1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2016, Free Software Foundation, Inc. --
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. --
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. --
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/>. --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
30 ------------------------------------------------------------------------------
32 with Debug; use Debug;
34 with Output; use Output;
35 with System; use System;
36 with Tree_IO; use Tree_IO;
38 with System.Memory; use System.Memory;
40 with Unchecked_Conversion;
42 pragma Elaborate_All (Output);
47 Min : constant Int := Int (Table_Low_Bound);
48 -- Subscript of the minimum entry in the currently allocated table
51 -- Number of entries in currently allocated table. The value of zero
52 -- ensures that we initially allocate the table.
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 function Tree_Get_Table_Address return Address;
64 -- Return Null_Address if the table length is zero,
65 -- Table (First)'Address if not.
67 pragma Warnings (Off);
68 -- Turn off warnings. The following unchecked conversions are only used
69 -- internally in this package, and cannot never result in any instances
70 -- of improperly aliased pointers for the client of the package.
72 function To_Address is new Unchecked_Conversion (Table_Ptr, Address);
73 function To_Pointer is new Unchecked_Conversion (Address, Table_Ptr);
81 procedure Append (New_Val : Table_Component_Type) is
83 Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
90 procedure Append_All (New_Vals : Table_Type) is
92 for J in New_Vals'Range loop
93 Append (New_Vals (J));
101 procedure Decrement_Last is
103 Last_Val := Last_Val - 1;
112 Free (To_Address (Table));
121 procedure Increment_Last is
123 Last_Val := Last_Val + 1;
125 if Last_Val > Max then
135 Old_Length : constant Int := Length;
140 Max := Min + (Table_Initial * Table_Factor) - 1;
141 Length := Max - Min + 1;
143 -- If table is same size as before (happens when table is never
144 -- expanded which is a common case), then simply reuse it. Note
145 -- that this also means that an explicit Init call right after
146 -- the implicit one in the package body is harmless.
148 if Old_Length = Length then
151 -- Otherwise we can use Reallocate to get a table of the right size.
152 -- Note that Reallocate works fine to allocate a table of the right
153 -- initial size when it is first allocated.
164 function Last return Table_Index_Type is
166 return Table_Index_Type (Last_Val);
173 procedure Reallocate is
174 New_Size : Memory.size_t;
175 New_Length : Long_Long_Integer;
178 if Max < Last_Val then
179 pragma Assert (not Locked);
181 -- Make sure that we have at least the initial allocation. This
182 -- is needed in cases where a zero length table is written out.
184 Length := Int'Max (Length, Table_Initial);
186 -- Now increment table length until it is sufficiently large. Use
187 -- the increment value or 10, which ever is larger (the reason
188 -- for the use of 10 here is to ensure that the table does really
189 -- increase in size (which would not be the case for a table of
190 -- length 10 increased by 3% for instance). Do the intermediate
191 -- calculation in Long_Long_Integer to avoid overflow.
193 while Max < Last_Val loop
195 Long_Long_Integer (Length) *
196 (100 + Long_Long_Integer (Table_Increment)) / 100;
197 Length := Int'Max (Int (New_Length), Length + 10);
198 Max := Min + Length - 1;
202 Write_Str ("--> Allocating new ");
203 Write_Str (Table_Name);
204 Write_Str (" table, size = ");
205 Write_Int (Max - Min + 1);
210 -- Do the intermediate calculation in size_t to avoid signed overflow
213 Memory.size_t (Max - Min + 1) *
214 (Table_Type'Component_Size / Storage_Unit);
217 Table := To_Pointer (Alloc (New_Size));
219 elsif New_Size > 0 then
221 To_Pointer (Realloc (Ptr => To_Address (Table),
225 if Length /= 0 and then Table = null then
227 Write_Str ("available memory exhausted");
230 raise Unrecoverable_Error;
240 Size : Memory.size_t;
243 Length := Last_Val - Int (Table_Low_Bound) + 1;
244 Size := Memory.size_t (Length) *
245 (Table_Type'Component_Size / Storage_Unit);
247 -- If the size of the table exceeds the release threshold then leave
248 -- space to store as many extra elements as 0.1% of the table length.
