File : table.adb
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- T A B L E --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2016, 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 -- --
19 -- --
20 -- --
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 with Debug; use Debug;
33 with Opt; use Opt;
34 with Output; use Output;
35 with System; use System;
36 with Tree_IO; use Tree_IO;
37
38 with System.Memory; use System.Memory;
39
40 with Unchecked_Conversion;
41
42 pragma Elaborate_All (Output);
43
44 package body Table is
45 package body Table is
46
47 Min : constant Int := Int (Table_Low_Bound);
48 -- Subscript of the minimum entry in the currently allocated table
49
50 Length : Int := 0;
51 -- Number of entries in currently allocated table. The value of zero
52 -- ensures that we initially allocate the table.
53
54 -----------------------
55 -- Local Subprograms --
56 -----------------------
57
58 procedure Reallocate;
59 -- Reallocate the existing table according to the current value stored
60 -- in Max. Works correctly to do an initial allocation if the table
61 -- is currently null.
62
63 function Tree_Get_Table_Address return Address;
64 -- Return Null_Address if the table length is zero,
65 -- Table (First)'Address if not.
66
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.
71
72 function To_Address is new Unchecked_Conversion (Table_Ptr, Address);
73 function To_Pointer is new Unchecked_Conversion (Address, Table_Ptr);
74
75 pragma Warnings (On);
76
77 ------------
78 -- Append --
79 ------------
80
81 procedure Append (New_Val : Table_Component_Type) is
82 begin
83 Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
84 end Append;
85
86 ----------------
87 -- Append_All --
88 ----------------
89
90 procedure Append_All (New_Vals : Table_Type) is
91 begin
92 for J in New_Vals'Range loop
93 Append (New_Vals (J));
94 end loop;
95 end Append_All;
96
97 --------------------
98 -- Decrement_Last --
99 --------------------
100
101 procedure Decrement_Last is
102 begin
103 Last_Val := Last_Val - 1;
104 end Decrement_Last;
105
106 ----------
107 -- Free --
108 ----------
109
110 procedure Free is
111 begin
112 Free (To_Address (Table));
113 Table := null;
114 Length := 0;
115 end Free;
116
117 --------------------
118 -- Increment_Last --
119 --------------------
120
121 procedure Increment_Last is
122 begin
123 Last_Val := Last_Val + 1;
124
125 if Last_Val > Max then
126 Reallocate;
127 end if;
128 end Increment_Last;
129
130 ----------
131 -- Init --
132 ----------
133
134 procedure Init is
135 Old_Length : constant Int := Length;
136
137 begin
138 Locked := False;
139 Last_Val := Min - 1;
140 Max := Min + (Table_Initial * Table_Factor) - 1;
141 Length := Max - Min + 1;
142
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.
147
148 if Old_Length = Length then
149 return;
150
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.
154
155 else
156 Reallocate;
157 end if;
158 end Init;
159
160 ----------
161 -- Last --
162 ----------
163
164 function Last return Table_Index_Type is
165 begin
166 return Table_Index_Type (Last_Val);
167 end Last;
168
169 ----------------
170 -- Reallocate --
171 ----------------
172
173 procedure Reallocate is
174 New_Size : Memory.size_t;
175 New_Length : Long_Long_Integer;
176
177 begin
178 if Max < Last_Val then
179 pragma Assert (not Locked);
180
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.
183
184 Length := Int'Max (Length, Table_Initial);
185
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.
192
193 while Max < Last_Val loop
194 New_Length :=
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;
199 end loop;
200
201 if Debug_Flag_D then
202 Write_Str ("--> Allocating new ");
203 Write_Str (Table_Name);
204 Write_Str (" table, size = ");
205 Write_Int (Max - Min + 1);
206 Write_Eol;
207 end if;
208 end if;
209
210 -- Do the intermediate calculation in size_t to avoid signed overflow
211
212 New_Size :=
213 Memory.size_t (Max - Min + 1) *
214 (Table_Type'Component_Size / Storage_Unit);
215
216 if Table = null then
217 Table := To_Pointer (Alloc (New_Size));
218
219 elsif New_Size > 0 then
220 Table :=
221 To_Pointer (Realloc (Ptr => To_Address (Table),
222 Size => New_Size));
223 end if;
224
225 if Length /= 0 and then Table = null then
226 Set_Standard_Error;
227 Write_Str ("available memory exhausted");
228 Write_Eol;
229 Set_Standard_Output;
230 raise Unrecoverable_Error;
231 end if;
232
233 end Reallocate;
234
235 -------------
236 -- Release --
237 -------------
238
239 procedure Release is
240 begin
241 Length := Last_Val - Int (Table_Low_Bound) + 1;
242 Max := Last_Val;
243 Reallocate;
244 end Release;
245
246 -------------
247 -- Restore --
248 -------------
249
250 procedure Restore (T : Saved_Table) is
251 begin
252 Free (To_Address (Table));
253 Last_Val := T.Last_Val;
254 Max := T.Max;
255 Table := T.Table;
256 Length := Max - Min + 1;
257 end Restore;
258
259 ----------
260 -- Save --
261 ----------
262
263 function Save return Saved_Table is
264 Res : Saved_Table;
265
266 begin
267 Res.Last_Val := Last_Val;
268 Res.Max := Max;
269 Res.Table := Table;
270
271 Table := null;
272 Length := 0;
273 Init;
274 return Res;
275 end Save;
276
277 --------------
278 -- Set_Item --
279 --------------
280
281 procedure Set_Item
282 (Index : Table_Index_Type;
283 Item : Table_Component_Type)
284 is
285 -- If Item is a value within the current allocation, and we are going
286 -- to reallocate, then we must preserve an intermediate copy here
287 -- before calling Increment_Last. Otherwise, if Table_Component_Type
288 -- is passed by reference, we are going to end up copying from
289 -- storage that might have been deallocated from Increment_Last
290 -- calling Reallocate.
