third_party/tcmalloc/vendor/src/page_heap_allocator.h

   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:
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   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
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  25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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  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
  41 namespace tcmalloc {
  42
  43 // Simple allocator for objects of a specified type.  External locking
  44 // is required before accessing one of these objects.
  45 template <class T>
  46 class 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_