr);
77 function Allocate (Num : Integer := 1) return Table_Index_Type is
78 Old_Last : constant Integer := Last_Val;
81 Last_Val := Last_Val + Num;
83 if Last_Val > Max then
87 return Table_Index_Type (Old_Last + 1);
94 procedure Append (New_Val : Table_Component_Type) is
96 Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
103 procedure Decrement_Last is
105 Last_Val := Last_Val - 1;
114 Free (To_Address (Table));
123 procedure Increment_Last is
125 Last_Val := Last_Val + 1;
127 if Last_Val > Max then
137 Old_Length : constant Integer := Length;
141 Max := Min + Table_Initial - 1;
142 Length := Max - Min + 1;
144 -- If table is same size as before (happens when table is never
145 -- expanded which is a common case), then simply reuse it. Note
146 -- that this also means that an explicit Init call right after
147 -- the implicit one in the package body is harmless.
149 if Old_Length = Length then
152 -- Otherwise we can use Reallocate to get a table of the right size.
153 -- Note that Reallocate works fine to allocate a table of the right
154 -- initial size when it is first allocated.
165 function Last return Table_Index_Type is
167 return Table_Index_Type (Last_Val);
174 procedure Reallocate is
178 if Max < Last_Val then
179 pragma Assert (not Locked);
181 while Max < Last_Val loop
183 -- Increase length using the table increment factor, but make
184 -- sure that we add at least ten elements (this avoids a loop
185 -- for silly small increment values)
187 Length := Integer'Max
188 (Length * (100 + Table_Increment) / 100,
190 Max := Min + Length - 1;
195 size_t ((Max - Min + 1) *
196 (Table_Type'Component_Size / Storage_Unit));
199 Table := To_Pointer (Alloc (New_Size));
201 elsif New_Size > 0 then
203 To_Pointer (Realloc (Ptr => To_Address (Table),
207 if Length /= 0 and then Table = null then
219 Length := Last_Val - Integer (Table_Low_Bound) + 1;
229 (Index : Table_Index_Type;
230 Item : Table_Component_Type)
232 -- If Item is a value within the current allocation, and we are going to
233 -- reallocate, then we must preserve an intermediate copy here before
234 -- calling Increment_Last. Otherwise, if Table_Component_Type is passed
235 -- by reference, we are going to end up copying from storage that might
236 -- have been deallocated from Increment_Last calling Reallocate.
238 subtype Allocated_Table_T is
239 Table_Type (Table'First .. Table_Index_Type (Max + 1));
240 -- A constrained table subtype one element larger than the currently
243 Allocated_Table_Address : constant System.Address :=
245 -- Used for address clause below (we can't use non-static expression
246 -- Table.all'Address directly in the clause because some older versions
247 -- of the compiler do not allow it).
249 Allocated_Table : Allocated_Table_T;
250 pragma Import (Ada, Allocated_Table);
251 pragma Suppress (Range_Check, On => Allocated_Table);
252 for Allocated_Table'Address use Allocated_Table_Address;
253 -- Allocated_Table represents the currently allocated array, plus
254 -- one element (the supplementary element is used to have a
255 -- convenient way of computing the address just past the end of the
256 -- current allocation). Range checks are suppressed because this unit
257 -- uses direct calls to System.Memory for allocation, and this can
258 -- yield misaligned storage (and we cannot rely on the bootstrap
259 -- compiler supporting specifically disabling alignment cheks, so we
260 -- need to suppress all range checks). It is safe to suppress this check
261 -- here because we know that a (possibly misaligned) object of that type
262 -- does actually exist at that address.
263 -- ??? We should really improve the allocation circuitry here to
264 -- guarantee proper alignment.
266 Need_Realloc : constant Boolean := Integer (Index) > Max;
267 -- True if this operation requires storage reallocation (which may
268 -- involve moving table contents around).
271 -- If we're going to reallocate, check wheter Item references an
272 -- element of the currently allocated table.
275 and then Allocated_Table'Address <= Item'Address
276 and then Item'Address <
277 Allocated_Table (Table_Index_Type (Max + 1))'Address
279 -- If so, save a copy on the stack because Increment_Last will
280 -- reallocate storage and might deallocate the current table.
283 Item_Copy : constant Table_Component_Type := Item;
286 Table (Index) := Item_Copy;
290 -- Here we know that either we won't reallocate (case of Index < Max)
291 -- or that Item is not in the currently allocated table.
293 if Integer (Index) > Last_Val then
297 Table (Index) := Item;
305 procedure Set_Last (New_Val : Table_Index_Type) is
307 if Integer (New_Val) < Last_Val then
308 Last_Val := Integer (New_Val);
310 Last_Val := Integer (New_Val);
312 if Last_Val > Max then