1/* Copyright (c) 2006, Google Inc.
2 * All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met:
7 *
8 *     * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 *     * Redistributions in binary form must reproduce the above
11 * copyright notice, this list of conditions and the following disclaimer
12 * in the documentation and/or other materials provided with the
13 * distribution.
14 *     * Neither the name of Google Inc. nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#if !defined(_BASE_LOW_LEVEL_ALLOC_H_)
32#define _BASE_LOW_LEVEL_ALLOC_H_
33
34// A simple thread-safe memory allocator that does not depend on
35// mutexes or thread-specific data.  It is intended to be used
36// sparingly, and only when malloc() would introduce an unwanted
37// dependency, such as inside the heap-checker.
38
39#include <config.h>
40#include <stddef.h>             // for size_t
41#include "base/basictypes.h"
42
43class LowLevelAlloc {
44 public:
45  struct Arena;       // an arena from which memory may be allocated
46
47  // Returns a pointer to a block of at least "request" bytes
48  // that have been newly allocated from the specific arena.
49  // for Alloc() call the DefaultArena() is used.
50  // Returns 0 if passed request==0.
51  // Does not return 0 under other circumstances; it crashes if memory
52  // is not available.
53  static void *Alloc(size_t request)
54    ATTRIBUTE_SECTION(malloc_hook);
55  static void *AllocWithArena(size_t request, Arena *arena)
56    ATTRIBUTE_SECTION(malloc_hook);
57
58  // Deallocates a region of memory that was previously allocated with
59  // Alloc().   Does nothing if passed 0.   "s" must be either 0,
60  // or must have been returned from a call to Alloc() and not yet passed to
61  // Free() since that call to Alloc().  The space is returned to the arena
62  // from which it was allocated.
63  static void Free(void *s) ATTRIBUTE_SECTION(malloc_hook);
64
65    // ATTRIBUTE_SECTION(malloc_hook) for Alloc* and Free
66    // are to put all callers of MallocHook::Invoke* in this module
67    // into special section,
68    // so that MallocHook::GetCallerStackTrace can function accurately.
69
70  // Create a new arena.
71  // The root metadata for the new arena is allocated in the
72  // meta_data_arena; the DefaultArena() can be passed for meta_data_arena.
73  // These values may be ored into flags:
74  enum {
75    // Report calls to Alloc() and Free() via the MallocHook interface.
76    // Set in the DefaultArena.
77    kCallMallocHook = 0x0001,
78
79    // Make calls to Alloc(), Free() be async-signal-safe.  Not set in
80    // DefaultArena().
81    kAsyncSignalSafe = 0x0002,
82
83    // When used with DefaultArena(), the NewArena() and DeleteArena() calls
84    // obey the flags given explicitly in the NewArena() call, even if those
85    // flags differ from the settings in DefaultArena().  So the call
86    // NewArena(kAsyncSignalSafe, DefaultArena()) is itself async-signal-safe,
87    // as well as generatating an arena that provides async-signal-safe
88    // Alloc/Free.
89  };
90  static Arena *NewArena(int32 flags, Arena *meta_data_arena);
91
92  // Destroys an arena allocated by NewArena and returns true,
93  // provided no allocated blocks remain in the arena.
94  // If allocated blocks remain in the arena, does nothing and
95  // returns false.
96  // It is illegal to attempt to destroy the DefaultArena().
97  static bool DeleteArena(Arena *arena);
98
99  // The default arena that always exists.
100  static Arena *DefaultArena();
101
102 private:
103  LowLevelAlloc();      // no instances
104};
105
106#endif
107