/thirdparty/breakpad/client/mac/handler/protected_memory_allocator.h

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29//
30// ProtectedMemoryAllocator
31//
32// A very simple allocator class which allows allocation, but not deallocation.
33// The allocations can be made read-only with the Protect() method.
34// This class is NOT useful as a general-purpose memory allocation system,
35// since it does not allow deallocation.  It is useful to use for a group
36// of allocations which are created in the same time-frame and destroyed
37// in the same time-frame.  It is useful for making allocations of memory
38// which will not need to change often once initialized.  This memory can then
39// be protected from memory smashers by calling the Protect() method.
40
41#ifndef PROTECTED_MEMORY_ALLOCATOR_H__
42#define PROTECTED_MEMORY_ALLOCATOR_H__
43
44#include <mach/mach.h>
45
46//
47class ProtectedMemoryAllocator {
48 public:
49  ProtectedMemoryAllocator(vm_size_t pool_size);  
50  ~ProtectedMemoryAllocator();
51  
52  // Returns a pointer to an allocation of size n within the pool.
53  // Fails by returning NULL is no more space is available.
54  // Please note that the pointers returned from this method should not
55  // be freed in any way (for example by calling free() on them ).
56  char *         Allocate(vm_size_t n);
57  
58  // Returns the base address of the allocation pool.
59  char *         GetBaseAddress() { return (char*)base_address_; }
60
61  // Returns the size of the allocation pool, including allocated
62  // plus free space.
63  vm_size_t      GetTotalSize() { return pool_size_; }
64
65  // Returns the number of bytes already allocated in the pool.
66  vm_size_t      GetAllocatedSize() { return next_alloc_offset_; }
67
68  // Returns the number of bytes available for allocation.
69  vm_size_t      GetFreeSize() { return pool_size_ - next_alloc_offset_; }
70  
71  // Makes the entire allocation pool read-only including, of course,
72  // all allocations made from the pool.
73  kern_return_t  Protect();  
74
75  // Makes the entire allocation pool read/write.
76  kern_return_t  Unprotect();  
77  
78 private:
79  vm_size_t      pool_size_;
80  vm_address_t   base_address_;
81  vm_size_t      next_alloc_offset_;
82  bool           valid_;
83};
84
85#endif // PROTECTED_MEMORY_ALLOCATOR_H__