1// Copyright (c) 2008, 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// Author: Sanjay Ghemawat <opensource@google.com>
32
33#ifndef TCMALLOC_PAGE_HEAP_ALLOCATOR_H_
34#define TCMALLOC_PAGE_HEAP_ALLOCATOR_H_
35
36#include <stddef.h>                     // for NULL, size_t
37
38#include "common.h"            // for MetaDataAlloc
39#include "internal_logging.h"  // for ASSERT
40
41namespace tcmalloc {
42
43// Simple allocator for objects of a specified type.  External locking
44// is required before accessing one of these objects.
45template <class T>
46class PageHeapAllocator {
47 public:
48  // We use an explicit Init function because these variables are statically
49  // allocated and their constructors might not have run by the time some
50  // other static variable tries to allocate memory.
51  void Init() {
52    ASSERT(sizeof(T) <= kAllocIncrement);
53    inuse_ = 0;
54    free_area_ = NULL;
55    free_avail_ = 0;
56    free_list_ = NULL;
57    // Reserve some space at the beginning to avoid fragmentation.
58    Delete(New());
59  }
60
61  T* New() {
62    // Consult free list
63    void* result;
64    if (free_list_ != NULL) {
65      result = free_list_;
66      free_list_ = *(reinterpret_cast<void**>(result));
67    } else {
68      if (free_avail_ < sizeof(T)) {
69        // Need more room. We assume that MetaDataAlloc returns
70        // suitably aligned memory.
71        free_area_ = reinterpret_cast<char*>(MetaDataAlloc(kAllocIncrement));
72        if (free_area_ == NULL) {
73          Log(kCrash, __FILE__, __LINE__,
74              "FATAL ERROR: Out of memory trying to allocate internal "
75              "tcmalloc data (bytes, object-size)",
76              kAllocIncrement, sizeof(T));
77        }
78        free_avail_ = kAllocIncrement;
79      }
80      result = free_area_;
81      free_area_ += sizeof(T);
82      free_avail_ -= sizeof(T);
83    }
84    inuse_++;
85    return reinterpret_cast<T*>(result);
86  }
87
88  void Delete(T* p) {
89    *(reinterpret_cast<void**>(p)) = free_list_;
90    free_list_ = p;
91    inuse_--;
92  }
93
94  int inuse() const { return inuse_; }
95
96 private:
97  // How much to allocate from system at a time
98  static const int kAllocIncrement = 128 << 10;
99
100  // Free area from which to carve new objects
101  char* free_area_;
102  size_t free_avail_;
103
104  // Free list of already carved objects
105  void* free_list_;
106
107  // Number of allocated but unfreed objects
108  int inuse_;
109};
110
111}  // namespace tcmalloc
112
113#endif  // TCMALLOC_PAGE_HEAP_ALLOCATOR_H_
114