1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- S Y S T E M . P O O L _ S I Z E --
9 -- Copyright (C) 1992-2007, 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 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.Soft_Links;
36 with Ada.Unchecked_Conversion;
38 package body System.Pool_Size is
40 package SSE renames System.Storage_Elements;
41 use type SSE.Storage_Offset;
43 -- Even though these storage pools are typically only used
44 -- by a single task, if multiple tasks are declared at the
45 -- same or a more nested scope as the storage pool, there
46 -- still may be concurrent access. The current implementation
47 -- of Stack_Bounded_Pool always uses a global lock for protecting
48 -- access. This should eventually be replaced by an atomic
49 -- linked list implementation for efficiency reasons.
51 package SSL renames System.Soft_Links;
53 type Storage_Count_Access is access SSE.Storage_Count;
54 function To_Storage_Count_Access is
55 new Ada.Unchecked_Conversion (Address, Storage_Count_Access);
57 SC_Size : constant := SSE.Storage_Count'Object_Size / System.Storage_Unit;
59 package Variable_Size_Management is
61 -- Embedded pool that manages allocation of variable-size data.
63 -- This pool is used as soon as the Elmt_sizS of the pool object is 0.
65 -- Allocation is done on the first chunk long enough for the request.
66 -- Deallocation just puts the freed chunk at the beginning of the list.
68 procedure Initialize (Pool : in out Stack_Bounded_Pool);
70 (Pool : in out Stack_Bounded_Pool;
71 Address : out System.Address;
72 Storage_Size : SSE.Storage_Count;
73 Alignment : SSE.Storage_Count);
76 (Pool : in out Stack_Bounded_Pool;
77 Address : System.Address;
78 Storage_Size : SSE.Storage_Count;
79 Alignment : SSE.Storage_Count);
80 end Variable_Size_Management;
82 package Vsize renames Variable_Size_Management;
89 (Pool : in out Stack_Bounded_Pool;
90 Address : out System.Address;
91 Storage_Size : SSE.Storage_Count;
92 Alignment : SSE.Storage_Count)
97 if Pool.Elmt_Size = 0 then
98 Vsize.Allocate (Pool, Address, Storage_Size, Alignment);
100 elsif Pool.First_Free /= 0 then
101 Address := Pool.The_Pool (Pool.First_Free)'Address;
102 Pool.First_Free := To_Storage_Count_Access (Address).all;
105 Pool.First_Empty <= (Pool.Pool_Size - Pool.Aligned_Elmt_Size + 1)
107 Address := Pool.The_Pool (Pool.First_Empty)'Address;
108 Pool.First_Empty := Pool.First_Empty + Pool.Aligned_Elmt_Size;
127 (Pool : in out Stack_Bounded_Pool;
128 Address : System.Address;
129 Storage_Size : SSE.Storage_Count;
130 Alignment : SSE.Storage_Count)
135 if Pool.Elmt_Size = 0 then
136 Vsize.Deallocate (Pool, Address, Storage_Size, Alignment);
139 To_Storage_Count_Access (Address).all := Pool.First_Free;
140 Pool.First_Free := Address - Pool.The_Pool'Address + 1;
154 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
156 -- Define the appropriate alignment for allocations. This is the
157 -- maximum of the requested alignment, and the alignment required
158 -- for Storage_Count values. The latter test is to ensure that we
159 -- can properly reference the linked list pointers for free lists.
161 Align : constant SSE.Storage_Count :=
162 SSE.Storage_Count'Max
163 (SSE.Storage_Count'Alignment, Pool.Alignment);
166 if Pool.Elmt_Size = 0 then
167 Vsize.Initialize (Pool);
170 Pool.First_Free := 0;
171 Pool.First_Empty := 1;
173 -- Compute the size to allocate given the size of the element and
174 -- the possible alignment requirement as defined above.