250 if Release_Threshold > 0
251 and then Size > Memory.size_t (Release_Threshold)
253 Extra_Length := Length / 1000;
254 Length := Length + Extra_Length;
255 Max := Int (Table_Low_Bound) + Length - 1;
258 Write_Str ("--> Release_Threshold reached (length=");
259 Write_Int (Int (Size));
260 Write_Str ("): leaving room space for ");
261 Write_Int (Extra_Length);
262 Write_Str (" components");
276 procedure Restore (T : Saved_Table) is
278 Free (To_Address (Table));
279 Last_Val := T.Last_Val;
282 Length := Max - Min + 1;
289 function Save return Saved_Table is
293 Res.Last_Val := Last_Val;
308 (Index : Table_Index_Type;
309 Item : Table_Component_Type)
311 -- If Item is a value within the current allocation, and we are going
312 -- to reallocate, then we must preserve an intermediate copy here
313 -- before calling Increment_Last. Otherwise, if Table_Component_Type
314 -- is passed by reference, we are going to end up copying from
315 -- storage that might have been deallocated from Increment_Last
316 -- calling Reallocate.
318 subtype Allocated_Table_T is
319 Table_Type (Table'First .. Table_Index_Type (Max + 1));
320 -- A constrained table subtype one element larger than the currently
323 Allocated_Table_Address : constant System.Address :=
325 -- Used for address clause below (we can't use non-static expression
326 -- Table.all'Address directly in the clause because some older
327 -- versions of the compiler do not allow it).
329 Allocated_Table : Allocated_Table_T;
330 pragma Import (Ada, Allocated_Table);
331 pragma Suppress (Range_Check, On => Allocated_Table);
332 for Allocated_Table'Address use Allocated_Table_Address;
333 -- Allocated_Table represents the currently allocated array, plus one
334 -- element (the supplementary element is used to have a convenient
335 -- way of computing the address just past the end of the current
336 -- allocation). Range checks are suppressed because this unit
337 -- uses direct calls to System.Memory for allocation, and this can
338 -- yield misaligned storage (and we cannot rely on the bootstrap
339 -- compiler supporting specifically disabling alignment checks, so we
340 -- need to suppress all range checks). It is safe to suppress this
341 -- check here because we know that a (possibly misaligned) object
342 -- of that type does actually exist at that address.
343 -- ??? We should really improve the allocation circuitry here to
344 -- guarantee proper alignment.
346 Need_Realloc : constant Boolean := Int (Index) > Max;
347 -- True if this operation requires storage reallocation (which may
348 -- involve moving table contents around).
351 -- If we're going to reallocate, check whether Item references an
352 -- element of the currently allocated table.
355 and then Allocated_Table'Address <= Item'Address
356 and then Item'Address <
357 Allocated_Table (Table_Index_Type (Max + 1))'Address
359 -- If so, save a copy on the stack because Increment_Last will
360 -- reallocate storage and might deallocate the current table.
363 Item_Copy : constant Table_Component_Type := Item;
366 Table (Index) := Item_Copy;
370 -- Here we know that either we won't reallocate (case of Index <
371 -- Max) or that Item is not in the currently allocated table.
373 if Int (Index) > Last_Val then
377 Table (Index) := Item;
385 procedure Set_Last (New_Val : Table_Index_Type) is
387 if Int (New_Val) < Last_Val then
388 Last_Val := Int (New_Val);
391 Last_Val := Int (New_Val);
393 if Last_Val > Max then
399 ----------------------------
400 -- Tree_Get_Table_Address --
401 ----------------------------
403 function Tree_Get_Table_Address return Address is
408 return Table (First)'Address;
410 end Tree_Get_Table_Address;
416 -- Note: we allocate only the space required to accommodate the data
417 -- actually written, which means that a Tree_Write/Tree_Read sequence
418 -- does an implicit Release.
420 procedure Tree_Read is
424 Length := Max - Min + 1;
428 (Tree_Get_Table_Address,
429 (Last_Val - Int (First) + 1) *
431 -- Note the importance of parenthesizing the following division
432 -- to avoid the possibility of intermediate overflow.
434 (Table_Type'Component_Size / Storage_Unit));
441 -- Note: we write out only the currently valid data, not the entire
442 -- contents of the allocated array. See note above on Tree_Read.
444 procedure Tree_Write is
446 Tree_Write_Int (Int (Last));
448 (Tree_Get_Table_Address,
449 (Last_Val - Int (First) + 1) *
450 (Table_Type'Component_Size / Storage_Unit));