291
292 subtype Allocated_Table_T is
293 Table_Type (Table'First .. Table_Index_Type (Max + 1));
294 -- A constrained table subtype one element larger than the currently
295 -- allocated table.
296
297 Allocated_Table_Address : constant System.Address :=
298 Table.all'Address;
299 -- Used for address clause below (we can't use non-static expression
300 -- Table.all'Address directly in the clause because some older
301 -- versions of the compiler do not allow it).
302
303 Allocated_Table : Allocated_Table_T;
304 pragma Import (Ada, Allocated_Table);
305 pragma Suppress (Range_Check, On => Allocated_Table);
306 for Allocated_Table'Address use Allocated_Table_Address;
307 -- Allocated_Table represents the currently allocated array, plus one
308 -- element (the supplementary element is used to have a convenient
309 -- way of computing the address just past the end of the current
310 -- allocation). Range checks are suppressed because this unit
311 -- uses direct calls to System.Memory for allocation, and this can
312 -- yield misaligned storage (and we cannot rely on the bootstrap
313 -- compiler supporting specifically disabling alignment checks, so we
314 -- need to suppress all range checks). It is safe to suppress this
315 -- check here because we know that a (possibly misaligned) object
316 -- of that type does actually exist at that address.
317 -- ??? We should really improve the allocation circuitry here to
318 -- guarantee proper alignment.
319
320 Need_Realloc : constant Boolean := Int (Index) > Max;
321 -- True if this operation requires storage reallocation (which may
322 -- involve moving table contents around).
323
324 begin
325 -- If we're going to reallocate, check whether Item references an
326 -- element of the currently allocated table.
327
328 if Need_Realloc
329 and then Allocated_Table'Address <= Item'Address
330 and then Item'Address <
331 Allocated_Table (Table_Index_Type (Max + 1))'Address
332 then
333 -- If so, save a copy on the stack because Increment_Last will
334 -- reallocate storage and might deallocate the current table.
335
336 declare
337 Item_Copy : constant Table_Component_Type := Item;
338 begin
339 Set_Last (Index);
340 Table (Index) := Item_Copy;
341 end;
342
343 else
344 -- Here we know that either we won't reallocate (case of Index <
345 -- Max) or that Item is not in the currently allocated table.
346
347 if Int (Index) > Last_Val then
348 Set_Last (Index);
349 end if;
350
351 Table (Index) := Item;
352 end if;
353 end Set_Item;
354
355 --------------
356 -- Set_Last --
357 --------------
358
359 procedure Set_Last (New_Val : Table_Index_Type) is
360 begin
361 if Int (New_Val) < Last_Val then
362 Last_Val := Int (New_Val);
363
364 else
365 Last_Val := Int (New_Val);
366
367 if Last_Val > Max then
368 Reallocate;
369 end if;
370 end if;
371 end Set_Last;
372
373 ----------------------------
374 -- Tree_Get_Table_Address --
375 ----------------------------
376
377 function Tree_Get_Table_Address return Address is
378 begin
379 if Length = 0 then
380 return Null_Address;
381 else
382 return Table (First)'Address;
383 end if;
384 end Tree_Get_Table_Address;
385
386 ---------------
387 -- Tree_Read --
388 ---------------
389
390 -- Note: we allocate only the space required to accommodate the data
391 -- actually written, which means that a Tree_Write/Tree_Read sequence
392 -- does an implicit Release.
393
394 procedure Tree_Read is
395 begin
396 Tree_Read_Int (Max);
397 Last_Val := Max;
398 Length := Max - Min + 1;
399 Reallocate;
400
401 Tree_Read_Data
402 (Tree_Get_Table_Address,
403 (Last_Val - Int (First) + 1) *
404
405 -- Note the importance of parenthesizing the following division
406 -- to avoid the possibility of intermediate overflow.
407
408 (Table_Type'Component_Size / Storage_Unit));
409 end Tree_Read;
410
411 ----------------
412 -- Tree_Write --
413 ----------------
414
415 -- Note: we write out only the currently valid data, not the entire
416 -- contents of the allocated array. See note above on Tree_Read.
417
418 procedure Tree_Write is
419 begin
420 Tree_Write_Int (Int (Last));
421 Tree_Write_Data
422 (Tree_Get_Table_Address,
423 (Last_Val - Int (First) + 1) *
424 (Table_Type'Component_Size / Storage_Unit));
425 end Tree_Write;
426
427 begin
428 Init;
429 end Table;
430 end Table;