176 Pool.Aligned_Elmt_Size :=
177 SSE.Storage_Count'Max (SC_Size,
178 ((Pool.Elmt_Size + Align - 1) / Align) * Align);
186 function Storage_Size
187 (Pool : Stack_Bounded_Pool) return SSE.Storage_Count
190 return Pool.Pool_Size;
193 ------------------------------
194 -- Variable_Size_Management --
195 ------------------------------
197 package body Variable_Size_Management is
199 Minimum_Size : constant := 2 * SC_Size;
202 (Pool : Stack_Bounded_Pool;
203 Chunk, Size : SSE.Storage_Count);
204 -- Update the field 'size' of a chunk of available storage
207 (Pool : Stack_Bounded_Pool;
208 Chunk, Next : SSE.Storage_Count);
209 -- Update the field 'next' of a chunk of available storage
212 (Pool : Stack_Bounded_Pool;
213 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
214 -- Fetch the field 'size' of a chunk of available storage
217 (Pool : Stack_Bounded_Pool;
218 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
219 -- Fetch the field 'next' of a chunk of available storage
222 (Pool : Stack_Bounded_Pool;
223 Addr : System.Address) return SSE.Storage_Count;
224 -- Give the chunk number in the pool from its Address
231 (Pool : in out Stack_Bounded_Pool;
232 Address : out System.Address;
233 Storage_Size : SSE.Storage_Count;
234 Alignment : SSE.Storage_Count)
236 Chunk : SSE.Storage_Count;
237 New_Chunk : SSE.Storage_Count;
238 Prev_Chunk : SSE.Storage_Count;
239 Our_Align : constant SSE.Storage_Count :=
240 SSE.Storage_Count'Max (SSE.Storage_Count'Alignment,
242 Align_Size : constant SSE.Storage_Count :=
243 SSE.Storage_Count'Max (
245 ((Storage_Size + Our_Align - 1) / Our_Align) *
249 -- Look for the first big enough chunk
251 Prev_Chunk := Pool.First_Free;
252 Chunk := Next (Pool, Prev_Chunk);
254 while Chunk /= 0 and then Size (Pool, Chunk) < Align_Size loop
256 Chunk := Next (Pool, Chunk);
259 -- Raise storage_error if no big enough chunk available
265 -- When the chunk is bigger than what is needed, take appropraite
266 -- amount and build a new shrinked chunk with the remainder.
268 if Size (Pool, Chunk) - Align_Size > Minimum_Size then
269 New_Chunk := Chunk + Align_Size;
270 Set_Size (Pool, New_Chunk, Size (Pool, Chunk) - Align_Size);
271 Set_Next (Pool, New_Chunk, Next (Pool, Chunk));
272 Set_Next (Pool, Prev_Chunk, New_Chunk);
274 -- If the chunk is the right size, just delete it from the chain
277 Set_Next (Pool, Prev_Chunk, Next (Pool, Chunk));
280 Address := Pool.The_Pool (Chunk)'Address;
288 (Pool : Stack_Bounded_Pool;
289 Addr : System.Address) return SSE.Storage_Count
292 return 1 + abs (Addr - Pool.The_Pool (1)'Address);
300 (Pool : in out Stack_Bounded_Pool;
301 Address : System.Address;
302 Storage_Size : SSE.Storage_Count;
303 Alignment : SSE.Storage_Count)
305 Align_Size : constant SSE.Storage_Count :=
306 ((Storage_Size + Alignment - 1) / Alignment) *
308 Chunk : constant SSE.Storage_Count := Chunk_Of (Pool, Address);
311 -- Attach the freed chunk to the chain
313 Set_Size (Pool, Chunk,
314 SSE.Storage_Count'Max (Align_Size, Minimum_Size));
315 Set_Next (Pool, Chunk, Next (Pool, Pool.First_Free));
316 Set_Next (Pool, Pool.First_Free, Chunk);
324 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
326 Pool.First_Free := 1;
328 if Pool.Pool_Size > Minimum_Size then
329 Set_Next (Pool, Pool.First_Free, Pool.First_Free + Minimum_Size);
330 Set_Size (Pool, Pool.First_Free, 0);
331 Set_Size (Pool, Pool.First_Free + Minimum_Size,
332 Pool.Pool_Size - Minimum_Size);
333 Set_Next (Pool, Pool.First_Free + Minimum_Size, 0);
342 (Pool : Stack_Bounded_Pool;
343 Chunk : SSE.Storage_Count) return SSE.Storage_Count
346 pragma Warnings (Off);
347 -- Kill alignment warnings, we are careful to make sure
348 -- that the alignment is correct.
350 return To_Storage_Count_Access
351 (Pool.The_Pool (Chunk + SC_Size)'Address).all;
353 pragma Warnings (On);
361 (Pool : Stack_Bounded_Pool;
362 Chunk, Next : SSE.Storage_Count)
365 pragma Warnings (Off);
366 -- Kill alignment warnings, we are careful to make sure
367 -- that the alignment is correct.
369 To_Storage_Count_Access
370 (Pool.The_Pool (Chunk + SC_Size)'Address).all := Next;
372 pragma Warnings (On);
380 (Pool : Stack_Bounded_Pool;
381 Chunk, Size : SSE.Storage_Count)
384 pragma Warnings (Off);
385 -- Kill alignment warnings, we are careful to make sure
386 -- that the alignment is correct.
388 To_Storage_Count_Access
389 (Pool.The_Pool (Chunk)'Address).all := Size;
391 pragma Warnings (On);
399 (Pool : Stack_Bounded_Pool;
400 Chunk : SSE.Storage_Count) return SSE.Storage_Count
403 pragma Warnings (Off);
404 -- Kill alignment warnings, we are careful to make sure
405 -- that the alignment is correct.
407 return To_Storage_Count_Access (Pool.The_Pool (Chunk)'Address).all;
409 pragma Warnings (On);
412 end Variable_Size_Management;
413 end System.Pool_Size;