Issue 202: reviewed by Waylonis

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@205 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/mac/handler/protected_memory_allocator.h

@@ -0,0 +1,85 @@
+// Copyright (c) 2006, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// ProtectedMemoryAllocator
+//
+// A very simple allocator class which allows allocation, but not deallocation.
+// The allocations can be made read-only with the Protect() method.
+// This class is NOT useful as a general-purpose memory allocation system,
+// since it does not allow deallocation.  It is useful to use for a group
+// of allocations which are created in the same time-frame and destroyed
+// in the same time-frame.  It is useful for making allocations of memory
+// which will not need to change often once initialized.  This memory can then
+// be protected from memory smashers by calling the Protect() method.
+
+#ifndef PROTECTED_MEMORY_ALLOCATOR_H__
+#define PROTECTED_MEMORY_ALLOCATOR_H__
+
+#include <mach/mach.h>
+
+//
+class ProtectedMemoryAllocator {
+ public:
+  ProtectedMemoryAllocator(vm_size_t pool_size);  
+  ~ProtectedMemoryAllocator();
+  
+  // Returns a pointer to an allocation of size n within the pool.
+  // Fails by returning NULL is no more space is available.
+  // Please note that the pointers returned from this method should not
+  // be freed in any way (for example by calling free() on them ).
+  char *         Allocate(size_t n);
+  
+  // Returns the base address of the allocation pool.
+  char *         GetBaseAddress() { return (char*)base_address_; }
+
+  // Returns the size of the allocation pool, including allocated
+  // plus free space.
+  vm_size_t      GetTotalSize() { return pool_size_; }
+
+  // Returns the number of bytes already allocated in the pool.
+  vm_size_t      GetAllocatedSize() { return next_alloc_offset_; }
+
+  // Returns the number of bytes available for allocation.
+  vm_size_t      GetFreeSize() { return pool_size_ - next_alloc_offset_; }
+  
+  // Makes the entire allocation pool read-only including, of course,
+  // all allocations made from the pool.
+  kern_return_t  Protect();  
+
+  // Makes the entire allocation pool read/write.
+  kern_return_t  Unprotect();  
+  
+ private:
+  vm_size_t      pool_size_;
+  vm_address_t   base_address_;
+  int            next_alloc_offset_;
+  bool           valid_;
+};
+
+#endif // PROTECTED_MEMORY_ALLOCATOR_H__