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 by a single
44 -- task, if multiple tasks are declared at the same or a more nested scope
45 -- as the storage pool, there still may be concurrent access. The current
46 -- implementation of Stack_Bounded_Pool always uses a global lock for
47 -- protecting access. This should eventually be replaced by an atomic
48 -- linked list implementation for efficiency reasons.
50 package SSL renames System.Soft_Links;
52 type Storage_Count_Access is access SSE.Storage_Count;
53 function To_Storage_Count_Access is
54 new Ada.Unchecked_Conversion (Address, Storage_Count_Access);
56 SC_Size : constant := SSE.Storage_Count'Object_Size / System.Storage_Unit;
58 package Variable_Size_Management is
60 -- Embedded pool that manages allocation of variable-size data
62 -- This pool is used as soon as the Elmt_sizS of the pool object is 0
64 -- Allocation is done on the first chunk long enough for the request.
65 -- Deallocation just puts the freed chunk at the beginning of the list.
67 procedure Initialize (Pool : in out Stack_Bounded_Pool);
69 (Pool : in out Stack_Bounded_Pool;
70 Address : out System.Address;
71 Storage_Size : SSE.Storage_Count;
72 Alignment : SSE.Storage_Count);
75 (Pool : in out Stack_Bounded_Pool;
76 Address : System.Address;
77 Storage_Size : SSE.Storage_Count;
78 Alignment : SSE.Storage_Count);
79 end Variable_Size_Management;
81 package Vsize renames Variable_Size_Management;
88 (Pool : in out Stack_Bounded_Pool;
89 Address : out System.Address;
90 Storage_Size : SSE.Storage_Count;
91 Alignment : SSE.Storage_Count)
96 if Pool.Elmt_Size = 0 then
97 Vsize.Allocate (Pool, Address, Storage_Size, Alignment);
99 elsif Pool.First_Free /= 0 then
100 Address := Pool.The_Pool (Pool.First_Free)'Address;
101 Pool.First_Free := To_Storage_Count_Access (Address).all;
104 Pool.First_Empty <= (Pool.Pool_Size - Pool.Aligned_Elmt_Size + 1)
106 Address := Pool.The_Pool (Pool.First_Empty)'Address;
107 Pool.First_Empty := Pool.First_Empty + Pool.Aligned_Elmt_Size;
126 (Pool : in out Stack_Bounded_Pool;
127 Address : System.Address;
128 Storage_Size : SSE.Storage_Count;
129 Alignment : SSE.Storage_Count)
134 if Pool.Elmt_Size = 0 then
135 Vsize.Deallocate (Pool, Address, Storage_Size, Alignment);
138 To_Storage_Count_Access (Address).all := Pool.First_Free;
139 Pool.First_Free := Address - Pool.The_Pool'Address + 1;
153 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
155 -- Define the appropriate alignment for allocations. This is the
156 -- maximum of the requested alignment, and the alignment required
157 -- for Storage_Count values. The latter test is to ensure that we
158 -- can properly reference the linked list pointers for free lists.
160 Align : constant SSE.Storage_Count :=
161 SSE.Storage_Count'Max
162 (SSE.Storage_Count'Alignment, Pool.Alignment);
165 if Pool.Elmt_Size = 0 then
166 Vsize.Initialize (Pool);
169 Pool.First_Free := 0;
170 Pool.First_Empty := 1;
172 -- Compute the size to allocate given the size of the element and
173 -- the possible alignment requirement as defined above.
175 Pool.Aligned_Elmt_Size :=
176 SSE.Storage_Count'Max (SC_Size,
177 ((Pool.Elmt_Size + Align - 1) / Align) * Align);
185 function Storage_Size
186 (Pool : Stack_Bounded_Pool) return SSE.Storage_Count
189 return Pool.Pool_Size;
192 ------------------------------
193 -- Variable_Size_Management --
194 ------------------------------
196 package body Variable_Size_Management is
198 Minimum_Size : constant := 2 * SC_Size;
201 (Pool : Stack_Bounded_Pool;
202 Chunk, Size : SSE.Storage_Count);
203 -- Update the field 'size' of a chunk of available storage
206 (Pool : Stack_Bounded_Pool;
207 Chunk, Next : SSE.Storage_Count);
208 -- Update the field 'next' of a chunk of available storage
211 (Pool : Stack_Bounded_Pool;
212 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
213 -- Fetch the field 'size' of a chunk of available storage
216 (Pool : Stack_Bounded_Pool;
217 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
218 -- Fetch the field 'next' of a chunk of available storage
221 (Pool : Stack_Bounded_Pool;
222 Addr : System.Address) return SSE.Storage_Count;
223 -- Give the chunk number in the pool from its Address
230 (Pool : in out Stack_Bounded_Pool;
231 Address : out System.Address;
232 Storage_Size : SSE.Storage_Count;
233 Alignment : SSE.Storage_Count)
235 Chunk : SSE.Storage_Count;
236 New_Chunk : SSE.Storage_Count;
237 Prev_Chunk : SSE.Storage_Count;
238 Our_Align : constant SSE.Storage_Count :=
239 SSE.Storage_Count'Max (SSE.Storage_Count'Alignment,
241 Align_Size : constant SSE.Storage_Count :=
242 SSE.Storage_Count'Max (
244 ((Storage_Size + Our_Align - 1) / Our_Align) *
248 -- Look for the first big enough chunk
250 Prev_Chunk := Pool.First_Free;
251 Chunk := Next (Pool, Prev_Chunk);
253 while Chunk /= 0 and then Size (Pool, Chunk) < Align_Size loop
255 Chunk := Next (Pool, Chunk);
258 -- Raise storage_error if no big enough chunk available
264 -- When the chunk is bigger than what is needed, take appropraite
265 -- amount and build a new shrinked chunk with the remainder.
