1/*
2 * Copyright (C) 2010 Apple Inc. 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
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef OSAllocator_h
27#define OSAllocator_h
28
29#include <wtf/UnusedParam.h>
30#include <wtf/VMTags.h>
31#include <wtf/VMTags.h>
32
33namespace WTF {
34
35class OSAllocator {
36public:
37    enum Usage {
38        UnknownUsage = -1,
39        FastMallocPages = VM_TAG_FOR_TCMALLOC_MEMORY,
40        JSGCHeapPages = VM_TAG_FOR_COLLECTOR_MEMORY,
41        JSVMStackPages = VM_TAG_FOR_REGISTERFILE_MEMORY,
42        JSJITCodePages = VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY,
43    };
44
45    // These methods are symmetric; reserveUncommitted allocates VM in an uncommitted state,
46    // releaseDecommitted should be called on a region of VM allocated by a single reservation,
47    // the memory must all currently be in a decommitted state.
48    static void* reserveUncommitted(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false);
49    static void releaseDecommitted(void*, size_t);
50
51    // These methods are symmetric; they commit or decommit a region of VM (uncommitted VM should
52    // never be accessed, since the OS may not have attached physical memory for these regions).
53    // Clients should only call commit on uncommitted regions and decommit on committed regions.
54    static void commit(void*, size_t, bool writable, bool executable);
55    static void decommit(void*, size_t);
56
57    // These methods are symmetric; reserveAndCommit allocates VM in an committed state,
58    // decommitAndRelease should be called on a region of VM allocated by a single reservation,
59    // the memory must all currently be in a committed state.
60    static void* reserveAndCommit(size_t, Usage = UnknownUsage, bool writable = true, bool executable = false);
61    static void decommitAndRelease(void* base, size_t size);
62
63    // These methods are akin to reserveAndCommit/decommitAndRelease, above - however rather than
64    // committing/decommitting the entire region additional parameters allow a subregion to be
65    // specified.
66    static void* reserveAndCommit(size_t reserveSize, size_t commitSize, Usage = UnknownUsage, bool writable = true, bool executable = false);
67    static void decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize);
68};
69
70inline void* OSAllocator::reserveAndCommit(size_t reserveSize, size_t commitSize, Usage usage, bool writable, bool executable)
71{
72    void* base = reserveUncommitted(reserveSize, usage, writable, executable);
73    commit(base, commitSize, writable, executable);
74    return base;
75}
76
77inline void OSAllocator::decommitAndRelease(void* releaseBase, size_t releaseSize, void* decommitBase, size_t decommitSize)
78{
79    ASSERT(decommitBase >= releaseBase && (static_cast<char*>(decommitBase) + decommitSize) <= (static_cast<char*>(releaseBase) + releaseSize));
80#if OS(WINCE) || OS(SYMBIAN)
81    // On most platforms we can actually skip this final decommit; releasing the VM will
82    // implicitly decommit any physical memory in the region. This is not true on WINCE.
83    // On Symbian, this makes implementation simpler and better aligned with the RChunk API
84    decommit(decommitBase, decommitSize);
85#else
86    UNUSED_PARAM(decommitBase);
87    UNUSED_PARAM(decommitSize);
88#endif
89    releaseDecommitted(releaseBase, releaseSize);
90}
91
92inline void OSAllocator::decommitAndRelease(void* base, size_t size)
93{
94    decommitAndRelease(base, size, base, size);
95}
96
97} // namespace WTF
98
99using WTF::OSAllocator;
100
101#endif // OSAllocator_h
102