267 if Size (Pool, Chunk) - Align_Size > Minimum_Size then
268 New_Chunk := Chunk + Align_Size;
269 Set_Size (Pool, New_Chunk, Size (Pool, Chunk) - Align_Size);
270 Set_Next (Pool, New_Chunk, Next (Pool, Chunk));
271 Set_Next (Pool, Prev_Chunk, New_Chunk);
273 -- If the chunk is the right size, just delete it from the chain
276 Set_Next (Pool, Prev_Chunk, Next (Pool, Chunk));
279 Address := Pool.The_Pool (Chunk)'Address;
287 (Pool : Stack_Bounded_Pool;
288 Addr : System.Address) return SSE.Storage_Count
291 return 1 + abs (Addr - Pool.The_Pool (1)'Address);
299 (Pool : in out Stack_Bounded_Pool;
300 Address : System.Address;
301 Storage_Size : SSE.Storage_Count;
302 Alignment : SSE.Storage_Count)
304 Align_Size : constant SSE.Storage_Count :=
305 ((Storage_Size + Alignment - 1) / Alignment) *
307 Chunk : constant SSE.Storage_Count := Chunk_Of (Pool, Address);
310 -- Attach the freed chunk to the chain
312 Set_Size (Pool, Chunk,
313 SSE.Storage_Count'Max (Align_Size, Minimum_Size));
314 Set_Next (Pool, Chunk, Next (Pool, Pool.First_Free));
315 Set_Next (Pool, Pool.First_Free, Chunk);
323 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
325 Pool.First_Free := 1;
327 if Pool.Pool_Size > Minimum_Size then
328 Set_Next (Pool, Pool.First_Free, Pool.First_Free + Minimum_Size);
329 Set_Size (Pool, Pool.First_Free, 0);
330 Set_Size (Pool, Pool.First_Free + Minimum_Size,
331 Pool.Pool_Size - Minimum_Size);
332 Set_Next (Pool, Pool.First_Free + Minimum_Size, 0);
341 (Pool : Stack_Bounded_Pool;
342 Chunk : SSE.Storage_Count) return SSE.Storage_Count
345 pragma Warnings (Off);
346 -- Kill alignment warnings, we are careful to make sure
347 -- that the alignment is correct.
349 return To_Storage_Count_Access
350 (Pool.The_Pool (Chunk + SC_Size)'Address).all;
352 pragma Warnings (On);
360 (Pool : Stack_Bounded_Pool;
361 Chunk, Next : SSE.Storage_Count)
364 pragma Warnings (Off);
365 -- Kill alignment warnings, we are careful to make sure
366 -- that the alignment is correct.
368 To_Storage_Count_Access
369 (Pool.The_Pool (Chunk + SC_Size)'Address).all := Next;
371 pragma Warnings (On);
379 (Pool : Stack_Bounded_Pool;
380 Chunk, Size : SSE.Storage_Count)
383 pragma Warnings (Off);
384 -- Kill alignment warnings, we are careful to make sure
385 -- that the alignment is correct.
387 To_Storage_Count_Access
388 (Pool.The_Pool (Chunk)'Address).all := Size;
390 pragma Warnings (On);
398 (Pool : Stack_Bounded_Pool;
399 Chunk : SSE.Storage_Count) return SSE.Storage_Count
402 pragma Warnings (Off);
403 -- Kill alignment warnings, we are careful to make sure
404 -- that the alignment is correct.
406 return To_Storage_Count_Access (Pool.The_Pool (Chunk)'Address).all;
408 pragma Warnings (On);
411 end Variable_Size_Management;
412 end System.Pool_Size;